ENGINEERS· ARCHITECTS· SCIENTISTS· PLANNERS· SURVEYORS … · FAX (817) 232-9784 March 23, 1996 AVO 14191 City of Mission 900 Doherty Mission, Texas 78572 Attn: Pat Townsend,

--

Halff Associates, Inc. ENGINEERS· ARCHITECTS· SCIENTISTS· PLANNERS· SURVEYORS

City of McAllen 1300 West Houston McAllen, Texas 78501

Attn: Mr. Tom Martin, P.E. Assistant City Manager

Re: Flood Protection Planning Study

MA~ 3C 1997

for Southern McAllen and Mission, Texas TWDB Contract No. 95-483-077

Dear Messrs. Martin and Townsend:

4000 FOSSIL CREEK BOULEVARD

FT. WORTH, TEXAS 73137

(817) 847-1422 • METRO (817) 429-9975

FAX (817) 232-9784

March 23, 1996 AVO 14191

City of Mission 900 Doherty Mission, Texas 78572

Attn: Pat Townsend, Jr. City Manager

Transmitted herewith are twenty (20) bOUllG copies of the Final Report entitled, Flood Protection Planning Study for Southern McAllen and Mission, Texas,

This report includes a brief executive summary and a detail discussion of study procedures, results of technical analyses, alternative improvements, and recometidations. A detailed watershed delineation, 10-, 25-, and 100-year flood plain delin.eations, and computed flood profiles of the Mission Floodway, for existing and ultimate land use conditions, are included.

It has been a privilege and a challenge for our firm to prepare this most important study. Halff Associates are especially appreciative of the cooperation of the members of the City Staff of McAllen and Mission who have assisted in the development of this study.

Sincerely,

HALFF ASSOCIATES, INC.

Michael A. Moya, P.E. enclosures

cc: Mr. Abu Sayeed, Texas Water Developmehc Board

O:\A VOII4191IWORDIREPOR1\LT03-23.96

FORT WORTH DALLAS ARLINGTON HOUSTON McALLEN CHICAGO

TRANSPORTATION WATER RESOURCES LAND DEVELOPMENT

SURVEYING GLOBAL POSITIONING SYSTEM (G.P.S.)

LANDSCAPE ARCHITECTURE

MUNICIPAL ENVIRONMENTAL

REMOTE SENSING AND MAPPING

PLANNING

STRUCTURAL

TABLE OF CONTENTS

Letter of Transmittal

Table of Contents ................................................. i

List of Figures .................................................. iii

List of Tables ................................................... iv

Acknowledgements ............................................... v

Glossary of Terms ..................... '. . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

I. INTRODUCTION

II.

A. Purpose of Report .......................................... 1-1

B. Community Description ...................................... 1-2

C. Principal Flood Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-3

STUDY PROCEDURES

A. Hydrologic Studies II-I

B. Hydraulic Analyses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-7

C. Study Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11-8

D. Flood Plain Delineation ..................................... 11-10

III. STUDY RESULTS

A. General .................................................. 111-1

B. Mission Inlet Floodway ..................................... III-5

C. Banker Floodway ........................................ III-10

D. Sharyland/Foreign Trade Zone '" ............................ III-lO

E. Single Occurance Flood Losses III-16

IV. ALTERNATIVE IMPROVEMENTS

A. General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-I

B. Mission Inlet Floodway ..................................... IV-2

C. Sharyland/Foreign Trade Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV-3

i

TABLE OF CONTENTS

(Continued)

APPENDICES

Appendix A Drainage Area Map

Appendix B Elevation-Storage Tables

Appendix C Flood Plain Maps lOO-Year, 25-Year, and lO-Year

Appendix D SCS Curve Number Computations

Appendix E Preliminary Estimates of Probable Construction Cost

Appendix F Computer Files of Hydrologic and Hydraulic Models (Computer Diskette)

Appendix G References

Appendix H Survey Control Data

ii

LIST OF FIGURES

No. Follows Page

1. Study Area Map ................................................ I-I

2. Hurricane Beulah Limits of Flooding McAllen, Texas . . . . . . . . . . . . . . . . . . . . .. 1-3

3. Drainage Area Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II-I

4. 1995 Existing Land Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. II-2

S. Assumed Ultimate Land Use ...................................... II-2

6. Hydrologic Soils for Watershed .................................... II-4

7. Detail Study Area - Flood Storage Cells .............................. II-8

8. Elevation-Discharge Relationship at Mission Outlet Structure ................ III-9

9. Mission Floodway 100-Year Flood Profile - Existing Land Use Conditions ...... III-9

10. Mission Floodway 100-Year Flood Profile - Ultimate Land Use Conditions ...... III-9

11. Detail Study Area - Drainage Areas ................................ III-I 0

12. Detail Study Area - Overall Flood Plain Map ......................... , III-IS

13. Depth of Flooding for Cell 9 - IOO-Year Flood Ultimate Land Use ........... III-IS

14. Proposed Modifications to Mission Inlet Floodway ....................... IV-2

IS. Proposed Levee Closure South of Cimarron ............................ IV-2

16. Mission Inlet Floodway Relief Storage - Gates Closed .................... IV-3

17. Proposed Drainage Improvements for Cells 1 & 2 . . . . . . . . . . . . . . . . . . . . . . . . IV-4

18. Proposed Drainage Improvements for Cells 3 - 9, Sheet 1 of 4 ............... IV-S




22. Proposed Drainage Improvements for Cell 10 ........................... IV-S

23. Proposed Drainage Improvements for Cell 11 ........................... IV-6

iii

LIST OF TABLES

~. Pqe

1. Characteristic Imperviousness for Land Use found in Study Area . . . . . . . . . . . .. 1I-3

2. Composite SCS Curve Numbers for the Land Use found in the Study Area. . . . .. 1I-5

3. Rainfall Depth / Duration for the Hidalgo County Study Area ............... 1I-6

4. Summary of Drainage Areas and Estimated SCS Curve Numbers ............. III-I

5. Mission Floodway Summary of Computed Peak Flood Discharges

Existing and Ultimate Land Use Conditions (Gates Closed) ................. 1II-6

6. Major Contributing Ditch Systems Summary of Computed Peak Flood Discharges

Existing and Ultimate Land Use Conditions (Gates Closed) ................. 1II-7

7. Mission Floodway Summary of Computed Peak Flood Elevations

Existing and Ultimate Land Use Conditions (Gates Closed) 1II-8

8. Mission Floodway Summary of Structure Crossings

Ultimate Land Use Conditions (Gates Closed) .......................... 1II-9

9. Sharyland/Foreign Trade Zone Computed Peak Flood Elevations

Existing and Ultimate Land Use Conditions ........................... III-ll

10. Sharyland/Foreign Trade Zone Computed lO-Year Ponding Elevations and

Flood Storage- Existing and Ultimate Land Use Conditions ................ 1II-13

11. Sharyland/Foreign Trade Zone Computed 25-Year Ponding Elevations and

Flood Storage- Existing and Ultimate Land Use Conditions . . . . . . . . . . . . . . .. 1II-14

12. Sharyland/Foreign Trade Zone Computed 100-Year Ponding Elevations

and Flood Storage- Existing and Ultimate Land Use Conditions ............. III-IS

13. Summary of IOO-Year Single Occurrence Flood Losses Ultimate

Land Use Conditions ........................................... 1II-17

14. Summary of Flooded Structures 10-,25-, 50-, and 100-Year Flood

Frequencies- Ultimate Land Use Conditions ........................... 1II-18

15. Sharyland/Foreign Trade Zone Summary of 100-Year Peak Storage

Requirements- Ultimate Land Use Conditions ........................... IV-I

iv

ACKNOWLEDGEMENTS

Halff Associates, Inc. wishes to acknowledge the valuable assistance of the various organizations

and individuals who have assisted in the preparation of the Flood Protection Planning Study for

Southern McAllen and Mission, Texas. We wish to express our gratitude to all those listed below

who have contributed their time and effort to this study.

The following have provided a tremendous amount of information and personal experience related

to flooding problems and have also provided valuable suggestions for solutions to these problems.

Mr. Tom Martin, P.E., City of McAllen City Engineer, Mr. Pat Townsend Jr., City of Mission City

Manager, Ms. Vona Walker, Hidalgo County, and Mr. Abu Sayeed, Texas Water Development

Board.

The employees of Halff Associates who have worked most closely with the project include: Mr.

Michael A. Moya, P.E., Ms. Emilia Salcido, P.E., Ms. Cindy Mosier, E.I.T., Ms. Dana Woods,

E.I.T., Mr. Ron Slonaker, Ms. Nancy MacSwain, Mr. Raul Wong, Jr., P.E., Mr. Celso Gonzalez,

E.I.T., Mr. Joe Novoa, P.E., and Mr. Martin Molloy, P.E. Halff Associates deeply appreciates the

dedicated efforts of all the groups and individuals who have helped in the performance of this

study.

v

GLOSSARY OF TERMS

BASE FLOOD. The flood having a one percent chance of being equalled or exceeded in any given year, the IOO-year flood. Note, for this study the base flood is based on a future fully urbanized watershed and existing channels and bridges with floodway encroachments in

place to account for potential upstream losses in valley storage. The FEMA base flood is based on existing land use and existing channels/bridges.

DISCHARGE. As applied to a stream, the rate of flow, or volume of water flowing in a given

stream at a given place and within a given period of time, usually quoted in cubic feet per second (cfs) or gallons per minute (gpm).

DRAINAGE AREA. The area tributary to a lake, stream, sewer, or drain. Also called catchment area, watershed, and river basin.

DTM. Digital Terrain Model, three dimensional digital surface model, with x, y, and z attributes, generated from field surveys and/or aerial photography

FLOOD. An overflow of land not normally covered by water and that is used or usable by man.

Floods have two essential characteristics: The inundation of land is temporary; and the land is adjacent to and inundated by overflow from a river or stream or an ocean, lake, or other

body of standing water. Normally, a "flood" is considered as any temporary rise is a stream

flow or stage, but not the ponding of surface water, that results in significant adverse effects in the vicinity. Adverse effects may include damages from overflow of land areas, temporary backwater effects in sewers and local drainage channels, creation of unsanitary

conditions or other unfavorable situations by deposition of materials in stream channels during flood recessions, and rise of ground water coincident with increased stream flow.

FLOOD FREQUENCY. A means of expressing the probability of flood occurrences as determined from a statistical analysis of representative stream flow, rainfall and runoff records. A

10-year frequency flood would have an average frequency of occurrence in the order of once in 10 years (a 10 percent chance of being equalled or exceeded in any given year).

A 50-year frequency flood would have an average frequency of occurrence in the order of once in 50 years (a 2 percent chance of being equalled or exceeded in any given year). A IOO-year frequency flood would have an average frequency of occurrence in the order of once in 100 years (a I percent chance of being equalled or exceeded in any given year). A 500-year frequency flood would have an average frequency of occurrence in the order of once in 500 years (a 0.2 percent chance of being equalled or exceeded in any given

year). FLOOD PEAK. The maximum instantaneous discharge of a flood at a given location. It usually

occurs at or near the time of the flood crest. FLOOD PLAIN. The relatively flat area or low lands adjoining the channel of a river, stream or

watercourse or ocean, lake or other body of standing water, which has been or may be

covered by flood water.

vi

GLOSSARY OF TERMS (Continued)

FLOOD PROFILE. A graph showing the relationship of water surface elevation to location, the

latter generally expressed as distance above the mouth for a stream of water flowing in an

open channel. It is generally drawn to show surface elevation for the peak of a specific

flood, but may be prepared for conditions at a given time or stage.

FLOOD STORAGE. The term used to describe a channel and flood plain's capacity to store some

portion of the runoff volume as a flood wave moves downstream.

FLOODWAY. The channel of a river or other watercourse and the adjacent land areas that must

be reserved in order to discharge the base flood without cumulatively increasing the water

surface elevation more than a designated height.

FULLY URBANIZED CONDITIONS. In the context of a drainage study, the watershed or drainage area of a stream is considered to be completely developed, i.e. all land is assumed to be functioning in it's ultimate use. Other descriptions include: Fully Developed, 100 Per Cent Urbanized, Ultimate Development or Land Use, and Maximum Development.

ONE HUNDRED YEAR FLOOD. A flood having an average frequency of occurrence in the order of once in laO years, at a designated location, although the flood may occur in any year and possibly in successive years. It would have a 1 percent chance of being equalled or exceeded in any year. In the past, this flood has been referred to as the Intermediate Regional Flood.

WATERSHED. The area contained within a divide above a specified point on a stream.

vii

EXECUTIVE SUMMARY

The Texas Water Development Board and the Cities of McAllen and Mission contracted Halff Associates in January 1995 to prepare a detail flood study for the developing areas of southern McAllen and southern Mission, located between the Old Mission Inlet and the Banker Floodway. The purpose of this study was to develop detailed hydrologic and hydraulic computer models of the watershed to analyze the existing drainage system, estimate potential flood damages, and evaluate alternative design schemes to alleviate flood damages.

Frequent flooding problems in the area are attributed to an insufficient drainage system, inadequate topographic relief, and low permeability of the soils. The most severe recorded catastrophic storm in the Lower Rio Grande Valley was Hurricane Beulah in September 1967. This event resulted in millions of dollars of flood related damages throughout south Texas. This storm produced a total rainfall of about 16 inches, observed in the City of McAllen. This corresponds to a return period of about 125 years.

The total contributing watershed draining to the Mission Inlet encompasses about 76 square miles. Contributing storm water runoff originates in the City of Penitas and from as far north as FM 1924 (Mile 3 North). The detail study area, referred to as "Sharyland/Foreign Trade Zone," is located between the Mission Inlet and the Banker Floodway. This detail study area includes about 16 square miles.

The Mission Inlet watershed is about 53% urbanized at this time. Existing non-urbanized areas include about 30% agricultural and 17% undeveloped open space. Anticipated future development, determined from available zoning and land use maps of various cities, will consist of about 76% urbanization with about 24% and 7% reserved for agriculture and open space respectively. The Sharyland/Foreign Trade Zone is about 89% undeveloped (includes 17% open space and 72% agriculture) at this time. Anticipated future development will include about 98% urbanization.

Soil types found in the Mission Inlet watershed generally have moderate to low permeability rates. The majority of the soils found in the Sharyland/Foreign Trade Zone have low permeability rates; thus, the detailed study area has a high runoff potential.

Hydrologic analysis were prepared for existing and future land use conditions. Peak flood discharges were computed for the 10-, 25-, 50-, and 100-year flood frequencies. These events have a 10,4,2, and 1 percent chance of being equalled or exceeded (one or multiple occurrences) during any single year. Differences in computed peak flood discharges, for contributing areas along the Mission inlet, generally varied less than 5% for existing and future land use conditions. This slight difference can be attributed to the estimated infiltration rates for irrigated cropland, which are only slightly less than those for residential (urbanized) land use.

viii

The Mission Floodway is about 10 miles is length, from the outlet structure to near FM 1016. The average levee height, from the top bank of the pilot channel, is about 15 feet. There are nine structures, including the structure at the levee closure, crossing the Mission Floodway. Assuming the outlet gates are closed, the computed future fully urbanized 100-year flood will overtop the existing roadway or embankment at six of these nine structures. In addition, the 100-year flood will overtop the existing levee at five (5) locations including; the levee closure, McAllen Miller International Airport, Palm View Golf Course, Cimarron Country Club, and at a location west of PM 1016. If flow is not diverted to the Banker and the Mission outlet gates are open, the Mission Levee will be overtopped at three (3) locations including the Miller International Airport, Cimarron Country Club, and at a location west of FM 1016.

Following Hurricane Beulah, the IBWC closed the Rio Grande diversion to the Mission Floodway and constructed the Banker Weir to permit an effective diversion of about 106,300 cfs to the Banker Floodway. Assuming this is the maximum permitable flow to the Banker Floodway, the estimated minimum freeboard (computed water surface to top of levee) is within 1 foot of the

top of levee at the Mission outlet structure.

As part of this study, a Digital Terrain Model (DTM) was developed from aerial

photography for the SharylandiForeign Trade Zone study area. Halff Associates utilized this DTM

to compute available flood storage volumes and subsequent flood elevations, for existing and future

land use conditions, for the low lying areas of widespread shallow ponding of flood waters. Generally, the difference in computed flood elevations for ultimate and existing land use conditions

is less than 0.4 feet, for the frequencies studied. This slight difference could be attributed the amount of existing agricultural land use, where the estimated loss rates (infiltration) for irrigated

cropland, for soils with low permeability, are only slightly less than those for urbanized land use.

In addition, this slight difference in computed flood elevations can be also attributed to the flood storage capacity of the land at shallow depths, where the difference in total flood storage is

somewhat more significant than the variation in actual depth of ponding.

The estimated total property inundated by the future (assumed ultimate land use) 100-year flood within the study area is approximately 7,681 acres. This includes about 2,590 acres within

the Mission Floodway and about 5,091 acres between the Mission and Banker Levees. Visual inspection of these flood plain areas indicate about 2,958 acres of 100-year flood plain consist of

agricultural cropland.

An inventory of existing structures indicate that there are about 1,236 structures with

estimated finish floor elevations below the computed future 100-year flood. The majority of these

structures (1,085) are residential properties located in Balboa Acres. An additional 75 flood prone residential structures are located in the Cimarron Country Club. As many as 955 residential

ix

structures, located in the Cimarron Country Club and Balboa Acres, are susceptible to the lO-year flood event, assuming ultimate development.

Recommended structural improvements to help alleviate flooding of existing structures

include reconstruction of the Mission Levee at Cimarron Country Club and excavation of about 2.4 million cubic yards of material for flood storage at Balboa Acres and the Foreign Trade Zone. The estimated cost to redirect flood water around Cimarron Country Club and provide flood protection for 75 existing residential structures is about $6.4 million. The estimated cost to alleviate flooding

of about 1,155 existing residential, warehouse, and commercial structures in Balboa Acres and the

Foreign Trade Zone is about $10.1 million.

Recommended future structural improvements for the Cities to consider include raising the

existing levee three feet above the 100-year flood (in accordance with FEMA criteria) at all locations where the computed future IOO-year flood will overtop the Mission Levee. In addition,

the Cities should consider constructing a designated emergency spillway at the Mission Floodway outlet structure to the Banker Floodway. The estimated cost for the emergency spillway is about

$2 million.

Halff Associates also recommends that the Cities consider adopting a flood plain

management policy that would require all new developments within the Sharyland/Foreign Trade

Zone provide a minimum of 0.8 acre-feet of flood storage for every one acre of development.

It is further recommended that the Cities formally adopt the flood levels shown in this report for their flood plain management program.

x

SECTION I INTRODUCTION

I. INTRODUCTION

A. PURPOSE OF REPORT

The purpose of this study is to develop detailed hydrologic and hydraulic computer models to analyze the existing drainage system and evaluate alternative design schemes to help alleviate existing and potential flood damages for the developing areas of southern McAllen

and southern Mission, Texas, located between the Old Mission Inlet Floodway and the Banker Floodway. The limits of the detail study area are illustrated on Figure 1.

This study identifies and quantifies existing and potential flooding problems endangering

the Foreign Trade Zone, Balboa Acres, Cimarron Country Club, the McAllen Sewage Treatment Plant, and other areas including significant amount of agricultural property. In

addition, the results of this study provides planning alternatives and design concepts to

improve the existing drainage system and help alleviate subsequent flooding. The

information presented in this report will provide the Cities of McAllen and Mission with the necessary updated drainage information to coordinate future development and help minimize existing and potential flood damages within the detail study area (SharylandJ Foreign Trade

Zone). For the purposes of this report, the detail study area shall be referred to as the

Sharyland/Foreign Trade Zone.

This report provides a summary of the procedures used to analyze the existing drainage system and associated flood problems and the results and recommendations that were

derived from the analyses. Additional information (i.e. 1995 topographic mapping, digital terrain model (DTM), photographs, work maps, and computer files) used in the production

of this report are available from Halff Associates and from the Cities of McAllen and

Mission.

Specific objectives of the Flood Protection Planning Study for Southern McAllen and

Mission, Texas are:

1. Establish survey control network (see Appendix H) for aerial mapping of the

project area bounded on the north by the Old Mission Inlet Floodway and

on the south by the Banker Floodway.

2. Compile pertinent existing engineering data and newly developed

information into a comprehensive report with an up-to-date, fullY developed

watershed. 10-, 25-, and IOO-year flood plain delineation of the study area.

1-1

\ ~

(,p,,-rf~ _.'" I"

J :- .. _._· ...... _.,;.1

"

...... , -'\.

\ \ ;,1 : \ )

\

I •• , .. ~. -._ •• _,1 -,/

"~."'("

L£~ .... ;.;/" .. ": ~ .. ,~;; ... Ul"'/C"'~ " !JET'" " sT'Jl' g. ", . .. _ .. , .. _.' ~_~UL ..... ~~ j,Ufii,£ otT'" Sf\J)t g. \

a£ .. r£OC...... i \ - ""~,... \_---

\

_. _ .' IJI'" <)IT!iIIf. ot'''' .... srW' g> '\

----~ \

\

___ \JArs Ii' !lEt'" sf\J)' ....... _. '<.,!% .. ~.";

SIUD~ AR£i\. ~

./'.~ ..... -.. ~. .. \' , . : i \ : • I I : ! !

\ ~". ...... _ .. ,

I-"S (.~_.", //"_~_h'-• .< '

i/I''l/iiOS \;:~ __ J

" ..

I

,..1 I

\------- ",." ,,-' ---

FLOOD l'RO'fECflON l'Li\J'lNING

s'fllllY

, ,0" solJ{ll£"" ~ .,.., ,,"SSlo1'l, ",,,,,,,

\~lla\fI As~~~~ -//-//////

\ .J.. ~':II"'I'E-t'{S.SCJVli\st; - -----"------'E.~AS • "AV'" ~

IL,' ~~_~:IJ~,,: .'L),,)l __

r" ~Ik£ 3 M3f1f1i!

...--/

ft,~rI"'" \! ~~ ~~. J) ~

"

\.~ t-=:: ........ £

~ ~ ~ . m ./ . , ~-'-'/' ~ ~

~ t "

~

" l

'I \

_."\ ......-' \ .. I

j -, 111\

'I \

3. Determine the impact of future urbanization of the contributing watershed on the study area.

4. Formulate conceptual plans and analyze the effects of proposed

improvements to reduce the flooding potential within the study area. Consideration of improvements to flood storage areas, channel flow

characteristics, gated outfall structures, existing levee, and possible secondary levee. Prepare pre-design estimates of probable cost for the various improvement plans.

5. Based on the analysis of various alternative plans to reduce flooding, make

specific recommendations to the Cities of McAllen and Mission.

6. Coordinate all phases of the study, from data gathering to final design recommendations, with the City Engineering Staff.

B. COMMUNITY DESCRIPTION

The study area is located in the south central region of Hidalgo County, commonly known as the Lower Rio Grande Valley. The detail study area includes the developing areas of

southern McAllen and southern Mission, Texas, located between the Old Mission Inlet

Floodway and the Banker Floodway. Existing land use within the detail study is

predominantly agricultural, consisting of vegetables, sugar cane, grain, and citrus. Major

existing development includes the Foreign Trade Zone and residential subdivisions including Balboa Acres, Cimarron Country Club, Madero, and Granjeno. Proposed future planned

development will most likely consist of warehousing/manufacturing and residential properties.

The study area's terrain is characteristic of the Texas Coastal Plains. The topography is

rather flat with elevations (in the detail study area) varying from about 92 feet to 112 feet

above the National Geodetic Vertical Datum of 1929 (NGVD). The soils in the area generally consist of moderately permeable loams and clays (Reference 1).

The climate of the study area is subtropical. Summers are hot and winters are short and mild. Extremes of temperature and precipitation are of relatively short duration. Temperatures range from an average July maximum of about 97°F to a January minimum

of about 49°F (Reference 2). The mean annual precipitation is about 20 inches. These

weather conditions, along with an plentiful source of water for irrigation from the Rio

Grande, sustain an ideal growing season of 327 day per year.

1-2

C. PRINCIPAL FLOOD PROBLEMS

Most of the frequent flooding problems in the area are attributed to an insufficient drainage system, inadequate topographic relief, and the low permeability of the soils. Drainage ditch

grades of 0.02 % (about 1 foot per mile) and flat grades for overland flow account for

widespread shallow ponding of excess storm water (Reference 2). In addition, the drainage

ditches in the study area outfall to the Mission Inlet through manually operated gated drainage structures that are often old and deteriorated and possibly frozen open or closed. During flood stage along the Mission Inlet, flood waters may surcharge these structures,

resulting in additional flooding problems.

The most severe recorded catastrophic storm in the Lower Rio Grande Valley was Hurricane Beulah in September 1967. This event resulted in millions of dollars of flood related

damages throughout south Texas. Thousands acres of land were inundated with flood

waters. Figure 2, taken from the Corps of Engineers' "Report on Hurricane Beulah" (Reference 3), is an illustration of the extent of flooding near the Miller International

Airport in McAllen, Texas. Ponding water was prevalent for months following the storm.

A total rainfall of about 16 inches was observed in the City of McAllen. This corresponds to a return period of about 125 years (Reference 3). As a result of Hurricane Beulah, the

Mission Inlet Floodway was abandoned as an overflow route to the Rio Grande. Today the

Mission Inlet Floodway is used to convey and store only local storm water runoff.

I-3

~

r::::1

B

b..m.t!Q.

NORMAL WATER LEVELS

STREAM OR SURFaCE RUNOFF FLOOOJNG

DEBRIS OR DRIFTUNE ELEVATION

NOTES:

8-21 SEPT. 1967

LIMITS OF FLOODING Me ALLEN. TEXAS

(SOUTH) SCALE OF FEET

'000

~ TO ACCOMPANY REPORT ON HURRICANE BEULAH

PLATE 1/.6

SECTION II STUDY PROCEDURES

II. STUDY PROCEDURES

A. HYDROLOGIC STUDIES

1. General

Hydrologic analyses were conducted by Halff Associates for the Mission Inlet

Watershed basin using the Corps of Engineers hydrologic computer program HEC-1 (Reference 5). This methodology is consistent with previous hydrologic studies

prepared by the Galveston District U.S. Army Corps of Engineers (Reference 6) and City of McAllen Study, dated May 1991, prepared by Phase V Engineering, Inc. in cooperation with Furlong Engineering, Inc. (Reference 7). Halff Associates utilized

portions of the City of McAllen HEC-2 model and associated work maps to develop an updated detailed HEC-1 model of the Mission Inlet watershed basin for this study.

Halff Associates' hydrologic analysis for this study was prepared using existing (1995) and future, fully-urbanized watershed conditions. Flood events of a magnitude

which are expected to be equalled or exceeded once on the average of any 10-,25-, 50-, and 100-years have been selected as having special significance for this study. These events have a 10, 4, 2, and 1 percent chance, respectively, of being equalled or exceeded (one or more occurrences) during anyone year. Tables of peak flood

discharges can be found in Chapter 3. Although the recurrence interval represents the

long term, average period between floods of a specific magnitude, rare floods could

occur at short intervals or even within the same year. The risk of experiencing a rare flood increases when periods greater than one year are considered. For example, the

risk of having a flood which equals or exceeds the 100-year flood (one percent chance of annual occurrence) in any 50-year period is about 40 percent (4 in 10), and for any

90-year period, the risk increases to about 60 percent (6 in 10).

2. Watershed

The total contributing Mission Inlet watershed encompasses approximately 76 square miles. Contributing storm water runoff originates in the City of Penitas, just west of

the intersection of U.S. Highway 83 (US 83) and Business Route 374 (Bus. 374). Runoff from the north drains to the Mission from near FM 1924 (Mile 3 North). Figure 3 is a schematic illustration of the study watershed depicting the major drainage systems including the Mission Inlet, Edinburg Canal & Mission Lateral,

Rado Alternate, Rado Drain, McAllen Airport, Rancho Santa Cruz, and the

SharylandIForeign Trade Zone.

II-I

\

~'.

"" '

-..

\ '" :,:

I "

" ... ~~- .. -.. ~~"{f

t>"",,~~, ~'... .'" ....... _. __ ... ( ..

~ ~~~~~y~.

~ Oll"'/C~""'S 1H oE.T 101-s'1tfl'f -. ..

El.E.'J"l'EOt~

___ "" U>II' '-'"

_ "'''' ""'~ oE'''sTUDy AJE~

\ ! (-;2. -\ ~ .p'" '" c' .,>-" "",<_. ",",.>% .I '. "'';;''~ ,. j

... ~.. \. ~ \. 1 t

'" 1It1I~ : \ , .. _ .. _ .. _u_....... " "\"")

". --"-'. ',,;~ ...... r .. ~:._.,

*'-~\. -"'" . .... \ ,/ "

'\

DF.:\l~AGE AREA MAl'

\

~,. FLOOD PROTIlCflON pLANNING stUDy ~!!~~~~~~__FO~ ~\lfIIE"" .. cALL'" .,.., ,"SSION. ~ \ o>"£,S,Df," _ ~_,~i\-----~ ~~;;,,'ti"I\ii"""~~~'" ,), 00h .'

-"""" __ '"''' '* oE'''- sNl'

".,... • fl."""'''' ...,.....,- "" ...... sYsT'" ~

"

\ _ --"!J'

iI.-,r .. m;,

~

~,~ c;~W"'

-' -' -'

FIGURE 3

,,, en"!' Of ""cALLE" -~

For this study, the watershed basin was sub-divided into approximately lOl subwatershed basins (see Appendix A - Overall Drainage Area Map). Watershed

characteristics such as drainage area, watercourse length, basin slope, land use, soil type, and channeVflood plain storage were determined for each sub-watershed basin.

The hydrologic procedure used in the preparation of this report includes the development of synthetic unit hydrographs at each of these sub-basin locations. Derived runoff hydrographs were then combined and routed through existing

channels. The program HEC-1 (Reference 5) was used to compute storm runoff

based on Soil Conservation Service (SCS) curve numbers (Reference 8), derived from land use and hydrologic soil types. The Snyder's unit hydrograph method and the

Modified Puls routing method were used to determine peak flood discharges for a given frequency rainfall.

3. Land Use

Existing land uses were determined from March 1995 aerial topography, for areas

within the detail study area (SharylandfTrade Zone). Available land use maps and

aerial photographs (dated 1992) were utilized for areas beyond the detail study area.

These existing land use classifications were then verified and adjusted based on field observations. Figure 4 is an illustration of the 1995 existing land uses assumed for this study.

As communities such as Mission and McAllen develop, farms and pastures are replaced with residential, commercial, and industrial land uses. Future land

classifications and growth patterns were generally determined from available

published city maps including the McAllen Physical Development Plan (adopted

September 12, 1993, the City of Mission Zoning Map, the of City of Mission-5 Mile Extra-Territorial Jurisdiction (ETl) Map, and Land Use Districts Conceptual

Development for Sharyland Plantation. Future land use classifications for areas beyond the ETJ were estimated based on present development trends and coordination

with City staff. Assumed ultimate land use for the study area is depicted on Figure

5.

4. bnpervious Coverage

Percent impervious is a function of the various land uses within the watershed basin.

Residential impervious coverage typically reflects the housing market by allowing greater building and pavement coverage as land prices increase. The assumed impervious coverage for land uses found in the study watershed area are summarized

in Table 1.

ll-2

N311'v'0Vl/ :10 A1.1:l

" IDIIl flU

; N

't\ ~) r;,=ZI('(

-.. {:~~~: -'\

svx:u. 'NOISSIW ONV XUfUS ~NINNV1d

j /"" / . \

:>ISfl ONV1

,.- i '\ i i \ :""-"-n;,;;'~--'-" . .' ( '. " i j \ \ ·,· .... ao_···ll !... '\,

" "

'saj'iii;OS'S'v'N3I".u' "'I'eiiii ~~~ ~ ---~---- ---~- ~~---,"o.a"'·';1

. .CJ. 1I0..ol

aOO'li( N3TIV:JW NlIIDUflOS NOI.L;)3J.OlId DNI.LSIX:>I S661

J I" Ii i II LL I-j t,,_!i_,~JI J [- ~ -: I

I i:I-, I I\H', Ju': I;', ! '.' j '-. .,. •• J" _<I llr.15 ....... ....

'... aT1VA :xJ1Ir~ or" " [:j 1'.'1 {I il"n

\ i i, "

f'F"I"="':',..1' 4:;~,", ,?:,< .. I.~ii'l~§r~-· .... )·-··-··-··'·\··"'

17:J i ,'JIJI Jd I' ! lij::J.'il' d. Ii, ,

-.. - .. " .. , '.

/ ("

I t. \

\ j

", '.-

I ,

1 ______ 1

1

1

1 1

1

1 1

1

1 1 1

1 1

1

1 1

1

1

1 1

1

1 1

1

1 1

1

1 1

1

1

1 1

1

1 1

1 1 1

1

r~' \ ~ _______ ~1

Residential land use classifications within the city limits were assigned a "Residential

l" land use category for this study. This classification was devised to simplify the

varying definitions for residential development within the Cities of McAllen and

Mission. For instance, low density residential development in the City of ·Mission

includes residential lots of 6,000 square feet or greater (Rl & RIA), while low

density residential development in the City of McAllen includes duplexes,

townhouses, and some mobile homes (R-2, R-3T, and R-4). "Residential-2"

classification was assigned for areas beyond the city limits, generally located west of

Mission, where typical observed residential lots are 112 acre or greater.

Percent impervious values were derived by Halff Associates using Corps of Engineers

and Soil Conservation Service (SCS) publications (References 6 and 8) and drainage

design manuals from various Texas cities. Halff Associates has also derived

impervious coverage values for typical Dallas-Fort Worth Metroplex and other Texas

Cities using detailed measurements of developed areas.

Table 1 Characteristic Imperviousness

for Land Uses found in the Mission Inlet Watershed

Land Use Classification Characteristic Imperviousness (percent)

Residential-l (1) 45%

Residential-2 (2) 30%

Warehouse I Manufacturing I Industrial 85%

Commercial I Office 90%

Mixed Use (3) 80%

Agricultural 0%

Schools I Public 30%

Parks I Golf Courses I Cemeteries I Open Space 5%

Undeveloped Areas (brush, range land) 0%

(1) All residential land use classifications within the city limits were grouped into "Residential-1" land use to simplify the different residential density definitions between the cities of McAllen and Mission.

(2) "Residential-2" classification was used for areas outside the city limits, generally west of Mission, where typical lots are 112 acre or more.

(3) Mixed Use land use classification within the Sharyland Plantation includes 75 % Warehousing and 25% Residential land uses.

II-3

----------------------- --------------

5. Soil Types

Hydrologic soil types are divided into four groups (A, B, C, and D). Group A soils

have the highest infiltration rates and the lowest runoff potential of the four soil

types. Group B soils have moderate infiltration rates. Group C soils have slow infiltration rates. Group D soils have the slowest infiltration rates and the highest runoff potential. Group A soils are usually well drained and consist of sand or gravel. Group D soils, on the other hand, are often clayey, have a high water table, or consist of bedrock or other nearly impervious material. Hydrologic Soil Types for the Mission Inlet watershed basin were estimated from the Soil Conservation

Service Hidalgo County, Texas Soil Survey (Reference 1). Figure 6 is an

illustration of the hydrologic soils typically found in the study watershed.

According to Figure 6, the majority of the watershed consists of type Band D soils with some C soils at the western boundary in the City of Penitas. The SharylandJForeign Trade Zone study area is predominantly type D soil (highest

runoff potential).

The antecedent moisture condition (AMC) defines the soil moisture condition prior

to a storm. The Soil Conservation Service has defined three levels of antecedent

moisture conditions (Reference 8).

AMC-I

AMC-JI

AMC-JII

Dry soils and low runoff potential (0 to 0.5" total rainfall in preceding 5 days)

Average soil moisture conditions (0.5" to 1.1" total rainfall in preceding 5 days)

Saturated soil condition from antecedent rains

(greater than 1.1" total rainfall in preceding 5 days)

An average antecedent soil moisture condition (AMC-II) was chosen for the

purposes of this study.

6. Loss Rates

The SCS Curve Number Method is a technique, developed by the Soil Conservation

Service (SCS) (Reference 8), for classifying land use and soil type using a single

parameter called the Curve Number (CN). The curve number is dependent on the

land use, impervious coverage, soil classification, and antecedent runoff conditions.

11-4

------------==--==--~ f f1l19Z. fJl/I.E J -, ", ,

~

LEGEND o H,t>\\\lLOGIC SOIl ~

\23 ~1\\f\OLOGIC SOIl C

~1\\f\QLOGlC SOIl 0

~

ll~OltOLOGIC soILS fOil ",;.TEttS

llEIJ

FLOOD PltO'f£CfION pl.J\NNING S'r~p'~ fOil sotl'flll'l'" ,",cALLE" ",,0 ,,"SS\O'" ,,,..,.,.

\~!'!~!~~

~

~,

~

FII 1924 IJlI/.£ J IiMTHJ

~

~ • $'

~

L-d ~-.. fttl

I»iK,WPk:~

/JUS 8J

-FIGURE 6

_ '!Crr<_oF""'Il:''' ~-~

Table 2 is a list of composite CN's for land uses and AMC-II hydrologic soil types representative of the study area.

Halff Associates computed SCS Curve Number's using a weighted average percent

imperviousness for individual soil types and land use within each sub-watershed basin. The composite CN's shown in Table 2 were computed using the assumed percent impervious values for the various land uses shown in Table 1.

The initial abstraction (IA) was computed for AMC-II (average) soil conditions using the following equation (Reference 5):

IA = 0.2 * (1000 - 10 * CN) I CN

Table 2 Composite SCS Curve Numbers for the Land Use found in the Study Area

Composite SCS Curve Number for each Hydrologic Soil Type

Land Use Classification Soil A Soil B Soil C Soil D

Residential-l 64 76 84 87

Residential-2 56 71 80 85

Warebouse I ManufacturinglIndustrial 87 90 92 93

Commercial/Office 89 92 93 94

Agricultural 64 75 82 85

Schools I Public 56 71 80 85

Parks I Golf Courses I Cemeteries 42 63 75 81

Undeveloped Areas 35 56 70 77

Composite Curve Numbers were computed using the average percentage of impervious area shown on Table 1. These curve numbers were computed assuming all impervious areas have a curve number of 95. Pervious areas are considered equivalent to open space in good hydrologic soil conditions (CN for soil A = 39, soil B = 61, soil C = 74, and soil D = 80). Undeveloped areas is considered equivalent to a mixture of brush and rangeland (CN for A soil= 35, B soil= 56, C soil = 70, and D soil = 77). Agricultural areas are considered equivalent to row crops with straight rows and crop residue cover in good condition (CN for A soil= 64, B soil= 75, C soil = 82, and D soil = 85).

7. Snyder's Unit Hydrograph

Snyder's Unit Hydrograph Lag Times (Tp) were determined from regional relationships, developed by the Corps of Engineers, of sub-basin geometry (Reference 9). These regional relationships are a function of watercourse length,

basin slope.

II-5

Halff Associates computed lag times for many of the smaller sub-basins (less than

2,000 acres) using the following equation (Reference 8):

Tp = 0.6 * Time of Concentration

Snyder's Peaking Coefficient (Cp) was determined from information developed

specifically for the Hidalgo County by the U.S. Army Corps of Engineers Galveston District (Reference 6).

8. Rainfall

Point rainfall depths for the Mission Inlet watershed were taken from the National

Weather Service Publication Technical Paper No. 40 (Reference 10) and from the

National Oceanic and Atmospheric Administration (NOAA) Technical Memorandum

Hydro-35 (Reference 11). The National Weather Service has developed a

relationship to convert point rainfall depths to areal average rainfall based on the

size of the drainage area and the duration of the storm. However, because of the

small drainage basin studied, areal reduction of point rainfall depths was not

necessary for this study.

Table 3 are the point rainfall depths used for this study for the 10-, 25-, 50-, 100-,

and 500-year flood frequencies.

Table 3 Rainfall Depth I Duration for the Hidalgo County Study Area *

Point Rainfall Depths (inches) for Hidalgo County Study Area Return Period

(years) S-min. IS-min. 60·min. 2-hour 3-hour 6·hour 12-hour 24·hour

2-Year 0.50 1.10 2.00 2.60 2.70 3.25 3.70 4.30

5-Year 0.58 1.28 2.57 3.40 3.70 4.40 5.20 6.00

10-Year 0.64 1.42 2.97 3.95 4.30 5.20 6.10 7.10

25-Year 0.74 1.63 3.53 4.60 5.00 6.20 7.20 8.50

50-Year 0.81 1.79 3.97 5.10 5.70 7.00 8.30 9.60

lOO-Year 0.88 1.95 4.40 5.70 6.30 7.80 9.50 11.00

500-Year 1.7 3.2 5.75 7.25 8.0 9.9 12.0 13.75

* Data taken from Technical Paper No. 40 and Technical Memorandum Hydro-35.

ll-6

9. Flood Routing

The Modified PuIs routing method was utilized by establishing storage-outflow

relationships from steady-flow water surface profiles determined from HEC-2

hydraulic analyses of the Mission Floodway. Storage-outflow relationships were determined for existing channel (floodway) conditions.

Halff Associates utilized a Digital Terrain Model developed for this study to

determine the elevation storage relationship routing data through the detail study

area (Sharyland/Foreign Trade Zone). For areas beyond the detail study area, Halff

Associates utilized available ditch system construction plans and prepared cursory

HEC-2 hydraulic models to develop storage-discharge relationships.

B. HYDRAULIC ANALYSES

1. General

Flood profiles for Mission Floodway and Banker Floodway were developed using

the Corps of Engineer's computer program HEC-2 (Reference 12). Halff Associates

developed a detail hydraulic model of the Mission Floodway to reflect 1995

floodway and bridge conditions. The Banker Floodway HEC-2 model, utilized for

this study, was obtained from the International Boundary and Water Commission

(IBWC). In addition, Halff Associates prepared cursory HEC-2 models of major

drainage courses (i.e. Mission Lateral, Rado Drain, Rado Alternate, Rancho Santa

Cruz, etc.) for flood storage routing purposes.

2. Existing Channel and Bridge Conditions

Cross-sections used in the Mission Floodway HEC-2 computer model were located

at close intervals above and below bridges, culverts, and elevated canal crossings in order to compute the significant effective flow and backwater effects of these

structures. Mission Floodway hydraulic cross-section data was obtained from the

1995 digital terrain model (DTM) developed for this study. Bridges, culverts, and

elevated canal crossings were modeled based on available construction plans.

Generally, these plans correlated well with the 1995 DTM.

Hydraulic models of the major drainage courses were developed from available

construction plans and field observations.

ll-7

------------------_._--_._-_ ..

Channel roughness factors (Manning's "n") were assigned on the basis of field

inspections of flood plain areas and from previous studies by the Corps of

Engineers. For study purposes, it was assumed that no clogging would occur and that all bridge structures would stand intact. Significant changes in this premise,

imposed by differing conditions of a future flood, could alter the estimated flood elevations and flood limits shown on the profiles and flood plain maps that

supplement this report. All elevations are measured from National Geodetic Vertical Datum of 1929 (NGVD).

C. STUDY ASSUMPTIONS

The development of detailed hydrologic and hydraulic computer models and the ensuing

conclusions of this study are based on a number of assumptions. Following is a brief summary of study assumptions.

1. Detail Study Area Modeled as Enclosed System

Halff Associates assumed that storm water runoff from the detail study area, the area

bounded by the Mission and Banker Levees (Sharyland/Foreign Trade Zone), could

not enter the Mission Floodway. This assumption is based on the premise that the Mission Floodway is flowing full; therefore, all gated structures along the interior levee are closed. Likewise, the Mission Floodway flood waters were not permitted

to enter the SharylandlForeign Trade Zone study area, with the exception of the Cimarron Country Club where the Mission levee has been removed.

The SharylandIForeign Trade Zone study area encompasses about 16 square miles

(10,240 acres). This area was divided into eleven (11) separate flood storage cells as illustrated on Figure 7. The configuration of each flood storage cell was

determined from topographic features. Halff Associates selected the boundary of each cell based on the relative grade change from one cell to another. These cell

boundaries were generally associated with a structure such as an elevated canal or roadway embankment. Stage-Storage (elevation-volume) relationships were

developed for each cell utilizing the 1995 DTM. This information was then used

to compute flood elevations for each cell.

2. Banker Floodway Full with Mission Floodway Outlet Structure Gates Closed

Following Hurricane Beulah, the IBWC closed the Rio Grande diversion to the

Mission Floodway and constructed the Banker Weir to permit an effective diversion of about 106,300 cfs to the Banker Floodway. This flow would produce a computed

1I-8

1 1

ro t- ::1

~ "S ~

6 '6 t S u

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

flood elevation in the Banker Floodway of about 101 feet at the Mission Floodway outfall closure levee; thus, requiring the Mission Hoodway outlet structure gates closed to prevent the Banker backwater from entering the Mission Hoodway.

Halff Associates assumed the Mission Hoodway outlet structure gates closed for this study. This assumption prevents Mission Floodway storm water from entering the Banker Hoodway, unless the levee is overtopped. Likewise, the Banker Floodway flows are not permitted to enter the Mission Hoodway. The limits of flooding depicted in Appendix C is based on future development with the Banker Floodway flowing full (106,300 cfs) (References l3 and 14) and the Mission Hoodway outlet structure gates closed.

3. Mission Floodway Modeled as Series of Reservoirs

The Mission Hoodway generally functions as a series of large linear flood storage reservoirs separated by eight outlet structures or hydraulic restrictions (i.e. Jackson Road, San Juan Elevated Canal, SH 336, Old FM 336, 23rd Street, Shary Road, Rio Grande Road, and FM 1016). In order to account for the variation in flood elevation over the entire length of the floodway, Halff Associates prepared a detailed hydraulic analyses along the Mission Hoodway. Headlosses were computed at all hydraulic restrictions. Available flood storage between each restriction were computed using the 1995 DTM. Information from the hydraulic analysis and DTM were then utilized to compute stage-storage relationships for flood storage routing through each reach of the floodway (see Appendix B). The resUlting analysis produced a flood profile depicting the varying flood elevations due to each roadway and elevated canal.

4. Mission Floodway Contributing Drainage Areas Regulated

Storm water runoff from west of the Mission Main Canal was generally permitted to enter Mission Floodway uncontrolled; thus, the detention effects of upstream ponding (at low areas, roadway embankments, etc.) were not accounted for in this

study.

Flows to the Mission Lateral were routed based on a typical cross sectional area of the drainage channel. Available record construction plans indicate Mission Lateral storm water flows are diverted at the Rado Drain. For this study, 50% (not to exceed 750 cfs) of the Mission Lateral flow was permitted to drain to the south, to the Mission Floodway, and the remaining flow was diverted to the north. This

assumption is based on a cursory analysis of the available head and tail water conditions at the diversion (7' X 6' box culvert) located at the intersection of the

Edinburg Canal and the Rado Drain.

II-9

Drainage ditches entering the Mission Flood way from the north (Rado Drain, Rado Alternate, 23rd and 18th Street Ditch, Rancho Santa Cruz, etc.) were regulated based

on a comparison of the timing of the computed flood stage of the subject drainage

ditch and the Mission FIoodway. Ideally, ditch flow should not be permitted to

enter the Floodway when the computed flood stage of the Floodway exceeds the stage of the subject drainage ditch. In order to model this scenario using HEC-1, a plot of stage vs time was prepared for the each drainage ditch and the Floodway at each corresponding location. Utilizing these plots, Halff Associates estimated a

time when flow could no longer enter the floodway. This time was then used to estimate the effective volume of storm water, based on the ditch flood hydrograph,

permitted to enter the Floodway. The remaining volume, from the contributing ditch hydrograph was diverted out of the system.

D. FLOOD PLAIN DELINEATION

The current flood regulatory maps for the project area are the FEMA Flood Insurance Rate Maps prepared for the 1991 City of Mission (Reference 15), 1980 City of McAllen (Reference 4), and the 1980 Hidalgo County Flood Insurance Studies (Reference 2). The

National Flood Insurance Program uses the 100-year flood (existing conditions) as the "base

flood" for insurance and mapping purposes. Since floods greater than the 100-year flood

may occur, citizens should bear in mind that if the level of protection is for a 100-year

flood, it is possible for flood levels to exceed this limit.

For this study, the 10-,25-, and lOO-year flood plain limits, ponding elevations, and flood

profiles were preparedfor existing (1995) topography, channel and bridge conditions with peak flood discharges based on existing and future (ultimate) land use conditions. Flood

plain maps are presented in Appendix C of this report. The delineation of the future fully urbanized flood plain for the Mission FIoodway and the SharylandlForeign Trade Zone

provides the Cities of McAllen and Mission with one of the basic tools of flood plain management. This data will be instrumental in the performance of many flood plain

management functions, some of which are listed below.

1. Formulation of flood plain management alternatives;

2. Outlining of flood-hazard areas; 3. Planning for parks and recreation in flood-prone areas; 4. Compliance with requirements of federal flood insurance programs;

5. Establishment of safe finished-floor elevations;

6. Planning of subdivisions to provide room for the passage of floodwater;

7. Design of roads, bridges, and utilities; and 8. Designation of easements or land to be purchased and used for open space.

ll-IO

Included in this study are computer diskettes contammg copies of all hydrologic and hydraulic computer model data used in the production of this report. These baseline

computer models will enable City Engineering staff to predict flood levels for flows based on existing and/or future land use conditions. The Cities of McAllen and Mission will also

have the ability to periodically update and modify the models prepared for this study to predict anticipated changes in land use and/or watershed characteristics.

ll-ll

SECTION III STUDY RESULTS

Ill. STUDY RESULTS

A. GENERAL

Halff Associates revised and updated previous hydrologic studies of the Mission Inlet

watershed basin and developed the detailed drainage area map provided in Appendix A.

This detailed drainage area map includes approximately 101 sub-basins, of which 19 sub

basins are located in the SharylandiForeign Trade Zone detail study area. Sub-basin names were assigned based on those of previous studies.

Table 4 is a list of computed drainage areas and estimated SCS Curve Numbers, for

existing and future (ultimate) land use conditions, for each sub-watershed basin in the study area.

Table 4 Summary of Drainage Areas and Estimated SCS Curve Numbers

Drainage Drainage Existing Future SCS Curve Area Area SCS Curve SCS Curve Number

Number (sm) Number Number Difference

MI-1 0.49 74.9 74.9 0.0

MI-2 0.62 74.9 74.9 0.0

MI-4 0.34 77.0 77.0 0.0

MI-5 0.13 77.0 77.0 0.0

MI-6 0.80 78.1 78.1 0.0

MI-7 0.77 83.8 83.8 0.0

MI-8 0.61 81.1 81.1 0.0

MI-9A 0.39 84.4 88.0 3.7

MI-9B 1.01 76.1 83.6 7.5

MI-9C 0.29 83.0 83.0 0.0

MI-lOA 0.54 83.2 83.2 0.0

MI-1OB 0.42 77.0 77.0 0.0

MI-10C 0.48 84.0 84.0 0.0

MI-IOD 0.41 78.0 78.0 0.0

MI-11A 1.25 77.9 81.2 3.3

MI-I1B 1.50 77.0 77.0 0.0

III-I




MI-13 0.73 76.5 80.4 3.9

MI-14 0.94 80.2 82.6 2.4

MI-15 1.17 82.4 82.4 0.0

MI-16 0.62 71.8 78.1 6.3

MI-17 0.36 82.6 83.3 0.7

MI-18 3.19 82.4 82.4 0.0

MI-19 0.47 83.0 83.0 0.0

MI-20 0.37 81.0 85.3 4.4

MS-1 0.37 72.6 80.3 7.7

MS-2A 0.53 88.5 88.5 0.0

MS-2B 0.82 80.1 80.1 0.0

MS-2C 1.39 79.8 79.8 0.0

MS-3A 0.82 82.0 84.3 2.3

MS-3B 0.68 75.7 78.8 3.1

MS-4A 0.70 79.1 79.1 0.0

MS-4B 0.54 78.1 78.1 0.0

MC-1A 1.39 85.1 88.3 3.2

MC-1B 1.52 72.5 78.2 5.7

MC-1C 0.21 74.8 79.4 4.6

MC-lD 0.07 66.2 76.3 10.0

MC-2A 0.90 85.6 85.6 0.0

MC-2B 0.37 90.6 90.6 0.0

MC-3 0.60 80.2 81.2 1.0

MC-4A 2.02 74.8 82.7 7.8

MC-4B 0.42 80.3 84.5 4.2

R-2 0.42 78.8 79.8 1.0

R-3 0.10 75.3 75.3 0.0

R-4 0.41 81.0 81.0 0.0

III-2




R-5A 0.13 73.7 78.3 4.6

R-5B 0.23 72.2 72.2 0.0

R-6 0.82 73.9 77.9 4.0

R-9 2.50 75.8 78.7 2.9

R-10 0.64 73.6 78.7 5.1

R-ll 0.97 77.7 78.7 1.0

R-13 2.77 69.9 76.5 6.5

R-14 0.32 66.8 7603 9.5

R-15 1.85 74.1 74.7 0.6

E1 0.26 73.6 73.6 0.0

E2 0.49 72.1 73.2 1.1

E3 0.44 69.4 70.3 0.9

E4 0.14 77.2 77.2 0.0

E5 0.35 71.5 71.5 0.0

E6 0.21 74.9 74.9 0.0

E7 0.34 76.1 76.1 0.0

E8 0.19 76.0 76.0 0.0

E9 0.22 84.5 84.5 0.0

ElO 0.25 78.0 78.0 0.0

Ell 0.19 56.0 76.3 20.0

E12 0.15 61.4 76.8 15.0

E13 0.17 57.0 76.8 19.0

E14 2.52 74.9 75.2 OJ

E15 0.50 73.3 76.0 2.7

E16 2.24 70.1 71.6 1.4

E17 0.27 76.5 76.5 0.0

E18 0.56 74.3 74.3 0.0

E19 0.36 79.1 79.3 0.2

III-3




E20A 2.05 76.9 76.9 0.0

E20B 1.24 7S.8 76.0 0.2

E21 0.10 82.4 82.4 0.0

E22 1.53 81.2 83.3 2.1

E23 0.52 76.6 82.9 6.3

E24 0.28 81.7 81.7 0.0

E25 0.25 73.7 81.S 7.8

E26 0.24 84.4 84.4 0.0

E27 0.26 76.3 76.3 0.0

ES1 0.69 82.7 82.7 0.0

TZ-1 0.75 81.7 87.8 6.1

TZ-2 0.68 83.2 92.9 9.7

TZ-3 0.91 81.2 89.S 8.2

TZ-4 0.61 79.8 88.8 9.0

TZ-S 1.74 82.7 8S.0 2.3

TZ-6A 0.57 83.0 89.6 6.6

TZ-6B 0.64 84.0 92.S 8.5

TZ-6C 0.58 84.5 92.6 8.1

TZ-6D 0.18 88.8 91.S 2.7

TZ-6E 0.51 84.7 92.8 8.1

TZ-6F 0.S5 76.8 89.8 13.0

TZ-7 0.69 77.2 90.5 13.3

TZ-8 2.36 79.4 89.1 9.7

TZ-9 1.06 80.0 91.3 11.3

TZ-10A 1.83 82.8 88.0 S.1

TZ-10B 0.59 83.2 86.8 3.6

TZ-llA 0.67 80.3 82.6 2.3

TZ-11B 1.03 80.0 81.4 1.4

TZ-11C 0.23 84.S 86.2 1.7

I1I-4

The results of this study includes flood information for the following land use and flood plain conditions:

o Flood discharges based on existing 1995 land use conditions with existing

topographic features. Note, this data could be very useful if the Cities of

Mission and McAllen decide to submit an update of the current FEMA Flood Insurance Rate Maps.

o Flood discharges based on fUture (ultimate) land use conditions (fully

urbanized watershed) and existing topographic features.

o 10-, 25, and 100-Year flood plain delineations for existing topographic

conditions with flood discharges based on future land use conditions. (See

Appendix C).

o Selective levee and flood storage (sump) improvements with flood discharges

based on future land use conditions (fully urbanized watershed).

B. MISSION INLET FLOODWAY

1. Description of Watershed

The Mission Floodway flows in a southeasterly direction. The study watershed includes the Cities of Penitas, Palmview, Palmhurst, Mission, McAllen, and Phar.

Contributing storm water runoff originates in the City of Penitas, just west of the intersection of U.S. Highway 83 (US 83) and Business Route 374 (Bus. 374). At

FM 1016, near the entrance to the Mission Levee, the total drainage area is about 16 square miles (10,240 acres). The total contributing area at the Mission Levee

closure is approximately 60 square miles (38,400 acres), excluding the 16 square

mile interior drainage area located between the Mission and Banker levees.

The Mission Inlet watershed study area is about 53% developed at this time (1995).

Existing land uses consist of approximately 17% undeveloped open space; 30% agricultural; 42% residential; 9% business!commercial!industrial areas; and scattered public/semi-public areas (i.e. schools, churches, etc.). According to information compiled from future land use maps, from cities within the watershed, anticipated

future development could consist of approximately 7% parks and undeveloped open space; 24% agricultural; 56% residential; 12% business/ commercial/industrial areas;

and scattered public/semi-public areas (i.e. schools, churches, etc.).

III-5

2. Hydrologic Study Results

Halff Associates prepared detailed HEC-l hydrologic computer models of the watershed to analyze existing land use conditions and projected future (ultimate)

land use conditions. Existing and ultimate land use conditions were analyzed with flood storage routing data based on existing topography and existing bridges and

culverts. Peak flood discharges calculated for this study include the 10-, 25-, 50-, and 100-year flood frequencies. Tables 5 and 6 contain peak flood discharge information at key locations along the Mission Floodway.

Table 5 is a summary of computed peak flood discharges at key locations along the Mission Floodway for existing and ultimate land use conditions, assuming the

Mission outlet gates are closed. A summary of computed existing and ultimate peak flood discharges at major contributing ditch systems to the Mission Floodway are

presented in Table 6. Note, the discharges presented in Table 6 do not necessarily

correspond to the actual amount of runoff permitted to enter the Mission Floodway

(see Chapter II, "Study Assumptions" for detail explanation).

Table 5 Mission Floodway

Summary of Computed Peak Flood Discharges Existing and Ultimate Land Use Conditions (Gates Closed)

Drainage Existing Peak Discharge (cfs) Ultimate Peak Discharge (cfs) Location Area

(sm) lO-yr 25-yr 50·yr lOO-yr lO-yr 25-yr 50-yr lOO-yr

At Mission Main Canal 12.5 7800 9900 11500 13200 8100 10200 11800 13500

At Confluence with Old Inlet 15.6 8800 11300 13400 15600 9100 11700 13700 15900

At PM 1016 - Conway Rd 16.0 9000 11600 13700 15900 9300 11900 14000 16200

At Rio Grande Rd 21.4 4500 6600 9100 11600 4600 7000 9500 12100

At Shary Rd 22.0 4500 6400 8200 10100 4600 6900 8500 10400

At 23rd Street 51.1 7400 10800 12600 15100 7500 11200 12900 15500

At San Juan Elevated Canal 57.2 4200 6700 8200 10500 4500 7000 8500 10800

At Jackson Road 58.1 2800 5700 7600 10000 3300 6000 7900 10300

Note: Peak discharges are based on existing and ultimate land use conditions with existing (1995) topography. See Figures 4 and 5 for assumed existing and ultimate land use.

III-6

Although assumed future development will increase from about 50% urbanization (existing) to about 76% urbanization (future), the difference in computed peak flood

discharges for ultimate and existing land use conditions, computed along the Mission Inlet Floodway, generally appear less than 5%. This slight difference could be

attributed the assumed portion of the watershed to be preserved for agricultural land use. The estimated loss rates (infiltration) for irrigated cropland are only slightly

less than those for residential (urbanized) land use (see Chapter II, Table 2 -Composite SCS Curve Numbers for Land Uses Found in the Study Area). The

percent of total urbanized and agricultural land use for existing and future conditions is about 83% and 93% respectively. Similarly, a comparison of future and existing

undeveloped open space is about 17% and 7% respectively. This comparison of non-urbanized areas (excluding agricultural land use) appears to compare fairly well

with the differences in computed peak discharges for existing and assumed ultimate land use conditions.

Table 6 Major Contributing Ditch Systems

Swnmary of Computed Peak Flood Discharges Existing and Ultimate Land Use Conditions (Gates Closed)

Drainage Existing Peak Discharge (crs) Ultimate Peak Discharge (crs) Location Area

I SO-yr (sm) 10-yr 2S-yr 100-yr 10-yr 2S-yr SO-yr 100-yr

Rado Alternate 27.0 4070 5410 6340 7360 4290 5610 6510 7520

Old Rado 3.0 620 800 940 1120 650 830 970 1150

23rd Street Ditch 1.5 1710 2070 2300 2560 1730 2080 2310 2570

South Airport 0.4 160 180 190 200 160 180 190 200

Airport Ditch 1.4 850 930 1020 1110 870 960 1040 1140

Rancho Santa Cruz Ditch 15 320 350 370 400 340 360 390 410

Note: Peak discharges are based on existing and ultimate land use conditions with existing (1995) topography. See Figures 4 and 5 for assumed existing and ultimate land use.

III-7

3. Hydraulic Study Results

The Mission Floodway is approximately 10 miles in length, from the levee outlet

structure to near FM 1016. The average pilot channel grade through the study area

is about 0.04%. The pilot channel is well defined with average depths of about 15

feet. Average height of levee, from the top bank of the pilot channel, is about 15 feet. A summary of computed peak flood elevations for the 10-, 25-, 50-, and 100-year flood frequencies (along the Mission Inlet Floodway) for existing and ultimate land use conditions, are presented in Table 7.


Smnmary of Computed Peak Flood Elevations! Existing and Ultimate Land Use Conditions (Gates Closed)

Existing Peak Flood Elevation (ft.) Ultimate Peak Flood Elevation (ft) Location

lO·Yr 25·Yr 50·Yr lOO·Yr lO-Yr 2S-Yr SO-Yr lOO-Yr

Cell 12 (Mission Levee CI~e to 96.2' 101.3' 102.7 103.4 96.9' 102.0 102.8 103.4 San Juan Canal)

Cell 13 (San Juan Canal to 23rd St) 103.2 103.9 104.3 104.8 103.3 104.0 104.4 104.9

Cell 14 (23rd St to Shary Rd) 103.7 104.3 104.6 105.2 103.7 104.3 104.7 105.3

Cell 15 (Shary Rd to Rio Grande Rd) 103.9 104.5 105.0 105.6 104.0 104.6 105.1 105.6

Cell 16 (Rio Grande Rd to FM 1016) 104.2 104.8 105.4 106.0 104.2 104.9 105.5 106.1

Cell 17 (FM 1016 to Old Inlet) 109.3 110.6 111.0 111.4 109.6 110.7 111.0 111.4

1. Peak flood elevations are based on existing and ultimate land use conditions with existing (1995) topography. See Figures 4 and 5 for assumed existing and ultimate land use.

2. The computed "po.st-stonn" flood pool is slightly above elevation 102, the minimum elevation of the Mission Levee at a location where flood waters overflow to the Banker Aoodway.

There area nine structures, including the structure at the levee closure, crossing the Mission Inlet Floodway. Pertinent data for each of these structures is summarized in Table 8. The computed future fully urbanized IOO-year flood will overtop the

existing roadway or embankment at six of these nine structures.

III-8

Bridge Upstream Identification Flowline")

Mission 73.9 Floodway Outlet

FM 2061 73.0 (Jackson Road)

San Iuan 76.6 Elevated Canal

SH 336 75.0 (10th Street)

Old FM 336 77.0

Spur 115 80.2 (23rd Street)

FM494 87.0 (Shary Road)

Rio Grande Dr. 89.1

Union Pacific 92.9 Roilroad

FM 1016 92.9 (Conway Rd)


Summary of Structure Crossings Ultimate Land Use Conditions (Gates Closed)

Low Top of X-Sect Q". lOO-Yr Chord(1) Road") Area (sf) (cfs)l') WSEV') Description

8104 101.9 322.5 4,000 103.5 2-7.5'x 7.5' and 6-7'x 5' gated box culverts

89.8 93.2 1600 11,600 103.5 Concrete Bridge wf5 Piers

9204 10704 1580 12,300 104.9 Concrete Bridge w flO Piers

95.0 96.2 2170 12,300 104.9 Concrete Bridge wn Piers

107.0 108.9 1170 15,800 104.9 Wooden Bridge wlPiers

93.9 94.9 790 15,800 105.3 Concrete Bridge w/3 Piers

101.0 100.7 640 10,800 105.6 Concrete Bridge w/3 Piers

99.0 101.2 430 12,100 106.1 Concrete Bridge wl2 Piers

106.6 108.6 760 16,200 106.1 Wooden Bridge wfPiers

104.0 10904 200 16,200 IlIA 2-10'x 10' box culverts

(1) Approximate elevations (NGVD) (l)

(3)

l00-year peak discharge based on ultimate fully urbanized watershed with existing (1995) topography and gates closed at Mission Levee closure. 100-Year peak flood elevation based on existing (1995) topography, channel, and bridgesfculverts.

Additional analyses were prepared for the Mission Floodway assuming no flow was

diverted to the Banker Floodway and the gates at the Mission outlet were open. A comparison of elevation vs discharge at the Mission outlet for gates open and closed

is illustrated on Figure 8.

Computed IOO-year flood profIles of the Mission Floodway are presented on Figures 9 and 10 for existing and ultimate land use conditions with gates open and with gates

closed. The effect of Mission outlet gates open is most apparent at locations downstream of the San Juan Canal. Upstream of the San Juan Canal, the effects of the open gates is much less. This is due to the restricted conveyance of the San Juan

Canal drainage structure and the limited flood storage capacity of the Mission Floodway. The estimated flood storage capacity of the Mission Floodway for varying

flood elevations, computed using the 1995 DTM, are presented in Appendix B.

III-9

~ ~

~ co

Elevation-Discharge Relationship Mission Inlet Floodway Outlet Structure

110~i------------~~~~--------------------------------------------------~ 10~· .......................................................................... ·· .. · .. ··v· .. ··· .......... ·:_ _______ _ ___ !. • .:.-.:. ..... ..,...,.ij

..., I -- • ____ ----.--------. . . . ----~- ----------. ".--

Top of Levee,' • Hl9.IJ.gi~h~'!I~t~!Jm~ .................................................... . 100+······························;r·······.·········· ............ "'no breaching of levee

'" I I

.....•................... ~~ ...................•..............................•.......•....•........•............•........................•....••.....•... - '" ¢:: I --- I C I

.() ................••. ~ ...................•................................•............................................................................... ro ' > " Q) , - ,

lLJ ......... ~.~ ............................................................................................................................................. .

" , , ,

acrt;rl ...................................................................................................................................................... .

7~ ......................................................................................................................................................... .

7"-v

o

Flowfine

T 5 1b T

15

Discharge (cfs) (thousands)

I 20

[---. Gates Open -+- Gat;ct~]

I 25 30

I--~

12~.00

120.00

f- 1 116.00 LLJ LLJ LL

~ z I 112.00 Q f-« > LLJ LLJI 108.00

I~.OO

100.00

LEGEND

...: -' w ...: '" a:

'" Z ::J

'" '" f-

",u

o~ lJ

L U D U

L :> '" ::J

W D '" of- 0 a: D '" "' "'

0 W '" f-

Z 0 '::! "' ::: -' '"

-u ,,~ u. IZ

~ >- '" " '" Z 0 f-

<OJ ::: u. "' '" W

'" "' '" -' 0 '" C! ::J "" f-a: u a: :I: :::l -' ::> -, « :::l

'" D- o U. Z

-, 0

flZ 0: JI:::lQ::

" , , '" '" ...... ,-.. "I

, , , , , , I I 'I I I I

'-".I

II·CIMARROll I I PALM VIEW I I

AIRPORT I I GOLF l r1 COURSE

-'li' , : "'1'..( \ J I ... 1' ...... I I ' ''',

I I "'" :; \d ......... ........ , 1\ ... _ L. ,

U , I , I

" , I , " '! I

" , " , " , " l ' : "'''' .. ~ ~

, 'I \ ..... \ ' ,1 ,I I I ,Ij' " I', ',\ !A

\ " : ~ J ~1 \ _~ ~ .(--},J ,i 111.4 :

I I""" \ 111.3

109.4

'I'

'f '" ," ," ," '" '" , , ,

, I't " I 1..... , , I .. _ ... -...... , , , , , , , I \ I , Ifo 108.9

/' t 1 [TOP ~ORTH LEVEE {-_'...\--', "'~~"'.. l ATOP SOUTHI LEVEE

\ ~ " II '"\ .. r '- / .

I I \ 1\ .' ~ I I .. ~ " • , .. , \- r -

106.0 I: : -........... \'" \ '1/100 YR ~ " -, r~ fn1-.~' ,I ... _/

:.. ,J05.6 I ,I GAT S CLOSED ' \ IT '.--,' -, -t -1 ,05•5

' + l..i ¥~' I 105.2' I \' ---:,' t<f\' -,"" I I 104.9 ~ '.: L 104.8' \ • " > 11"1~ i \...... .. \ I __ 1 I .. '... " \' 1 102.4 \.,-,,' I I 103:4 •

'1'100.7 I I I \'00 ~;I-----f----II' GATES bPEN I

'1'101.2 'I' 1102.0

52000.00 ~8ooo.oo 44000.00 40000.00 36000.00 32000.00 28000.00 2~000.00 20000.00 16000.006

120d0.aa. _ .lIOOO.Qj)~:§..4llOOJlO.. __ 0.00 I I I I I I I I I I -9 .a 1 I I _ I

DISTANCE IN FEET

'I' TOP OF ROAD

~ WATER SURFACE

FIGURE 9 .:':'. =~= Half I Associates EHGIHEERS • ARCHITECTS' SCIENTISTS' PLANNERS' SURVEYORS

I'flOrIL£UY,'l

MISSION INLET FLOOD PROFILE 100 YEAR EVENT - EXISTING LANDUSE

FLOOD PROTECTION PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION, TEXAS CITY OF McALLEN

Assuming the Mission outlet gates are closed, the computed 100-year flood will overtop the Mission Levee at five (5) locations including; the levee closure, McAllen Miller International Airport, Palm View Golf Course, Cimarron Country Club, and at a location west of FM 1016. If flow is not diverted to the Banker and the Mission outlet gates are open, the Mission Levee will be overtopped at three (3) locations

including the Miller International Airport, Cimarron Country Club, and at a location

west of FM 1016. These locations are depicted, for existing and ultimate land use

conditions, on the flood profiles presented on Figures 9 and 10 respectively. In

addition, graphical representation of these and other potential flooding areas along the

Mission Inlet are presented on the flood plain maps and flood frequency profiles in

Appendix C of this report.

C. BANKER FLOODW A Y

The IBWC closed the Rio Grande diversion to the Mission Floodway and constructed the

Banker Weir, following Hurricane Beulah, to permit an effective diversion of about 106,300

cfs to the Banker Floodway (Reference 13). Halff Associates conducted a cursory hydraulic

analysis of the Banker Floodway utilizing the IBWC HEC-2 hydraulic computer model.

Additional hydrological analysis for the Banker Floodway were not performed, for this study,

an effective flood discharge of 106,300 cfs was used for the Banker hydraulic analysis.

Assuming this is the maximum permitable flow to the Banker Floodway, the estimated

minimum freeboard (computed water surface to top of levee) is within 1 foot of the top of

levee at the Mission outlet structure.

D. SHARYLANDIFOREIGN TRADE ZONE

1. Description of Watershed

The SharylandIForeign Trade Zone study area includes the area bounded by the

Mission and Banker Levees. The total study watershed for this region includes about

16 square miles (10,240 acres). Figure 11 is a detail watershed map of the

SharylandIForeign Trade Zone study area.

The study area is about 89% undeveloped at this time (1995). Existing land uses

consist of approximately 17% undeveloped open space; 72% agricultural; 7%

residential; 4% business/comrnerciallindustrial areas; and scattered public/semi-public

areas (i.e. schools, churches, etc.). According to information compiled from future

land use maps, projected development could consist of approximately 1 % parks and

undeveloped open space; 1 % agricultural; 44% residential; 53% business/

commercial/industrial areas; and scattered public/semi-public areas (i.e. schools,

III-lO

r

1-W W LL

Z

Z o 1-« > w ....J W

• •• • ENGINI ,,,, 'II[

r-::~-

12S.00 ', .... \lV

~ ~ -" w «>u . '" '" I V1 >- 2 ::J

O~ V1 "' >-

-u "0 J: U 0 U ,

::;;'{ L '" ::J I

W 0 "' +- :> 0 '" C- O "' "" "" o w '"

>-

12~.00 12 2 0 Co! "" ::: -" Vl

,.~ g '" U"> ::; "' 0

II::J >- ::: C- "" 2 V1 W Cl

'" "" "' "" --'

"I ::J >-

0 "' a:: 0 U

" I --' ::; --, "'

::J ii' ::J 0 , , V1 CL 0 C- 2 --, , , I I I I I "' I I ' , V1

120.00 -- -, ' , -;- j, .... ... .. ', L CIMARRON

I AIRPORT I , 1 , PALM VIEW , 1 .... ,~ ........

1 -I GOLF 11 , I

I " COURSE , 1 \<, " , 1

116.00 , 1 .. , ' ...... ....... ~,- , ,

I I " , 1 , ' I I I , " ~ ,~ I I I I , " II I .~ , " \ ~ I ~ .... , , " " I

, ~ I I I ' , , , "

, I "I ~ , "

, I I I' " \

112.00 , " 'u' I" I! \ I I ",I,,--'{ .. ' ,

I III 4 ," ," I' , , , , , 111. 3 ," , , ,

-/ ' , /,

'" , I , I

109.4 '" , I ...... -- .........

1--~--,?-- ..... ,[ ," , , _.:-== .... ", -TOP ',~,I)U!H LC .E'.

t ," , , , \ , / ' , , \ , " {t_I08.9

10S.00 10 .6 , , :. \' ... --, , '\ , , , , ' \ 1 ,..- .. ~f fu~.~'" ,I '-." , , , - ............ ,

, \ , ' , , , \ , , ' 'r-- ... __ \. ... • '1 106.1 , , - , \ , , ' \ .......

. _ ' 'lOS. I '~""\J ...... ( ' ... -, ..

105.5

, <7 105.3 \ I , ' iTOP

, >

11'105.t'", ~ 104.9 ~ , ' , ,

.~ \ ' , 'I ORTH LEVEE

' , 10~.00

104.2 .... _- " , I. 103.4.sl I-..l._~

'.' I ~GATES I CLOSED t 102.0

100.00 t 101 •2

t IOO•7 I

I J;~T: OPEN

I _21... 1----

96.00 52D<!0'00 4SD<!0.00 ~4D<!0'00 ~OO~O.OO 360~.00 32D<!0.00 2SD<!0.00 24D<!0'00 200~0.OO 1~·~6.?,.'200,o.00 800jl'OO 4000.00 O,pO

OIST ANCE IN FEET T

LEGEND

t TOP OF ROAD

= WATER SURFACE

MISSION INLET FLOOD PROFILE

•• FIGURE 10

I HaitI Associates 100 YEAR EVENT - ULTIMATE LANDUSE

III CITY OF McALLEN FLOOD PROTECTION PLANNING STUDY

:ERS .. ARCHITECTS .. SCIENTISTS .. PLANNERS .. SURVEYORS FOR SOUTHERN MCALLEN AND MISSION, TEXAS ." _. .. i-"""_R~"'A ",,_ rl"A on ,n"'" /lQ lVI- 1<;

... -.. _ ...... "'~

,.0

/I/~ J Me" ,~ . ,.02"" ' ~, ~

1 011""

115 ,.14 ""

'{!

§ ~ Tl'

0.61 liM

~ ----1 ~

ik --':II, FU 1016 --

_J- l I \ \ i i

/ UNION PIC/FIe RNLRIJAD

"" l1tt i/ ,~O po 0"

>- I ___ ~----------~ - .

\.

i ",,~ .~"... ~'.-" ~ .. ' '''<'',--~ I '.. ~ . .r---' .. -......... .Yl \" '" ' // ~.

"-"-"----" ./ //

, <' .-.......... -'

" -- ------ ----~-.

, .. _ .. _ .. __ .r"-"-,:_"-,,_,,, '-'-"/' ; " ,1'.-.. .---

\ ' ' \ ',! \" ,,-,,-.. -.. -,.-.. ~.,~

", ",

-......

fOR sou\1JER1' ",aLL'" """ ""sstON, TEJ<"S ~ ... ~----------~." .... ~

\ 'l1l.ac~~~.".;.",,~.~~~·~}.~~~O:= (HGtE.£fl.S." ,- .--\""i,··'''N - ---- -

~,.

l

FIGuRE U

churches, etc.). Note, this study proposes large portions of land to be dedicated to stOlTIl water retention (flood storage); therefore, resulting in additional open space.

2. Hydrologic Study Results

Halff Associates prepared detailed HEC-l hydrologic computer models of the

Sharyland/Foreign Trade Zone watershed to analyze existing land use conditions and projected future (ultimate) land use conditions. The study area was divided into

eleven (11) separate flood storage cells. Cell boundaries were generally associated with a structure such as an elevated canal or roadway embankment. Flood storage routing data was obtained for each cell utilizing the 1995 DTM. Elevation-storage relationships for each cell are included in Appendix B. This information was then

used to compute peak flood elevations and flood storage at each cell for the 10, 25,

50, and 100-year flood frequencies. A summary of computed peak flood elevations,

within the Sharyland/Foreign Trade Zone, for ultimate and existing land use conditions is presented in Table 9.

Table 9 Sharyland/Foreign Trade Zone

Summary of Computed Peak Flood Elevations Existing and Ultimate Development Conditions

Existing Peak Flood Elevation (ft) Ultimate Peak Flood Elevation (ft) Location

lO-Yr 2S-Yr SO-Yr lOO·Yr lO·Yr 2S-Yr SO-Yr lOO-Yr

Cell 1 111.8 112.0 112.1 112.1 111.8 112.0 112.1 112.1

Cell 2 105.1 105.3 105.4 105.6 10S.1 10S.3 10S.5 10S.6

Cell 3 106.2 106.3 106.4 106.5 106.3 106.4 106.S 106.S

Cell 4 103.7 104.1 104.2 104.4 104.1 104.3 104.4 104.6

Cell S 105.3 10S.S 10S.6 10S.6 lOS.S 10S.6 10S.6 lOS.7

Cell 6 101.7 101.9 102.1 102.3 101.9 102.1 102.3 102.6

Cell 7 10S.1 10S.2 10S.3 10S.4 10S.1 10S.3 lOS.4 10S.4

Cell 8 103.0 103.2 103.2 103.3 103.0 103.2 103.2 103.3

Cell 9 100.8 101.3 101.6 102.0 101.1 101.5 101.9 102.3

Cell 10 9S.6 96.1 96.3 96.S 96.0 96.3 96.S 96.7

Cell 11 92.S 92.9 93.1 93.3 92.7 93.0 93.2 93.S

Note: Peak flood elevations are based on existing and ultimate land use conditions with existing (199S) topography. See Figures 4 and S for assumed existing and ultimate land use.

III-II

A graphical representation of the peak flood elevations presented in Table 9 is

presented on Figure 12, Detail Study Area Overall Flood Plain Map. Additional detail is provided on the flood plain maps in Appendix C of this report.

Although assumed ultimate development will increase from approximately 11 %

urbanization (existing) to about 98% urbanization (future), a comparison of computed

flood elevations for ultimate and existing land use conditions is generally less than 0.4 feet, for the frequencies studied. This slight difference could be attributed the

amount of existing agricultural land use. The estimated loss rates (infiltration) for irrigated cropland are only slightly less than those for urbanized land use (see Chapter

II, Table 2 - Composite SCS Curve Numbers for Land Uses Found in the Study Area). The percent of total urbanized and agricultural land use for existing and future conditions is about 83% and 99% respectively. Similarly, a comparison of existing

and future undeveloped open space is about 17% and 1 % respectively. Thus, the

actual difference in total potential runoff is not as great as the difference in existing

and ultimate per cent urbanization may indicate.

In addition, this slight difference in computed flood elevations can be attributed to the

flood storage capacity of each drainage cell at shallow depths. Comparisons of existing and ultimate ponding elevations and associated flood storage for the 10-, 25-,

and 100-year flood frequencies are presented in Tables 10, 11, and 12 respectively. The information presented in these tables indicate the difference in total flood storage

appears somewhat more significant than the variation in actual depth of ponding.

The results of this study indicate Cell 9 contains the greatest amount of flood storage in comparison to the other Flood Storage Cells in the Sharyland/Foreign Trade Zone

study area. This is because excess overflow from adjacent cells drain to Cell 9. Flood depths in Cell 9 range from 0 to 7 feet. Figure 13 is an illustration of the

variation in depths of flooding in Cell 9 for the future (assumed ultimate land use)

100-year event.

III-I 2

Table 10 SharylandIForeign Trade Zone

Comparison of Existing and Ultimate 10-Year Ponding Elevations and Flood Storage

lO-Year Peak Flood Elevation (ft) lO-Year Peak Flood Storage (ac-Ct) Location

Existing Future Difference Existing Future Difference

Cell 1 111.8 111.8 0.0 94 96 2

Cell 2 105.1 105.1 0.0 76 78 2

Cell 3 106.2 106.3 0.1 280 318 38

Cell 4 103.7 104.1 0.4 99 137 38

Cell 5 105.3 105.5 0.2 166 222 56

Cell 6 101.7 101.9 0.2 56 67 11

Cell 7 105.1 105.2 0.1 261 279 18

Cell 8 103.0 103.0 0.0 182 188 6

Cell 9 100.8 101.1 0.3 3390 3944 554

Cell 10 95.6 96.0 0.4 417 502 85

Cell 11 92.5 92.7 0.2 195 222 27

Note: Peak flood elevations and flood storage are based on existing and ultimate land use conditions with existing (1995) topography. See Figures 4 and 5 for assumed existing and ultimate land use.

III-l3


Comparison of Existing and Ultimate 2S-Year Ponding Elevations and Flood Storage

25-Year Peak Flood Elevation 25-Year Peak Flood Storage Location (feet) (acre-feet)


Cell 1 111.9 112.0 0.1 106 108 2

Cell 2 105.3 105.3 0.0 102 104 2

Cell 3 106.3 106.4 0.1 325 362 37

Cell 4 104.0 104.3 OJ 135 176 41

Cell 5 105.5 105.6 0.1 225 251 26

Cell 6 101.9 102.1 0.2 69 88 19

Cell 7 105.2 105.3 0.1 302 319 17

Cell 8 103.2 103.2 0.0 212 215 3

Cell 9 101.3 101.5 0.2 4355 4946 591

Cell 10 96.1 96.3 0.2 534 625 91

Cell II 92.9 93.0 0.1 250 279 29

Note: Peak flood elevations and flood storage are based on existing and ultimate land use conditions with existing (1995) topography. See Figures 4 and 5 for assumed existing and ultimate land use.

1II-14


Comparison of Existing and Future 100-Year Ponding Elevations and Flood Storage

lOO-Year Peak Flood Elevation lOO-Year Peak Flood Storage Location (feet) (acre-feet)


Cell 1 112.1 112.1 0.0 127 131 4

Cell 2 105.6 105.6 0.0 144 147 3

Cell 3 106.5 105.5 0.1 389 420 31

Cell 4 104.4 104.6 0.2 193 218 25

Cell 5 105.6 105.7 0.1 272 296 24

Cell 6 102.3 102.6 0.3 125 172 47

Cell 7 105.4 105.4 0.0 353 364 11

Cell 8 103.3 103.3 0.0 236 239 3

Cell 9 102.1 102.3 0.2 6192 6846 654

Cell 10 96.5 96.7 0.2 737 833 96

Cell 11 93.3 93.5 0.2 346 377 31

Note: Peak flood elevations are based on existing and ultimate land use conditions with existing (1995) topography. See Figures 4 and 5 for assumed existing and ultimate land use.

ill-IS

: :'::~::.::: ". . . . o· / '>~ .' ~. 1 /\"'''~

i "~"\ ,. ~ .' \ I I • • :! i !; :

-'I '--': I \~r:! ,/ \\"' i /

ii, '.. i ,. '.., : ........... \,

\ ....... -

CDIElUI. MOT[So

,W::AiJJiJ,\5 DW

I. TIPOGItIIPWf I'lMti IWICM.lftI! .,. 'IIIII..IJ&.II SUCPCIUSl,. SAIl M"."TL

2. ~~n.Mff~~'lIAt8ISIm ). IIASf. FLOOD D.£Y'TlOIIS FDR .-EJt fUIOOIII'" * USED

ON TME ...... AtUJUIl.( 0MR5I0II n.o. DoIOl,lOO en). 4. n.ooo £UV'TlOIIS " mSlON "'U Ft.OUDIIA' IIo\SUI C*

G,t.T[S ClOSO n mSIOJII OlI1LET.

LEGEIIl

II • ./l.fIJ\I\IIJVV 8o\SI: FLOOD D.EYAlJ)M

CELL J 100 YUA FLOOD W:Y"lJ)M

("_O'

j

\ '.\

\"\

\ \

* LEY£[ O'I(lIfOfftD 81 100 1'£A1t FLOOD

1~IHalff Associates ENGINEERS. ARCHITECTS 0 SCIENTISTS 0 PLA~ERS • SLAVEYORS

OVERALL 100 YR. FLOOD PLAIN MAP _ • FLOOD PROTECTION PLANNING STUDY ~. ~ FOR SOUTHERN MCALLEN AND MISSION, TEXAS . \. -: .• l

N

t

.-._.-.

FIGURE 12

CITY OF McALLEN

AIISSION

- Di~TiCUY~LUOtJING--FOKTELL9---

, , , , ,

, , , ,

I I , , , ,

I I

, , , I

, i

i i

i i

i

, i

i i

i i

i i

i

, , , i

N

i 'm... .... _n~-----1i""

DEPTH OF FLOODING

o - l'

e::::::J l' - 2'

I"'yi, 2' - 3'

"" I 3' - 4' _4'-5'

~5'-6'

_6'-7'

FIGURE 13

I ~'. . 100 YEAR FULLY URBANIZED CONDITIONS 1 .. 1 Halff Assocl3tes FLOOD PROTECTION PLANNING STUDY ~ ~ ••• CITY OF McALlEN ~"ii~j-:R;~:,ECTS:SClEN~ISTS'PL'NNERS'SURVEYORS FOR SOUTHERN MCALLEN AND MISSION, TEXAS' I

E. SINGLE OCCURRENCE FLOOD LOSSES

The estimated total property inundated by the future (assumed ultimate land use) lOO-year flood within the study area is approximately 7,681 acres. This includes about 2,590 acres

within the Mission Floodway and about 5,091 acres between the Mission and Banker Levees.

Visual inspection of these flood plain areas indicate about 2,958 acres of 100-year flood plain consist of agricultural cropland.

Flood profiles, developed for this project, were utilized to determine a relationship of damageable properties to both elevation and flood frequency. The 1995 DTM was utilized

to identify flood prone properties and estimate fmished floor elevations of structures. Generally, finished floor elevations of structures were assumed about twelve (12) inches

above the elevation shown on the 1995 DTM. Finish floor elevations of some warehouses

and commercial structures were estimated as high as four (4) feet above the DTM. Criteria

for estimating floor elevations was determined from field observations.

Flood prone properties were classified as residential, warehouse, commercial, and other (including churches, schools, and public buildings). An inventory of existing structures,

indicate that there are about 1,236 structures with estimated finish floor elevations below the computed 100-year flood. The majority of these structures (1,085) are residential properties

in Balboa Acres located in Cell 9. Table 13 is a summary of flood plain acres and estimated single occurrence flood losses for the 100-year flood frequency, assuming ultimate land use

conditions. All known flood prone structures are located within the Mission Floodway, Cell

9, and Cell 11. Flooding at these locations include the residential neighborhoods of Cimarron

Country Club, Balboa Acres, and properties located along Jackson Road. The greatest concentration of warehouse and commercial flooding occurs within the Foreign Trade Zone.

A summary of the estimated number of structures with finish floor elevations below the

computed 10-, 25-, 50-, and lOO-year flood frequencies, for ultimate land use conditions, is provided in Table 14. As many as 955 residential structures, located in the Cimarron Country

Club and Balboa Acres, are susceptible to the lO-year flood event, assuming ultimate

development. The computed existing lO-year flood elevations at Cimarron and Balboa are less than 0.05 feet and 0.2 feet lower than computed ultimate flood elevations. Thus, the difference in the number of structures with estimated finish floor elevations below the existing and ultimate 10-year flood is within the accuracy of the assumption and subsequent results

of this study.

III-I 6

I

Location

Mission Floodway

Cell 1

Cell 2

Cell 3

Cell 4

Cell 5

Cell 6

Cell 7

Cell 8

Cell 9

Cell 10

Cell 11

Total I

Table 13 Summary of lOO-Year Single Occurrence Flood Losses

Ultimate Land Use Conditions

Total Cropland Number of Structures in Flood Zone Flood Plain Flood Plain

(acres) (acres) Residential Warehouse Commercial

2590 160 75 0 0

118 118 0 0 0

110 110 0 0 0

419 298 0 0 0

158 150 0 0 0

179 67 0 0 0

181 181 0 0 0

237 195 0 0 0

196 115 0 0 0

2715 1079 1085 18 47

540 365 0 0 0

238 120 6 0 0

7681 I 2958 I 1166 I 18 I 47 I

Other

0

0

0

0

0

0

0

0

0

5

0

0

5

Note: Peak: flood elevations are based on ultimate land use conditions with existing (1995) topography. See Figure 5 for assumed ultimate land use. Flood prone properties were classified as residential, warehouse, commercial, and other (including churches, schools, and public buildings).

IlI-I7

I

Location Flood Event

10-yr

Mission 25-yr

FIoodway 50-yr

l00-yr

lO-yr

Cell 9 25-yr

50-yr

l00-yr

lO-yr

Cell 11 25-yr

50-yr

l00-yr

10-yr

Total 25-yr

50-yr

l00-yr '--- -

Table 14 Summary of Flooded Structures

10-,25-,50-, and 100-Year Flood Frequencies Ultimate Land Use Conditions

--- - .. _-- -

Estimated Number of Structures in Flood Zone

Contribution of Inundated Structures per Event Total Structures Inundated for Event

Residential Warehouse Commercial Other Residential Warehouse Commercial

29 0 0 0 29 0 0

0 0 0 0 29 0 0

46 0 0 0 75 0 0

0 0 0 0 75 0 0

926 9 46 4 926 9 46

0 0 0 0 926 9 46

0 0 0 0 926 9 46

159 9 1 1 1085 18 47

0 0 0 0 0 0 0

6 0 0 0 6 0 0

0 0 0 0 6 0 0

0 0 0 0 6 0 0

955 9 46 4 955 9 46

6 0 0 0 961 9 46

46 0 0 0 lOO7 9 46

159 9 1 1 1166 18 47

Other

0

0

0

0

4

4

4

5

0

0

0 ,

0 I I

4

4

4

5

SECTION IV ALTERNATIVE IMPROVEMENTS

IV. ALTERNATIVE IMPROVEMENTS

A. GENERAL

Conceptual design improvements were prepared to help alleviate flooding and the

subsequent potential damages. Improvements along the Mission Floodway include modifications to the existing levee to help prevent overtopping and alleviate flooding of residential properties. Basic design criteria within the SharylandIForeign Trade Zone was

to provide adequate flood storage for the future (ultimate land use conditions) lOO-year

frequency flood. Proposed sump storage areas were generally located at natural low areas

in non-urban areas in an attempt to minimize disruption to the land and to avoid major

utility crossings. A summary of required flood storage for areas within the SharylandIForeign Trade Zone are presented in Table 15.

Table 15 Sharyland/Foreign Trade Zone

Summary of 100-Year Peak Storage Requirements for Ultimate Land Use Conditions

100-YEAR PEAK STORAGE REQUIREMENT

DRAINAGE AREA AREA AREA PEAK STORAGE STORAGE/ACRE (sm) (ae) (ae-ft) (ae-ftlae)

Cell 1 0.67 429 313 0.73

Cell 2 1.26 806 586 0.73

Cell 3 2.36 1510 1205 0.80

Cell 4 0.69 442 364 0.82

Cell 5 1.06 678 558 0.82

Cell 6 0.58 371 311 0.84

Cell 7 1.83 1172 922 0.79

Cell 8 0.59 378 293 0.78

Cell 9 4.80 3072 2441 0.79

Cell 10 1.59 1018 835 0.82

Cell 11 0.75 480 377 0.79

Total 16.18 10355 8201 0.80 ae~e-ft I ae~e

Note: Flood storage requirements are based on ultimate fully urbanized watershed with existing (1995) topography. See Figure 5 for assumed ultimate development.

IV-I

B. MISSION FLOODWAY IMPROVEMENTS

1. Mission Floodway Emergency Spillway

The computed future 100-year flood will overtop the Mission Levee at five locations, assuming the Banker Floodway is flowing full and the Mission outlet gates are closed. The Federal Emergency Management criteria for levees requires a minimum three (3) feet freeboard above the 100-year flood. Proposed levee modifications are depicted for each of these five locations on Figure 14.

In order to prevent the Mission Levee from breaching, during the 100-year event, an adequate emergency spillway is needed. A proposed 800 foot length rock lined emergency spillway will be required to convey the future 100-year flood, assuming gates closed. The proposed spillway crest shall be constructed at elevation 102 feet, the lBWC regulated flood elevation of the Banker floodway at the proposed spillway location is about 101 feet. In addition, about 3,000 linear feet of the existing levee will be raised to elevation 105 feet. Note, the purpose of these improvements is to protect the levee from breaching, not to alleviate flooding of properties.

A conceptual illustration of the Mission Floodway Emergency Spillway is presented on Figure 14. The estimated construction cost of these improvements is about $2,033,000. An itemized statement of probable cost is provided in Appendix E.

2. Mission Floodway Relief Flood Storage

An alternative plan to the aforementioned proposed Mission Floodway Emergency Spillway, is to provide adequate flood storage at a location upstream of the Mission outlet. In order to retain the ultimate 100-year flood (assuming outlet gates are closed) to below elevation 103.5 feet, an additional 5,660 acre-feet of flood storage are needed. One possible location for this proposed retention pond is within Cell 11. Construction of a 13 foot high levee located just west of Jackson Road and excavation of about 1.6 million cubic yards of material will provide approximately 5,660 acre-feet of flood storage, at an elevation of about 103 feet. In addition, about 3,000 linear feet of the existing levee will be raised to elevation 105 feet.

A conceptual illustration of the Mission Floodway Relief Flood Storage is presented on Figure 15. The estimated construction cost of these improvements is about $7,108,000. An itemized statement of probable cost is provided in Appendix E.

IV-2

am. =~=HaJff Associates ENCUHRS • ARCHITECTS. SCIENTISTS. PLANNERS 0 SURVEYORS

~---~~.---- -------

100-YR GATES CLOSED EL. = 103.5 100-YR GATES OPEN EL. = 97.7

PROPOSED LEVEE MODIFICATIONS MISSION INLET FLOODWAY

FWOD PROTECTION PLANNING STUDY FOR SoU'tHERN MCAlLEN AND MISSION, TEXAS

PROP. ELEV. 105.0'

1~ 2 ::Jl ~ ~ T 2 EL. 102.0'

I'

y ~BANKER FLDWY. DESIGN WS [LEV. e MISSION INLET 101.0'

EMERGENCY SPILLWAY

N

o 599 1000 tsoc SCALE IN FEET

FIGURE 14

III CITY OF McALLEN {j.',

NOTE.

FOR 'GATES CLOSED' SCENARIO ADDITIONAL STORAGE REOUIRED. 5660 ao. ft. FOR 100 YR. EVENT.

IIDIiHaUI As · =~= SOclates EHGINUHS • ARCHfT[CTS • SCEmSTS • PlANNERS • SURVEYORS

TOP OF EXIST. LEVEE EL. 107'

PROPOSED LEVEE TOP ELEV. 105.0

MISSION INLET FLOODWAY RELIEF STORAGE FOR 100 YR ULTIMATE LAND USE (GATES CLOSED)

FLOOD PROTECflON PLANNING STUDY FOR SOU1'HERN MCALLEN AND MISSION, TEXAS

N

....

FIGURE 15

OF McALLEN C[i!'I,

A second possible alternative location for flood storage is within the eXlstmg Mission levees. Approximately 5,660 acre-feet of flood storage could be obtained by excavating an average depth of about 2.5 feet throughout an area of 2,260 acres. This would require excavation along the entire floodway, excluding the Palm View Golf Course and Cimarron Country Club.

3. Mission Levee Reconstruction at Cimarron Country Club

Modifications of the south Mission levee at Cimarron Country Club are needed to

help alleviate flooding to approximately 75 residential structures and to prevent

Mission flood waters from exiting the floodway. The estimated lowest fmished floor

elevation (assumed elevation 12" above the 1995 DTM) at Cimarron is about 104

feet. The computed ultimate 100-year flood elevation at Cimarron is approximately

105.6 feet.

One possible solution to reduce the flooding at Cimarron, is to direct flood waters

around the Cimarron development. This would include construction of a relief

spillway just upstream of Rio Grande Drive and an overflow floodway along the

south side of Cimarron. The proposed 340 foot wide relief spillway will convey the

computed ultimate 100-year peak flow at about 5 feet depth. Flows will be directed

along the south boundary of Cimarron where the south levee will be reconstructed

to an elevation of about 108, approximately 4 feet above existing ground elevations.

The proposed overflow floodway could be constructed as a series of linear lakes with a minimum 250 foot bottom width, 3:1 side slopes, and 12 foot depth. A flap

gated outlet structure with an emergency manually operated backup gate will be

required downstream of Shary Road to prevent back flow into Cimarron. In

addition, a new bridge will be required where Shary Road crosses the proposed

overflow floodway.

A conceptual illustration of the Mission Levee Reconstruction at Cimarron is

presented on Figure 16. The estimated construction cost of these improvements is

about $6,371 ,000. An itemized statement of probable cost is provided in Appendix

E.

C. SHARYLANDIFOREIGN TRADE ZONE

1. Cell 1 Improvements (Outlet No.1)

The Cell 1 flood storage necessary to reclaim about 70 acres of property inundated

by the future (ultimate development) 100-year flood is approximately 313 acre-feet.

IV-3

100 YR. EL. 108.00' 106'

~1_.E~01.00'--L 340,j

c:JCl

......,.-?

~ ''\

,;::.Z;, -' .' ~ CIMARRON

COUNTRY CLUB

.-,~- .. '-.

-7;,:-

~'--, ::v.-r' / ,', I 'Y/ 'J ; ,I

, \.., /' /~\

/I ~ __ . _._l~~~~ _.1,;'\ • - ,,---:.:::-. ,-_' ,.".,.' <

,I -.=- ........ '-=.><='-.- .- ,1."" _.-'--.~

,/ ,"~ \..,J

,~;~);~7;,:;;,,~"0'''~;'~~/'~ .---

~ _ .... " ./ ,('Ie)

./ ... r;" /' //;.'

- i~'('"/

-; "7" RaP. --=-- - ' p -.~ - FL89.o

LZ50,J TYPICAL EMERGENCY FLOODWAY

_OIilB 1ft." As • =~= al.ll. SOclates ENGINEERS. ,ARCHITECTS. SCIENTISTS. PLANNERS. SlJW(YORS

RECONSTRUCT LEYEE TO ELEY 108.0

__ p.-----~ .. ....:::;--:c:-;...:~--~_:~~_ ~ .•. __ __

.-::-...-:' ,-' I , ,

I ,

PROPOSED DRAINAGE IMPROVEMENT FOR CIMARRON RECONSTRUCTION OF SOUTH LEVEE

FLOOD PROTECflON PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION, TEXAS

~~--~f

./.:c-'--"-""-="~'='-:"-:.J c-:: .. """-~ .. -=-~'--="~

'''::-~ '-, \'

'I, U II II

'), If " u \, I

FIGURE 16

CITY OF McALLEN UMARON.DGN

About 13 I acre-feet (ultimate I OO-year flood) are currently stored in Cell I at a peak

elevation of I I 2. I feet, the minimum top of the Mission Levee is about I I I feet.

AIl flows above elevation 1 I I feet currently spill into Mission Floodway. The

future IOO-year peak flood elevation of the Mission Floodway at this location is

about I 11.4 feet. Cell I improvements include raising the Mission levee to 113.4

feet (2 feet above the computed ultimate IOO-yr flood elevation) and providing

adequate flood storage to retain all runoff within Cell I. A flap gated 6' X 4' box

culvert outlet structure, with a manually operated emergency backup gate, will also

be required at Outlet No. I to drain to the Mission Floodway.

A possible configuration of proposed sump areas and storage ditches draining to

Outlet No. I are illustrated on Figure 17. The estimated construction cost of these

improvements is about $2,252,000. An itemized statement of probable cost is

provided in Appendix E.

2. Cell 2 Improvements (Outlet No.2)

Approximately 586 acre-feet of flood storage is required in Cell 2 to reclaim about

25 acres of property inundated by the future (ultimate development) 100-year flood.

Currently, about 147 acre-feet, for future IOO-year flood, are stored at a computed

peak flood elevation of I05.6; the remaining runoff overflows to Cell 8 and

. eventually to Cell 9. Proposed Cell 2 Improvements include a 2 foot high berm

along Stewart Road and provisions for adequate sump storage to retain the future

IOO-year flood. A flap gated 8' X 5' box culvert outlet structure, with a manually

operated emergency backup gate, will also be required at Outlet No.2 to drain to

the Mission Floodway.

A possible configuration of proposed sump areas and storage ditches draining to

Outlet 2 are illustrated on Figure 17. The estimated construction cost of these

improvements is about $4,093,000. An itemized statement of probable cost is

provided in Appendix E.

3. Cells 3 to 9 Improvements (Outlet No.3)

Cells 3 thru 9 were divided into 2 improvement zones draining to Outlet No.3 and

Outlet No.4. Cells 3 thru 8 and a portion of Cell 9 drain into Outlet No.3, the

remaining Cell 9 (Balboa Acres and Foreign Trade Zone) drain to Outlet No.4.

These zones are separated by a 3 foot high berm generally situated encircling the

existing developed areas of Balboa Acres and the Foreign Trade Zone.

IV-4

I L:\: 101 /J I 2 2

N

l-200,-J TYPICAL

LINEAR SUMP XSECTloN

500 1000 1500

SCALE IN FEET

I~ 10' AI 2 I t I 2

f.,- 15' ----l TYPICAL

DRAINAGE STORAGE

DITCH

HaIff Associates

'I ,; .I /,

/) { .~ ..

STOR:~-l t c :~~---- -~~:i ... ~lh; 9~C~'ft. mITCH.E .. S, .FOR I . . ,. 100 YR OUTLET No 2i I L" . : L.:.C..-'-"-__ ---.J ~BOc~ft. I /' t --= 1 - --1 '. Ii -====,~'--.' ~'l ;'r: , ..... :.', :~ -:-=.;../---.-- -,

?J r ~. l),rCf' .'. IF~-'~-I f~~~-.· t ,1.L2~~J~---~~~:~~ ,!. /1_. :...1_.-6. ... ;.:.:~ .. -·Jf\-~-.. ~- ·f

Dr~+' . L/·;L· ±i',;'."r--,· .:"-~-=' . '=jl .: .... '" .' .... ~='C"=':"'=r=- !!" -.:...~~

! • _ . . . il,l .1. . .-·i 'Ii~. r ~rc"",-~=--~

'" ff} }·\c7,~UJ~=~~r"~~l PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 1 & 2

FLOOD PROTECTION PLANNING STUDY FIGURE 17

I

FOR SOUTHERN MCALLEN AND MISSION, TEXAS CITY OF McALLEN I cc '/1. ?[)C';

The flood storage necessary to reclaim about 1,820 acres of property inundated by

the future (ultimate development) 100-year flood is approximately 4,793 acre-feet,

including about 169 acre-feet from Cimarron. Note, following implementation of

the Mission Levee Reconstruction at Cimarron, the required flood storage to Outlet

No.3 will be about 4,624 acre-feet. Outlet No.3 improvements include the

excavation of about 7.5 million cubic yards of material for sump storage and two

proposed 10' X 10' box culverts in addition to the existing five 4' X 4' box

culverts. Flap gates with manually operated emergency backup gates will be

required at all proposed and existing culverts draining to the Mission Floodway.

A possible configuration of proposed layout of sump areas and storage ditches draining to Outlet No.3 are illustrated on Figures 18, 19,20, and 21. The estimated

construction cost of these improvements is about $31,340,000. An itemized

statement of probable cost is provided in Appendix E.

4. Cells 3 to 9 Improvements (Outlet No.4):

The flood storage necessary to alleviate flooding of approximately 1,155 residential,

warehouse and commercial structures, located in Balboa Acres and the Foreign

Trade Zone, currently inundated by the future 1 OO-year flood is approximately 1,470

acre-feet. Proposed improvements draining to Outlet No.4 include the excavation

of about 2.4 million cubic yards of material for sump storage and a proposed 10' X

10' box culvert outlet structure. In addition, a flap gate with manually operated

emergency backup gate will be required at the outfall to Outlet 4.

A possible configuration of proposed layout of sump areas and storage ditches

draining to Outlet NO.4 are illustrated on Figures 19, and 20. The estimated

construction cost of these improvements is about $10,147,000. An itemized

statement of probable cost is provided in Appendix E.

5. Cell 10 Improvements (Outlet No.5):

Cell 10 improvements are bounded by the McAllen Main Canal and the San Juan

elevated canal. The total flood storage necessary to reclaim about 100 acres of

property inundated by the future (ultimate development) 100-year flood is

approximately 780 acre-feet. Proposed improvements draining to Outlet No. 5

include the excavation of about 1.3 million cubic yards of material for sump storage.

A flap gated 10' X 6' box culvert outlet structure, with a manually operated

emergency backup gate, will also be required at Outlet NO.5 to drain to the Mission

Floodway.

IV-5

N

---/,

·:h. . I ~\ I / .' . '0 '?<,;~ .. , • -" , /. . . ~,,, ". I ..... ~r~LT~ft~ ....... S .. UMP): ~-":' .. -. -, '. t I ... : .... 1 .. ~~Iblb 0 .~ tl%.<:l J~~c;.~ I . " = ff. ", . 'C<. I I . -' . ., ~.> ' ",~".,." '.. < , f-- ' CDITCHES FOR I L I . I I ! I

--- '""" ,,,.", ' . ...L-t IJ~ ?C-,-f~. I·· -. --i ~~.. __ I I --~- '-'1, .I '1:, ~ -I -_.- , I ", "

I I ------1 I It I ,_~ ,_ _, _', __ .~, .. L __ . ___ ~~~. Iblb ~ r--:--. --4f· t! -':--=-;;;;;;;;~2~~;;;-f ' I , "~ a

I' , ~---- .L . • ,"U. I~ · , I r . "__. , ",." I · . -~----. f: J. 1 - I ~I ( "--, " . . --~~- , f

······ ..... : "'';) 1._' -':::" ='~~~--. .. I ___ ':' __ D.!L r ... I I 1/. w w , · , I,. " " ___ . "

I

c

I .' I ~ '~j '" .. .' .:

' '" .,:.... 0 ? :--~.,,-,~ ..... ===-~~ .. '.~r~I~~. . ···--;-·=;-;=-t--·r~:-:-'·7r·~~-=-·" // .... " .. ~ . • '\ . l_'-__ -~ c- I ,._!. _, , I I I . \. I f1STORAGE = #. -;, ~'l-I .. - -.:.c'" .... ~ .' .

• \ '. ww" < <'. --. _ .~ c II .' ". \ '.' .. ' I . 11.1 .. 10. a c. ft"4. . ~"" ... ~(,~ttf'~. ' .. , .' :""_-,t: I' \ / 1 ... , <:l<:ld~·"'oo •. , 0::, . 'O'?~ r---

~MADERO

• ARtHITECTS • SCl9ITISTS • PlANJ£RS • SURVEYORS

it~ i. . . ..... '. i:.. I .. , ". '.~S\ .. 'l. 1."'... . i . «.."""'~(,\~'. I ~ ~~~~"'-:; -- . ~ ~ ,. ~I, ----'- "$.f'" " ::t ~. :EI . '.' <8,~ :sr" fl\.--;2, /'if ~. 1 te< ~ "-.. , I F.W • , , 'c"-i--:' i .. ~"Ib' ~ 0:; ...... .:..--~- ~ . . .... 1 1.-

10'-.1 • ~LSlb I 1 lIi/ ~"''''''';l! '. TYPICAL . '" I I ~'1q -.0....-: STORAGE DITC.H t;i Ii I

MATCH LINE SEE FIGURE 20 PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 3 - 9

SHEET 10F 4 FLOOD PROTECTION PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION, TEXAS

FIGURE 18

CE~~ '?-

®

7 :..1.11 .. 0H1 'f'

TYPICAL LINEAR SUMP

XSECTION

, -.:-C T --, I - I

. I I

I: b--~m r)/ Irek§1r J[ f21 I -iii \@ ,1!~ 'lftft ' N30~Ac~Eft·1

Halff Associates ENQI£ERS • ARCHITECTS. SOOITISTS • PLANNERS. SURVEYORS

MATCH LINE SEE FIGURE 21 PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 3 - 9

SHEET 2 OF 4 FLOOD PROTECTION PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION. TEXAS

FIGURE 19

OF McALLEN r:r~ I G-7 111~'

N

HaIff Associates ENCIlERS • ARCHTECTS • SCIENTISTS • ~s • SURVEYORS

MA TCH LINE SEE FIGURE 18

1 I, I' I J

'11 F/J 1016 iJllur Af?( RD.

<::i Q::

"----

b .~ ... ,''::. '. 1

(' '-

~"II. @ • ~ .0' ",

Pf·. r-~* I ©~~ ~p-," ; •. t-"J ",= :/~;7_'" -: .. ~J ~r -- "=- f. ••• b'" i I . """ ". I

. II ---II

Jll' ~~.,·:~t<;)~~~~"'~ I ".~~~~(, I ~c.,<,-Q I ;

PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 3-9 SHEET 3 OF 4

FWOD PROTECTION PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION, TEXAS

...----

II Ilj

V1

II J

./

r: U f<r: 2

CITY OF McALLEN ~;:-~ L 9 3.~G~,1

-------------------------------------------------------------------MA TCH LINE SEE FIGURE 19

~ 1-1 -~---O;:~

~tC'Ju"~.n .. :.L.~.U~~.~i:: .. ;t .-~ l-oV!l ~Ol_~~~f~~·~.~ jt~IIIH R~p~~·-(i;fll_1 r ~UMr '-' 'Irl . lWl1Ir::·~~ 7 indIO? dtJf ORr~AD" U ~. .•. ... ..~. __ LL .

W W V) I

w l----J ?

-.l

:c u I<:(

:::!!

c'i.\..\..}' I''i.~~ \\~,o '''£.~l,ot~~. -it.

-HaUf Associates DiCJ£[RS • ARCWJ[CTS • SC£HTISTS • PlANNERS. MVEYORS

5' ri

,f!:fV" ~~ PROPOSED

PROTECTIVE BERM

/--

PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 3 - 9 SHEET 4 OF 4

FLOOD PROTECl'ION PLANNING STUDY FOR SOUTHERN MCAlLEN AND MISSION, TEXAS

N

FIGURE 21

CITY OF McALLEN CELL9-~_DGN

i I !

I

-~ I ;s::-~, /'J I

2 j-rJ 2

k-20'----J TYPICAL STORAGE

DITCH

II?" t 11' ~ I l-130' --J

TYPICAL LINEAR SUMP SECTION

.1iB. =~=HaItT Associates ENGINEERs. ARCtllT[CTS • SCIENTISTS. pl..J.Nt£RS • SURVEYORS

.

W~ ". ~!iv:.··"., ... " .•.. ~ ,I I ; . Ii .. , ' 11ft; , ~ I~ • .; -+----~ .. PROPOSED DRAINAGE IMPROVEMENT FOR CEIL-IO ••

FLOOD PROTECTION PLANNING STIJDY ; .. '_ .: FOR SOUTHERN MCALLEN AND MISSION, TEXAS +'" ,,"

MCAUEN MIUER

INTERNATIONAL AIRPORT

)W,ra t"w ~ Z

500 1000 1500

SCALE IN t- ttl

FIGURE 22

II/CITY OF McALLEN

CE.~L 10.DGr

A possible configuration of proposed layout of sump areas and storage ditches draining to Outlet NO.5 are illustrated on Figure 22. The estimated construction

cost of these improvements is about $5,667,000. An itemized statement of probable cost is provided in Appendix E.

6. Cell 11 Improvements (Outlet No. 6):

Cell I I improvements are bounded by the San Juan elevated canal and the Mission

and Banker levees. The total flood storage necessary to alleviate flooding of

approximately 6 residential structures, located along Jackson Road, and reclaim

about 180 acres of property, inundated by the future (ultimate development) 100-

year flood, is approximately 377 acre-feet. Proposed improvements draining to

Outlet No.6 include the excavation of about 607,000 cubic yards of material for

sump storage. A flap gated 6' X 4' box culvert outlet structure, with a manually

operated emergency backup gate, will also be required at Outlet No.6 to drain to

the Mission Floodway.

A possible configuration of proposed layout of sump areas and storage ditches

draining to Outlet NO.6 are illustrated on Figure 23. The estimated construction

cost of these improvements is about $2,756,000. An itemized statement of probable

cost is provided in Appendix E.

IV-6

i.

I~ 10' AI 2 L f I 2

15' --..I TYPICAL

DRAINAGE STORAGE

DITCH

Halff Associates :NQHE[ftS • ARClUECTS • SClEHnSTS • PUmERS • SURVEYORS

~ IL":\, 10' AI

2 L f I 2 100'--..1

. BANKER FLUlJWI

PROPOSED DRAINAGE IMPROVEMENTS FOR CELL-ll FLOOD PROTECTION PLANNING STUDY FOR SOU'tHERN MCALLEN AND MISSION, TEXAS

N

~

I

.."

FIGURE 23

CITY OF McALLEN C[I~I. l1.DG~~

SECTION V RECOMENDATIONS

V. RECOMMENDATIONS

A. PRIORITY RECOMMENDED STRUCTURAL IMPROVEMENTS

Based on the results of this study, the need to address imminent flood damages to

property and structures, and a review of the various improvement plans (described in

detail in Chapter IV), Halff Associates' initial recommendations include implementation

of flood damage reduction improvement plans in the following order of priority:

1. Mission Levee Reconstruction at Cimarron Country Club

Modifications of the south Mission levee at Cimarron Country Club are needed

to help alleviate flooding to approximately 75 residential structures and to prevent

the Mission flood waters from exiting the floodway. Re-directing flood waters

around the Cimarron development would include construction of a relief spillway

just upstream of Rio Grande Drive and an overflow floodway along the south side

of Cimarron. The proposed 340 foot wide relief spillway will convey the

computed ultimate lOO-year peak flow at about 5 feet depth. Flows will be

directed along the south boundary of Cimarron where the south levee will be

reconstructed to an elevation of about 108. The proposed overflow floodway

could be constructed as a series of linear lakes with a minimum 250 foot bottom

width, 3: 1 side slopes, and 12 foot depth. A flap gated outlet structure with an

emergency manually operated backup gate will be required downstream of Shary

Road to prevent back flow into Cimarron. In addition, a new bridge will be

required where Shary Road crosses the proposed overflow floodway. The

estimated construction cost of these improvements is about $6,371,000.

2. Cells 3 to 9 Improvements (Outlet No.4):

Approximately 1,470 acre-feet of flood storage is required to alleviate flooding of

approximately 1,155 residential, warehouse and commercial structures, located in

Balboa Acres and the Foreign Trade Zone, currently inundated by the future 100-

year flood. Proposed improvements draining to Outlet No. 4 include the

excavation of about 2.4 million cubic yards of material for sump storage and a

proposed 10' X 10' box culvert outlet structure. In addition, a flap gate with

V-I

manually operated emergency backup gate will be required at the outfall to Outlet

4. The estimated construction cost of these improvements is about $ IO, 147,000.

B. OTHER RECOMMENDED STRUCTURAL IMPROVEMENTS

1. Raising the Mission Levee

Halff Associates recommend the Cities consider raising the existing levee, in

accordance with FEMA criteria, at the all locations where the computed future

IOO-year flood will overtop the Mission Levee. According to FEMA "Riverine

levees must provide a minimum freeboard of three feet above the water surface

level of the base flood. An additional one foot above the minimum is required

within 100 feet in either side of structures (such as bridges) riverward of the levee

or wherever the flow is constricted. An additional one-half foot above the

minimum at the upstream end of the levee, tapering to not less than the minimum

at the downstream end of the levee, is also required." (Reference 20).

2. Mission Floodway Emergency Floodway

In order to prevent the Mission Levee from breaching, during the IOO-year event,

an adequate emergency spillway is needed. A proposed 800 foot length rock lined

emergency spillway will be required to convey the future IOO-year flood,

assuming gates closed. In addition, about 3,000 linear feet of the existing levee

will be raised to elevation 105 feet Note, the purpose of these improvements is

to protect the levee from breaching, not to alleviate flooding of properties. The

estimated construction cost of this improved spillway is about $2,033,000.

C. GENERAL WATERSHED RECOMMENDATIONS

1. To minimize land erosion and the subsequent sediment loading and siltation in the

channels, the Cities should consider requiring large construction projects to be

phased to limit the land area that is bare at anyone time. Vegetation should be

left undisturbed wherever possible. Graded areas should be replanted as soon as

possible, and mulches should be used during periods that are not suitable for

replanting. Hay bales and/or silt fences should be properly located and included

in general construction plans and specifications.

V-2

2. Halff Associates recommends that the Cities inspect all eXlstmg and future

channels periodically to identify potential stream obstructions before they occur.

Periodic inspections should identify City controlled floodway areas in which

siltation has decreased the flood-storage capacity of the channel and culverts.

3. Halff Associates recommend the Cities replace all gated outlet structures to the

Mission Floodway with operable flap gates and emergency backup gates. Periodic

inspections of these structures is also recommended.

4. City flood plain zoning maps should be revised to correspond to the revised

100-year flood delineation at the appropriate time.

5. Stream crossings that are hazardous during floods with a return period of 100

years or less, should be marked with a active or passive flood warning system.

Passive warning systems are feasible on lightly travelled streets where motorists

are familiar with the area and at crossings with minor flooding. Active flood

warning systems are necessary on heavily travelled thoroughfares. Guardrails

should be installed at hazardous crossings subject to flooding. Guardrails are also

useful in indicating the edge of the trafficable road surface to pedestrians and

motorists, where flood waters may mask the location of the road surface.

6. The Cities should continue with its present policy of monitoring new development

and requiring developers to submit a detailed drainage study of existing (pre

development) and post-development conditions with corresponding hydrologic

and/or hydraulic computer models. Halff Associates also recommends the City

require an analysis for a full range of flood frequency events (minimum of 2-,5-,

10-, 25-, 50-, and lOO-year flood events), this especially important in the

development of an effective detention pond design.

7. The Cities should encourage homeowners subject to flooding to participate in the

National Flood Insurance Program. Although flood insurance does not prevent

damages from occurring, the purchase of flood insurance could provide some

monetary relief from expensive flood damages.

V-3

D. UPDATING HYDROLOGIC AND HYDRAULIC COMPUTER MODELS

Included in this report are the computer data diskettes containing the hydrologic and

hydraulic computer models used in the production of this report. These baseline models

will enable the City Engineering staff to predict effects of anticipated changes in land use

and/or watershed characteristics upon flood levels using an IBM or compatible Personal

Computer. Halff Associates recommends that the Cities require developers to provide

updated "as-built" hydrologic and hydraulic computer models as channel and/or flood

plain conditions are modified.

Generally, the HEC-l hydrologic computer model used in this report should be applicable

for a fully developed watershed, provided development occurs as predicted by the future

land use maps of the cities within the watershed. Halff Associates recommends the City

consider updating the hydrologic and hydraulic computer models prepared for this study

a minimum of every five (5) years.

E. FLOOD PLAIN MANAGEMENT POLICIES

Halff Associates recommends that the Cities consider adopting a flood plain management

policy that would require all new developments within the Sharyland/Foreign Trade Zone

provide a minimum of 0.8 acre-feet of flood storage for every one acre of development.

It is further recommended that the Cities formally adopt the flood levels shown in this

report for their flood plain management program.

V-4

APPENDIX A Drainage Area Map

\ ~

.... "',., .. , •.. ( >... .. "-"-"'\ ( / ;" '., .. ~.. \

i \~\;7~'. . ,.. i { 1

~ (JiCI4/C~Jl.~ III DE.,.NL. s'tuoy ~" ST~ ~J)lt ltlE o.JTsIDE OET~ snlO'f ¢ ...

'i. .... E\I.TED C"tl~l

0'1'1' I,..\ltDT 1..U£ ont'l'l \YJ.1:SIDE t£l-'

IL

S1o,J)Y .. RE." -- ,.,,,, _____ Llt4llS '$ oEt All. S n.iO

Y

~vERS 10 RQIX'IW,t.'tS

~ ...... GE ,yO'''' \l\'i\llf

. " I I . \',.,," ',. '-. \ : / '",". f '. \ I

"\, ,/ "" i \

\.- .. -~~ .. -.. ' .. ,..' ""'-"-'}-.. _ .. _., (-~.., ..

<JI,-~/;"A~ \,

....... \.,.

UETAIL uRAINAGE AJtEA MAl' FLOOD Pltot£CflON pLt\!lN1NG stUD)' fO" souru""" ",e""""" ",0 ",\SS\o", 'fEl'AS ~--

\~!!~~?~~!!~'

>I

\\

\ ~

0' G~"~~

.-' .-

t\.ppF,NDI'X 1\

l) ••• CI\'f Of' McALLEN

.~'-

APPENDIXB Elevation-Storage Tables

2 3 4 5 6 7 8 9 10 11 12 13 14 15

Time in Hours

2500

2000

J!! U1500

== ~1000

500

0 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Time in Hours

Regulated Flows of Contributing Ditch Systems to the Mission Inlet Floodway

g c o 'ro ~ ill

)

Elevation-Storage Relationship Mission Inlet Fldwy-Total (Cells 12-17)

)

110: ~ · · I · I I · · · · · . It' I

I · · I · · I · · • I _____________________ L _____________________ ~ __________ ___________ A _____________________ J __

----------------~--------------.------~--------------- ------· . . I I I · . . · . . • I I · . . · . . · . · · · · · .

· · · · Lowest T dp of Levee · ·

I • . .

· . I • I I I f ------_·_·----_··-·--r------·····-----_····,·- -----·-···---··--T-------·-----···-----~-·-·---·----------.-.~---..... ---.---.-.. -.~---... ------------.--• , I I I I I I I I I , · · · · ,

· · , , I I I I I __ L _____________________ & _____________________ & _______ ______________ J _____________________ J _________________ ____ ~ ____________________ _

I I I • , I , I I I I I I I I I I I I I I .. .

" , ,. , · . , I · , · , , , · , • I I "

----------------~-------------.-------.----------.--------... ~--------.------.----~---------------------~---------------------~-.-------------------I I I • I I I I I I I I I I I I I I I I I · ,

• I · , · , • I • I · I

I I I I • I

····················~·····-·····--·-·····-f····-·--··------··--·1--------·------------;---·----------------·i--·------------·------~-·----------------·--, I I I • I .. , " , ,. . · . I • , . ,

I , , I

I I I I I I

.------------.-------~-.--.--------.--.-.--.---------- -----------.---------------------.------------------_.-~---------------------~---------------------

o

I I I I I I I I I I , I I I • I I I I I I I I I , . . , • I . , . , , . , I • , • I , . . I , I , . . 5 10 15 20

Volume (acre-ft) (Thousands)

25 30 35

g C o

1 ill

Elevation-Storage Relationship CELL 1

115: ...........

11

· • • • · · · I I • • • I

· • · · · · · . --------------~--------------~-------.-------~.-------------_&_-------------_&---------------~------.

~ ___ ~ ______________ J _________ • _____ J ______________ _

• , I • I I . . . , • I I · . I I I I · . I • I • · . I I I I · . I I I I · . I I • I · . I I • I · . I I I I · . · . . I I I 1 I

---------.----~--------------~--.----.-------,.------- --- ,------·--------.---------------r--------------~--------------,--------.------~-----------.---· . . I I I • I I · . . t • I I I • · . I • I I • I · . I I r I I , · . I I I I I I · · . · . · . I I I I I I • • ___________ J. _____________ .J _______________ & __________ _____ & _______________ ~ ______________ ~ _____ • ________ J __ ____________ .J ______________ _

I I I I I I I I · . " . I • I I I I • I' , · ., . I I I I I I I • I I I • I t I •

I I I I • I I I • . ~------~-~----~-------~-----.-.-------,--------------·T---------------T---------------~-·------------~----- ---------,---------------,---------------I I t I I I I I I I I , • I I • • •

• •• I I , I I ., • I • I I •• .,. I

'I I I

• I I I I. ,. • I I • , I I I ,

- ____________ ~-_____________ 4 _______________ ~ _________ - _____ • _______________ • _______________ • ______________ ~ ______________ ~-______________ ~ ______________ _

I , • • • • • I •

• • • • I • I

• I • " I. · , • I' •• • I • I' I I I I I I I , I I

I I I • I • I I

-------------~--------------~---------------~---------------i---------------i---------------~--------------~--------------~--------------~~---------------I I I I , I I I I • I I I I I I I I I •• I ••• I I I. • I I I " I. I I • fl. f I I I I , ,. • I

I • I I I I ----- _________ ~ ______________ 4 __ • _______ • ____ 4-~ ______ - ______ • _______________ • _______________ ~ ______________ ~-- ____________ ~ _________ • _____ ~- _____________ _

I I I I • I I • I , I • •• ••• I I I • I • I I • I I I. " I I " I • I • I I I , I I I

I • " I

--------------~---------------~---------------~-.-------------i---------------i---------------~----·---------~--------------~---------------~--.------------I I I I I I I I I I I • I I I I I I I I I. , , I I I I J I I I I · . . · . . · . . I I t I I I I I I

• _____________ ~-- ____________ 4- ____________ ._4 ________ - ______ • _______________ • _______________ ~ ______________ ~- _____________ 4 _________ • _____ ~- _____________ _

• I • I , I • • I

• " I I

• '" I , • I. I I 'I I I I I I I I I I I I I I I I I I

a 100 200 300 400 500 600 700 800 900 1000

Volume (acre-ft)

g c o

l ill

1


, , , , , , , , , , , I • • • ---------.---------------~ _________________________ ~ __ -- _________ • ___ • _______ e _________________________ 4 ____ ---

I , • • , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

. , , , , ----------------.-------------------------. , , , , , , , , , , , , , , _________________________ 4 _________________________ ~ ____________________ _ .e __ • ______________________ 4. _________________________ • ________________________ _

, , , , , , , , , , , . , . , . , , , , , , , . , , , , , , , , , -----.-.. -------.-.. -----~------.. -. , , , , , ,

, , , , , , , . . . -.. ---------~.------.. ------------.. --.----.-----------._.----_ ... -------_.----------------.---------------------.... • • I • • • I • · . . . I • I I

• • I • , , . , , , · , . , , , • • • I •

______ 4 _________________________ ~ _________________________ e _________________________ • _______________________ ---.-----••••• _--------------

I I • • •

• t • t • I • , , , , I • • • I • • I I , • , • I

• • • • I , " , " · ., , .. • I • • •

________ •••• _________ J _________________________ ~ ______ ___________________ t _________________________ J __________________________ L ________________________ _

I • • • • · . . . . · , , , , , I • , •

• I • • • I I • • I · . . . . • I • t • • • • t • · . . . . · . . . . I I I • ,

________________________ J ______ • __________________ ~ ___ ______________________ a _________________________ J __________________________ L ________________________ _

, I • • I

• I • • • · . . . . I I I I I • , • • I • • • I , , , . , . I • , I • · . . . . I • • • I I • • • I · . . . . _________________________ J _________________________ -L _________________________ a _________________________ J __________________________ L ________________________ _

• I • • I • I • • t • , I • • · . . . . · . , . . I • • I I

• • • • I , • • • I I • I • t • I , • I • • I • I

100. iii i i o 1000 2000 3000

Volume (acre-ft) 4000 5000 6000

g c o

~ Q)

w


116 ,

1

, , , , , , , , , , I I • I

, , , , , -------------------------~---------.-.-------------~------.------------------.-------------------------~---- ----- ~--------------.-------------------------I I • I ,

• , , I , , , , , , , , , ,

I I I I , , , , , , , , , , , , , , -------------------------~-------------------------"--- ----------------------- -----------------------.--------------------------~--- -_.-------------------, , , , , , , , , , , , , ,

, , , , , , , ,

...... --_ .............. -.. -... -..... _-.... . , , , , , , , , ,

, , I I I I I I I ,

-----~.------------.-------.. --.----.----------.------ .... -------.... -.. ----.--.-........ ----..... ---.. -------I I I • , • I • I , I I I • I • f I I , I I I I " , " , " , " ,

I • I • I I I I I

----.----.--------.--------.--~.------------.--------- --.-------------------------.-------. __ ._ ... _--_. __ .-- -~---.-.. --.-.------.-.--.-I I I t I I I I I I • I I I I I I , " , " , " , , , , , , , ,

, , I I I ________ • _____________ ~. _______________ ._. ____ ._~ _________ • _________ • _____ , ______________ • __ • _______ ~ __ • ____ • ________ • _________ L ___ • ____ •• ________ ._. ___ _

I I I I , I I I , I I I • I I I • I I I I , I I t I I • I , , , , , , , , , , , I I , I • ____ •• ________ •• _________ ~ ___ • ____ • ______ •• __ • _____ ~ _________________________ , ______ ._. _______ • ________ ~ ____ ______________________ L __ • _____________________ _

I I I I • I • • , ,

, It' , I I I • , I I I I I I I • I I I I I I I I I I I I I I I I I I

I I , I I

----------------------.-.~-.-----.---.----.--------~---.------------------.--,-------.-------------~--.~---.. -.-.-------.-----.---~-.----.----------------.-I I I I I I I I I I I , I I I I , I I I • 'I, t • I I I I I I , , , , , , , , ,

100 I 1 1 o 2 4 6


8 10 12

g C o 1u > Q.)

ill


107 i :;::oA

1

, , , , , , , , , I , I I

, , , , , , , , , -.. -----------.-.. ~------------------~--.--.-------------.-------------------.------------------ ----------------~------------------~-------------------I • I • , , , , , , , , , , ,

---------------L------------------1----------------

, , , , , , , , , , , , , , , , , , • I , I • I , I

.-------------------.-------------------~------------------~------------------~--.----------------• I • I , " , " , , , , , , , , " I I --..........• -------------_ ... _ ... _._._------------.- .... -.. ---------.-----------.... ---.-.~--------... -.-------... _----------.... • I I I I I I , • I I I ., I f I

I I I I I ,I I I I , , , , , , , , , , , , , , , , , ,

• I I • I I I

-----------~-------------.----.-------------------.--- --------------_ .. -------------------.----------------- -~-----------------.~------------.------I • I • I I • t. • I I I I • I ' I' • I I

I' • • I I • • ., . . I I • • I I • • I I • • I I • I I I I I I I I

_________________ ~ __________________ ~ _________________ __ A ___________________ A ___________________ L ____ • ______ ________ L __________________ ~ __________________ _

I I I • I I I I I I • I I I I I I • I I I . .. .

I I I I I I I I , , , , , , , , , , , , , , ,

I I I I I I , ________ • ________ ~ _________________ .J _________________ __ 4 __________________ .A ___________________ L ___________ _______ ~ __________________ J __________________ _

I • • I I I I I • I I I , t

• • I I I I I I ' I I •

I ,I '" I I I ••

• • I I I I • I I , , , , , , , , I I I , • • •

__________________ ~ __________________ ~ ________________ ___ A ___________________ A. __________________ L __________ ________ ~ __________________ ~ __________ • _______ _

o

I I • • I I •

I " I I • f I I • f I I ., I. I ,I I I f' I I • I •• , , , , , , , , , , , , , I ,

100 200 300 400

Volume (acre-ft) 500 600 700 800

g c o

l w

Elevation-Storage Relationship CELLS

-T"------------------------~------------------------ :' , ,

· . : . ------------116 ;: ................. j.

·························j··························r··· .................... :........ : · • ----------.--------_ •......... _ .. _ .. •

1

1

· · • · . . · . . ................. . .... ; ......................... + ......................... : .. . · · · · ·

· . ~------------------~-----------.--------------~-------------------------· • · · • · · · · · · ·

-------------------------1---------------------

: --~--------------·--·······--i-------·--------------·--~------.--.-.... -----..... -.--.... -------.. ---.----.-• • I •

• I I , I • I • · · · · • · · .. · .. · .. · . · . · . I I I I

---------.-----------~---------------------.---.-------------------------~--------------------------~-.----- ----_.------------I I I I · . · . · . · . · . · . • · · . I I I I I

--------------,-------------------------~------------- ------------y-------------------------,---------------·_---------r---·---------------------t I I I I

" 'I I' I I I I I I .. . .. . .. . .. . .. . I' I I ...... -.. -........... -.. ~ .•.......•• --.-.. -....... ~-.. --....... _ .. _ .. -.-... _.\-------.. -.•••....... __ .. {-----------_._---_ .... _---.---.--_._._._-------.... .

I I I I • .. . .. . .. . · . · . · . · . · . I I I I I -.-....... ----.---.-... --~--------.... -.-.. -.. -.. -.~--._---------_ .. _ .... _-_._--_._._--------------------_ ..... -.. -.--.-----.. --.. ~.------... -... ---------.. I I • I I I I • I I .. . .. . .. . · . · . · . · . I I I I I .. -.... -... -.-.. -.----... ~ ..........• -.. -..... -.----~ .. _ ........... _ .. _ .. _ .. _.\-----.-.. -..... _ ........ _;-_.----_ .. -_._ ........ -.. -..... -..... _--... -....... .

o

I I • I t • I I I I I I I I • I I I I 'I I I • I I I I I I I • I I I • I I I I I I

1000 2000 3000

Volume (acre-ft) 4000 5000 6000

-.t= ----C

)


105 ~

104

1

_. ______________ J _________________ A ________________ ~ ________________ • _________________ ~ __ ___________ J _________________ ~ ________________ ~ _______ ____ a_AM.

.••••••••••••••• ~ ••••••••••••••••• + •••• · · · · · ·

· . . · . · . · . · . · . · . · · • · · · · · · · · · ·

· · · · · · · · . .

·················I·················~················~· ....•••••..•... ~~ ..•••••••••••... ~ ••••.••.....•••• · . · . · .

0 . - 10 ro .

----------------~----------------.-----------------~----------------~-----------------~----------------~---- ---------.--· . · > Q)

· · · • · ill · · · 101 · . .

-············i················-I················-~··-·--····--··-·I······-···-------~-·······-·······i--··------.. --.. -~.-•.•..•... ---.--~.-......•. ------· . . · · · · · · · • · · • · · • · . . ---------------~-----------------T-----------------~----------------w-----------------r----------------~-----------------r----------------~----------------I I I • I I 10

, I I • I I , I I. I I I I. I ·

99. o 100 200 300 400 500 600 700 800 900

Volume (acre-ft)

)

Elevation-Storage Relationship CELL?

108 :

1

£1 .......... c o

1u > Q)

W

, , , , , , , I I I • •

, , , , , , -----------.--~----.--.------~---------------~---------------t--------------~

._. ___ .~ ______________ ~ ____________ ._J _______________ J ______________ _

I • • I

, , , , , , ----.----------~--------, , ,

: : 1 : I -+ I I

, , , , , , , , , , , , , ", I I I I I I • I I I I I • I I

----~---------------,---------------~----------.----y--------------·r--------------~--------------,--·------ ------,---------------I • I I I • I • I I I • I I • I

• I I I • I • I I,. I ., ,.., ., • I ,

I t I I I

• I I I • I I I I I , • I I

____________ ~ ______________ J _______________ J __________ _____ ~ _______________ & _______________ ~ ______________ ~ _ _____________ J _______________ J ______________ _

• I I I • I • I I I I " I I I I I I' t I I I I I " , , , I I • I I I I • • , I I I I I I • , I , I • • I I I _a_. ________ ._~--------------~---------------,---------------y---------------y---------------r-------------- ~--------------~---------------~---------------I I I I I I I , I I I I I I I I, I I I, I I I I' I I • I I I I I I I I I I I I I I ' I I.

I , • I I I I • •

-----------.--~--------------~-------------.-~---------------.. ----------.---.-------.-----.-~--------------~--.-----------~---------.-----~-----.----.----I I • , I I I • I

• I I • I I I I I' 'I , I, ., • I I

I I , I I I I • I I

I I • I I".

--------.-----~--------------~-.-------------~---------------i---------------i---------------~--------------~--------------~.--------------~---------------, I I I I I • I I • I I I I I I I I I I • I ,. I , , I I I I I I I • I "I

I I I I • I I I , • I I I , ,

t I I I • , , , I ___ ~ ________ •• ~ _________ M ___ .~ ____________ • __ ~ ______ • __ • _____ • _______________ • _____________ ._~ ______ ~ ______ .~ _________ • ____ ~ _____ • __ • ______ ~ __ • ___________ _

t I I • I I I I • I I , I I .,'

I I I • I '. I • I , I' • I I • I I • I I, J I I I I I I I • • • I I' I I I " I, I

--------------~---------------~---------------~.--------------i--------·-·----i---------------~----·----------}--------------i---·-----------~-------a-------, , I I I , I • • I I I I I I I I I

• I , • • I I I I • I , I I I

I I , • I I I , I I I •

, I I I • I I I I ----.---.. ----~ ... -----------~----.------.---~---------------.--.--------.---.---------------~------------.-~---------.-.--~---------------~-------------.-t • I I I I • • , , , I I , 'I I I I I I I. • I I I , •• • • I I I •• I I I I I I I I I 'I I I.

I , • I , I I I • •

o 100 200 300 400 500 600 700 800 900 1000

Volume (acre-ft)

c.. --..c en c a

-10 -Q)

0: co Q)-.J O}-.J CUw ~()

I C a

~ Q) -W

r-------~------~----_::-------:------~------~------~-------r-------rR • · • · · · • · · • · · • · · · · · ......... -- .... _ ............ t .. - .. --- .. -.... J .. ___ ......... 00 .. -i .... 00- -- - .......... ~ .... _ .... - _ .. -- ... :---- .. --- - .. - i .... -- ...... -. -- -,"-""'- -- .. ---· . • · · • · · • · · · · · • · · • · · • · · . -------- -~---------_&_---------~ .. ---------· . · . · , · , , , , , · . · . · , · . · . · . · . · . • • · . · . · . · .

· . · . · . · . · . · . · . · . • • · . · . • • · . · . · . · . · . · . · . · . -----------~- .. --------~---------_&_---------~--------- ..

· • · . . ---------- -----------.----------~---------- -----------~----------~---------- ----------~----------· · · • · · • · · • • · · · · • · · · · --------i----------- ----------f-----------~---------- · -- -- - - - - -- -1-- --- --- -- -.-- - -- ------· . ...... -.. _-- ....... --· • · · • · · • · · • · · · · · · · · · · .. ---------~----

• · • · · , ------ .. ---~--------

· . • • · . · . · . · . · . • • · . · . • • · . · . · . · . · . · . · . · . • • · . ----------~-------- .. -.-----------~----------~--------- .. • · · · · · • · · • · · • · · • · · • · · .

• • • • · · · · • · · · · · • · · · · · • · ----------~--- .. -.. ----

-~----------~----------T-----------~----------~----------T----------,-----------· .. · .. · .. · .. • • · . · . • • · . · . • • · . · . • • · . • • · . • • • • · .

C) C) LO

C) C) v

C) C) (')

C) C) N

C) C) .-

f-----------~----------~----------~==--~----i·----------~·r_--------~r_--------~t_--------~r_---tt-----t-C)

(ij) UO!lBA8/3

a? Q) lo-U co --Q)

E ::J

g.

)


110 .....

• , , ,

)

10 r··-··-···--·---------~---·------------------r---------.------.----~--------------.------· . ---------------------~-------.------------.-,--------. ---.------· · · · · • · · · • · · • · · • · · ·

, ,

$'1 · ------.-----~----------------------,---------------------~-------·-------·-----T----------------------r---------------.-----~-.-------------------I I I I , I I I I I · , , -.......

c o

1u > (I)

W

9

851

· . . · . , · . · . · . · · · · · , · • · · . . I • I I I

---------------------i---------------------.f-·.··.·--·-···-------~--------------·------I-------·--------------.--------------- ______ c _____________________ _ I I I t I I I I · • · · · · · •

· • , · • · It, I f I I I

------ --- --- --------- i- --- --- ---- -- ---- --- --1--- -- - - - --.- - - - --- - - - -:- --' - - - - - -- - - - - - - - - - - -1- - - - - - -- - - - - - - - - - - - - - -. --. - - - - -- --- - - - - - -- - - -:-.- - - --.- - - - -- - - - - - - --I I I I I • I I · • ·

o 5 10 15 20


25 30 35

g c o

l w

)


11 0 ::;::oA

10

1

8

o o o o o o o o o o o o o o

o o

---------------------~---------------.-----_&------------------.-.~.---.----------.-----,-----

______________ L _________ • ___________ ~ _________________ ___ _

o 0 o 0 o 0 o 0

o 0 o 0 o 0 o 0 o 0 o 0 o 0 o 0 o 0 o 0 o 0 o •••.................. { ............... . • •• j ••••••••••••••••••••• ~ ••••••••••••••••••••• j •••••••••••••••••••••• ~ •••••••••••••••••••••• o o o o

o o o o o o o

------------------~----.-----------------

o o o o o o o o o o o o o o o

o 0

---------------------~---------------------.----------------------~---------------------~---------------------o 0 o o o o o o o o

o o o o o

I I I I

••••••••••••••••••••• { •••••••••••••••••••••• j •••••••••••••••••••••• ~ ••••••••••••••••••••• j •••••••••••••••••••••• ~ ••••••••••••••••••••• ~ •••••••••••••••••••••• o o o o o o o o o o o o o o o o

• ___ w _______ • ________ , ____ • ________ •• _______ ,. ________ -------------~------------.--------,------_-_-_----------.r---.----.. -----------~------.--------------o o o o o

80~1--------~r_--------r---------T_--------;_--------_r--------_+--------~ o 2 4 6 8


10 12 14

g c o ~ 5; w


110 .

1

1

9

8

· · · · · • · · • · · · · · . . .. __ . ______ . ____ ._~ _______ ._. _____ . __ ~ ___________________ • ___________________ ~-------------------L---- • ____ • ______ ~ __________________ J ___________ • ______ _

· · · · · · · · ·

···················i···················.·············· .... ~---.-.--.--.--.--.~-.--.-----.. -.--.. -• • I I I I I I • I , I t I I · ..

-----.---.. -----.-!------.-----.. -.--.~-------.--.--.----, · · · · · , · · ,

· .. · .. · • · · • · · • · t I ,I' ---.-.-------------.-------.----.------ -------------------~------------------~------------------~-------------------· . · . · . · . · . · . · . · . · . · . · . • • · . · . , . · .

r···-··--··------··~----··-·---···--·-·f--··-·-··-···· -----f·--·-·--·--------··.--··-----·---------,----··--------.-.-~ .. ---.-----.. -.---. , I I I · .. · .. , .. · .. · ., · .. · , · · · , · • • I I ,

------------------~------------------,--.----------------y-------------------y-------------------~------------------~------------------,-----------.-------• · · • · , • · · • • • , · · 80 I i

o 1000 2000 3000 4000

Volume (acre-ft) 5000 6000 7000 8000

g c o

1u > Q)

ill

1

Elevation-Storage Relationship Mission Outlet to San Juan C. - CELL 12

, , , , , , , , , , , , , I I I I • I

, , , , , , , , , , , .-----------.-~--------------,-----------.---,------------.--~------------.--y----.---------- M __________ ~----_---------~---------------~----------- ___ _

I I • I • I I • I • I , I I I I I I I I , I , I I I I I I I I • I , " , , , , , , , ,

, , , , , , , , , , ,

, , , , , , , , , , , ,

, , I I I I I I

---------------~--------------,-------------- --------------y--------·_·----y---------------r------- -------~--------------,---------------,---------------, , , , o 0 , , , ,

I I I I I I •• I I I I., f t I I I I I I I , , , , , , I I I I

-.. -.. :-----.. --------.. ~- .. --- .. ----·-.. --~ .... -- ...... --- .. ----i-- .. -.. --.. ---.. -- .. i .... --- .. ---....... -- .. ~ .. ---- .. ---- .. -- .. -:------- .. ------ .. ~-- ...... -- .. -.. --- .... ~-- .... -.. -.... ------I I • I • I I I I I , I I I I I I

I I • I I I I • • I

• I • I I I I • I

• I I I • I I • • I • I I • I • I • • • I' I.,.

I • I , t I • , I

- - - - - - -- - -- -:-- - - - - - - - - - - -- - ~- - - -- - -- - - - - - - - ~ --- - - - - -- - - - - -- t -- - - - - - - - - -- -- - t -- -- - - - - -- - -- - -~ - - - - -- - - - - -- - - -:- - - - - - - - - - - - - - - ~ - - - -- - - -- - - - -- - ~-- - - - - - - - - - - - --I I • I • I I • • I I , I I I • I I I I I 'I. I , I I I I I I I , I I I I I I I I , I I • I I I I I I I I I I I I I • , , , , , , , , , I' I I I I I

I , I I I I I I I

- -- -- -- - -- --- -:- - --- - -- --- ---- ;-- --- ------ ----i ---- -- ------- -- t --------------- t ---------------;. ---------------:- --------------; ---------------;---------------I I I • I I I , I I I • I I I I • I

I I I • , I I I I , I I I I I • , I , • I • , I I I I • I • I I I I I I I' I I I I I I I

• I I I • I • I I I I I • I. I I I • • I I • I

..... -- ......... -.. ---- .. :·- .. -.. -.... --- .. -.. -~ ...... ----.... ·- .... · .. i- .. -.... -- .. -.. --- ..... i ........ -.. -...... -...... -i-.... -.... -.. -............ ~ .. -.. -..... -.. -- .......... :-- .... -- .. ----........ -~ .. -- ..... -.. ------ .. -i .... -- .... -.. ------ .. I I , I I I I I I I I I I • I • I I I I •• I • • I I' I I I I I I

I I I. I I • • I I I I I • I I I I • I I • I I • I , • I • f I f • I • I • I • I , I I

• I I • I • I I I I I I

o 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Volume (acre-ft)

g c o

~ (])

w

1

l

Elevation-Storage Relationship San Juan Canal to 23rd st. -CELL 13

, , , , , , , , , ,

, , , , , , , , , , , , , , , , , , , , • ____ • ___________________ , _________________________ -r __ -----------------------.----------------------~--------------------------r-------------------- -----, , , , , , , , , , , , , , , , , , , , , , ,

, , , , , , , , , , , , , , , , , , , , , , , .------------------------,-------------------------~--- -------------------.-------------------------,--------------------------r-------------------------, , , , , ,

, 0 ,

• 0 · , · . , , o . , o · , ,

-i------·------------------~--·-----------------------i-------------------------~--------------------------~-------------------------I I I I I I I I I I , ,. . ,.

o 0, , 0' , " , " . . , , o , o 0

------------------i------------------·------~--------------------------i-------------------------~--------------------------~-------------------------I I I I I I I I I I

• I I ' t I I I I I " I I • I

• I t I ,I " " I I I I I I I I 'I

• I I.

-----------------------i-----·---------------·----~-------------------------i-------------------------~--------------------------~-------------------------I I • I I I I • I I o. 0

" , 0' • • 0 • " , " 0 " . " , 0' , 0' •

-------------------------i-------------------------·~-------------------------i--·----------------------~--------------------------~-------------------------

o

I I I I I I , I • • I I • I I I , I I I I I • I I o , , · . , , • 0

o • • · . , o , , , . , , . ,

1000 2000 3000

Volume (acre-ft) 4000 5000 6000

g c o 15 > CD W

1

)

Elevation-Storage Relationship 23rd st. to Shary Rd. - CELL 14

· • · · · · · · · . .-----------------------.,------.------------------~-------------_.----_._-----· . · . · . · . · . · .

· · · · • · · · • · • - . . .a-------------------~--------------------------r-----___________________ _ · . · . · . · . · . · . · . · . · · · · · .

· · · · · · · · I I I I -----------------_._-----,- ----------------------~-------------------------y----- --------------------~--------------------------r------ -------------------I • I I · .. · . · . · . · · · · • · · . . ---------------------~-.-----------.-----------~--------------------------i-------------------------~--------------------------~-------------------------t , • • •

I I , I • · . · . · . · . · . · . · . · . · . I I I I I , • I I

------------------------i------------------·------~--- -----------------------.-------------------------;---- -----------------.----~-------------------------I I I I I I I I I , · . • • · . · · · · · · · . .

-------------------------~--.--------------.------.~-----·--------·--------·-·i---------------·---------~---------------.--.--.----~.-------------.. --.------I I • I I t I • I •

• I. • I I I I

I " • I •• I I •• • I • I I · • • · . . I • • I I

-------------------------i-------------------------~--------------------------1-------------------------1--------------------------~-------------------------

o

I I I I I I , • I I

2

.. . .. . .. . .. . .. . .. . .. . •• • .. . .. . .. . 4 6


8 10 12

g c o ~ > (!)

w

1

Elevation-Storage Relationship Shary Rd to Rio Grande Rd - CELL 15

I I I I · · · · · · · · ·

· , · · · · · · · · · · . . I I I •

~.--.----------.,.----------------.----.--.-.------~----.------~ y-----------------r----------------~-----------------r---------.--.---~----------------• • I • I t I I · . . I I It. · . • I I I • · . I I I I I · . I I I • · . I " I I • • I', I I',

I I I • I I I ,

• I I • . . I •

I I , t • I •

---------------.-----------------~----------------T-----------------r----------------~-----------------r----------------~----------------I I I I I I • • I • • , , , I • I " I I I I I.,

• I' I I • I I I I I I I. 'I , • I I. , I I •• I 'I • I • I I I. I ,I • I •

.................................. i .... -- -_ ... -- .................... i ......... -- ............... -- ... -:- ......................................... i ..... -_ .................. -_ ........ ~ ............................. -....... ~ ......... -- .............................. ~ ................ --_ ......... -:- ..... --. ---.... -_ ..... .. I I • I I I I • I I I I I • • I I I I 'I I • I I, I I I I I I I • I I •

• I , I I • I I I I I I · .. · .. · .. I • I I

................... -- ........ -~ .. ----...... -.... -- .. -.... i .............. -- .......... _- -:- ............ -.. -.... -- .... -i _ .... -- -........ --.... --.. ~ ---............. -.... -...... ~ .. -- ........ -.. -.. ----.... ~ .... _ .... _ ........ -_ .. -.. --: ............ -.................... .. , I I • I I I • I I I • I I , I I , I I I ', I I I I I I • I I 'I ". I 'I I I I I I I I. I · · · I • I I I I

...... -.. -.. -.. -- .......... ~ .......... -_ ........ _ .......... i .... -_ .. -.......... -- -- .. -:- .. -_ .. _ ...... -_ .. _ ........ i -.. --........ -_ .......... -.. ~ .. -.............. -............ ~ -.... -- ................ -.. --~ ............................... -: .......... ----.... -.. -... -.. I I I • I I , • I I • • I I I • I I I I 'I f I I I I. , I I I • I , I 'I I f I I I I • I I I I I • I I I I I I I I • I

• • I •

-.. -· ...... -.... -.. --- .. ~ .... -- ........ -- ......... -.... f---- .. ---- .... -........ -~ .. -- ....... -.... -.. --- .. -i-.... -........ -- .. --- ...... ~ .... -- .. -.... ·-.... -.. --~-- .. -- .. ------ .......... ~ .. -.... -...... --... -- .... ~ .. -...... -- ................ .. I I I I I I I • • I , • • I I , I , • • I I • I , I I I I I • I I I I • I I • t

I I I " I I' I I I • I I I , I • I I I I I , I • I I I • I I I 'I

o 200 400 600 800 1000 1200 1400 1600 1800

Volume (acre-ft)

£ ......... c o ~ > Q)

w

1

1

1

)

Elevation-Storage Relationship Rio Grande Rd to FM 1016 - CELL 16

· • · · · · · . . · · . .. -----------------------~-------------------------~------------------------_._-------------~ _______ J __________________________ L ________________________ _

· . . · . · . · . · , , , ,

· . , , , , , . , , · . . , , ---------------.---------,-------------------------~-- ~-------------------y-------------------------,--------------------------r-------------------------, · · , , · , · ·

· · , · , · ·

, , , . . . , , ,

I • I •

-------------------------~.- ----------------------~-------------------------!-------------------------~--------------------------~-------------------------, , .. · .. · .. · . · . · . · • • I I I I •

. -----------,-------------.-----------~.------------------------.-------------------------~--------------.. ----------r-------------------------I • I I • I • • I •

I I • • I • I I I I I • .. . .. . .. .

I , • I I

----------.. --.---~----------.----------.---~-------------------------.--.----------------------~--------------------------~.----.-------------------I I I I · .. , .. · .. · . , . · . · . ---------------------i--------------------------~-------------------------i-------------------------~--------------------------~--.----------------------I I I I ,

I I I I I .. . ., . .. . .. . .. . ., . I I • I •

-~---------.-------------~--------.----------.-----~-------------------------.-------------------------~---------------------.----~-------------------------, I • I • I I • • • I I I I I I I • I I I I ' I I I I I I I I I I I I I I I I I I

-.------.----------------~---.------------.--------~-----------------·_-·-----1-------------------------;--------------------.-----~-------------------------I • , I I

• • • I • .. . .. . .. . · • • I I I I I

---.---------------------~-------------------------~-------------------------.-------------------------~--------------------------~-------------------------

o

I I • I I I I ' • I I' • I I. • I I. • I I I I • I. • · . . · . ,

500 1000 1500

Volume (acre-ft) 2000 2500 3000

g c o

l w

1

Elevation-Storage Relationship FM 1016 to Mission Closure - CELL 17

, , , , , , , , , , , , , , , , , , , , , , I I' 'I I •

. ---------------~-----------------.---------------.~--- --------.-----------------.----------------~-----------------~----------------~----------------I' I I I I • I I I I ' I I I I I I I I I. I I I I , " , " , , , , , • I I • I I I • I I I •

---------~-----------------.----------------~----------------.-----------------~----------------~------------.----~----------------~----------------• I 'I • t • • I I I I I I I I • • I • I I I I • I I I I I , , , , , , , , , , , , ,

I I I '" ------.--.-.. --.. -.-.-... -.------.. -.... -.. --.-.--.~ .. -.-.----.---... -.. ----.. -.. -------.... -----.-.---~--.. -.. ---... -.--~----... -.. ----.. ------------... -.. • I I I I I. • I I I I ,. I I I I I I I I I I I I I I I I I I I , I I I I , , , I I • • I I • •

----------------.-----------------.----------------~----------------.-----------------~----------------~-----------------.------------.---~---.------------I I I I I I I I I I I I

I I " I • t I , , , , , . I r I I I

I I I I I I I • ________________ J ____ • __________ ._A. ________________ ~ _______________ .& _________________ ~ _______ • _____ • __ J ___ _____ • ______ ._~. _______________ ~ _______________ _

I • I I I I , • I I I I r I I I , I I • I I I I I I I I I • I ,I I I I I I' I' I

I I I I I I I I I ,

I ' "' I I I ,. r I f I

I I I I I I • I ________________ J _________________ ~ ______________ ._~ __ ______________ & _______________ ._L ________________ ~ ___ • _____________ L ______________ ._~ ___________ • ___ _

I I I , I I I I I I I , I I • , , I I • I I • • I I I I I I I I I I I • I I I I

• I' I I • I I, I I I I • I I , I I , I I I I I. I , I. I I • • I I I I ________ • __ • ____ J _______________ ._~ _________ •• _____ ~ __ • ____________ .& ___________ • _____ L ________ • ______ .J ____ ___________ ._L ___________ • ___ .~ ____ • ______ • ___ _ I I I I I I I I

o 500

I • • I I I I I I I I , I I ,

I " • , I I , I I I I , , , , , , , , ,

1000 1500 2000 2500

Volume (acre-ft) 3000

, ,

3500 4000 4500

APPENDIX C Flood Plain Maps

INDEX OF SHEETS

DESCRIPTION

FLOOD PLAIN MAP

SHEET No.

C-1. C-2. C-3. C-4. C-5. C-6. C-7. C-8

MISSION INLET FLOOD C-9 PROFILE - 10.25.50 AND 100 YEAR EVENTS FULL Y URBANIZED CONDITIONS (GATES CLOSED)

MISSION INLET FLOOD C-)O PROFILE - 10. 25. 50 ANO 100 YEAR EVENTS EX)STING CONDITIONS (GATES CLOSED)

·1~IHalff Associates ENGINEERS. ARCHH£CTS II SCIENTISTS" PLANIoI[RS .. SURVEYORS

<LO'!'.Dcr, Hr' "9'

r·· .. · \'\.-4:..:}."/( 1

..... .. \

\ "'.

\ ...

FLOOD PLAIN KEY MAP

FLOOD PLAIN MAPS AND FLOOD PROFILES FLOOD PROTECTION PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION, TEXAS

/gm~'-"'%:\ 'f~ (" : - . . .' ~~;; \~

_.-.-.

APPENDIX C

III CITY OF McALLEN

1~IHaIfT Associates ENCINEERS • ARCHITECTS. SCIENTISTS'" PlANNERS'" SURVEYORS

"~,Ii "."'"')1 ;:\~"nli';j(5i1~i;;,,;' n';'; 115 il'lO~ la'Aofs;

,1 ~ 6-V'~ ~"~

,<+'~ ~ ... ,.,." ,,~~ ,"'

,"

FLOOD PLAIN MAP FLOOD PROTECTION PLANNING STUDY

MISSION, TEXAS FOR SOUTHERN MCALLEN AND

I'~~~

~gJ ~"."~'" '~~D~ __ ,_

~ I, TOf"OIiIUrIn' nOWll1UollOl,11!'5 IIf ...........

STACIllIClU$£, $AN .,,0tI0. n. 2. fLOOD I'UIoI lIlTS &t.5ED C.

DlSlN) nftill TOI'O(;lII,U'KY W!TlI FUT1JIIE Fl.U.r I.NAIIZED II'UERSHW.

1. FlOOO Q..£nTlDMS fOR Tt£ IISSIaN IUT FlOOOII'AI ARE &t.SlD 011 ~SSLND U.BlAll LAllI USE CONOITIOICS I'mI GA rES Q.0S0l.

4, IlASEF\.OOOo.oj,TlDMS ~0It~ FlOOO'IU MIlE BASED 011 Tll!1IWC Allo.iIAE IIWJtSIOH fLOI' «)olO6.lOO CfS!.

LEGEND

FLOOD £L£YAnoNS

CELL 2

""'- """" tOO YR. 105.' 105.6 25 YR. 105.3 105.3 10 YR 105.1 105.1

~ '00 "'" ,uw" .. "' ....... fl.OOO LMTS

2!i ytI,A ll.BIo\T( DE'tD.0Pt«Ifl W>, ' F\.OOO U,rTS '~". . " "'" "--" .. "' .......

Fl.ooo 1.IoI1S * uvtt OYtIITilf'I'£O If 100 l'(.M fLOOO

C-2 -"t C-' -~ --_C~7~] C-5

C-8

N

:iiiiili!:4 .. ,,;-,;,7 Y'

SHEET C-l

CITY OF McALLEN --~~-------

!-! Halff Associates ENGINEERS. f,RCHITECTS • SCIENTISTS 0 f>t.ANNERS 0 SURVEYORS r~,(J(" ,v<) ,.,",

e \~nn\ I HQf\r"l rlnn n .. r 11$ iOIl~ 11" ~D' iii

FLOOD PLAIN MAP

FLOOD PROTECTION PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION, TEXAS

(e

GOOAI. NOTES.

I. TCIPOCIW'In' no ... IWICH, 1!'1S IIV n.UAIII STAm«IVSE. SAN ANIOIIO. Ill.

L flOOD PUIN lUTS I14stO 011 UlSI'lC liftS) TOI'OCIW'HY 11TH FUT(jII£ F'lLLr IRWIZ£D .ATElISMUI.

!. flOOD EUY4f1ON5 fOR fM[ ..s5ION N.£f f\.OODIIAY AlII! 8AS£O ON .I.SSUIm lAnu.rE UNO US( COIIlI1IIN5 11TH "rES Cl.OS£D.

4. IASl FUIOO IUYA1lONS 'OR I.UGIt I"I.OODIIAl AIlE. !lASED ON Til! 1II'1t M.l.OI'AII.£ 0I'ItRSICIN FlOW 10"O5.lOO CFSI.

LEGENO

FlOOD EL£VATIOMS

CEU, 2

"" ... "'''''' 100 YR. 105.6 105.6 25 YR. 105.3 IOS.J 10 YR. 105.1 1115.1

:---! 100 YE.t.IIlLTIU.TE D£VElJ)PWNT I . FlOOD LN'S

S .... ·. ..... 1 25 'fUR lA,.'''''[ IXI'£lOPllENT .;;.:;'::/j:'.::: _ 1'1.000 lMlS

10 YLUllLTMlI[ DEYElOl'WEHT '~~ __ J FlOOD LNTS

* LEY£[ OY£lffOl'I'fD It 100 TEN! HOOD

C-1 I Co]

C-5 C-6 C-)

N

SHEET C-2

CITY OF McALLEN ------ -'----'._-

1 ~ '"

!-! HaItI Associates ENGINEERS 0 ARCHITECTS. SCIENTISTS 0 PLANNERS 0 SURVEYORS , • .",', 0,' ""

r' \~".. .. I HOI',., ",,~ n", I~ .[10<': 1,)~::1


lJCl<J£N IIIU£R

"fTERNATKJNAL NRPMT

7

~ I. 10f"0GltV'llY nOWN YARCK, 1995 IT 'lLUo\W

ST.t.CMWSE. SM NrlTOfIO. Til.

l. ~~~~O:'N FUTIR F\.l.lY I.NMIIlm W"[ItSH[J).

1. fLOOD EL£'I4lKWS ,Oft T14E ~$OI IJrUT

~u:l ~ :TN1.~a.~'E to IIA5E n.ooo D..£Yj,TIONS nlll IWIIEII

~&~ ~oJ't.~.JOO CfS1.

LEGEND

flOOD EUVJ.1lOMS

CELL 2 "",no

100 YR. 105.' 25 YR. 105.3 10 YR. 105.1

"""" 10S.6 105.3 105.1

g ", ....... 'w" .......... : 'f\.00D LMTS

2S YEAR .... """"1£ DEVO.OI'M:II' ;; . fLOOD LMTS

;' '" ....... ,w" .. "'....., ROOD L"'S * L.£YU: 1JV£IIT0Pf'£D BY 100 I'EMI FlOOD

c-, c-, C-3

c-, C-5 C-G I-~-J CO,

N

~'7::::o.:f,,"; .. '''' 'j

SHEET C-3

FOR SOUTHERN MCALLEN AND MISSION, ~EXAS__ ~'~S7 ~~'Y ••• CIJY Or:JY1cALLE~

•••• =~= Haiti Associates

L. '. NG'.NEERS. ARCHITECTS. SClEN .. TlSTS. Pl..' ..... '"' .• SURVEYORS ',0011 ."~ "'"

- r;;~~j1\"i'\;:T~-'11100~ i'-~-7'i'5"----

FLOOD PLAIN MAP


~ I. TOI"OCIW'II'I' FlOIIN IUJt(H. 1," IIY "WAll

STACIlHOUSl, UN AHTotIO. TX.

2. FI.OOO f'UIII .... 'S &ism 011 DlSTNO 0"" TOI"CCItWHY fill" fUTlIIf: FlllY LfI8UIlDI .,UDtSHED.

1. f1,.OODD..[U'llONSFOIl TIlEWIS$OtIM.£T' fl.OODII'A' I#IE. IIA$[D 011 A$~ I.l.TW.TE L.AICI USi CQCIfTlON$ 111M ;l 1(S CLOSED.

" lAS[ FI.OOII l1.£VAfIONS FOR &lfGR

~~~ ~OII~T:&o CfSl.

LEGEND

flOOD n£VAT1ON5

CELL 1 EXlS1'Nl fUTUI£

100 YR. 105.' 105.6 25 va. 115.3 105.3 10 YR. 105.1 105.1

g '" "",u.'~"~""" flOOD LIlTS

2S 'f'EAIt 1.l.TW.T£ 0£Yfl.~ FlOOD 1..1.1$

'( 10 'f'EAIt IA.YWf[ 0£'fO.0I"II€If1' nOClll LJoIllS * 1.£Vtt00000T~BYlOOl'ENln.0CIII

;a-~---~~6 - c-r-.J

'---+~--tl-

N

SHEET C-4

CITY OF McALLEN

\

\ \ ';J.!~~~~~~~~!!~

i;.""';'''',',,,':;', M" p" ,0 ,00', ,'" "

fLOOD pLAIN MAP FLOOD 1'IloTtCflON pLJ\NNING STIlD'\' FOR SOUTllmt" ",CALl"''' ",,0 ""SS\ON.'rE

XAS

-------------------- -- -

~ t'1~.~~~T~8l tLl.l""

2. 1\.000 pV@ LIII'!~_!!~ o:.TII ~ ~~Il$iIllI'

• ~'fJ:~?t~$t." '" tf5l~afo'I .. ~(QlI ~ ';tr'Cil~~:r()ll~~ Cf$)·

~ f\.O(III~.lI(jIIS

cELL 1 ",,- ..

tOO 'i\'.. 105.6 105_6 l5 YlL 18S.J 105

3

\0 \'R. 105.1 lOS.!

:_', ,F\.i:f33""'$ ;fL, ~'(01t\f,._~(I(dl.~

'" ' flOOD lIftS ;;_i - " ..... ,,"""","""'.'" ~

'" """-,.,,,.--

I /" !UJOO ~!> * ..... --""'''''''''''''

II\-:-I---\ :-_~ _ ::-~-:~. -~-T] l --~ - _J--

I C-' -~

1'1

-~ .~'Fli-'

SllEE'f C-5

--;;...., \ 4[~-'~"

\:\, H ,~~~~"~~crrY OF M<ALl£N,

I el,~~"~~~,~~~!~,~, FLOOD PLAIN MAP a/~. ~

FLOOD PROTECTION PLANNING STUDY .~.- f.~. FOR SOUTHERN MCALLEN AND MISSION, TEXAS ~,:~~ ~~,

~----~----- ..

~ I. ~~ ~onAH=-T~ liT WLLJA/II

2.. f1.000 ..... LMTS ..... 5£0 011 DlSTJIG n~ TOI"OGIW'MY ... lM FUTtJI£ FlLLT IJI8AtIZm W..,T[ItSII[ll.

S. FLOOD n£VA 1'lON5 ,Oft TlI: YSSION KCT

rrutl ~= ::l~~a.~':T[ 4. lAS[ F\.OCIO B.£'IAllONS 'OA IWItEII

FlOOOlll ... , AIlE eASf:O ON TIE. IHC 4UOW*E 0I'IEJtSI)N FLOW 1Q.,0l,.30Q Cf$).

LEGEND

FLOOD atVATlONS

CEIL 2

"" ... """" 100 YR. 105.6 105.6 2S YR. 105.3 105.3 10 YR 105.1 105.1

g...

......... . 100 YEAIIILT ..... TE DlYn.OPMEIIT FlOOD LIlTS

2!i Y£.UI !LauTE DEVnOl"EJO ,,' __ '. flOOD lVTS

:,' - 10 YEAJt lJ. TMI. T[ Dl'IELOPM[~ ;, flOOD lMrS * I.£\IEE O\IERTIPI'£D BT 100 YEAR fLOOO

C-3

'-----+-~If_C::_L ~~-l

N

1iI...'" !!"

so.n "';f('

SHEET C-6

CITY OF McALLEN

i-i Halff Associates ENGINEERS. ARCHITECTS. SC!ENTISTS 0 PLANNERS 0 SURVEYORS

'.I",,, ,"' IJ"

'~ ',~",~·\j,illii·';'~ ",," r.,,; .6 loai:; ~'~l' 1ii

FLOOD PLAIN MAP FLOOD PROTECTION PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION, TEXAS

---- --- -_. ----

COERAI. NOTES.

I. TOI"OCIIAI'IIY non fIWICH. 1995 '" 'AUAW SfWIICUS£, SAN ¥lTOMO. fit.

2. nOOD PUIN lMT5 at.$EO OM EllS r"'IG Utt5ITOf'OCIIoU'Ifr .,TM fUTtIR£ flUY 1A!114MltD W,t,T[ft5H[ll,

1. ~~.W~no:~g"~~S=t.N1TE UII) USE COtCllTIOJCi 11TH GATES Q.OS(o.

4. IASII'lOOO €l.E'I.l.TIONS FOIl UIGIt FlOOOtl,V .tJIIE !A.SEO Ott Tl£ INC AU.o.A8LE crvEASION flOW IQ'IQ6..}OO as,.

LEGEND

nooo ELE ..... TOIS

CELL 2

"'''''' "'"'" 100 YR 105_6 IDS.' 2S YR.. 105.3 105.3 10 YR. 105.1 105J

~ 100 't'E.4R ll.TIU.f( D(VELOf'1oEJIT

""" "'" 2!! rEAR ll.BU.fi OEVtlJlPt€JIT FlOOD LNTS

•. < ' 10 'ft..I.R tLfIIU,t£ DEVELCftI(NT / FlOOD lilli'S * LEYU OV£RTtlf'I'fD Br 100 'EN! flOOD

~··cc~T~ L:"_~ r -I

C-7 !

N

. 5S' ''''''', .. ,IT,lL _---fi

SHEET C-7

~~~ -=~~-~~:' --- OF McALLEN

IIIHaifT Associates ENGINEERS 0 ARCHITECTS 0 SCIENTISTS 0 PLANNERS 0 SURVEYORS ~:;,O(;N AVO 141'11 fOal=; rp· :Ii- ~R

f" rlnl"l {lIial',. rI" ..... Oor 1Q

N 16586700

GDERAL NOTES.

I. TOPOGIlAPHY FLOIfli MARCH. 1995 BY WR.UAW STACKHOOSE. S.<N ANTOIIO. TX.

2. FLOOD PLAIN L""'TS BASED 011 EXISTING II99!\) TOI'OGIIAPHY WITH FUTURE FULLY lIUIAMZED WATERSH£D.

3. FLOOD aEVATlONS FOR THE IofISSION RET FLOOOWAY ARE BASED ON ASSUMED ULT .. ATE LAND US£ CONDITIONS WlTM GATES CLOSED.

4. eASE FLOOD ELEVATIONS FOR BAMCER FLOODWA Y ARE BASED ON THE I8WC ALLOWABLE DIVERSION FLOW (0,106.300 CFS).

LEGEND

FLOOD ELEVATIONS

CELL 2 EXlSTt«l FUTURE

100 YR. IOS.6 105.6 25 YR. 105.3 105.3 10 YR. lOS~ IOS.1

~ 100 YEAR ULTIiATE OEVE!.CPMEIIT

.•• ' .. ;:.; .. FLOOD LIMTS

...•.•.•••. ' ..•.........•....••••... : .•..•.•••...•....•.•. ' . :IS vEAl! UL TIIoI4TE DEVELOPUEHT ';"/.'. FLOOD LilTS

• ;;... 10 YEAR ULTliATE OEVEl.OPUENT ::;>:<~/?:,(".":,:,, ;., FLOOO lNrS * LEVEE OVERTOPPED BY 100 YEAR FLOOD

C-l C-2 C-3

C-4 c-s C-G

C-8

N

! i

-seAL E IN FEET

N 16571700

SHEET C-7

-~ III CITY OF McALLEN

•• =~=HaIfT Associates £~r~~EEFt~ ~~,~~CHITECTS • SCIENTISTS 0 PLANNERS· SURVEYORS

',;n;;\r11i:\T\~I'i';"" r'I", 'Q JMI'; IIT-f.ll\l


MISSION, TEXAS FOR SOUTHERN MCALLEN AND , ,~-::

----.--

~.~ ~~"'~~'~~ "t~!...>

~ ~

ODEJW. ICIt£So

,. T~ Flon IWICH. 1'J!') !IT .... U ..... STjQ,MOU$(, SMt .."fOllO. TX.

1. FlOOD PI...tI't LKTS IIA$C) ON ElIISTNl (lml TOI'OGIW'HY liN FUlLl!( FtUY I.fIIWIZED .UEJlSll[l).

1. FlOOD [l£W"llONS FOIl! TIl[ IIS~ M.tT FlOOD',""f AIlE IASO ON USlIofED tA.TIM4TE UICI US( C0MlI1lONS II'HI Q,t, Tts ClOS£O .

... lIS( FUIOD EUYAfIOHS 'OIIIANUR FLOODWU MIl! IIAStD ON Til[ ewe: 4LL0I'''II.£ DfVOtSIOH now IO"06..JOO CF~.

~ rLOOO ELEV.lllOltl:

CELL 2

"" ... """" 100 YR. lOS.6 JD5.6 25 YR. 105.3 105.3 10 YR., 105.1 105.1

g 100 'rUJI l.\.UU,TE DEVll~T ROOD l ... TS

25 TUR l1.nu.TE [I[V[UlP'-:IIT flOOD LMTS

, to Y[..UIl.\.TIIATE D£YD,OI't€IH nooo lllolTS * LEV(.[ OYEIITOI'!'£CI aT 11)0 rEAR FlOOO

t~:~-r .. _. :_:-f::; -1 c-o j

N

C-7

SHEET C-8

CITY OF McALLEN =='--- -------------

r 128.00

I 12~.00

120.00

104.00

100.00

96.00

LEGEND

f TOP OF ROAD = WATER SURF ACE

...... 1 .....

uou o~ -u

« "'D-"-IZ liZ. 0::: 11:::10:::

"I r I r r r r r r r r

52000.00 ~8oo0.00 r I

!~!HaItf Associates ENGINEERS 0 ARCHITECTS. SCIENTISTS 0 PlA~ERS 0 SURVEYORS

L~...!~

-' w f- >-' « DO

'" Z OJ

'" « f-D

I:. u 0 U

L :> « OJ

w 0 uo +- 0 <r 0 « "" "" 0 w <r f-

z 0 ~ "" co -' V>

'" en :> uo

Z 0 f-

a >- ::: "- "" '" w

<r "" « '" -'

0 « '" 0 OJ U f-

ir I OJ -' '" -,

<! OJ

'" D- O "- Z -, 0

I I 'I I I « I I Vl

CIMARRON 1"1 I I PALM VIEW I

I AIRPORT T

I-I

GOLF n COURSE

I. E'IEE

f 101 •2

'---y - --------T-i~~..:jI t------Jl-------- -- -1- - -,~- - - - t- '-' -------: _______ ------"'1' --i----t- -----7

. 50 YR 1,125 YR

102.0

i 100•7

I

t~Y~~_+----t_---~~000.00 ~0000.00 36000.00 32000.00 28000.00 2~000.00 20000.00 16000.00 12000.00 8000.00 ~ooo.oo 0.00

r r I ___ ~ _____ ~_ -------.L_ ---.l.

DISTANCE IN FEET MISSION INLET FLOOD PROFILE

10, 25, 50 AND 100 YEAR EVENT FULLY URBANIZED CONDITIONS (GATES CLOSED)


..l ~ I I I

C-9

CITY OF McALLEN

128.00

124.00.

120.00 ...... 1-,

cow c) L;

"-' <{ 2(L U. 12 lIZ a: II:=lo::

" t " I I , I , I , I

- l- • h" " J " ..... \ : ""~"

w '" 0 « 2 0

a:

'" 0>-a:

0 <i

it' I CO

CIMARRON PALM VIEW GOLF

--" w cr >- ...: <i OJ Z c'

co co <{ u u '" '"

D 1::

:> <{ cr L co +- 0 >-'" '" 0 W cr Vl "' --" !C!

0 >-

'" cD w en '" 2 V> --" ;:: u. '" «

'" >-0 ::J U ::J a: '"

-, <{

0 --" -, ::J 0 U. (L 2

I I I "I I I <( V>

I AIRPORT I n COURSE II I-I , I'

I V,

~~~~--~---------t----r-~'-1-----'~I~tt~~~~~~~----t---------~-------t--------~--------t---------~------~--------~--------l---------1--LL I J U ,

, ,

. "I \1' 1\ ,~'" '. ; ,; ... II • \ I I I ' " , "

I I' I I I I I' \ "

II 'v' I ,J " \ I ~ ~ - -.,,1 I

I ,,, - I I

---,11 I 1'1 1 ,'" I'" ... \) I I I f- __ ..:._--,_ :::: \ ',,/ '- /' r "1 . ;! 109.4 1'1 I I .... ,_--...... \ V TOP

INORTH LEvE

W '--1"- :::: \ "1--\--,- ", -l 10800 10 .6 • I I 1 J '- ,- -"'--'" ./ /J- TOP SOUTH W • I I I I" : \. 1':' ...

I I \ I \ \ ...... ,I \ \ r_ J' I I

LEVEE

104.00

100.00

96.00

LEGEND

'1' TOP OF ROAD

.2 WATER SURF ACE

I I ,_.' 1 • "--r1('"~''' --.1 I I I I I ....... ' \ .. \ I I "" .... '" , ".:

~~t ~,\: \ \ " !: "',,"- '-- \.. .. ;'" \ , .....

_TI- __ ~-'!l..:.lll 1 t ... -- --------t------]:.. ... I \ ' I I \"'\, ..... ( '-'\

1.1- !,~",:- _____ =-~------------'-- I ______ 1 I 1 100 YR'I • '- / .- ..l." .... ~. - ~----=--... -~~---:'T~~ \ .. \. /

52000.00 48000.00 ..L I

'1' 101.2

- ---,-·--~II 'I 1 ~ - - -I- ----t - - - -I--- -~ l= - - ---t -D~I

t 100.7

r- ------------fT-----2s-y;;7 i;, -;RY+-- __ '1'

I

" :1'0 YR~

102.0

44000.00 40000.00 36000.00 32000.00 28000.00 24000.00 20000.00 16000.00 12000.00 ..L

8000.00 L

4000.00 0.00 I , t I I I I

DIST ANCE IN FEET MISSION INLET FLOOD PROFILE

I I

"",",,7~

I-I Half I Associates

10, 25, 50 AND 100 YEAR EVENT EXISTING CONDITIONS (GATES CLOSED)


C-IO·

CITY OF MoALLEN j ENGINEERS D ARCHITECTS 0 SCIENTISTS 0 PLANNERS" SLflVEYORS

~'.:..:!!... -~-~--~-~

.-

APPENDIX D SCS Curve Number Computations

CLIENT: City of McAllen

PROJECT: McAllen Drainage Study


4000 Fossil Creek Boulevard

Fort Worth, Texas 76137

817·847·1422

COMPARISON OF EXISTING VS FULLY DEVELOPED

SCS CURVE NUMBER

Area Are. Existing Area Area Fully

Number (sq. mi.) Conditions Number (sq. mi.) Urbanized CN CN

MI·l 0.49 74.9 MI·l 0.49 74.9

MI·2 0.62 74.9 MI·2 0.62 74.9

MI·4 0.34 77.0 MI·4 0.34 77.0

MI·5 0.13 77.0 MI·5 0.13 77.0

MI·6 0.80 78.1 MI·6 0.80 78.1

MI·7 0.77 83.8 MI·7 0.77 83.8

MI·8 0.57 81.1 MI·8 0.57 81.1

MI·9A 0.39 84.4 MI·9A 0.39 88.0

MI·98 1.01 76.1 MI·98 1.01 83.6

MI·9C 0.29 83.0 MI·9C 0.29 83.0

MI·l0A 0.54 83.2 MI·l0A 0.54 83.2

MI·l08 0.42 77.0 MI-l08 0.42 77.0

MI·l0C 0.35 84.0 MI·l0C 0.35 84.0

MI·100 0.54 78.0 MI·l0D 0.54 78.0

MI·llA 1.25 77.9 MI·llA 1.25 81.2

MI·118 1.50 77.0 MI· 11 8 1.50 77.0

MI·13 0.73 76.5 MI·13 0.73 80.4

MI·14 0.94 80.2 MI·14 0.94 82.6

MI·15 1.17 82.4 MI·15 1.17 82.4

MI·16 0.62 71.8 MI·16 0.62 78.1

MI·17 0.36 82.6 MI·17 0.36 83.3

MI·18 3.19 82.4 MI·18 3.19 82.4

MI·19 0.47 83.0 MI·19 0.47 83.0

MI·20 0.37 81.0 MI·20 0.37 85.3

MS·l 0.37 72.6 MS-l 0.37 80.3

MS·2A 0.53 88.5 MS·2A 0.53 88.5

MS·28 0.82 80.1 MS·28 0.82 80.1

MS·2C 1.39 79.8 MS·2C 1.39 79.8

MS·3A 0.82 82.0 MS·3A 0.82 84.3

MS·38 0.68 75.7 MS·38 0.68 78.8

MS·4A 0.70 79.1 MS·4A 0.70 79.1

MS·48 0.54 78.1 MS·48 0.54 78.1

MC·1A 1.39 85.1 MC·1A 1.39 88.3

MC·18 1.52 72.5 MC·18 1.51 78.2

MC·1C 0.21 74.8 MC·1C 0.21 79.4

MC·1D 0.07 66.2 MC·1D 0.07 76.3

MC·2A 0.82 85.6 MC·2A 0.62 85.6

MC·2B 0.37 90.6 MC·28 0.37 90.6

MC·3 0.60 80.2 MC·3 0.60 81.2

CNEXIST.XLS 12/14/95 7:39 PM

Difference

0.0

0.0

0.0

0.0

0.0

0.0

0.0

3.7

7.5

0.0

0.0

0.0

0.0

0.0

3.3

0.0

3.9

2.4

0.0

6.3

0.7

0.0

0.0

4.4

7.7

0.0

0.0

0.0

2.3

3.1

0.0

0.0

3.2

5.7

4.6

10.2

0.0

0.0

1.0




4000 Fossil Creek. Boulevard

Fort Worth, Toxas 76137

817-847·1422


SCS CURVE NUMBER

Area Area Existing Area Area Fully

Number 'sq. mi.) Conditions Number 'sq. ml.) Urbanized CN CN

MC·4A 2.02 74.8 MC·4A 2.02 82.7

MC·4B 0,42 80.3 MC·4B 0.42 84.5

R·2 0.42 78.8 R·2 0.42 79.8

R·3 0.10 75.3 R·3 0.10 75.3

R·4 0.41 81.0 R-4 0.41 81.0

R-5A 0.13 73.7 R·5A 0.13 78.3

R·58 0.23 72.2 R·5B 0.23 72.2

R-6 0.82 73.9 R·6 0.82 77.9

R·9 2.50 75.8 R·9 2.50 78.7

R·l0 0.64 73.6 R·l0 0.64 78.7

R·ll 0.97 77.7 R·ll 0.97 78.7

R·13 2.77 69.9 R·13 2.77 76.5

R·14 0.32 66.8 R·14 0.32 76.3

R·15 1.85 74.1 R·15 1.85 74.7

El 0.26 73.6 El 0.26 73.6

E2 0.49 72.1 E2 0.49 73.2

E3 0.44 69.4 E3 0.44 70.3

E4 0.14 77.2 E4 0.14 77.2

ES 0.35 71.S E5 0.35 71.S

E6 0.21 74.9 E6 0.21 74.9

E7 0.34 76.1 E7 0.34 76.1

E8 0.19 76.0 E8 0.19 76.0

E9 0.22 84.5 E9 0.22 84.5

El0 0.25 78.0 El0 0.25 78.0

Ell 0.19 56.0 Ell 0.19 76.3

E12 0.15 61.4 E12 0.15 76.8

E13 0.17 57.0 E13 0.17 76.8

E14 2.52 74.9 E14 2.52 75.2

E15 0.50 73.3 E15 0.50 76.0

E16 2.24 70.1 E16 2.24 71.6

E17 0.27 76.5 E17 0.27 76.5

E18 0.56 74.3 E18 0.56 74.3

E19 0.36 79.1 E19 0.36 79.3

E20A 2.05 76.9 E20A 2.0S 76.9

E20B 1.24 75.8 E20B 1.24 76.0

E21 0.10 82.4 E2l 0.10 82.4

E22 1.53 81.2 E22 1.53 83.3

E23 0.52 76.6 E23 0.52 82.9

E24 0.28 81.7 E24 0.28 81.7

E25 0.25 73.7 E25 0.25 81.5


Difference

7.8

4.2

1.0

0.0

0.0

4.6

0.0

4.0

2.9

5.1

1.0

6.5

9.5

0.6

0.0

1 .1

0.9

0.0

0.0

0.0

0.0

0.0

0.0

0.0

20.3

15.4

19.8

0.3

2.7

1.4

0.0

0.0

0.2

0.0

0.2

0.0

2.1

6.3

0.0

7.8






817-847-1422


SCS CURVE NUMBER

Ar •• Area EXisting Area Area Fully

Number (sq. mI.) Conditions Number (sq_ml.) Urbanized CN CN

E26 0.24 84.4 E26 0.24 84.4

E27 0.26 76.3 E27 0.26 76.3

ESI 0_51 82.7 ESI 0_51 82.7

Total 59.1 Total 59.1

TZ-l 0.75 81.7 TZ-l 0.75 87.8

TZ-2 0.68 83.2 TZ-2 0.68 92.9

TZ-3 0.91 81.2 TZ-3 0.91 89.5

TZ-4 0_61 79.8 TZ-4 0.61 88.8

TZ-5 1.74 82.7 TZ-5 1.74 85.0

TZ-6A 0.57 83.0 TZ-6A 0.57 89.6

TZ-68 0.64 84_0 TZ-68 0.64 92.5

TZ-6C 0_58 84_5 TZ-6C 0.58 92.6

TZ-6D 0_18 88.8 TZ-60 0.18 91.5

TZ-6E 0_51 84_7 TZ-6E 0.51 92.8

TZ-6F 0.55 76.8 TZ-6F 0.55 89.8

TZ-7 0.69 77.2 TZ-7 0.69 90.5

TZ-8 2.36 79.4 TZ-8 2.36 89.1

TZ-9 1.06 80.0 TZ-9 1.06 91.3

TZ-l0A 1.83 82_8 TZ-l0A 1.83 88.0

TZ-l08 0.59 83.2 TZ-l08 0.59 86.8

TZ-llA 0.67 80.3 TZ-llA 0.67 82.6

TZ-118 1.03 80.0 TZ-118 1.03 81.4

TZ-ll C 0.23 84.5 TZ-l1 C 0_23 86.2

Total 16.18 16.18


Difference

0.0

0_0

0.0

6.1

9.7

8.2

9.0

2.3

6_6

8_5

8_1

2.7

8.1

13.0

13.3

9.7

11.3

5.1

3.6

2.3

1.4

1.7





817·847·1422


MISSION FLOODWAY DRAINAGE AREA· FULLY DEVELOPED

LAND USE FOR AREA NUMBER

SUMMARY

~ "! - -Drainage Future ..!. .. l Are. a :li ~ :! Area Contitions ~ c:

Number Isq. ml.l CN .. .. .<: ~ E .. ~ ~

.... E ~ ~ , .. .. ~] o ~

0: 0: uo

MI·l 0.49 74.9 0 0 0

MI·2 0.62 74.9 0 0 0 0

MI·4 0.34 77.0 0 0 0 0

MI·5 0.13 77.0 0 0 0 0

MI·6 0.80 78.1 0 0 0 0

MI-7 0.77 83.8 237 0 0 0

MI-8 0.57 81.1 363 0 0 0

MI·9A 0.39 88.0 62 0 89 23

MI·9B 1.01 83.6 275 0 65 65

MI·9C 0.29 83.0 0 0 0 0

MI·l0A 0.54 83.2 0 0 0 4

MI·l08 0.42 77.0 0 0 0 0

MI·l0C 0.35 84.0 0 0 0 0

MI·l00 0.54 78.0 0 0 0 0

MI·llA 1.25 81.2 640 0 0 0

MI·118 1.50 77.0 0 0 0 0

MI·13 0.73 80.4 449 0 0 0

MI·14 0.94 82.6 247 0 0 0

MI·15 1.17 82.4 15 0 0 0

MI·16 0.62 78.1 321 64 0 0

MI·17 0.36 83.3 0 98 0 0

MI·18 3.19 82.4 149 63 0 0

MI·19 0.47 83.0 32 194 0 0

MI·20 0.37 85.3 158 79 0 0

MS·l 0.37 80.3 188 0 0 49

MS·2A 0.53 88.5 51 0 0 237

MS·2B 0.82 80.1 346 0 0 131

MS·2C 1.39 79.8 632 0 0 178

MS·3A 0.82 84.3 333 0 192 0

MS·3B 0.68 78.8 337 0 39 20

MS·4A 0.70 79.1 341 0 0 86

MS·4B 0.54 78.1 321 0 0 0

MC·1A 1.39 88.3 80 0 160 569

MC·1B 1.51 78.2 851 0 0 48

MC·1C 0.21 79.4 134 0 0 0

MC·l0 0.07 76.3 45 0 0 0

MC·2A 0.82 85.6 173 0 302 0

MC·2B 0.37 90.6 0 0 237 0

CNFUT.XLS 12/14/95 7:45 PM

OATE: 12/95

AVO: 14191

FILE: MASTER

EMP: ES,DW,MM

CH

.. ..,

I .. .. l

Q. .. -~

.2 .. .. .., ~ u 0 - .. > ED U 0 .. .., u = 0 .. ~ i " .0'<: ~ ~ ..,

~ , u ~u

c a g g ::; ... o..CIl '" 0 0 0 314 31 0 282

0 0 0 397 40 0 357

0 0 0 217 0 0 217

0 0 0 83 0 0 83

0 0 269 243 26 0 486

256 0 0 0 99 0 394

0 0 0 0 195 0 168

76 0 0 0 62 0 187

242 0 0 0 323 0 323

186 0 0 0 37 0 149

342 0 0 0 69 0 277

269 0 0 0 215 0 54

224 0 0 0 22 0 202

346 0 0 0 242 0 104

160 0 0 0 400 0 400

960 0 0 0 768 0 192

19 0 0 0 280 0 187

355 0 0 0 180 0 421

734 0 0 0 150 150 449

12 0 0 0 298 20 79

133 0 0 0 35 0 196

1,830 0 0 0 510 102 1,429

75 0 0 0 45 15 241

0 0 0 0 0 47 189

0 0 0 0 213 0 24

0 51 0 0 170 0 170

0 0 0 0 472 0 52

0 80 0 0 801 0 89

0 0 0 0 367 0 157

0 21 0 0 392 0 44

0 0 0 426 0 22

0 24 0 0 276 0 69

0 80 0 0 801 0 89

0 0 68 0 773 0 193

0 0 0 0 94 0 40

0 0 0 0 45 0 0

0 14 35 0 236 0 288

0 0 0 0 180 0 57





817·847·1422


MISSION FLOODWAY DRAINAGE AREA· FULLY DEVELOPED


SUMMARY

~ N - -Drainage Future ;i; ;i; .. 'ii

Area !ii 'll Area Contitions E E ~

Number ~E .. .. E .. (sq. mI.l CN ~ :!1 .. " E U

" ~ ~ .. " ~1! 0::

a: a: uo MC·3 0.60 81.2 150 0 77 61

MC·4A 2.02 82.7 931 0 0 362

MC·48 0.42 84.5 170 0 0 99

R·2 0.42 79.8 172 0 0 59

R·3 0.10 75.3 0 0 0 0

R·4 0.41 81.0 167 0 0 59

R·5A 0.13 78.3 40 a 0 23

R·5B 0.23 72.2 49 a a 21

R·6 0.82 77.9 378 0 0 42

R·9 2.50 78.7 1,200 0 0 320

R·l0 0.64 78.7 307 0 0 82

R·ll 0.97 78.7 515 a a 53

R·13 2.77 76.5 461 576 0 160

R·14 0.32 76.3 205 0 0 0

R·15 1.85 74.7 426 616 0 0

El 0.26 73.6 83 0 0 17

E2 0.49 73.2 53 130 0 0

E3 0.44 70.3 0 253 0 0

E4 0.14 77.2 47 0 0 21

E5 0.35 71.5 146 0 0 0

E6 0.21 74.9 121 0 0 0

E7 0.34 76.1 187 0 0 0

E8 0.19 76.0 116 0 0 0

E9 0.22 84.5 28 0 0 85

El0 0.25 78.0 128 0 0 0

Ell 0.19 76.3 122 0 0 0

E12 0.15 76.8 96 0 0 0

E13 0.17 76.8 109 0 0 0

E14 2.52 75.2 667 474 0 0

E15 0.50 76.0 305 0 0 0

E16 2.24 71.6 100 1,334 0 0

E17 0.27 76.5 138 0 0 17

E18 0.56 74.3 39 274 0 45

E19 0.36 79.3 185 0 0 45

E20A 2.05 76.9 784 164 0 56

E20B 1.24 76.0 575 174 0 45

E21 0.10 82.4 38 0 0 26

E22 1.53 83.3 313 0 0 79

E23 0.52 82.9 0 113 0 25

CNFUT.XLS 12/14/957:45 PM

" ."

e .. .. 'C C. .. ~ " 0

" -.!! C 'ii

." ~ U 0 > .. ." U =~ - .. .. 'C ~ 5 ."

i~ 9 '§ U C Q,C/) !.u :>

0 31 65 0

0 0 0 0

0 0 0 0

0 0 38 172

0 a 64 0

0 a 36 a a a 20 a 0 0 77 0

0 42 63 0

0 0 80 0

0 0 21 a a 53 0 a

452 124 0 a 0 0 0 0

142 0 0 0

17 0 50 83

61 70 0 0

0 0 28 0

0 0 21 0

0 0 78 0

0 0 13 0

0 31 0 0

0 6 0 0

0 28 0 0

32 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

473 0 0 0

0 0 16 0

0 0 0 0

0 0 17 0

0 0 0 0

0 0 0 0

203 0 105 0

0 0 0 0

0 0 0 0

588 0 0 0

195 0 0 0

ID

~ 307

1,034

180

215

19

197

75

140

420

1,600

410

528

1,596

205

1,066

166

304

282

85

224

134

207

122

141

128

122

91

103

1,452

310 1,434

173

358

230

1,050

794

64

0

15

DATE: 12/95

AVO: 14191

FILE: MASTER

EMP: ES,DW,MM

CH

U 0

~ ~ 0 77

0 259

a 89

0 54

0 45

a 66

0 8

0 7

0 105

0 a a 0

0 93

0 177

0 0

0 118

0 0

0 9

0 0

0 5

0 0

0 0

0 11

0 0

0 0

0 32

122 0

91 5

103 5

1,452 32

0 10

0 0

0 0

0 0

0 0

197 66

0 0

0 0

979 0

251 67

CLIENT: City of MCAllen




817-847-1422


MISSION FLOOOWAY DRAINAGE AREA- FULLY DEVELOPED


SUMMARY

~ N - -Drainage Future .l.

~ G i Area a ~ii Area Contitions ~ o "C G

Number G G .<: ~ E G (sq. mI.) eN .",

~ .... E U -;; ~ ~ .. G ~J 0::

'" '" uo E24 0.28 81.7 0 42 0 3

E25 0.25 81.5 28 0 0 0

E26 0.24 84.4 0 0 0 0

E27 0.26 76.3 166 0 0 0

ESl 0.51 82.7 22 0 0 0

59.1

Outside Trade Zone 16544 4648 1160 3213

% 43.8% 12.3% 3.1% 8.5%

TZ-l 0.75 87.8 240 120 0

TZ-2 0.68 92.9 22 109 304

TZ-3 0.91 89.5 247 0 339

TZ-4 0.61 88.8 273 0 117

TZ-5 1.74 85.0 668 0 319

TZ-6A 0.57 89.6 172 193 0

TZ-68 0.64 92.5 0 410 0

TZ-6C 0.58 92.6 0 371 0

TZ-6D 0.18 91.5 0 115 0

TZ-6E 0.51 92.8 0 326 0

TZ-6F 0.55 89.8 88 224 0

TZ-7 0.69 90.5 0 442 0

TZ-8 2.36 89.1 140 1,285 0

TZ-9 1.06 91.3 0 339 0

TZ-l0A 1.83 88.0 586 0 0

TZ-l0B 0.59 86.8 378 0 0

TZ-l1A 0.67 82.6 430 0 0

TZ-llB 1.03 81.4 659 0 0

TZ-ll C 0.23 86.2 147 0 0

Trade Zone Subtotal 4047.8 3935 1079

% 39.1% 38.0% 10.4%

16.18

f e £ -.!! ..

~ u 0 .", ~ u .. .", :: 0

~~ .. ~. .0'<: ~ u

Q.CI)

134 0

132 0

154 0

0 0

307 0

0 9106 656

0.0% 24.1% 1.7%

0 120 0

0 0 0

0 0 0

0 0 0

0 0 15

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 40

0 0 0

0 0 0

339 0 0

586 0 0

0 0 0

0 0 0

0 0 0

0 0 0

925 120 55

8.9% 1.2% 0.5%

OVERALL

%

20591

42.8%

4648 5095 4292 925 9226 711

9.6% 10.6% 8.9% 1.9% 19.2% 1.5%

CNFUT.XLS 12/14/95 7:45 PM

.. .! G

C - G ~ ~ :'u

0

0

0

0

0

1165

3.1%

0

0

0

0

0

0

0

0

0

0

0

0

85

0

0

0

0

0

0

85

0.8%

1250

2.6%

.", G a.

.!2 G > G

.", c:

::>

0

0

0

0

0

1509

4.0%

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.0%

1509

3.1%

'" $ 10

24

0

166

54

25506

67.5%

0

22

92

0

334

18

41

19

52

0

18

353

453

237

234

0

172

329

7

2381.9

23.0%

27888

57.9%

DATE:

AVO:

FILE:

EMP:

U

$ 159

120

31

0

88

3927

10.4%

0

0

0

0

0

0

0

0

0

0

0

0

76

0

0

0

0

33

0

108.5

1.0%

4035

8.4%

12/95

14191

MASTER

ES,DW,MM

CH

c

~ 11

16

123

0

187

10036.86

26.5%

480

413

493

390

780

347

369

353

63

326

334

88

982

441

937

378

258

296

140

7867.224

76.0%

17904.08

37.2%





817·847-1422


MISSION FLOODWAY DRAINAGE AREA- EXISTING DEVELOPMENT


SUMMARY

~

~ - -Orainag Existing ~

e ]I Area !:ca ~

e Area Conti1ions r: O'r: .. Number " e -= ~ E ..

(sq. mI.) eN l! :2 " " e 2 " "

~ ~

e " ~"l! 0::: 0: 0: uo

MI-l 0.49 74.9 0 0 0

MI-2 0.62 74.9 a a a a MI-4 0.34 77.0 0 0 a a MI-5 0.13 77.0 a a a a MI-6 0.80 78.1 0 0 0 0

MI-7 0.77 83.8 237 0 0 0

MI-8 0.57 81.1 363 0 0 0

MI-9A 0.39 84.4 62 0 62 23

MI-9B 1.01 76.1 107 0 a 0

MI-9C 0.29 83.0 0 0 0 0

MI-l0A 0.54 83.2 0 0 0 4

MI-l0B 0.42 77.0 0 0 0 0

MI-l0C 0.35 84.0 0 0 0 0

MI-l0D 0.54 78.0 0 0 0 a MI-llA 1.25 77.9 100 a 0 0

MI-llB 1.50 77.0 0 0 0 0

MI-13 0.73 76.5 262 a 0 a MI-14 0.94 80.2 247 0 0 0

MI-15 1.17 82.4 15 a a a MI-16 0.62 71.8 111 64 0 a MI-17 0.36 82.6 0 76 0 0

MJ-18 3.19 82.4 149 63 0 0

MI-19 0.47 83.0 32 194 0 0

MI-20 0.37 81.0 125 a a a

MS-l 0.37 72.6 55 a a 0

MS-2A 0.53 88.5 51 0 0 237

MS-2B 0.82 80.1 346 a a 131

MS-2C 1.39 79.8 632 0 a 178

MS-3A 0.82 82.0 333 a 100 0

MS-3B 0.68 75.7 337 a a 20

MS-4A 0.70 79.1 341 0 0 86

MS-4B 0.54 78.1 321 0 0 0

MC-1A 1.39 85.1 80 0 160 489

MC-1B 1.52 72.5 348 0 0 0

MC-1C 0.21 74.8 0 0 0 0

MC-1D 0.07 66.2 22 0 0 0

MC-2A 0.82 85.6 173 0 302 0

MC-2B 0.37 90.6 0 0 237 0

CNEXIST.XLS 12114/95 7:48 PM

e " ." ~ e ."

~ r: ~~

DATE: 12/95

AVO: 14191

FILE: ASTER

EMP: W,MM

CH

!

~ -.!! u 0 := 0

1: ... -= ~ ~ u

0.0)

0 0

a a 0 a a a a 0

256 0

0 0

39 0

333 0

186 0

342 0

269 0

224 0

346 0

580 0

960 0

93 0

178 0

734 0

0 0

133 0

1,830 0

75 0

a a

119 21

0 51

0 0

0 80

a 0

a 21

0

0 24

0 80

213 45

100 0

0 0

0 14

0 0

" ."

i e Co

~ r: > - " .. ~ ~ ."

r: ~u ::J

a 314

a 397

a 217

a 83

269 243

0 0

a 0

0 64

0 207

0 0

0 a 0 0

0 0

0 a a 120

0 a 0 112

a 177

0 a 0 222

0 22

0 0

0 0

76 36

0 43

a a 0 0

a 0

0 92

a 39

0 0

0 0

0 80

68 300

0 34

0 22

35 0

0 0

III U " ] ~ ~

31 a 282

40 a 357

a 0 217

a a 83

26 0 486

99 0 394

195 0 168

62 a 187

323 0 323

37 0 149

69 0 277

215 0 54

22 0 202

242 0 104

400 0 400

768 a 192

280 a 187

180 0 421

150 150 449

238 0 159

35 0 196

510 102 1,429

45 15 241

25 34 177

213 a 24

170 0 170

472 a 52

801 0 89

276 a 249

392 0 44

426 0 22

276 0 69

801 0 89

734 45 193

94 0 40

45 0 0

236 0 288

180 0 57





817-847-1422




SUMMARY

~ N - -Orainag Existing ~ i • ]!

Area ~ii ~ ';> e Area Contitions c c 0"" " Number " " .c ~ E " (sq. mI.) CN

.., :2 " . ;; ~ ~ E ,!,!

" " " ~~ 0::: a:: a:: uo

MC-3 0.60 80.2 150 0 77 61

MC-4A 2.02 74.8 504 0 0 259

MC-4B 0.42 80.3 0 0 0 91

R-2 0.42 78.8 129 0 0 54

R-3 0.10 75.3 0 0 0 0

R-4 0.41 81.0 167 0 0 59

R-5A 0.13 73.7 19 0 0 23

R-5B 0.23 72.2 49 0 0 21

R-6 0.82 73.9 315 0 0 0

R-9 2.50 75.8 960 0 0 240

R-l0 0.64 73.6 328 0 0 0

R-ll 0.97 77.7 53 0 0 53

R-13 2.77 69.9 461 417 0 0

R-14 0.32 66.8 61 0 0 0

R-15 1.85 74.1 426 349 0 0

El 0.26 73.6 83 0 0 17

E2 0.49 72.1 53 81 0 0

E3 0.44 69.4 0 220 0 0

E4 0.14 77.2 47 0 0 21

E5 0.35 71.5 146 0 0 0

E6 0.21 74.9 121 0 0 0

E7 0.34 76.1 187 0 0 0

E8 0.19 76.0 116 0 0 0

E9 0.22 84.5 28 0 0 85

El0 0.25 78.0 128 0 0 0

Ell 0.19 56.0 0 0 0 0

E12 0.15 61.4 23 0 0 0

E13 0.17 57.0 0 0 0 0

E14 2.52 74.9 253 474 0 0

E15 0.50 73.3 207 0 0 0

E16 2.24 70.1 0 1.334 0 0

E17 0.27 76.5 138 0 0 17

E18 0.56 74.3 39 274 0 45

E19 0.36 79_1 151 0 0 45

E20A 2.05 76.9 784 164 0 56

E20B 1.24 75.8 448 175 0 45

E21 0.10 82.4 38 0 0 26

E22 1.53 81.2 294 0 0 0

E23 0.52 76.6 0 113 0 25

CNEXIST.XLS 12/14195 7:48 PM

" • ." ~ " ." ~j

OATE: 12/95

AVO: 14191

FILE: ASTER

EMP: W,MM

CH

~ '3 -.!!

,g g " "" .c.c ~ ~ " "-,,, 0 31

52 0

119 0

54 0

0 0

0 0

0 0

0 0

0 42

160 0

0 0

463 53

239 124

51 0

315 0

17 0

82 70

23 0

0 0

0 0

0 0

0 31

0 6

0 28

32 0

0 0

0 0

0 0

887 0

65 0

0 0

0 0

0 0

34 0

203 0

126 0

0 0

588 0

114 0

. ."

" " ·c '" " .2 ;: " > - " " "S ~ ." c

"-u ::>

0 65

0 478

59 0

0 129

64 0

36 0

15 26

77 0

63 105

80 160

82 0

0 0

0 532

0 92

0 93

50 83

0 27

0 39

21 0

78 0

13 0

0 0

0 0

0 0

0 0

0 122

0 73

0 109

0 0

16 33

0 100

17 0

0 0

0 0

105 0

0 0

0 0

0 98

0 81

III U 0

~ ~ ~ 307 0 77

1,034 0 259

180 0 89

215 0 54

19 0 45

197 0 66

75 0 8

140 0 7

420 0 105

1.600 0 0

410 0 0

528 0 93

1,596 0 177

205 0 0

1,066 0 118

166 0 0

304 0 9

282 0 0

85 0 5

224 0 0

134 0 0

207 0 11

122 0 0

141 0 0

128 0 32

122 122 0

91 91 5

103 103 5

1,452 1.452 32

320 0 0

1,434 0 0

173 0 0

358 0 0

230 0 0

1,050 197 66

794 0 0

64 0 0

0 979 0

96 171 67


HALFF ASSOCIATES. INC.


Fort Worth. Texas 76137

817-847-1422




SUMMARY

Orainag Area

e Area Number

(sq. mI.)

E24 0.28

E25 0.25

E26 0.24

E27 0.26

ESI 0.51

59.1

Outside Trade Zone

%

TZ-l 0.75

TZ-2 0.68

TZ-3 0.91

TZ-4 0.61

TZ-5 1.74

TZ-6A 0.57

TZ-68 0.64

TZ-6C 0.58

TZ·6D 0.18

TZ·6E 0.51

TZ·6F 0.55

TZ-7 0.69

TZ-8 2.36

TZ-9 1.06

TZ-l0A 1.83

TZ-l08 0.59

TZ-ll A 0.67

TZ-118 1.03

TZ-l1C 0.23

Trade Zone Subtotal

%

OVERALL

%

16.18

Existing Contitions

eN

81.7

73.7

84.4

76.3

82.7

81.7

83.2

81.2

79.8

82.7

83.0

84.0

84.5

88.8

84.7

76.8

77.2

79.4

80.0

82.8

83.2

80.3

80.0

84.5


0;- N

i ;; E ." c .. .. ." ." ;; ;; .. .. 0: 0:

0 42

28 0

0 0

166 0

22 0

11969 4037.3

31.7% 10.7%

4

26

28

0

473

0

0

0

0

0

0

0

83

10

26

0

0

55

0

705.1

6.8%

12674 4037.3

26.3% 8.4%

-.. g;; .t:"5 .... ~ ~

~~ 0

0 0

0

0

938

2.5%

0

0

0

0

77

0

0

0

94

91

0

6

0

15

0

0

0

0

0

283

2.7%

1221

2.5%

-~ .. E .. ." ; H .. ."

~~ uo 3

0

0

0

0

2413 0

6.4% 0.0%

0 0

0 0

10 0

24 0

90 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

2 0

0 0

0 0

0 0

0 0

0 0

0 0

125.9 0

1.2% 0.0%

2539 0

5.3% 0.0%

DATE: 12/95

AVO: 14191

FILE: ASTER

EMP: W.MM

CH

i -.!! u 0 u = 0 "C .o.t: : ~ u 0..0>

134 0

23 0

154 0

0 0

307 0

11249 722

29.8% 1.9%

279 0

334 0

389 0

86 0

312 15

299 0

410 0

371 0

21 0

134 0

0 40

436 0

1.209 0

592 0

1.129 0

292 0

392 0

604 0

147 0

7434.3 54.5

71.8% 0.5%

" .. i

" - .. -; ~ o..u

0

0

0

0

0

1224.5

3.2%

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0.0%

." .. Co .2 .. > .. m ." C ~ :> 0 10

109 24

0 0

0 166

0 54

5379 25431.7

14.2% 67.3%

197 0

74 22

155 87

280 0

147 334

66 18

0 41

0 19

0 52

102 0

312 18

0 353

217 453

61 237

17 234

86 0

37 172

0 329

0 7

1751 2376.72

16.9% 23.0%

18684

38.8%

776 1224.5 7130 27808.4

1.6% 2.5% 14.8% 57.7%

u 0

~ ~ 159 11

120 16

31 123

0 0

88 187

3857.7 10186.7

10.2% 26.9%

0 480

0 413

0 495

0 390

0 780

0 347

0 369

0 353

0 63

0 326

0 334

0 88

76 982

0 441

0 937

0 378

0 258

33 296

0 140

108.46 7869.111

1.0% 76.0%

3966.2 18055.81

8.2% 37.5%

APPENDIXE Preliminary Estimates of Probable Construction Cost

CUENT: City of McAllen

ALBERT H. HALFFASSOCIATES, INC. 4000 Fossil Creek Boulevard

Fort Worth, Texas 76137 (817)847-1422

PROJECT: Rood Protection Planning Studt for Southern McAllen and Mission

ITEM NO.

Emergency Spillway al Mission Oullel levee

STATEMENT OF PROBABLE COST

DESCRIPTION QUANTITY UNIT

------------------- -----1 Compacted Select Fill 14,000 2 Rock Riprnp 11,450 3 Groutscf Rock Rip rap 10,080 4 Seeding 20,000 5 0 6 0 7 0 8 0 9 0

10 0 11 0

----------------------------------------Subtotal

20 % contingency

--------------------------------TOTAL

Note: Estimale does not indude Engineering, Adminstration, Surveying, or Legal fees

This statement was prepared utilizing standard cost estimate practices. It is understood and agreed thai this is an estimate only, and thai Engineer shall not be ~able to Owner or to a third party for any failure to accurately estimate the cost of the project. or any

CY CY SY SY SY CY EA EA EA LF SY

---

---

PAGE: DATE: BY:

PRICE

$10.00 $90.00 $50.00 $1.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00

COST-M1 12195

eshnamlchm

MPUNT

$140,000 $1,030,500

$504,000 $20,000

$0 $0 $0 $0 $0 $0 $0

$1,694,500

$338,900

$2,033,000

CUENT: City of M::AIIen

ALBERT H. HALFF ASSOCIATES, INC. 4000 Fossil Creek Boulevard

Fort Worth, Texas 76137 (817)847-1422

PROJECT: Rood Protection Planning Study for Southern M::AIIen and Mission

ITEM NO.

Relief Storage for 10o-Year Gates Closed



------------------- ------1 Compacted Select Fill-Mission ou~et levee 2 RockRprap 3 Grouted Rock Rip rap 4 Tripl&-10' x 10' Reinforced Cone. Box Culvert (150 It) 5 Rap Gates 100xlO' 6 Excavatioo 7 8 9

10 11

Subtotal 5 % U~ity Adjuslment 20 % contingency

-------------------------------------------TOTAL

This estimate does not indude ROW acquisition

17,500 5,050 2,200

435 3

1,600,100 0 0 0 0 0

Note: Estimate does not indude Engineering, AdminSiration, Surveying, or Legal fees

This statement was prepared utifizing standard cost estimate practices. It is understood and agreed that this is an estimate ooly, and that Engineer shaD not be Dable to C>.vner or to a third party for any failure to a~raIe1y estimate the cost of the project, or any

CY CY SY CY EA CY EA EA EA LF SY

PAGE: DATE: BY:

PRICE

$5.00 $90.00 $50.00

$400.00 $20,000.00

$3.00 $0.00 $0.00 $0.00 $0.00 $0.00

COST-M2 12195

eslmam/chm

M10UNT

$87,500 $454,500 $110,000 $174,000

$60,000 $4,800,300

$0 $0 $0 $0 $0

$5,686,300 $284,315

$1,137,260

$7,108,000


Fort Worth, Texas 76137 (817)847-1422


PROJECT: Rood Protection Plaming Study for SoUlhem McAllen and Mission

ITEM NO.

Reconstrucdon of the Soulh Levee al Cimarron


DESCRIPTION

------------------1 2 3 4 5 6 7 8 9

10 11 12 13 14 15

ROW Preparation Compacted Select FiD-Levee EJccavation Salvage Topsoil Seeding RockRiprap Grouted Rock Rip rap Five-l0' x 10' Reinforced Cone. Box Culvert (SO ft) Flap Gates 10" x 1 0' Bridge at Shary Road

-- - -------------------Subtotal 10'% Utility Adjustments 20 % contingency

------------------TOTAL

This estimate does not indude ROWacqJisition

OUANTITY

65 n,400

864,400 33,600

314,600 2,445 2,990

260 5 1 0 0 0 0 0

Note: Estimate does nolindude Engineering, Adminstration, Surveying, or Legal fees

This statement was prepared utilizing standard cost estimate practices, II is understood and agreed thai this is an estimate only, and thai Engineer shaD not be iable to C>.vner or to a third party for any failure to accurately estimate the cost of the project, or any

UNIT PRICE

---AC $1,000.00 CY $5.00 CY $3.00 CY $2.00 SY $1.00 CY $90,00 SY $50,00 CY $400.00 EA $20,000,00 LS $900,000,00 EA $0,00 EA $0,00 EA $0,00 LF $0.00 SY $0,00

---

-------

PAGE: DATE: BY:

COST-CIM 12195

es/mam/chm

M10UNT

$65,000 $387,000

$2,593,200 $67,200

$314,600 $220,050 $149,500 $104,000 $100,000 $900,000

$0 $0 $0 $0 $0

$4,900,550 $490,055 $980,110

$6,371,000


ALBERT H. HALFFASSOCIATES, INC. 4000 Fossil Creek Boulevard Fort Worth, Texas 76137

(817)847-1422

PROJECT: Rood Protection Planning SbJd/ for Southern McAllen and Mission

ITEM NO.

Oralnage Improvemenls for CeIl-1 ( Oullel No.1)



---------------------- ------1 ROW Preparation 2 Excavation 3 Levee Excavation for CSC installation 4 Salvage Topsoil 5 Seeding 6 Sigle-6' x 4' Reinforced Conc. Box Culvert (150 ttl 7 Flap Gates 6· x 4' 8 Compacted Select RI~Mission Levee 9

10 11

Subtotal 5 % Utility Adjustment 20 % contingency

TOTAL

25 508,000

1,390 13,600

121,000 77

1 9,800

0 0 0

Note: Estimate does not indude Engineering, Adminstration, Surveying, or Legal fees

This statemenl was prepared U1iUzing standard cost estimate practices. II is understood and agreed 1I1at 1I1is is an estimate only, and 1t1at Engineer shaU not be nabla III ONner or to a third party for any failure to a=rately estimate the cost of 1119 project, or any

AC CY CY CY SY CY EA CY EA LF SY

---

---

PAGE: DAlE: BY:

PRICE

$1,000.00 $3.00

$10.00 $2.00 $1.00

$400.00 $11,000.00

$5.00 $0.00 $0.00 $0.00

COST-C1 12195

eshnamlctvn

AMOUNT

$25,000 $1,524,000

$13,900 $27,200

$121,000 $30,800 $11,000 $49,000

$0 $0 $0

$1,801,900 $90,095

$360,380

$2,252,000

CUENT: City 01 M::AJlen


Fort Worth, Texas 76137 (817)847-1422

PROJECT: Rood Protection Planning Studt for Southern M::AJlen and Mission

ITEM NO.

Drainage Improvements for Cell-2 ( Outlet No.2)


DESCRJPTION OUANllTY UNIT

--------------------- ------1 ROW Preparation 2 Excavation 3 Levee Excavation for CBC installation 4 Salvage Topsoil 5 Seeding 6 Sigle-B' x 5' Reinforced Cone. Box Culvert (150 tt) 7 Rap Gates 8 9

10 11

---------------------------------------Subtotal 5 % Utility Adjustment 20 % contingency

--------------------TOTAL

45 947,500

5,780 23,900

215,400 127

1 0 0 0 0


This statement was prepared utilizing standard cost estimate practices. It is understood and agreed thai this is an estimate only, and thai Engineer shall not be liable to C>.vner or to a third party for any failure to aa:urate!y estimate the cost of the project, or any

AC CY CY CY SY CY EA EA EA LF SY

---

---

PAGE: DATE: BY:

PRJCE

$1,000.00 $3.00

$10.00 $2.00 $1.00

$400.00 $15,000.00

$0.00 $0.00 $0.00 $0.00

COST-C2 12195

esImamIchm

AMOUNT

$45,000 $2,842,500

$57,800 $47,800

$215,400 $50,800 $15,000

$0 $0 $0 $0

$3,274,300 $163,715 $654,860

$4,093,000


ALBERT H. HALFF ASSOCIATES, INC. 4000 Fossil Creek Boulevard Fort Worth, Texas 76137

(817)847-1422

PROJECT: Rood Protection Planning Studt for SoUlhem McAllen and Mission Drainage Improvements for Cells 3-9 ( OuUet No, 3)

STATEMENT OF PROBABUE COST

ITEM NO. DESCRIPTiON QUANTiTY UNIT

------------------ ------1 ROW Preparation 2 Excavation 3 Levee Excavation for CBC installation 4 Salvage Topsoil 5 Seedng 6 Double-l0· x 10' Reinforced Cone. Box Culvert (150 It) 7 Flap Gates- 10' x 10' 8 AapGates-4x4 9 36" Class III R.C.P.

10 11

------------------Subtotal 2 % Utility Adjustment 20 % contingency

320 AC 7,732,700 CY

4,430 CY 172,100 CY

1,548,800 SY 331 CY

2 EA 5 EA

200 LF 0 LF 0 SY

---

---------------------- -----TOTAL

Note: Estimate does not indude Engineering, Adminstraticn, Surveying, or Legal fees

This statement was prepared utilizing standard cost estimate practices. It is understood and agreed that this is an estimate only, and that Engineer shall not be nabla to ONner or to a third party for any failure to a=rately estimate the cost of the projec~ or any

PAGE: DATE: BY:

PRJCE

$1,000.00 $3.00

$10.00 $2.00 $1.00

$400.00 $20,000.00 $10,000.00

$53.00 $0.00 $0.00

COST-C9B 12195

esIrnamIchm

AIv'OUNT

$320,000 $23,198,100

$44,300 $344,200

$1,548,800 $132,400

$40,000 $50,000 $10,600

$0 $0

$25,688,400 $513,768

$5,137,680

$31,340,000

CUENT: City of M:Allen


(817)847-1422

PROJECT: Rood Protection Planning Study for Southern M:Allen and Mission Drainage Improvements for Cells 3-9 (OuUel No, 4)

fTEMNO.


DESCRIPilON

-------------------1 ROW Preparation 2 Excavation 3 Levee Excavation for cae installation 4 Salvage Topsoil 5 Seeding 6 Single-l0' x 10' Reinforced Cone. Box Culvert (150 tt) 7 Rap Gates 10 x 10 8 42" Class III R.C.P. 9 Single-l0' x 5' Reinforced Cone. Box Culvert (200 tt)

10 11

-------------------Subtotal 5 % Utility Adjusbnenl 20 % contingency

TOTAL

QUANTITY

104 2,371,600

3,950 70,350

502,400 238

1 400 172

0 0


This statement was prepared utilizing standard cost estimate practices. It is understood and agreed thai this is an estimale only, and thai Engineer shall not be Rabie to Owner or to a third party for any failure to aocurately estimate the cost of the project. or any

UNIT PRICE

---AC $1,000.00 CY $3.00 CY $10.00 CY $2.00 SY $1.00 CY $400.00 EA $20,000.00 LF $80.00 CY $400.00 LF $0.00 SY $0.00

PAGE: DATE: BY:

COST-C9A 12195

eslmarrVdlm

AMOUNT

$104,000 $7,114,800

$39,500 $140,700 $502,400

$95,200 $20,000 $32,000 $68,800

$0 $0

$8,117,400 $405,870

$1,623,480

$10,147,000


CUENT: City of M=Ai1en

Fort Worth, Texas 76137 (817)847-1422

PROJECT: Flood Protection Planning Study for Southern M=Ailen and Misslon Drainage Improvements for Cell-l 0 (Outlet No, S)

ITEM NO.

STATEMENT OF PROBABUE COST

DESCRIPnON

-------------------1 ROW Preparation 2 Excavation 3 levee Excavation for CBC instaJlaJion 4 Salvage Topsoil 5 Seating 6 Single-l0' x 6' Reinforced Cone. Box Culvert (200 ft) 7 Rap Gates 10 xS 8 30· Class III R.C.P. 9 3S· Class III R.C.P.

10 48" Class III R.C.P. 11 SO· Class III R.C.P.

-------------------Subtotal 5 % Utility Adjustment 20 % contingency

-------------------TOTAL

QUANTIlY

75 1,256,900

8,500 41,000

367,800 267

1 100 100 100 100

Note: Estimate does not indude Engineering, Adminstration, Surveying, or legal fees

This statement was prepared utilizing standard cost estimate practices. It is understood and agreed that this is an estimate only, and that Engineer shall not be ~able to Owner or to a third party for any fallure to accurately estimate the cost of the project. or any

UNIT PRICE

---AC $1,000.00 CY $3.00 CY $10.00 CY $2.00 SY $1.00 CY $400.00 EA $18,000.00 LF $42.00 LF $53.00 LF $80.00 LF $108.00

PAGE: DATE: BY:

COST-Cl0 12195

es'mamlchm

MOUNT

$75,000 $3,770,700

$85,000 $82,000

$367,800 $106,800

$18,000 $4,200 $5,300 $8,000

$10,800

$4,533,600 $226,680 $006,720

$5,667,000


(817}847 -1422

CUENT: City of M::AIIen

PROJECT: Rood Protection Planning SlUcIy for Southern M::AIJen and Mission Drainage Improvements for Cell-11 (Outlel No.6)

ITEM NO.


DESCRIPTION

-------------------1 ROW Preparation 2 Excavation 3 Levee Excavation for CBC installation 4 Salvage TopsOIl 5 Seedng 6 8;gl9-6' x 4' Reinforced Cone. Box Culvert (200 It) 7 Rap Gates 6x4 8 24" Class III R.C.P. 9 36" Class III R.C.P.

10 48" Class III R.C.P. 11 60" Class III R.C.P.

Subtotal 5 % Utility Adjustment 20 % contingency

TOTAL

OUAN11TY

41 606,700

4,270 22,050

198,400 107

1 100

0 0 0


This statement was prepared utilizing standard cost estimate practices. It is understood and agreed !hat !his is an estimate only, and !hat Engineer shall not be fiable to ONner or to a third party for any failure to accurately estimate the cost of !he project, Of any

UNIT PRICE

---AC $1,000.00 CY $3.00 CY $10.00 CY $2.00 SY $1.00 CY $400.00 EA $12,000.00 LF $34.00 LF $53.00 LF $80.00 LF $108.00

PAGE: DATE: BY:

COST-Cll 12195

eslmam'chm

AMOUNT

$41,000 $1,820,100

$42,700 $44,100

$198,400 $42,800 $12,000 $3,400

$0 $0 $0

$2,204,500 $110,225 $440,900

$2,756,000

APPENDIXF Computer Files of Hydrologic and Hydraulic Models

(Computer Diskette)

APPENDIX G References

- \

-',\

APPENDIX G REFERENCES

1. Soil Survey of Hidal!!o County. Texas, United State Department of Agriculture Soil Conservation Service, June 1981.

2. Flood Insurance StUdy. Hidal!!o County. Texas, Federal Emergency Management Agency, July 2, 1980.

3. Report of Hurricane Beulah, U.S. Army Corps of Engineers, Galveston District, September, 1968.

4. Flood Insurance Study. City of McAllen. Texas. Hidallw Count v , Federal Emergency Management Agency, December IS, 1980.

5. HEC-l Flood Hvdrograph Packa!!e, U.S. Army Corps of Engineers. Hydrologic Engineering Center, Davis, California, September 1990.

6. Lower Rio Grande Basin. Texas Flood Control and Major Draina!!e Project. Phase 1 -General Design Memorandum Main Report and Final Environmental Impact Statement with Appendices 1-8, U.S. Army Corps of Engineers, Galveston District, August, 1982.

7. Draft Report - Mission Inlet Pilot Channel Improvements, Phase V Engineering Inc. in cooperation with Furlong Engineering, Inc., May 1991

8. SCS National En!!ineering Handbook. Section 4. Hvdrologv, United States Department of Agriculture Soil Conservation Service, 1969.

9. Hidal!!o County Draina!!e Plan, Melden and Hunt, Inc. and Sigler, Winston, Greenwood and Associates, Inc., March 14, 1985.

10. Technical Paper No. 40, Rainfall Frequency Atlas of the United States, National Weather Service, May 1961.

11. Technical Memorandum HYDRO-35, National Oceanic and Atmospheric Administration, June, 1977.

12. HEC-2 Water Surface Profiles, U.S. Army Corps of Engineers, Hydrologic Engineering Center, Davis, California, May 1991.

13. Status of Convevin!! Capacity of the Lower Rio Grande Flood Control Project, International Boundary & Water Commission United States and Mexico, United States Section, El Paso, Texas, June 1992

14. En!!ineerinl! Report. Mission Floodway Closure, International Boundary & Water Commission United States and Mexico, United States Section, El Paso, Texas, July 1972

'"

,

APPENDIX G REFERENCES(Continu~)

15. Flood Insurance Stud". Citv of Mission. Texas, Hidalgo County, Federal Emergency Management Agency, November 20, 1991.

16. Hapnv Trails Flood Studv, L.L. Rodriguez and Associates, Inc., February 1985.

17. Preliminarv Enl!ineerinl! Report for the Relocation of the Water District No.3 Siphon and Drainal!e Improvements to the South 18th Street and Balboa Acres Drainal!e Svstems, L.L. Rodriguez and Associates, Inc., November 1983

18. Master Drainage Plan for Mission Inlet and South Rado Drain-Hidalgo County Drainal!e District No. I, Melden and Hum, Inc. and Sigler, Winston, Greenwood and Associates 1985

19. Rado Drain Alternative Stud" for Hidall!o Countv Drainal!e District. No.1

20. National Flood Insurance Program and Related Regulations, Federal Emergency Management Agency.

APPENDIX H Survey Control Data

ANZALDUAS PANEL POINT GPS ADJUSTMENT SUMMARY

Panel Points for aerial photogrammetry were placed as indicated on layout provided by Robert Stackhouse Aerial Company. Panels were placed as 4'x4' chevrons with 112-inch iron rods set flush with the ground at the interior corner of each panel. Panels were made with l' wide white plastic sheets held in place by nails and shiners.

Static GPS observations were performed on March 8, 9, and 10, 1995 by Halff Associates personnel using Trimble 4000ST receivers. GPS observations were reduced using Trimnet software. The GPS network was adjusted and WGS-84 ellipsoid heights were computed using GEOLAB software. The GPS network was constrained horizontally to NGS first order triangulation station "HICKLEY" NAD 83 coordinate values.

The GPS network was constrained vertically to IBWC benchmarks as follows:

AL01 direct GPS observation of IBWC BM No. 266 AL-PH. BM02 direct GPS observation of IBWC brass disk on south side of the Anzalduas wier. AL07 level loop to IBWC brass disk on Structure No. 300. AL08 level loop to IBWC brass disk on Structure No. 301. AL21 leve1loop to IBWC brass disk on Structure No. 316. AL28 level loop to IBWC brass disk on Structure No. 323.

All panel points were adjusted by least squares computations using the six IBWC benchmarks described above.

Surface coordinates were computed using a combined scale factor of 0.99999588.

Conversion factor from meters to U.S. survey feet = 0.304800609601 meters/foot.

• ~'-''-'.., c ,,"v,r::.\...l1UN YLANN1NG STUDY FOR SOUTHERN McALLEN AND MISSION,1EXAS ALL COORD! rn VALVES ARE NAD83 - TEXAS SOUTII ZONE 4205 I , ADJUSTED H(JKIZONT ALLY FROM TRIANGULATION STATION "IDCKLEY 2"

)

ALL ELEVATIONS ARE ADJUSTED VERTICALLY FROM mwc BENCHMARKS PANEL GRID PANEL ELEVATION SCALE SURFACE SURFACE ELEVATION NATURAL , POINT NORTIIING EASTING ABOVEMSL FACTOR NORTHING EASTING ABOVEMSL GROUND I

(METERS) (METERS) . (METERS) (l{l:ili" 1') . (FEET) (METERS) (METERSl ALOl 5056704.7435 315418.9699 38.4322 0.99999707 16,590,273.8472 1,034,841.3350 38.43 37.37 AL02 5058234.5784 315811.5320 33.3171 0.99999367 16,595,293.0012 1,036,129.2711 33.32 33.32 AL03 5058743.4684 317069.8965 34.0817 0.99999256 16,596,962.5913 1,040,257.7723 34.08 34.08 AL04 5056700.6945 316759.4967 33.7987 0.99999708 16,590,260.5630 1,039,239.3981 33.80 33.80 AL05 5054933.7598 317078.3642 34.3812 1.00000108 16,584,463.5209 1,040,285.5535 34.38 34.38 AL06 5053744.1339 317231.6657 37.2438 1.00000382 16,580,560.5405 1,040,788.5123 37.24 37.24 AL07 5051963.7175 318551.5646 33.4762 1.00000798 16,574,719.2669 1,045,118.8984 33.48 33.48 AL08 5051417.7240 320108.5796 32.0802 1.00000928 16,572,927.9459 1,050,227.2262 32.08 32.08 AL09 5052383.9394 320205.7232 32.2470 1.00000700 16,576,097.9506 1,050,545.9395 32.25 32.25 ALIO 5054265.6527 320350.1739 32.1961 1.00000263 16,582,271.5638 1,051,019.8601 32.20 32.20 AL11 5055411.8034 320650.9136 31.3736 1.00000001 16,586,031.9087 1,052,006.5410 31.37 31.37 AL12 5057086.6398 319295.1610 34.9186 0.99999623 16,591,526.7904 1,047,558.5243 34.92 34.92 AL13 5057132.5828 320914.2227 31.0032 0.99999613 16,591,677.5224 1,052,870.4178 31.00 31.00 AL14 5058551.7773 318710.4405 34.7544 0.99999298 16,596,333.6822 1,045,640.1459 34.75 34.75 AL15 5058210.0138 321077.0670 33.8525 0.99999374 16,595,212.4085 1,053,404.6850 33.85 33.85 AL16 5057841.8994 323488.3725 33.3578 0.99999456 16,594,004.6815 1,061,315.8091 33.36 33.36 AL17 5056315.6270 323297.9649 32.0671 0.99999797 16,588,997.2155 1,060,691.1109 32.07 32.07 AL18 5055440.9348 323183.5421 30.2369 0.99999995 16,586,127.4844 1,060,315.7072 30.24 30.24 AL19 5053890.0257 322942.9751 30.3768 1.00000350 16,581,039.1891 1,059,526.4437 30.38 30.38 AL20 5052324.3466 322668.7265 34.6539 1.00000715 16,575,902.4358 1,058,626.6761 34.65 34.06 AL21 5052279.0067 325885.4467 33.8115 1.00000727 16,575,753.6825 1,069,180.2424 33.81 33.81 AL22 5053417.5694 326069.0432 29.1753 1.00000461 16,579,489.1324 1,069,782.5944 29.18 29.18 AL23 5055217.5613 326341.1581 32.4579 1.00000047 16,585,394.6301 1,Q70,675.3617 32.46 32.46 AL24 5056297.1968 326707.3824 29.7501 0.99999803 16,588,936.7488 1,071,876.8876 29.75 29.75 AL25 5056176.0076 329146.4741 29.5686 0.99999831 16,588,539.1456 1,079,879.1739 29.57 29.57 AL26 5054698.7862 328920.9554 31.7968 1.00000167 16,583,692.6085 1,079,139.2816 31.80 31.80 AL28 5053006.2848 329949.5596 30.0960 1.00000559 16,578,139.7706 1,082,513.9745 30.10 30.10 AL29 5051716.5561 328477.2284 27.6979 1.00000861 16,573,908.3682 1,077,683.4813 27.70 27.70 BM02 5052629.6321 317683.7738 37.4386 1.00000642 16,576,904.0307 1,042,271.8097 37.44 37.44

IDCKLEY2 5053067.4427 322863.0322 34.2781 1.00000541 16578,340.4203 1 059,264.1633 34.28 34.28 AVERAGE ELEVATION (METERS) 32.7973 AVERAGE SCALE FACTOR 1.00000103 SEA LEVEL REDUCTION FACTOR 0.99999485 COMBINED SCALE FACTOR 0.99999588

-

''WORK SESSION" PRESENTATION OF PRELIMINARY RESULTS

\ . I •

Tl~ ! l'\ ! ,. '''''

NOVEMBER 2l, 1995

,

FLOOD PROTECTION PLANNING STUDY FOR

SOUTHERN MCALLEN AND MISSION, TEXAS

HaItY Associates CITY OF McALLEN

, " < < , < .

Flood Protection Planning Study for Southern McAllen and Mission, Texas

OUTLINE OF PRESENTATION

t Introduction

II. Study Procedures

III. Results of Baseline Conditions

IV. Conceptual Design Solutions

V. Summary of Findings


INTRODUCTION

• Project Milestones

• Purpose of Study

• Description of Watershed


PROJECT MILESTONES

• September 1994 - Application for TWOB Grant

• January 1995 - Notice-to-Proceed

• March 1995 - Aerial Surveys Flown

• September 1995 - Final Mapping Received

• November 1995 - Work Session to Present Preliminary Results


PURPOSE OF STUDY

The purpose of this study is to develop detailed hydrologic and hydraulic computer models to analyze the existing drainage system and evaluate alternative design schemes to help alleviate existing and potential flood damages for the developing areas of southern McAllen and southern Mission, Texas, located between the Old Mission Inlet Floodway and the Banker Floodway.


DESCRIPTION OF WATERSHED

• Total Contributing Drainage Area is 75 sm.

• Detail Study Area (SharylandlTrade Zone) is 16 sm.

~:,..-.-.-o;~~~,~'). .-,

'\~-.-.-~-.- ........

n ~ ~ -c: ~ ~

~ ~ ~ -'in z

./

, ,-

1

FM 231

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

" '-.

LEGE~

CITY lNtT L~E

!>TCH

ROAD

-...... ,

..... ..- ..... DRAINAGE SYSTEM DlVIOE

.... ". , . ....... _._.(.

I , . '-\. "",tJjV'/:Ni/' .... :,>, ,'.r~_

'to.t' tr

'''~. \

'. . ..... _ ~!'.t:i!'!. • _ • .J

.- ..... /,- \

i j . . , , ,/ \. I "I . ...... ,

'----. ...... ..,,,,~' ,~

J ,..

\

'. \ . DRAINA(;E AREA MAl'

i-i Halff Associates ENGINE[RS • ARCHITECTS. SCIENTIS TS • PLANNERS. SURVEYORS

FLOOD PROTECTION Fon S()(JTIIERN I\1CALLEN

PLANNING STUDY AND MISSION, TEX\S

I! .! " ,

N

! '----~

~ ! ii

, \l\

, ~\i'''~ .-.-'

FHalRE 2

CITY OF McALLEN


STUDY PROCEDURES

• Data Collection

• Study Assumptions

• Hydrologic and Hydraulic Computer Modeling


DATA COLLECTION

• Aerial Surveys by Williams-Stackhouse Inc.

• Previous Studies - Federal Emergency Management Agency, Corps of Engineers, International Boundary & Water Commission, and Phase V Engineering

• Future Land Use Maps for McAllen an~ Sharyland

• Hidalgo County Soil Survey

• Record Bridge/Roadway Construction Plans

• Field Observations

:.()" ,~r

c::::::J

, 1

lill!!Q

NORMAL WATER LEVELS

SHIEAN OR SURfACE RUNOF". fLOODING

DEBRIS OR ORI"'TLH~E ELEVATION

NOTES:

TO MEAN

HURRICANE BEULAH B~21 SEPT. 1967

LIMITS OF FLOODING Me ALLEN, TEXAS

(SOUTH) or FEET

>0""

~~I TO ACCOMPANY REPORT ON HURRICANE BEULAH

PLATE ~6

1 1

----- ------------

--_._--,,- \

i..---""' r " ~

~ " 'i ~

'i d z ';& ~

0

'" " " \ co

0 e 'f, n

~ ~ \'l V> \'l " '" r

" 0

/'

'1 '~)---+-+~ f

\

\ \

----

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

I 1

\ 1 1 1

\ 1 \1

1 1

\ 1 1 1 1 1 1 1 1 1 1 1 1 1

\, ~ 1 1 1 1 1 1 1 1

\ <

\ \

\ \ <

\

\

( \

f I { •

----------------------

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1


STUDY ASSUMPTIONS

• Future Development

• Undeveloped Areas Assigned Agricultural Land Use

• Detail Study Area Modeled as Enclosed System with Eleven Separate Flood Storage Cells

• All Contributing Areas, Except Sharyland/Trade Zone Area, Permitted to Enter Mission Inlet

• Mission Inlet Floodway Modeled as Series of Reservoirs

• Mission Inlet Gates Closed and Banker Floodway Full

I 'i";

ft';

?

i \ i \

\ \ " ;

,~.

\

"

" _._.-'I

."._ • .-i'

I , \

" '-

\_\RaUl Associates "",Nt'RS • ,,,",,t.<" • ,,,"I'''' . Pl''''''-'' • ,,""',""

~

\ ~

l"\GllR\~ 5

f,ANlo.:' f; I p)f""'~'

Cln' Or McALLEN


HYDROLOGIC AND HYDRAULIC COMPUTER MODELING

• HEC-1 Flood Hydrograph Package / HEC-2 Water Surface Profiles

• Soil Conservation Service Loss Rate Method

• Modified Puis Reservoir Flood Routing - Digital Terrain Model (DTM) Utilized to Compute Stage-Storage-Discharge Relationships

• Rainfall Depth/Duration Taken from Technical Paper No. 40 and Technical Memorandum NWS HYDRO-35

ELEVATION-STORAGE RELATIONSHIP MISSION PUMP TO MISSION INLET (91-7)

110 I ~.

1 O~---------------------------------------------------------------------------------------~--------------------------------------------------------

f 1 00----------------------------------- ......................................... . ----- ... ... - -- - .... _- ------ -------------------

~ ~!:)----------------- ... -------------------------------------------------------------------------------------------------------------------------------o ~

~ W -J W

~O---- ... --------------------------------------------------------------------------------------------------------------------------------------------

l:l!:)---------------------------------------------------------------------------------------------------------------------------------------------------

l:l0 ... ------------------------------------------------------------------------------------------------------------------------------------------------

7~. I I I I I I I o ~ 10 1 ~ 20 2~ 30 3~

VOLUME (ACRE-Fl) (Thousands)

ELEVATION-STORAGE RELATIONSHIP MISSION PUMP TO SAN JUAN CANAL (91-84)

105 I ---

1 OO~--------------------------------------------------------------------------------------- .... ------------------------------------------------------

f ~5~------------------------'--' ...................................................................... . .. -- .... -. __ ........ -- -----

~ ~o~-------- .... -------------------------------------------------------------------------------------------------------------------------------------o ~

~ W -l W

~5~-... ---------------------------------------------------------------------------------------------------------------------------------------------

~o--..-----------------------------------------------------------------------------------------------------------------------------------------------

~5 ... ------------------------------------------------------------------------------------------------------------------------------------------------

~o I I I I I I I I I I I o 1000 2000 3000 4000 5000 6000 ~OOO 8000 ~OOO 10000

VOLUME (ACRE-FT)

ELEVATION-STORAGE RELATIONSHIP SAN JUAN CANAL TO 23RD ST (84-74)

110, ~

1 (:)~--....................................................................................... ..-r- ••••••••••••••••••••••••••••••••••••••••••••••••••••••

f 1 00 ~----- ------------ ------ --- ----------~ ------------------------- ----- ----------------------- -----

~ !:t~--................... ~ .......................................................................................................................... . o

~ w ~ w

!:to--···· ... ·············································· ........................................................................................... .

~!:i----.............................................................................................................................................. .

~o .... ············································ ----------------------------------------.------------.--------------------------------------------_.

7~'" I I I I I I o 1000 2000 3000 4000 ~OOO 6000

VOLUME (ACRE-FT)

ELEVATION-STORAGE RELATIONSHIP 23RD ST TO SHARY RD (74-26)

110· ---

1 O~-t--------------------------------------------------------------------~~--------------------------------------------------------------------

f 100 ..... ---------------------------------- -----~ ......................... . ----- ...... -.. _----- .. --- -- .. -----_._ .. ----- .... _---

z 9 ~ ..... --------------------------- ------------------ --- ------------ --- ------------ --------- --------- ------ --------- ------- -- --------- ------ -----------o r= ~ 90 w --I

W ~~

~O ... ------------------------------------------------------------------------------------------------------------------------------------------------

75- I I I I I I o 2 4 6 8 10 12

VOLUME (ACRE-FT) (Thousands)

ELEVATION-STORAGE RELATIONSHIP SHARY RD TO RIO GRANDE RD (26-25)

110, =-1 O!)-t------------------------------------------------------~---------------------------------------------------------------------------------

f 100 ..... -·--··········---·····-··-····-········· ~ ... . ..... ~- .... -- ------------------- ....... _---- .... ---------------------

~ ~!)------.- .. -... -....... --.-..... -.. -----------.-.. --........ _---I-- .................................................................................... .

~ W -J W

~O ... --------------·----··--··---·---------------------------.-... --------------------------------------- .... -... -.-------.. -.---.-... -..... ---- .....

~!) ..... -............. --.-.................... -............ _ ............... _.- ...... -......... __ ._ ....... _ ....... '."'--'.'." .. _"' ..... '-._"'." .. '

~O"'·········-·····························- ------ .... _------ .. -.--------------------_ .. _------------------------------------------------------ .. --_.-

7!). I I I I I I I I I o 200 400 600 ~OO 1000 1200 1400 1600 1800

VOLUME (ACRE-FT)

ELEVATION-STORAGE RELATIONSHIP RIO GRANDE RD TO FM 1016 (25-14)

110 ~.

1 O~~··················································· .................................. ~ ....................................................... .

1 0E3~··················································~ .......................................................................................... .

~ 1 O~ ~··························IO·······················.·· ••••...........................••••.•......................••.•••.....••..........•...••...

'---' 1 O~~·········~········································· .......................................................................................... . z o ---- 1 OO~···· ... ·············································· ........................................................................................... . ~ ::=- ~f3~ ................................................................................................................................................ . W ....J w ~E3 ~ -4 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• - •••• - •• - ••• -. - •••••• - •• -. - •• - ••• - ••• - •••• --

~~-4 ••••••• --.- ••••• - •• --•• --.-••••••• --•••••• - ••••••• -. ____ ••• _ •••••••••• _ ••• _. __ • __ •• _ •••• _ ••• __ ••• _ •• __ •• _-._._ •••••• __ ••••••• _ •••• __ ••••••• __ ._ ••

~~-o.- •• - ••••••••••• - ••••• --•••• - •• - ••••• - •• - •••••• - •• - ••••• _ ••••••• _ •••••••• _ ••••• _ •• _ •• _ •••••• ____ ••••••• ____ ••• _._ ••••• _ •••••••• __ • __ ._ •• __ •• _ ••••

~O. I I I o 500 1000 1500 ~OOO ~500 3000

VOLUME (ACRE-FT)

ELEVATION-STORAGE RELATIONSHIP FM 1016 TO MISSION INLET (14-7)

11S •

1 1 ()Jl--------------------______________________________ -..... ----------------------------------------------------------------------------------------1

1 OSC······· ~ ............. ~ ................•••.•..•.••.••••.•.•........•.....•...• lL. 1 ()() ---------- ------------------ ------------------------ --------------

....J 90-............................ . LJLJ ................................................................................................................... .

t:lS-··················································· ............................................................................................. .

t:lO--··················································· ............................................................................................. .

7S. I I I I I I I I I o 500 1000 1500 2000 2S00 3000 3S00 4000 4S00

VOLUME (ACRE-FT)


Table 1 Rainfall Depth / Duration for the Hidalgo County Study Area *

Point Rainfall Depths (inches) for Hidalgo County Study Area Return Period

(years) 5-min 15-min 60-min 2-hr 3-hour 6-hr 12-hr 24-hr

, 2-Year 0.50 1.10 2.00 2.60 2.70 3.25 3.70 4.30

5-Year 0.58 1.28 2.57 3.40 3.70 4.40 5.20 6.00

10-Year 0.64 1.42 2.97 3.95 4.30 5.20 6.10 7.10

25-Year 0.74 1.63 3.53 4.60 5.00 6.20 7.20 8.50

50-Year 0.81 1.79 3.97 5.10 5.70 7.00 8.30 9.60

100-Year 0.88 1.95 4.40 5.70 6.30 7.80 9.50 11.00

500-Year 1.7 3.2 5.75 7.25 8.0 9.9 12.0 13.75

I * Data taken from Technical Paper No. 40 and Technical Memorandum Hydro-35. I


RESULTS OF BASELINE CONDITIONS

• Computed Peak Flood Discharges at Key Locations

• Flood Elevations for Mission Inlet

• Flood Elevations for Sharyland/Trade Zone

• Single Occurrence Flood Losses

• Peak Storage Requirements

• Sensitivity Analysis


Table 2 Summary of Computed Peak Flood Discharges·

Mission Inlet Floodway Baseline Conditions - .. _------- ~~ - ----- - --

Drainage Computed Peak Flood Location Area Discharges

(sm) 10-yr 25-yr 50-yr 100-yr

, At Mission Main Canal 12.5 8500 10600 12200 13900

At Mission Inlet 12.5 9600 12200 14200 16400

At FM 1016 16.0 3900 6400 8600 11100

At Rio Grande Rd 22.6 5200 7800 9800 12200

At Shary Rd 23.2 5200 7800 9700 12100

At 23rd Street 64.3 6300 9100 12400 15800

At San Juan Elevated Canal 71.9 5500 8900 12200 16300

At Jackson Road 73.6 5500 9000 12300 16500

Note: Baseline condition peak discharges are based on fully urbanized watershed with existing (1995) topography.


Table 3 Summary of Computed Peak Flood Discharges*

Major Contributing Ditch Systems Baseline Conditions

Drainage Computed Peak Flood Location Area Discharges

(sm) 10-yr 25-yr 50-yr 100-yr

Rado Alternate 20.2 1980 2960 3440 4030

II Old Rado Alternate 3.0 700 880 1030 1200

II 23rd Street Ditch 1.5 1730 2130 2430 2750

I Airport Sump 0.4 160 170 190 200

Airport Ditch 1.4 740 870 940 1030

Rancho Santa Cruz Ditch 1.5 460 610 730 870

Note: Baseline condition peak discharges are based on fully urbanized watershed with existing (1995) topography.


Table 4 Summary of Computed 100-Vear Flood Elevations

Mission Inlet Floodway Baseline Conditions

100-Vear Location Flood

Elevation

Cell 12 (Mission Pump to San Juan Canal) 103.9

Cell 13 (San Juan Canal to 23rd St) 104.7

Cell 14 (23rd St to Shary Rd) 105.1

Cell 15 (Shary Rd to Rio Grande Rd) 105.7

Cell 16 (Rio Grande Rd to FM 1016) 106.2

Cell 17 (FM 1016 to Mission Inlet) 111.5

Note: Baseline condition flood elevations are based on fully urbanized watershed with existing (1995) topography.

----::.:.-"'--! =:. ;:;.~

---"! ..... =.,....--r-_

" ,.... ~ -... '-"'--"-:?'/-- ----." ".,. '-----~ ~7,-:::.

/ ,;:;. -:~

;, ,... ~/ L- _

-==.-;/ ~~

7 --c'. <-' -~ -I'2-~ f· _

-;: .... -/ -r" . ~. --

3 ~ ~ n

~ ~ ;Z

;

--.-~ . --,.. -~

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

_'t. 1 ~ 1

1 1 1

IW W LL

z z o I« > w ..J W

• •• • [HCINI

,2B.00

124.00 ;

I

, I

120.00 -- ' . ~ ,

'h " , , " " - , "

, " " "

116.00 If , "

, -,

" ,i

" " " " " r--U2.00 " "

10B.00

.

104.00

100.00

520~0.00 4B~0.00

iHalfT Associates OilS 0 ARCHITECTS. SClfNTI$TS • PLA"'ER$ 0 SLflVEYORS -~ ~-, ,- --~ -~------

,

:

" , I I I

!

I,r 'I.j'r I

' i l I f,~ I,.! VI~

!

, , ' ' , , " , , , ' ,

, " , , , " .

" , , " ' , ; I I" , , ! ! I \ " :,1 :1 \

, ' , , ;' ; , ,

, ' . , , "

, "

, , "

, , , "

, , ':

, , , " - >. , , ,

\' , , ; , , , '-. , , , , , . , , ,

-_C . [.:.' , , , ,

[~-- - :l , ~

, ",,-

,

Lj-

44~.00 4oo~0.00 36~.00 32~.00 2B~O.00 24~0.00 2oo~0.00

DISTANCE IN FEET

I\IJSSIIY\ H~LEI 1 LOOD PROFILE IOU YEAR EVENT

FLOOD PROTECTION PLANNING STUDY FOH SOUTHERN MCALLEN AND MISSION, TEXAS

:,

" ., ;

I I ., I

"1' ' I 1- -I : .

. . . , ' " , , ". , ,

I' / , I ,

, I 'r--, I - -, v '"\ t ~.. , , I 1/ , I " , - , , , I 1 ' . .1 t- :J, . , = ;,,:;F I

- I \

I II-- --I. I-

1600,0.00 1200,0.00 BOD?'OO 4OD?'00 o.po

1'1(;1 'in 7

OF McALLEN -~.~.--------

fW W u.. z

z o f<t > W -l W

• •• • ENGIN

,,,-v.vv

r-!,2MO

!

120.00 -- -,

li\ " , " \

" . \

" \ 1\ I

" I, ,

" 116.00 " \

" Ii II

" " " " r-lli'oo " 'I - -.:--

108.00

-- '"

I 104.00 -

100.00

52~0.00 48000.00

iHaUT Associates :RS" ARCHITECTS .. SCIENTISTS" P\. ........ ERS .. SlflVEYORS

"

: I .' ~: , _.

! I

I , I

,

I

!.I ", ,I,

I I 1-I

, \ I

" I " \ I I , I, \ I \

I I \ -2 I,

" I I : /:1'1 , I I , , Ii: :: \ \ " ' , I I ~ ... ' \ , \ . , I

I I I ,

\

" \ '\

I' \ " \

"

\ I I , , "

\ I I , '-11· \ I ' ,-- '-' ..... I I 'I " ,1 I, \1 , I , ,.. .. -.-'

, I \

"

, , , I , '-- , \ I I .... ' \ , I I \ I ..... '" - ... - -

I I I I '" /( t ..... I I - \ I I

I " ~--- -" I \' I .., - - - - - - - _ __.I. _y " - -

I --'- " , - -- - - ---- -1 I..." - - - - - ~ , I

- " - -------- ------~- -------- t" --~-I .... " C-:"':"':"'!..

- - - ~ - - --' ----.:0-- - --

I I I I I

\ ------J-- -------- -------

44~0.00 4oo~0.00 36~.00 32~0.00 28~.00 24~0.00 2oo~o.oo 160~.00 1200,0.00 80D?00 40D?00 O.pe

DIST ANCE IN FEET

'II~Sllll, I " 1,1 , I U)( JI) I'HOFlU J\J(;'II~I' g 111.25,511 \'\ I) I I I!) \ I',i II FYENP:

FLOOD PRO J IT' [I ,le,; !' L \ \1 N J r~ ( ; '., U!>'I Fon S (HIT H E H "I \1(\111\ , ''',1 rlW;SH1:';,1 F\ \<; OF McALLEN


Note:

Table 5 Summary of Computed 100-Year Flood Elevations

SharylandITrade Zone Baseline Conditions

Location 100-Year Peak Flood Elevation

Cell 1 112.1

Cell 2 105.6

Cell 3 106.6

Cell 4 104.6

Cell 5 105.7

Cell 6 102.7

Cell 7 105.4

Cell 8 103.3

Cell 9 102.3

Cell 10 96.7

Cell 11 93.5

Baseline condition flood elevations are based on fully urbanized watershed with existing (1995) topography.


Table 6 - Summary of Baseline Condition 100 Year Single Occurrence Flood Losses -

Total Cropland Number of Structures in Flood Zone

Location Flood Plain Flood Plain Acres Acres Residential Warehouse Commercial Other

Mission Inlet 2590 N/A 75 0 0 0

Cell 1 118 118 0 0 0 0

Cell 2 110 110 0 0 0 0

Cell 3 298 298 0 0 0 0

Cell 4 158 150 0 0 0 0

Cell 5 67 67 0 0 0 0

Cell 6 181 181 0 0 0 0

Cell 7 195 195 0 0 0 0

Cell 8 152 115 0 0 0 0

Cell 9 2715 1079 1085 18 47 5

Cell 10 540 365 0 0 0 0

Cell 11 238 120 6 0 0 0

I Total I 7362 I 2798 ! 1166 I 18 I 47 I 5 I

I=' 106 w w LL ....-Z o 105 I-

~ W -.J w 104

SINGLE OCCURRENCE FLOOD LOSSES MISSION INLET (CIMARRON)

o 5 10 15 20 25 30 35 40 45 50 NUMBER OF STRUCTURES

SINGLE OCCURRENCE FLOOD LOSSES CELL 9

103

r=-tlj 102 u.. --Z o 101

~ (fj 100 -.J w

98.5 ~ I

0 50 100 150 200 250 300 350 400 450 NUMBER OF STRUCTURES

l" WAREHOUSE • RESIDENTIAL IIIC()MMERCIAL IlIII OTHER

~ 94

SINGLE OCCURRENCE FLOOD LOSSES CELL 11

w !:S. ! j \7 i 100 YEA!p ELEV. 93.47 Z o i= ~ ~ 93 w

o 1 234 NUMBER OF STRUCTURES

\111 RESIDENTIAL-I

5 6


Table 7 Summary of 100-Year Peak Storage Requirement

For Sharyland/Trade Zone Baseline Conditions

100-YEAR PEAK STORAGE REQUIREMENT

DRAINAGE AREA AREA PEAK STORAGE STORAGE/ACRE AREA (sm) (ac) (ac-ft) (ac-ftlac)

Cell 1 0.67 429 317 0.74

Cell 2 1.26 806 589 0.73

Cell 3 2.36 1510 1249 0.83

Cell 4 0.69 442 364 0.82

Cell 5 1.06 678 555 0.82

Cell 6 0.58 371 311 0.83

Cell 7 1.83 1172 916 0.78

Cell 8 0.59 378 293 0.78

Cell 9 4.80 3072 2491 0.81

Cell 10 1.59 1018 835 0.82

Cell 11 0.75 480 383 0.80

Note: Baseline condition flood elevations are based on fully urbanized watershed with existing (1995) topography.


Table 8 - Sensitivity Analysis Summary

I Scenario Tested I Results

Gates Open at Mission • 100-yr elevation at Pump Station decreased from 103.8' to 100.3' I

Inlet Pump Station • 100-yr elevation at Shary Rd decreased from 105.7' to 105.2'

Mission Inlet Pumps in • No significant differences from baseline conditions. Operation

Adjust Loss Rates to 1" for • 1 OO-yr elevation at Pump Station decreased from 103.8' to 103.7' Agricultural Areas and 0" • 100-yr peak discharge decreases 6-14% throughout floodway. for Urban Areas

Drainage from Edinburg- • 100-yr elevation at Pump Station decreased from 103.8' to 102.8' Mission Lateral System • 100-yr peak discharge at confluence node decreased from 15,760 Excluded cfs to 9,520 cfs (40%).

! Note: All scenarios compared to Baseline Conditions, fully urbanized watershed with existing (1995) topography.


CONCEPTUAL DESIGN SOLUTIONS

• Mission Inlet Levee Modifications

• Mission Inlet Relief Spillway

• Proposed Flood Storage Sump Area Locations

100-YR GATES ULV'~V 100-YR GATES ~~_oo _0

_0_ I =~=HaUJ Associates

EHG11££RS • AROITECTS • SCIENTISTS· PLANNERS. SlJtVEYOR5 --"----

PROPOSED LEVEE MODIFICATIONS MISSION INLET FLOODWAY

FLOOD PROTECflON PLANNING STUDY FOR SOU'IHERN MCALLEN AND MISSION, TEXAS

N

PROP. ELEV. 105.0'

~O~' ~ " -, ~

\\/ !\ "',,'- ,.. v - -J

FIGURE 9

CITY OF McALLEN r:FlIINI/Y-

NOTE,

FOR 'GATE CLOSED' SCENARIO ADDITIONAL STORAGE REQUIRED, 7050 CC. ft. FOR 100 YR. EVENT 3830 cc. ft. FOR 50 YR. EVENT.

----. a

!'\ ~- I ----~ ~-----~,.,.

.0. =!= Halfi' Associates ENGINEERS • ARCHITECTS. SCENTISTS • PlANl£RS • SURVEYORS

~ ~ '6 ~

~ --<\

~

~ "?L.

TOP OF EXIST. LEVEE EL. 107'

~

I I --l..- 92.0'

STORAGE REQUIREMENT FOR 100 YR GATES CLOSED SCENARIO

PROPOSED LEVEE TOP ELEV.l05.0

FLOOD PROTECflON PLANNING STUDY FOR SOU1'HERN MCAU.EN AND MISSION, TEXAS

-~~---.-.-------

N

FIGURE 10

CITY OF McALLEN

1 I~ 11' ~I 2, f , 2

"

I--- 200'---1

TYPICAL LINEAR SUMP

XSrCTION -----

N

~ -" . KiLl .. nat

-~ I~~' ~I

2 r----r-I 2 LI5,--l TYPICAL

DRAINAGE STORAGE

DITCH

'.rn. IllHalff Associates ~ • ARCtITECTS • 5C£NTISTS • PlAN£RS • SlRV£YORS

PROP. OUTLET 1-6' X 4' GATED BOX CULVERT f.l. 97'

lOa YR. PEAK STORAGE = 317 00. ft. I ~

~ I~ 11' ~I 2, t , 2

I--- 225'---1

--~STORAGE = . f49 00, ft.

~-----

/,

-~~~--( t :------STORAGE I ' (DITCHES I I ,

1:~:~t'l, _ _~ ~===~=~

iJ' : --=-~:: . .-/-=-~-~ I

11'--- __ 4 I t ,-------------1 __ ~__ 10-0~Y-R.~P-EA~K~ I l

STORAGE = 589 --~ / --""'".-=~-=~""""---- ~ I o. n. : ), L_____ ~-1 ~ I I /-- __ ~I----- I ~:...; ~/- 'YI j ;~-- - j' ~... . I J-~=--_~=~~_~ 1/ -~

~ /, . \ / r~~~~lt7;~:~~ .~ I \ I ~ /I ~ "" ~~-; II \ / ~ II H "" """, "" ~!~~

~ff--~-r ~=l,._L~~ -J ,)1'--~/ r " r- ""/ '" II II /I

,lU\5_iill MADERO

PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 1 & FLOOD PROTECl'ION PLANNING STUDY FOR SOUTIIERN MCAlLEN AND MISSION, TEXAS

FIGURE 11

OF McALLEN

N

=-----' .,. ~.-

I

rl~-~-. - -~ , -- r

. f----j - I' 1 -- ~L.,.. ____ _

-- ----I' --,----,-

I -------1 I I I I

I

I :~-:---,..,I I

PROPOSED

_i ... ,UlAn Associates EtQ££RS _lADIT£CTS • SaEH1lSrs. PlAIKRS • SLRVEYDRS

I I I ~ '1~~~ I

Irrl

!:,~\..'v"'~ ~ ~ I o ",G ~~' ~Q~OC.·

I

I S 0,-" I W

, 'j; I 0::

, :::J C)

u... w w If)

w Z --1

:r: u I-<t

~ __ ~=..,. __ .... ".,' :::2:

~~-®{ I I .-- .{! I

FIGURE 12

CITY OF McALLEN

w Z ---1

MA TCH LINE SEE FIGURE 15 PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 3 - 9 .0.. SHEET 2 OF 4

TYPICAL LINEAR SUMP

XSECTION

. , ~~~-----T-~~

\. , I' \ \ . \

FIGURE 13

I =~=HaJff AsSOCiates FWOD PROTECI'lON PLANNING STUDY .... "'.RS·'RC..-rms·sO.HTISTS·P!..ANNERS·StJlvrYORS FOR SOUTHERN MCALLEN AND MISSION, TEXAS ~ ~ ••• CITY OF McALLEN I

N

~~--SW-"iiIT

HaUl Associates

MATCH LINE SEE FIGURE 12

LO ';. at -I ~r- --, '" ' ' ~~llll ~

fW 'IIF~/ gj

j~~~~r--··~'·~·~~~*r~=n~ ~ l .'_._ ". "-.'00 c' 'Lng 1 , ~"'h i w

~,... ~l W K- _. I , Vl

PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 3-9 SHEET 3 OF 4

FLOOD PROTECfION PLANNING STUDY FOR SOUTHERN MCALLEN AND MISSION, TEXAS

::1;'I=r-= .cl~ 3 I .:c I < u

• r· • ~

• \ 1249 00. ft.

I a STORAGE = I. 89 00. ft.

A 1/ I r r-f' ,,~,~.,~ , 80

I ~

/.,

FIGURE 14

CITY OF McALLEN

MA TCH LINE SEE FIGURE 13

<;T

w

~ I 'tmVO

oe. n. ~~~." ~ L~~ 1: ft~. ~ ;~~u u C)7/////!i%~ ... rT-1l;O~.. ~~! ~ LL . /. .. .?f!oPOSED " - I ) I~ f'£J F-ili ORCHARD fl . :::.". W W Vl

W Z -.l

I U f-« ~ It--~

c<.'-'-~~ ?<.~~ ~oo ' r.<.O S\ol'-~" ~~~~ oC.

~ ~ l\" l\" '-~ '-

.0. . =~=HaltJ Associates EHCtNE£RS. ARCHTECTS • SaEHTISTS • PlANNERS' SllW£YORS

5' li If~ 1~Lsl

PROPOSED BERM TOP ELEV. 103.0

PROPOSED DRAINAGE IMPROVEMENT FOR CELLS 3 - 9 SHEET 4 OF 4

FWOD PROTECTION PLANNING STUDY FOR SOUTHERN MCAlLEN AND MISSION, TEXAS

1'1

FIGURE 15

CITY OF McALLEN


SUMMARY OF FINDINGS

• The computed 100-year flood (with gates closed) will overtop Mission Inlet levee at five locations.

• The computed 100-year flood (with gates open) will overtop Mission Inlet levee at three locations.

• The estimated average freeboard at the Banker Floodway (for 106,300 cfs) is about 2 feet.

• Appproximately 1236 structures are inundated by the computed 100-year flood.

• The required flood storage required to provide flood relief for structures located in Balboa Acres and the Trade Zone is about 1470 acre-feet.

Documents

ENGINEERS· ARCHITECTS· SCIENTISTS· PLANNERS· SURVEYORS … · FAX (817) 232-9784 March 23, 1996 AVO 14191 City of Mission 900 Doherty Mission, Texas 78572 Attn: Pat Townsend,