EXECUTIVE SUMMARY of Houston Projects/Reports a… · 2004-10-20 · SUBJECT: WO132 – Binglewood Tropical Storm Imelda Analysis EXECUTIVE SUMMARY Halff Associates, Inc. (Halff)

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Halff Associates, Inc. 14800 St. Mary’s Lane, Suite 160

Houston, Texas 77079 (713) 588-2450

MEMORANDUM

TO: Melissa Jefferson, P.E. Kevin Hammond, P.E.

DATE: April 10, 2020

FROM: C. Andrew Moore, P.E., CFM

Water Resources Team Leader

AVO: 31051 – WO132

EMAIL: [email protected] SUBJECT: WO132 – Binglewood Tropical Storm Imelda Analysis

EXECUTIVE SUMMARY

Halff Associates, Inc. (Halff) has been contracted to provide technical support services for the City of Houston Storm Water Engineering Program Support (the City). The purpose of this work order is to evaluate the constructed conditions and ultimate designed conditions of the Binglewood drainage system for the rainfall that occurred during Tropical Storm Imelda.

The Binglewood project area located in northwest Houston near HWY 290 experienced significant rainfall during the Tropical Storm Imelda resulting street ponding and structural flooding. At the time of the storm event, Binglewood drainage improvements were being constructed that included the installation of storm sewer and the conversion of streets from using roadside drainage ditches to using curb and gutter. Upon completion of construction, the drainage report stated that the drainage improvements would provide a minimum 10-year level of service with some parts of the system providing a level of service up to 100-year. A 10-year level of service is defined as a storm sewer system that has the capability to contain the 10-year frequency design storm event within the City Right-of-Way. The outfall for the Binglewood drainage system is Brickhouse Gully (HCFCD Unit. No E115-00-00). The FEMA effective models for the channel show that it has the capacity to contain a 10-year level of service. Since the storm sewer system outfalls into the channel, the channel elevations will be the lowest water surface elevation in the Binglewood drainage system. Water surface elevations upstream of the outfall channel will only increase in elevation due to friction of the storm sewer pipes and flow restrictions from inlets and manholes. Since the design of the project, The National Oceanic and Atmospheric Administration has released a revised rainfall analysis for the State of Texas hereby known as Atlas 141. The document showed that frequency rainfall rates for the Harris County region should be higher than previously estimated. As an example, the Pre-Atlas 14, 100-year design storm event for the Harris County region was approximately 13-inches in a 24-hour period. The Atlas 14 document showed that the 100-year design storm event is

1 NOAA Atlas 14 Precipitation-Frequency Atlas of the United States Volume 11 Version 2.0: Texas

mailto:[email protected]

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Houston, Texas 77079 (713) 588-2450

approximately 18-inches in a 24-hour period. Since this project was designed prior to the rainfall update, all rainfall frequencies hereby described will relate to the previous rainfall. Per City information, residents noted they did not experience flooding during Hurricane Harvey, a storm event that affected the greater Houston area and lasted multiple days, when the previous roadside drainage ditches were in place. Hydrologic and hydraulic models of the neighborhood drainage system were obtained from the City and used to simulate several drainage conditions and scenarios to determine the cause of flooding in recent storm events. The simulations were compared to high water marks obtained from the City and flooding photographs provided by residents to confirm the model results. The events and scenarios included:

• Tropical Storm Imelda Construction Conditions – Model modification to simulate the actual constructed conditions during the tropical storm. Construction conditions were provided by City staff.

• Tropical Storm Imelda Proposed Conditions – The proposed conditions model assuming the entire project had been built according to design during the tropical storm

• Tropical Storm Imelda Pre-Existing Conditions – The pre-existing conditions model prior to any construction in the neighborhood

• Hurricane Harvey Pre-Existing Conditions – The pre-existing conditions model prior to any construction in the neighborhood simulated for Hurricane Harvey.

The hydrologic and hydraulic models for the Binglewood drainage system were simulated for the Tropical Storm Imelda rainfall to determine the ponding elevations throughout the Binglewood project area and to examine the source of flooding for residents within the neighborhood during the storm event. The analysis was performed under the following assumptions that were provided per record of City staff:

• The drainage system was not connected to the outfall at Hollister Road during the storm.

• The north half of Sonneville Drive had not yet been reconstructed.

• The tailwater condition at the outfall by Hollister Road was determined using the gage elevation curve during the storm.

• The tailwater conditions at the two upstream outfalls were determined using the FEMA HEC-RAS profile.

• The backflow preventers at all three outfalls had not yet been installed.

The ponding results were validated using photographs provided by Binglewood residents. Based on this analysis conducted, the Binglewood drainage system appears to be designed in accordance with the City of Houston’s 10-year design criteria. Rainfall information obtained from Harris County suggests that Tropical Storm Imelda resulted in up to 4.4 inches in one hour, which is approximately a 100-year storm event (based on Pre-Atlas-14 rainfall intensities), stressing the storm sewer system beyond the capacity. The HCFCD gage also recorded near record elevations reaching 76.70’ on the downstream side of the Hollister, with potential higher elevations upstream due to flow restriction of the bridge crossing as shown in hydraulic modeling of the channel. This stage results in a high tailwater for the drainage system. The intense rainfall along with the high tailwater in Brickhouse Gully appears to be the cause of structural flooding within the neighborhood. A proposed construction scenario was conducted, assuming the designed Binglewood construction had been completed at the time of Tropical Storm Imelda. This scenario assumed that backflow preventers were installed at each outfall and that the outfall at Hollister Road was connected to the storm sewer system. The same outfall conditions were assumed as with the constructed conditions scenario. The results suggest that had the construction been complete, the Binglewood area would have still seen high elevations and structures may have still been impacted due to the high tailwater condition in Brickhouse Gully and intense rainfall.

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Houston, Texas 77079 (713) 588-2450

A Hurricane Harvey scenario was conducted to validate the analysis and compare to the Tropical Storm Imelda information since the residents stated they did not experience as much ponding during Hurricane Harvey. While Hurricane had less intense rainfall and lower elevations in Brickhouse Gully which allowed the storm sewer systems to drain. The Imelda storm event was also modeled for pre-construction conditions (roadside ditches) to simulate how the system may have functioned during the tropical storm. In general, the completed project provides overall benefit to the area and ponding during the tropical storm would have been worse in pre-construction conditions. The designed improvements reduce the amount of backflow from Brickhouse Gully. Elevations on Knoll St. were similar to the proposed construction scenario.

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Houston, Texas 77079 (713) 588-2450

INTRODUCTION

The City requested Halff simulate the Tropical Storm Imelda rainfall to determine the source of flooding for residents within the neighborhood for the Tropical Storm Imelda event. This memorandum summarizes the detailed hydrologic and hydraulic analysis conducted to determine the reason for street and structural flooding within the Binglewood neighborhood, here after referred to as Binglewood. The analysis consisted of the following goals:

• Conduct field survey of the finished floor elevations of the structures on Knoll Street

• Revise existing hydrologic and hydraulic models to simulate the Tropical Storm Imelda storm event

• Determine the source of residential structural flooding during the Imelda event

• Evaluate the existing conditions models for the Hurricane Harvey storm event

PROJECT LOCATION

The study area is located east of Blalock Road, south of Clay Road, west of Hollister Road, and north of Brickhouse Gully in northwest Houston. The study area in shown on Exhibit 1. According to City staff, the residents within the project who experienced flooding during Tropical Storm Imelda were all structures along Knoll Street and the northwest corner or Sonneville Drive at Hollister Road. The drainage system for this area consists of interconnected storm sewer that conveys flow south to Brickhouse Gully (HCFCD Unit No. E115-00-00) through three outfalls. The area adjacent to the project area on the north, east, and west side were considered for generating potential offsite flow for the study.

DATA COLLECTION

Halff used hydrologic and hydraulic models and reports for the Binglewood drainage system, field investigation, available construction plans, and 2018 Houston-Galveston Area Council (HGAC) LiDAR2 as part of the analysis.

Hydrologic and Hydraulic Models The HEC-HMS hydrologic model, 2D XPSWMM model, and the effective HEC-RAS model of Brickhouse Gully were obtained from the City of Houston from the Binglewood Area Improvements Drainage Impact Analysis3 (2017 Study). The boundaries of the XPSWMM model reach Clay Road to the north, Peppermill Road to the west, and Hollister Street to the east. Figure 1 shows a layout of the storm sewer system used in the XPSWMM model.

2 Light Detection and Ranging (LiDAR) is remote sensing technology that measures distances, elevations, or

surfaces by illuminating a target with a laser and analyzing the reflected light (HGAC). 3 Binglewood Area Improvements Drainage Impact Analysis, IEA, Inc. (2017)

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Houston, Texas 77079 (713) 588-2450

Figure 1 ‒ Layout of Binglewood Storm Sewer System (source: 2017 Study)

Plan Drawings Construction plans were used to obtain offsite storm sewer information for the trunkline along Clay Road (Plan No. 44055 & 18115), north of the Binglewood project area, to add to the XPSWMM model as potential overflow.

Field Investigation A field investigation was conducted on November 21, 2019 to obtain culvert sizes for the neighborhood east of the project area verify the completion of construction on Binglewood, verify the installation of flap gates at the outfalls, and verify other storm sewer sizes. Figure 2 shows a typical culvert size along the overflow area from the residential area west of the Binglewood storm sewer system. During the field visit, it was observed that the proposed streets in Binglewood have been completed since Tropical Strom Imelda and backflow preventers have been added to all Binglewood (M-000293-0001-4) project outfalls.

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Figure 2 – November 2019 site investigation of Culvert at Pitner Road and Galway Lane

intersection (left side). Backflow preventer at Outfall C located close to Hollister Road (right side).

Terrain A terrain dataset was developed to define the ground surface for a “rain on grid” analysis and to delineate drainage basins adjacent to the project area for potential overflow. The terrain information for each area was developed from the 2018 Houston-Galveston Area Council (HGAC) 1-foot contour LiDAR dataset. The terrain model and potential overflow basins are shown on Exhibit 2.

Survey Finished floor elevations were surveyed for the nine flooded structures along the Knoll Street cul-de-sac and one structure on Sonneville Drive to aid in the calibration of the XPSWMM model to Tropical Storm Imelda conditions. All ten structures were surveyed at the front entrance of each residence and at the ground level near the location where the highwater marks were measured. The elevations at the highwater mark location were compared to the results from the XPSWMM model. Figure 3 shows an overview of the finished floor elevations for each structure and the location in which the highwater mark for each structure was taken. Exhibit 3 shows the survey completed for this analysis.

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Houston, Texas 77079 (713) 588-2450

Figure 3 – Surveyed Finished Floor Elevations

Imelda Flooding Photographs Information was also provided from the City summarizing the Binglewood Resident’s account of Tropical Storm Imelda, including photographs. The photographs were taken on September 19, 2019, but the approximate time of the photos was not provided. Below is a summary of the observed event:

• There was excessive street ponding along Colleen Road, at Peppermill Road in front of Binglewood Park, and at the Pitner and Mona Lee Lane intersection during the Tropical Storm Imelda event.

• Ponding observed during Tropical Storm Imelda exceeded the ponding observed during Hurricane Harvey 2017.

• The photographs show standing water along Colleen Road (Figure 4), at the intersection of Pitner and Mona Lee Lane (Figure 5), and at Peppermill Road facing Binglewood Park (Figure 6).

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Houston, Texas 77079 (713) 588-2450

Figure 4 ‒ Colleen heading east toward Mona Lee Ln

Figure 5 ‒ Intersection at Pitner Road and Mona Lee Lane

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Houston, Texas 77079 (713) 588-2450

Figure 6 ‒ View of Binglewood Park from Peppermill Road

According to City staff, the Binglewood Area Drainage and Paving project was under construction during Tropical Storm Imelda. City staff indicated that the storm sewer improvements had not been completed at the time of the event. They indicated the following conditions during construction:

• The Binglewood outfall along Sonneville Road was not connected to the Hollister Road storm sewer.

• The backflow preventers had not yet been installed at each project outfall into Brickhouse Gully.

• The north side of Sonneville Drive had not yet been constructed.

Rainfall and Gage Information Rainfall data for Tropical Storm Imelda 2019 was obtained from both the Harris County Flood Warning System (HCFWS) rainfall gage network and from the National Weather Service (NWS). The HCFWS gage nearest to the project area is Gage 582: E115_582 Brickhouse Gully @ Hollister. The HCFCD FWS gage rainfall was compared to the NWS Radar data to validate both the Radar data and that the gage was functioning properly during the event. Figure 7 shows the comparison graph for both rainfall sources. As seen in the graph, the HCFWS gage begins to record rainfall at 9:00AM hours with an intensity of approximately 3.5 in/hr. In contrast, the NWS rainfall does not begin to show rainfall intensity until an hour later. After the first hour, the NWS rainfall intensity is slightly higher than the HCFWS gage for every hour. For this analysis, the HCFCD gage rainfall data was used instead of the NWS rainfall data since the gage is located within the project boundary.

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Houston, Texas 77079 (713) 588-2450

Figure 7 ‒ Rainfall Data for Tropical Storm Imelda Comparison of Gage and NWS Radar

Figure 8 shows the total rainfall experienced on September 19, 2019 at Binglewood by hour as reported by the HCFWS Gage 582. A total of 7.9 inches of rainfall were reported by the gage in a 6-hour period.

Figure 8 – Tropical Storm Imelda Rainfall

Tropical Storm Imelda resulted in significant rainfall on September 19, 2019 in northwest Houston. Figure 9 shows a table from the HCFCD report titled “HCFCD Immediate Flood Report - #1 September 19, 2019” in which HCFCD reported rainfall and flood information for all streams within the county.

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Figure 9 – Rainfall Intensity at Gage 582 During Tropical Storm Imelda

Gages 580 and 582, which are both near the project area, recorded 4.4 inches in one hour and over 6 inches in a two-hour time interval. For both the one-hour and two-hour time periods, the neighborhood was receiving 100-year4 rainfall depths (Pre-Atlas 14 rainfall).

Gage 582 at Hollister Road also recorded a peak stream elevation of 76.7 feet. Figure 10 shows a graph from the HCFWS, displaying the stream elevation on the downstream end of the Hollister Road bridge for Brickhouse Gully. The figure shows flooding was likely when the channel water surface elevation was above 76 feet downstream of Hollister Road from approximately 12:00PM to approximately 3:00PM.

Figure 10 – Stream Elevation of Brickhouse Gully at Hollister During Tropical Storm Imelda

The FEMA effective HEC-RAS model was used to estimate tailwater conditions for the two outfalls upstream of Hollister. Figure 11 shows the profiles for the storm events from the HEC-RAS model. The model shows that there is potential headloss across the Hollister Road bridge which can cause higher elevations in the Binglewood area that what is reported at the gage.

4 The figure from the HCFCD Immediate Flood Report shows that maximum intensity was approximately a 50-year

storm event. However, this rainfall is assuming Atlas 14 design frequencies.

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Figure 11 – FEMA Effective 50-year Profile for Brickhouse Gully

Binglewood Area

Hollister Road

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CONSTRUCTED CONDITIONS ANALYSIS

The two-dimensional5 (2D) XPSWMM6 model provided by the City was used as the base for this analysis. According to the previous report, the Rational Method was used to compute peak flows for the drainage basins. Runoff hygrographs for the 10- and 100-year events were then computed using the Clark Unit Hydrograph Method in HEC-HMS. Time of concentration from the Rational Method was used to calibrate the storage value for the 10- and 100-year storm events until the hydrograph’s peak flow matched the peak flows obtained from the Rational Method. The HEC-HMS basin model for the 100-year event was used to develop hydrographs for Tropical Storm Imelda since the rainfall rates for the tropical storm were closer to a 100-year event. The rainfall hyetograph from the HCFWS Gage 582 was input into the HEC-HMS model provided to generate the runoff hydrographs for each drainage area. The runoff hydrographs were then input into the hydraulic model. Boundary Conditions There are three outfalls (Outfalls A, B, and C) for the Binglewood system into Brickhouse Gully. For the eastern outfall (Outfall C) located at Hollister Road, the tailwater was set to a variable elevation recorded by Gage 582 during Tropical Storm Imelda. There were no gage readings or high-water marks available at the time of this report for the remaining outfalls A and B. Therefore, elevations for Outfalls A and B were estimated assuming a similar elevation shape to the outfall at Hollister Road, but with a higher peak elevation. The peak elevation was estimated at approximately 82 feet from the 50-year water surface elevation profile on the FEMA HEC-RAS model. Overflow The residents indicated that during Imelda, flow from Clay Road to the north and Pitner Road to the west overflowed into the Binglewood neighborhood. A “rain on grid” analysis confirmed the potential overflow. Overflow from these areas was added to the constructed conditions model using construction plans and field visits to obtain any necessary culvert and trunkline geometry information. Figure 12 shows the overflow coming from Clay Road and west of the project area.

5 Hydraulic modeling approach where overland sheet flow can travel in multiple directions similar to actual flow

patterns. 6 Proprietary hydraulic modeling software used to determine flow rates and water surface elevations that result from

rainfall events for a drainage network.

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Figure 12 ‒ Overland Flow Analysis

Constructed Conditions Tropical Storm Imelda occurred while the improvements to the Binglewood system were under construction. The model was adjusted as follows to reflect the constructed conditions at the time of Tropical Storm Imelda:

• The 8’x4’ RCB on Sonneville Street had not been connected to the 36” RCP outfall on Hollister Road. In the model, the 36” RCP connecting to the 8’X4’ RCB upstream was deleted to simulate its disconnection from Outfall C during Tropical Storm Imelda.

• The two empty lots on the southwest intersection of Hollister Road and Sonneville Drive were used for stockpiles of construction material. The terrain for two empty lots on the southwest intersection of Hollister Road and Sonneville Drive was elevated fifteen feet above the normal ground in the hydraulic model to simulate piles of construction material.

• The three backflow preventers on the Brickhouse Gully outfalls had not been installed. These were removed from the model to allow flow to both leave the drainage system into Brickhouse Gully and backflow from Brickhouse Gully into the drainage system.

• The north side of the street at Sonneville Drive had not been constructed; therefore, the roadside ditches and roadway were still in place. This portion of the model was replaced with the previous terrain elevations and the lateral pipes on the north side of the street were disconnected from the inlets.

Figure 13 shows the construction plans and highlights some of the elements considered to build the constructed conditions model.

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Figure 13 – Binglewood Construction Conditions

No BDP installed

Lot raised with material

North side unconstructed

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Results The constructed conditions model was simulated for the Tropical Storm Imelda event to determine the ponding elevations and sources of flooding. The 2D XPSWMM model results were validated with the ponding photographs provided by residents. The results show similar extents to the ponding observed in the photographs. The model ponding and photographs are shown in Figure 14 to Figure 17.

Figure 14 – Peppermill Road Results for Tropical Storm Imelda

Street ponding can be observed along Peppermill Road from a resident’s window overlooking Binglewood Park. As seen on this figure, there is standing water along Pitner Road that covers the curb.

Figure 15 – Colleen Road and Mona Lee Lane Results for Tropical Storm Imelda

Street ponding can be observed at the intersection of Colleen Road and Mona Lee Lane. Figure 15 shows both the resident’s photo and the model results. As seen in the images, standing water completely ponded the street and neared the entrance of the homes.

Colleen Road

Mona

Le

e L

ane

Pep

perm

ill Ro

ad

Source: City of Houston


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Figure 16 – Colleen Road by Outfall B Results for Tropical Storm Imelda

Street ponding can be observed at the intersection of Colleen Road and Valleyfield Drive at approximately the limits of the curb. As seen on Figure 16, there is standing water along Colleen Road near the top of curb.

Figure 17 – Mona Lee Lane and Pitner Road Results for Tropical Storm Imelda

Street ponding can be observed at the intersection of Pitner Road and Mona Lee Lane. As seen on Figure 17, standing water at the intersection completely submerged the curb. The 2D XPSWMM model shows that all structures on Knoll Street experience flooding during Tropical Storm Imelda. Significant ponding can also be observed at the Knoll Street cul-de-sac as seen on Figure 18. An overall ponding map for constructed conditions can be found in Exhibit 4.

Pitner Road Mona

Le

e L

ane

Colleen Road

Water on Colleen Rd

covers the curb, but

inundation boundary does

not reach structures.



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Figure 18 – Inundation at Knoll Street

Finished floor elevations were surveyed for all structures on Knoll Street. These surveyed elevations were used to calculate the high-water mark elevations that were measured by the City. Table 1 shows the surveyed finished floor elevation, the ponding depth observed by the City, the calculated highwater mark elevations (finished floor plus ponding depth) and the ponding elevations calculated by the 2D XPSWMM model.

Kno

ll Stre

et

Sonneville Drive

Hollis

ter R

oad

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Table 1 Highwater Mark Elevations During Tropical Storm Imelda

The average difference between the 2D XPSWMM model ponding elevations on Knoll Street and the highwater mark elevations is less than 3 inches. However, the model ponding elevation at the structure on Sonneville Drive is lower than the highwater mark by almost 10 inches. A high-level “rain on grid” analysis was performed to observe if any overflow from the system east of Hollister Road may have contributed to flooding. Figure 19 shows that no overland sheet flow occurred from east of Hollister Road through 8802 Sonneville which would have caused additional flooding shown in Table 1. A possible storm sewer system backup or clogged inlets on the drainage system east of Hollister Road during Tropical Storm Imelda could have resulted in additional flooding along Sonneville.

Figure 19 – Rain on Grid of Hollister Road and Sonneville Drive Intersection

Velocity vectors from the 2D XPSWMM model show the overland flow direction during the storm events. The flow patterns for the southern section of the model during the Tropical Storm Imelda simulation are shown on Figure 20. In general, runoff flows from the Northwest to the Southeast. Knoll Street sits in the Southeast portion of the neighborhood and has some of the lowest terrain elevations. Stormwater runoff

Address

Survey

Finished Floor

Elevation (ft)

Ponding

Depth (in)

High Water Mark

Elevation (ft)

SWMM

WSEL (ft)

3302 Knoll 78.6 6 79.1 79.0

3307 Knoll 78.8 5.5 79.3 79.0

3306 Knoll 78.6 8.5 79.3 79.0

3310 Knoll 78.2 13.5 79.3 79.0

3402 Knoll 78.7 8 79.4 79.0

3406 Knoll 78.9 7 79.5 79.0

3407 Knoll 78.4 15 79.7 79.1

3403 Knoll 78.5 10 79.3 79.0

3311 Knoll 78.7 5 79.1 79.0

8802 Sonneville 78.8 7 79.6 78.8

Sonneville Drive

Ho

llis

ter

Ro

ad

Homes on Colleen

Meadows Circle

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that cannot enter the drainage system overflows southeast towards the intersection of Sonneville Drive and Hollister Road.

Figure 20 – Velocity Vectors During Tropical Storm Imelda

The model also confirms overflows from Clay Road and Pitner Road from adjoining neighborhoods. Approximately 60 cfs overflowed from Clay Road into the neighborhood. However, most of this flow was captured by the storm sewer along McKean Drive and was conveyed by the storm sewer to Brickhouse Gully. Running the model both with and without overflows show that the overflows contribute to additional ponding in the neighborhood, the additional ponding is localized near the overflow area. Flows from the Clay Road only affect roads near Clay Road and flows from Pitner Road only affect the areas near Pitner Road. Figure 21 shows the overflow patterns on the north side of the Binglewood neighborhood.

Figure 21 - Overflow Patterns from Clay Road

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Approximately 55 cfs overflowed from the Pitner Road system into Binglewood. However, most of this flow is captured by the Peppermill Road storm sewer and conveyed either to the detention pond or into Brickhouse Gully. Figure 22 shows the overflow patterns on the west side of the Binglewood neighborhood.

Figure 22 - Overflow Patterns from Pitner Road

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COMPLETE PROJECT CONDITIONS ANALYSIS

Tropical Storm Imelda was also simulated for the completed project conditions to determine if the ponding would have been reduced had the project been completed. For proposed conditions, the 36” RCP, which connects to the 8’X4’ RCB storm sewer on Sonneville, was added to connect to Outfall C by Hollister Road as shown in final construction plans. The backflow preventers were also added at each of the three outfalls which prevent flow from Brickhouse Gully from entering the Binglewood neighborhood. The north side of the street at Sonneville Drive was modeled as complete with curb and gutter street sections. The project complete conditions simulation for the Tropical Storm Imelda event show a reduction of street ponding of approximately 5 inches at the intersection of Mona Lee Lane and Colleen Road. There is a reduction of 8 inches at the intersection of Mona Lee Lane and Opelika Street and a reduction of approximately 7 inches at the intersection of Mona Lee Lane and Autauga Street. Figure 23 compares the ponding along the three intersections for both constructed and final conditions. The reduction is attributed to the installation of the BPDs which prevent flow from Brickhouse Gully from entering the storm sewer and the connection of the system to Outfall C on Hollister Road.

Figure 23 – Street Ponding Comparing Project Complete Conditions (left) and Constructed

Conditions (right)

Mo

na

Le

e L

an

e

Mo

na

Le

e L

an

e

Colleen Road Colleen Road

Opelika Street

Opelika Street

Autauga Street

Autauga Street

Maximum Depth 1.4’


Maximum Depth 1.6

Maximum Depth 2’


Maximum Depth 2’

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The Knoll Street cul-de-sac shows no significant difference in ponding depths. Figure 24 shows that ponding is still 1.6 feet deep at the intersection of Sonneville with Knoll Street. This suggest that structural flooding may have still occurred had the backflow preventer been in place and the outfall connected by the 36” RCP. Exhibit 5 shows the overall ponding map of the Binglewood drainage system proposed conditions.

Figure 24 – Maximum Ponding at the Sonneville and Knoll Intersection Final Construction

An additional iteration was explored to determine if the backlot storm sewers along Knoll Street and Mona Lee should be removed or left in place. These storm sewers were part of the original system that provided an additional outfall for the cul-de-sacs. The XPSWMM model for the constructed conditions was simulated for the Tropical Storm Imelda event for both including and removing the outfall conditions. The model indicates that including the side lot outfalls increase the ponding on Knoll Street when the Brickhouse Gully is higher than the street of the cul-de-sacs. The storm sewer allows backflow from the gully into the streets. Since the area is suspectable to backflow from the Gully, it is recommended to remove or abandon these outfalls.

Sonneville Drive

Kno

ll Stre

et


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TROPICAL STORM IMELDA PRE-CONSTRUCTION VS. CONSTRUCTED CONDITIONS COMPARISON

The Imelda storm event was also modeled for pre-construction conditions to simulate how the pre-construction system would have functioned during the tropical storm. The existing conditions hydrologic and hydraulic models prepared by IEA, Inc. were used to simulate the pre-construction conditions. Figure 25 compares the street ponding during Imelda for the pre-construction and completed construction conditions. Knoll St. and Sonneville Dr., located in the southeastern portion of the neighborhood, show similar water surface elevations between pre-construction and post construction. Railton St, Opelika St, and Collen Rd show a reduction in water surface elevation in the constructed conditions due to the BDPs which prevent flow from the channel from entering the neighborhood. Springview Lane shows a potential increase in water surface elevation by 0.1 feet from the pre-existing condition to the constructed condition. The neighborhood was designed for a minimum 10-year event and Imelda was a 100-year storm event (Pre-Atlas 14 rainfall) which is likely the cause of the slight 0.1-foot increase.

Figure 25 Street Ponding Comparing Pre-Existing Conditions (left) and Constructed Conditions

(right) during the Simulated Tropical Storm Imelda Event

WSEL = 78.9’

WSEL = 80.9’

WSEL = 79.8’

WSEL = 78.9’

WSEL = 80.8’

WSEL = 80.0’

Railton Street

Colleen Road

Autauga Street

Opelika Street

Kn

oll S

treet

Sonneville Drive

Railton Street

Colleen Road

Autauga Street

Opelika Street

Kn

oll S

treet

Sonneville Drive

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HURRICANE HARVEY MODEL VALIDATION

A Hurricane Harvey simulation was used to validate the 2D XPSWMM model. This simulation was performed using conditions prior to construction, (i.e. when the the Binglewood drainage system consisted of roadside ditches). To validate the model, damage claims were obtained from Harris County for the Hurricane Harvey event. Figure 26 show the general location of areas with claims as reported by the county. These claims do not specify claim type but rather served as a general guide to validate the results of the Hurricane Harvey model.

Figure 26 – Harris County Claim Areas During Hurricane Harvey

HCFWS Gage 582 at Hollister Road had not yet been installed at the time of Hurricane Harvey. To simulate this event, Gage 580 Brickhouse Gully @ Costa Rica, the next gage downstream on Brickhouse Gully, was used to obtain rainfall information. A total 31.1 inches of rain fell over the area serviced by the gage during August 25, 2017 to August 31, 2017. Figure 27 shows a graph of the rainfall depth every hour.

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Figure 27 – Rainfall Depth by Hour During Hurricane Harvey

Areas of White Oak Bayou recorded rainfall intensities surpassing a 2,000-year storm event. However, more frequent durations, which is what stress storm sewer and channel capacities, were equal to or less than 25-year event (Pre-Atlas 14 Rainfall). Throughout White Oak Bayou, Hurricane Harvey had less rainfall accumulation during shorter durations than Tropical Storm Imelda. For example, Tropical Storm Imelda brought 6.6 inches in 2 hours, but Harvey only brought 4.6 inches in 2 hours. Figure 28 shows the rainfall intensities for White Oak Bayou as reported in HCFCD report titled “HCFCD Immediate Report – Final Hurricane Harvey – Storm and Flood Information”.

Figure 28 – Rainfall Intensities for White Oak Bayou During Hurricane Harvey7

Brickhouse Gully reached an elevation of 76.4 feet at Hollister Road during Hurricane Harvey as reported in HCFCD highwater marks. This stream elevation is lower than the elevation recorded at the gage during Tropical Storm Imelda by several inches, suggesting that a higher tailwater during the tropical storm caused may have prevented flow from leaving the Binglewood storm sewer system. The stream elevation curve recorded by Gage 580 was modified with the highwater mark at Hollister Road to create a tailwater condition at Outfall C of varying elevation. To develop the tailwater conditions for Outfall A and B, the outfalls upstream of Hollister Road, the same shape of the elevation curve at Hollister Road was used but with a higher peak elevation. The peak elevation at both upstream outfalls was determined using the profile of the FEMA HEC-RAS model for Brickhouse Gully. The peak elevation for the two outfalls upstream of Hollister Road was determined to be 78.9 feet.

The ponding elevations resulting from the Hurricane Harvey model show lower ponding than Tropical Storm Imelda for residents on the Knoll Street cul-de-sac. Figure 29 compared the ponding at Knoll Street cul-de-sac during Hurricane Harvey and Tropical Storm Imelda as simulated by the XPSWMM model. As seen

7 The figure from the HCFCD Immediate Flood Report for Hurricane Harvey shows that maximum intensity was

approximately a 25-year storm event. This figure uses Pre-Atlas 14 rainfall.

27


Houston, Texas 77079 (713) 588-2450

in this figure, Hurricane Harvey did not cause the street to become fully submerged as Tropical Storm Imelda did. In addition, the maximum ponding boundaries during Hurricane Harvey on the left do not expand to the structures as they do on the right image.

Figure 29 – Ponding at Knoll cul-de-sac during Hurricane Harvey (left) and Tropical Storm Imelda (right)

Only one structure shows flooding in the cul-de-sac, which appears to match the claim area highlighted on Figure 26.

In comparison with the Tropical Storm Imelda, street ponding is less along Springview Lane, Pitner Road, Peppermill Road, Aruba Drive, Colleen Road, Sonneville Drive, Railton Street, and Autauga Lane. Figure 30 below compares the maximum ponding depth at Colleen Road close to Outfall B.

Figure 30 – Ponding at Colleen Road by Outfall B for Hurricane Harvey (left) and Tropical Storm

Imelda (right)

Kno

ll Stre

et

Kno

ll Stre

et

Colleen Road

Colleen Road

28


Houston, Texas 77079 (713) 588-2450

As seen in this figure, there is no street ponding at Colleen Road at this location. In contrast, the image on the right shows heavy ponding on the street.

Reductions in ponding are also observed in the Binglewood Park area. Figure 31 shows a comparison of the ponding extents in this area. The figure shows that Peppermill Road was not inundated during Hurricane Harvey but did experience street ponding during Tropical Storm Imelda. An increase in ponding boundaries is also observed along Aruba Drive and Pitner Road.

Figure 31 – Ponding at Peppermill Road by Binglewood Park for Hurricane Harvey (left) and

Tropical Storm Imelda (right)

A Hurricane Harvey overall ponding map can be found in Exhibit 6. The results confirm that the lower local rainfall intensity experienced during Hurricane Harvey along with lower boundary conditions at Brickhouse Gully caused less ponding on the streets of Binglewood and smaller ponding boundaries for the residents on the Knoll Street cul-de-sac.

Pep

perm

ill Ro

ad

Aru

be

Driv

e

Pep

perm

ill Ro

ad

Aru

be

Driv

e

Pitner Road Pitner Road

29


Houston, Texas 77079 (713) 588-2450

CONCLUSIONS

The hydrologic and hydraulic analysis on the Binglewood drainage system was conducted simulating the Tropical Storm Imelda rainfall to determine the ponding elevations throughout the Binglewood model and to determine the source of flooding for residents within the neighborhood during the storm event.

The ponding results were validated using photographs provided by Binglewood residents. Based on this analysis conducted, the Binglewood drainage system appears to be designed in accordance with the City of Houston’s 10-year design criteria. Rainfall information obtained from Harris County suggests that Tropical Storm Imelda resulted in up to 4.4 inches in one hour which is approximately a 100-year storm event ( Pre-Atlas 14 rainfall), stressing the storm sewer system beyond capacity. The HCFCD gage also recorded near record elevations reaching 76.70’ which results in a high tailwater for the drainage system. The intense rainfall along with the high tailwater in Brickhouse Gully appears to be the cause of structural flooding within the neighborhood. A proposed construction scenario was conducted, assuming the designed Binglewood construction had been completed at the time of Tropical Storm Imelda. This scenario assumed that backflow preventers were installed at each outfall and that the outfall at Hollister Road was connected to the storm sewer system. The same outfall conditions were assumed as with the constructed conditions scenario. The results from the model suggest that had the construction been complete, the Binglewood area would have still seen high ponding depths and structures may have still been impacted due to the high tailwater condition in Brickhouse Gully and intense rainfall. A Hurricane Harvey scenario was conducted to validate the analysis and compare to the Tropical Storm Imelda information since the residents stated they did not experience as much ponding during Hurricane Harvey. The rainfall analysis indicated that Hurricane Harvey had less intense rainfall than Tropical Storm Imelda and lower elevations in Brickhouse Gully, which allowed the storm sewer systems to drain. The Imelda storm event was also modeled for pre-construction conditions (roadside ditches) to simulate how the pre-construction system would have functioned during the tropical storm. In general, the area would not have flooded as it would have under pre-construction conditions. The designed improvements reduce the amount of backflow from Brickhouse Gully. Elevations on Knoll St. were similar to the proposed construction scenario. If you have any questions or need additional information, please do not hesitate to contact me. HALFF ASSOCIATES, Inc. Texas Firm Registration No. 312

C. Andrew Moore, P.E., CFM TX PE No. 124910 Water Resources Team Leader

µ

Exhibit1

PROJEC

T AVO

31051

DATUM

& COO

RDINA

TE SYS

TEM

City of H

ouston

WO132

- Bing

lewood

Tropic

al Storm

Imelda

Analys

isVic

inity M

ap

HALFF ASSOCIATES, INC.100 I-45 North, Suite 260Conroe, Texas 77301-2701www.halff.comTTBPE Firm No. F-312

0 16,0008,000 Feet1 inch = 8,000 feet

NAD 1

983 Sta

tePlan

e Texas

South

Centra

l FIPS

4204 F

eet

LegendStudy AreaCounty

HARRIS

FORT BEND

LIBERTYMONTGOMERY

WALLER

BRAZORIA GALVESTON

Grimes

Study Area

Study Area

E115-04-00 (Tributary 1.61 to Brickhouse Gully)

E115-09-00 (Unnamed Tributary to Brickhouse Gully)

E115-05-00

E115-00-00 (Brickh

ouse Gully)

E115-04-0

2

E115-08-00

E 115-07- 00

E115-07-01

E115-06-00

BLALOCK RD

ROSE

NAMORACT

RAILTONCT

THEYSE

NCIR

CAMEO

DR

PEAVINE CIR

SPENW

ICKDR

MILLSPRINGDR ELEGIA DR

COLLEEN RD

CLANTON ST

KNOLL S

T

BASCOMLN

BIRCHTONST

PINEHILL LN

PINEWICKLNACORN ST

ARUBA DR

GRANIERMOUNTAIN DR

FARMINGTONST

BURR OAK DR

MAYSEL

ST

SEQUOIA DR

THUNDERBIRDRD

LAVERN

E DR

W WINGFOOT RD

WILLOW

SPRING

S LN

COLLEENMEADOWS

CIR

TED ST

GRANITE ST

DOW RD

SEMMONS RD

GUHN RDMC KEAN DR

SOWAY ST

SPRING

MEADOW

SST

RAILTON ST

VALLEYFIELD DR

OPELIKA ST

GOLD CREEK DR

POPPY ST

MIDFIELD DR

SPRINGVIEW LN

RYSON ST

ROY BEAN DR

STEADMONT DR

AUTAUGA ST

MALIBU DR

ROCKHURST DR

PEPPERMILL RD

LODGE ST

COTTON DR

ELDORA DR

LANGTRY ST

CLEMSON ST

STAGECOACH DR

LAZY SPRING DR

FELDSPAR ST

LANGTR

Y LN

WAY OU

T WEST

DR

BAYTHORNE DR

OUTPOST DR

UNDERHILL ST

GREINER DR

KEMPWOOD DR FOREST GROVE DR

ROMA ST

MONA LEE LN

DERRIK DR

DAYCO

ST

THEYSEN DR

CLARK

RD

NORTHFIELD LN

LIMESTONE ST

PINE TIMBERS ST

GALWAY LNCITA

DEL LN

MORNINGVIEW DR

PITNER RD

LANGFI

ELD RD

RANNIE RD

PINEMONT DR US 290

FRONTI

ER DR

THORNWALL ST

SONNEVILLE DR

BARNEY RD

RAYSON RD

CAMPBELL RD

HOLLISTER ST

BLANKENSHIP DR

TILSON LNSOU

THERLA

ND RD

43RD

SOWDEN RD

CLAY RD

BINGLE

RD

HEMPSTEAD RD

µ

Exhibit2

PROJEC

T AVO

31051

DATUM

& COO

RDINA

TE SYS

TEM

City of H

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WO132

- Bing

lewood

Tropic

al Storm

Imelda

Analys

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0 1,600800 Feet1 inch = 800 feet

NAD 1

983 Sta

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South

Centra

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4204 F

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LegendPotential OverflowWatershed BoundaryHCFCD Channel

Terrain (ft.)High : 103.514Low : 55.788

COLLEEN RD

SONNEVILLE DR

KNOLL

ST

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E115-00-00 (Brickhouse Gully)

COLLE

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KNOLL

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ELEGIA DR

COLLEEN RD

CAMEO DR

COLLEEN MEADOWS CIR

MONA LEE LN

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SONNEVILLE DR

µ

Exhibit3

PROJEC

T AVO

31051

DATUM

& COO

RDINA

TE SYS

TEM

City of H

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WO132

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Tropic

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0 200100 Feet1 inch = 100 feet

NAD 1

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Legend!( Structures

Watershed BoundaryHCFCD Channel

Address: 8802 Sonneville Dr.Finished Floor Elev: 78.8 ft.High Watermark Elev: 79.6 ft.

Address: 3402 Knoll St.Finished Floor Elev: 78.7 ft.High Watermark Elev: 79.4 ft.










E115-08-00

E115-06-00


CLARKRD

THEYSE

N CIR

CAMEO

DR

PEAVINECIR

ELEGIA DR GOLDCREEK DR

COLLEEN RD

CLANTON ST

ROSSETTE DR NAMORA LN

KNOLL S

T

BARNEY RD

BIRCHTON ST

PINEHILL LN

ARUBA DR

DERRIK DR

FARMINGTON ST

MAYSEL

ST

LAVERN

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COLLEENWOODS CIR

KEMPWOOD DR

OJEMAN RD

LANGTR

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COLLEENMEADOWS CIR

MC KEAN DR

SOWAY ST

PINE TIMBERS ST

RAILTON ST

PINEMONT DRVALLEYFIELD DR

PHILCO DR

43RD

OPELIKA ST

SPRINGVIEW LN

RYSON ST

OUTPOST DR

AUTAUGA ST

ROCKHURST DR

PEPPERMILL RD

ELDORA DR

LAZY SPRING DR

WAY OUT

WEST D

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GREINER DR

NORTHFIELD LN

FOREST GROVE DR

ROMA ST

MONA LEE LN

THEYSEN DR

RAYSON RD

SONNEVILLE DR

RANNIE RD

GALWAY LN

TILSON LN

MORNINGVIEW DR

PITNER RD

SOWDEN RD

HEMPSTEAD RD

HOLLI

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T

BLANKENSHIP DR

CLAY RD

µ

Exhibit4

PROJEC

T AVO

31051

DATUM

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City of H

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Tropic

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0 1,000500 Feet1 inch = 500 feet

NAD 1

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South

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4204 F

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LegendWatershed BoundaryHCFCD Channel

Ponding (ft.)High : 4.90Low : 0

COLLEEN RD

SONNEVILLE DRKNO

LL ST


E115-08-00

E115-06-00


CLARKRD

THEYSE

N CIR

CAMEO

DR

PEAVINECIR


COLLEEN RD

CLANTON ST


KNOLL S

T

BARNEY RD

BIRCHTON ST

PINEHILL LN

ARUBA DR

DERRIK DR

FARMINGTON ST

MAYSEL

ST

LAVERN

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COLLEENWOODS CIR

KEMPWOOD DR

OJEMAN RD

LANGTR

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COLLEENMEADOWS CIR

MC KEAN DR

SOWAY ST

PINE TIMBERS ST

RAILTON ST


PHILCO DR

43RD

OPELIKA ST

SPRINGVIEW LN

RYSON ST

OUTPOST DR

AUTAUGA ST

ROCKHURST DR

PEPPERMILL RD

ELDORA DR

LAZY SPRING DR

WAY OUT

WEST D

R

GREINER DR

NORTHFIELD LN

FOREST GROVE DR

ROMA ST

MONA LEE LN

THEYSEN DR

RAYSON RD

SONNEVILLE DR

RANNIE RD

GALWAY LN

TILSON LN

MORNINGVIEW DR

PITNER RD

SOWDEN RD

HEMPSTEAD RD

HOLLI

STER S

T

BLANKENSHIP DR

CLAY RD

µ

Exhibit5

PROJEC

T AVO

31051

DATUM

& COO

RDINA

TE SYS

TEM

City of H

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WO132

- Bing

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Tropic

al Storm

Imelda

Analys

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Map


0 1,000500 Feet1 inch = 500 feet

NAD 1

983 Sta

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South

Centra

l FIPS

4204 F

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SONNEVILLE DRKNO

LL ST

COLLEEN RD


E115-08-00

E115-06-00


CLARKRD

THEYSE

N CIR

CAMEO

DR

PEAVINECIR


COLLEEN RD

CLANTON ST


KNOLL S

T

BARNEY RD

BIRCHTON ST

PINEHILL LN

ARUBA DR

DERRIK DR

FARMINGTON ST

MAYSEL

ST

LAVERN

E DR

COLLEENWOODS CIR

KEMPWOOD DR

OJEMAN RD

LANGTR

Y LN

COLLEENMEADOWS CIR

MC KEAN DR

SOWAY ST

PINE TIMBERS ST

RAILTON ST


PHILCO DR

43RD

OPELIKA ST

SPRINGVIEW LN

RYSON ST

OUTPOST DR

AUTAUGA ST

ROCKHURST DR

PEPPERMILL RD

ELDORA DR

LAZY SPRING DR

WAY OUT

WEST D

R

GREINER DR

NORTHFIELD LN

FOREST GROVE DR

ROMA ST

MONA LEE LN

THEYSEN DR

RAYSON RD

SONNEVILLE DR

RANNIE RD

GALWAY LN

TILSON LN

MORNINGVIEW DR

PITNER RD

SOWDEN RD

HEMPSTEAD RD

HOLLI

STER S

T

BLANKENSHIP DR

CLAY RD

µ

Exhibit6

PROJEC

T AVO

31051

DATUM

& COO

RDINA

TE SYS

TEM

City of H

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WO132

- Bing

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Tropic

al Storm

Imelda

Analys

isHur

ricane H

arvey I

nundat

ion Ma

p


0 1,000500 Feet1 inch = 500 feet

NAD 1

983 Sta

tePlan

e Texas

South

Centra

l FIPS

4204 F

eet



SONNEVILLE DRKNO

LL ST

COLLEEN RD

31051 - WO132_BinglewoodTropicalStormImelda_202040931051 - WO132_BinglewoodTropicalStormImelda_2020032431051 - WO132_BinglewoodTripicalStormImelda_202003122020031217340931051 - WO132_BinglewoodTripicalStormImelda_2020031220200312173409

31051 - WO132_BinglewoodTripicalStormImelda_02142020

Documents

EXECUTIVE SUMMARY of Houston Projects/Reports a… · 2004-10-20 · SUBJECT: WO132 – Binglewood Tropical Storm Imelda Analysis EXECUTIVE SUMMARY Halff Associates, Inc. (Halff)