Jabez Branch 3

Watershed Restoration Implementation Plan

Existing Conditions Evaluation

April 2015

Prepared For:

707 North Calvert Street

Baltimore, Maryland 21202

Prepared by:

1

Contents Introduction: ................................................................................................................................................. 4

Table 1: Jabez Branch 3 Watershed Land Use Data ................................................................................. 4

Background: .................................................................................................................................................. 6

Stream Assessment: ...................................................................................................................................... 7

Procedure: ................................................................................................................................................ 7

Table 2: Rapid Stream Characterization Summary Table ........................................................................ 8

Reach 1 ..................................................................................................................................................... 9

Reach 2 ..................................................................................................................................................... 9

UT 1 ..................................................................................................................................................... 10

UT 2 ..................................................................................................................................................... 10

Reach 3 ................................................................................................................................................... 11

UT 3 ..................................................................................................................................................... 13

UT 4 ..................................................................................................................................................... 13

Reach 4 ................................................................................................................................................... 13

UT 5 ..................................................................................................................................................... 14

UT 6 ..................................................................................................................................................... 15

Reach 5 ................................................................................................................................................... 15

UT 7 ..................................................................................................................................................... 15

Reach 6 ................................................................................................................................................... 15

Reach 7 ................................................................................................................................................... 16

Habitat Assessment Results ........................................................................................................................ 17

Forest Resources ......................................................................................................................................... 18

Jabez Branch 3 Watershed Pollutant Loading ............................................................................................ 20

Table 4: Pollutant Loading Rates for Jabez Branch 3 Watershed .......................................................... 20

Table 5: Equivalent BMP Types .............................................................................................................. 21

BMP Assessment and Subwatershed Summary ......................................................................................... 23

Table 6: Subwatershed Summary Table................................................................................................. 23

Existing BMPs .............................................................................................................................................. 24

Subwatershed 1: .................................................................................................................................... 26

2

Subwatershed 2: .................................................................................................................................... 26

Wakefield Business Park and Strayer University (BMP #2) ................................................................. 26

Subwatershed 3: .................................................................................................................................... 27

Classic Collision Repair (BMP #3) ........................................................................................................ 27

730 Generals Highway (BMP #7) ........................................................................................................ 28

Canterbury Square (BMP #8-11) ......................................................................................................... 28

BMPs in median between 97 NB and 3 EB (BMP #12) ........................................................................ 28

Opportunity Builders (BMP #14) ......................................................................................................... 29

Subwatershed 4 ..................................................................................................................................... 29

Subwatershed 5 ..................................................................................................................................... 29

BMP at 97 Southbound (BMP #27) ..................................................................................................... 30

Subwatersheds 6 & 7: ............................................................................................................................ 30

BMP at Route 3 to Route 32 (BMP# 26) ............................................................................................. 30

Subwatershed 8: .................................................................................................................................... 30

BMP at 97 ramp to 32 west (BMP #16)............................................................................................... 31

Subwatershed 9: .................................................................................................................................... 31

Subwatershed 10: .................................................................................................................................. 31

BMP at Route 3 to 32 East (BMP #17) ................................................................................................ 32

Severn Run Evangelical Presbyterian Church (BMP #22) .................................................................... 32

Devonshire BMP (BMP #18) ................................................................................................................ 32

BMPs without Detailed Analysis Completed: ........................................................................................ 33

1700 Charles Road (BMP #25) ............................................................................................................ 33

Millersville Elementary School Parking Lot (BMP #24) ....................................................................... 33

1357 Coleus Drive (BMP #23) ............................................................................................................. 33

Overlea Farms Trench (BMP #21) ....................................................................................................... 33

Cecil Avenue South (BMP #19) ........................................................................................................... 33

Cecil Avenue North (BMP #15) ........................................................................................................... 34

1526 Jabez Run (BMP #13).................................................................................................................. 34

733 Generals Highway (BMP #6) ........................................................................................................ 34

Lonergan’s Charter Services (BMP # 4-5) ............................................................................................ 34

609 N Cecil Avenue (BMP #1) ............................................................................................................. 35

Summary ..................................................................................................................................................... 36

3

Next Steps ................................................................................................................................................... 37

References: ................................................................................................................................................. 38

List of Figures

Map 1: Jabez Branch 3 Subwatersheds and Stream Reaches

Map 2: Forest Resources, Public Parks, and NWI Wetlands

Map 3: Existing BMP Locations

Appendix 1: Existing BMP Summary Table

Appendix 2: Jabez Branch 3 Subwatershed Mapping

4

Introduction: The objective of this report is to determine the current conditions of the Jabez Branch 3

watershed. Streams, forested areas, subwatersheds and existing Best Management

Practices (BMPs) were inventoried and evaluated throughout the watershed. All current

conditions were evaluated at the planning level (i.e., GIS data visually verified in the

field). The mainstem and tributaries of Jabez Branch 3 were walked where permission had

been granted and visually inspected for signs of erosion and instability. Forests were

inventoried by location using existing GIS data and the most recent aerial imagery

available. Ten (10) subwatersheds and the BMPs therein also were visually evaluated to

determine the amount of impervious surface, existing pollutant loadings, and the

potential amount of treatment provided by the existing stormwater management

facilities. Additional details on methodology and results are presented below. The

information summarized in this existing conditions report will be used to help prioritize

proposed watershed improvements. These proposed conditions will be presented in a

separate document.

Located in Anne Arundel County, Maryland, Jabez Branch is a tributary to the Severn Run

and ultimately to the Severn River. The Severn River is located in the western Coastal Plain

Physiographic province of Maryland and is characterized by unconsolidated

sedimentary deposits. The Jabez Branch watershed has four (4) branches within it. This

report will focus on the Jabez Branch 3 watershed, which can be seen on Map 1. The

Jabez Branch 3 watershed drains the most eastern portion of the overall Jabez Branch

watershed and includes the Interstate 97 (I-97) and Maryland Route 32 (Route 32)

interchange. The Jabez Branch 3 watershed has many diverse land uses. A breakdown

of the land use found in the watershed can be found in Table 1 below.

The Jabez Branch 3 is subject to stream degradation and excessive channel erosion.

These impacts are largely caused by high runoff volumes originating from impervious land

use areas that are located on the State, County, and privately-owned properties

throughout the watershed. There are numerous stakeholders interested in seeing the

Jabez Branch 3 watershed restored.

Table 1: Jabez Branch 3 Watershed Land Use Data

Landuse Classification Landuse Area

(acres) Percentage of

Watershed Area

Commercial or Industrial 38.9 5.1%

Agricultural ( Row Crops, Pasture, Hay, Open Space) 107.3 13.9%

Residential (0.5, 1, and 2 acres) 258.8 33.6%

Transportation and Utility 87.8 11.4%

Forest (Woods) 276.8 36.0%

Water 0.3 < 0.1%

5

6

Background: Jabez Branch 3 has a drainage area of approximately 769.2 acres and includes the

Route 3, Route 32 and I-97. These major roadways along with secondary roads make up

16% of the total land cover and the majority of the approximately 122.0 acres of

impervious surface. Within the remaining pervious areas, there is a large amount forest

(277.3 acres) according to available Anne Arundel County Office of Information

Technology data (Anne Arundel County, accessed 2014).

There have been a small number of actions taken by multiple jurisdictions to ensure the

health and conservation of the Jabez Branch 3 watershed. For example, there are

currently 19 existing BMPs on State, County, and Privately-held land within the Jabez

Branch 3 watershed. These BMPs are in place to manage stormwater peak flow rates as

well as reduce the volume of stormwater and nutrient pollution that are contributed to

Jabez Branch 3.

Jabez Branch 3 has many different stream and channel characteristics. Most of the

channel sections upstream of I-97 are intermittent or ephemeral. Similarly most of the

small tributaries to Jabez Branch 3 are also intermittent channels that originate from

underground seeps or springs. Some areas of the Jabez Branch 3 channel are contained

in man-made concrete channels or conveyed through large culverts. Channel areas in

the downstream section of Jabez Branch 3 are made up of a variety of different channel

forms. These include braided stream sections and unstable, entrenched channels. These

entrenched channels deliver heavy sediment loads to the downstream reaches of Jabez

Branch 3 and to other downstream reaches.

7

Stream Assessment:

Procedure:

The planning level evaluation of Jabez Branch 3 and its tributaries was completed on July

14, 2014. The planning level stream evaluation was based primarily on Rosgen

Methodology, which includes a broad geomorphological assessment that evaluates the

stability of the stream system in different reaches and tributaries (Map 1). Characteristics

that the Rosgen method is based on include stream sinuosity, width/depth ratio, channel

slope and channel material. Detailed measurements were not taken in the field, rather

channel dimensions and characteristics were estimated. The geomorphological

assessment was conducted by walking the Jabez Branch 3 in areas where access was

granted and noting specific features about the stream such as degree of vegetative

cover on banks, bank slope, channel width and depth and the relationship to bankfull

(floodplain) features. Unstable reaches are discussed specifically, including potential

causes for observed degradation. Table 2 (below) summarizes several criteria for each

reach of Jabez Branch 3 such as Rosgen Stream Classification and Maryland regional

rural and urban curves. The curves provide detailed data for stream parameters at a

determined bankfull stage, such as cross section area (Abkf), Stream Width (Wbkf) and

Depth (Dbkf). This table also summarizes the Incision ratio, a ratio of width to depth in the

stream channel. The Bank Erosion Hazard Index (BEHI) and high Near Bank Stress (NBS)

are estimates of the erosion potential of the streams banks and are also summarized in

this table.

8

Table 2: Rapid Stream Characterization Summary Table

Abkf Wbkf Dbkf Abkf Wbkf Dbkf

1 F4 1.160 11.5 10.9 1.1 45.2 22.0 2.0 Unstable Widespread Aggrading 9.0 Unstable Widespread 28.8 Moderate - High Moderate

2 F4 1.163 11.5 10.9 1.1 45.2 22.1 2.0 Unstable Widespread Stable 1.5 Unstable Localized 33.1 High High

3 F4 1.167 11.5 10.9 1.1 45.3 22.1 2.0 Unstable Localized Stable 1.3 Unstable Localized 29.9 Moderate - High Low

4 F4 -> C4 1.170 11.5 10.9 1.1 45.4 22.1 2.0 Unstable Localized Stable 1.8 Stable 24.4 Moderate - Low Moderate

5 F4 1.162 11.5 10.9 1.1 45.2 22.0 2.0 Unstable Widespread Degrading 5 Unstable Widespread 37.9 Very High Moderate - High

6A D5 / E5 0.545 6.8 8.2 0.8 26.6 15.1 1.7 Stable Stable 1.0 Stable 14.75 Low Moderate

6B D5 / C5 0.545 6.8 8.2 0.8 26.6 15.1 1.7 Unstable Localized Degrading 1.3 Stable 18.6 Low - Moderate Low

7 C5 -> F5 1.020 10.5 10.4 1.0 41.3 20.6 2.0 Unstable Localized Degrading 1.5 Unstable Localized 23.6 Moderate Moderate

8 E5 -> C5 0.960 10.0 10.1 1.0 39.6 20.0 2.0 Unstable Localized Degrading 2.5 Unstable Localized 27.2 Moderate - High Moderate

9 F4/3 0.650 7.6 8.7 0.9 30.1 16.5 1.8 Unstable Widespread Degrading 6.0 Unstable Widespread 45.0 Extreme High

9.5 F4/3 -> C4 0.690 8.0 8.9 0.9 31.4 17.0 1.8 Unstable Widespread Aggrading 4.5 Unstable Widespread 37.5 High Moderate - High

10 C4 0.730 8.3 9.1 0.9 32.6 17.4 1.8 Unstable Localized Aggrading 2.0 Unstable Localized 27.9 Moderate - High Moderate

11 PAVED SWALE 0.790 8.8 9.4 0.9 34.5 18.2 1.9 Stable Aggrading 1.3 Stable 7.9 Very Low Low

12 UT05 Bc/3 0.014 0.5 2.0 0.3 2.0 2.4 0.7 Stable Aggrading 1.2 Stable 17.5 Low Moderate

20 A2 0.010 0.4 1.8 0.2 1.6 2.0 0.7 Unstable Widespread Degrading 4.0 Unstable Widespread 32.0 High Moderate-High

21 B3 0.005 0.3 1.4 0.2 1.0 1.4 0.6 Stable Stable 1.0 Stable 7.0 Low Low

22 B4 0.002 0.1 1.0 0.1 0.5 0.9 0.5 Stable Stable 2.0 Stable 8.0 Low Low

23 5 F4/5 0.600 7.2 8.5 0.9 28.5 15.8 1.8 Unstable Widespread Unstable 12.0 Unstable Widespread 50 Extreme High

26 6 C5 0.49 6.3 7.9 0.8 24.7 14.3 1.7 Stable Stable 1.0 Stable 6.0 Low Low

27 6 E5 0.4 5.4 7.3 0.8 21.4 12.9 1.6 Stable Stable 1.0 Stable 5.0 Low Low

UT SW

Form No. ReachRosgen

Classification

Rapid Stream Characterization Summary Table - Jabez Branch 3 (Anne Arundel County, MD)

WSA

4

2

1

3

Rural Curves (McCandless, 2003) Urban Curves (Powell, 2007)

NBSBEHI RatingBEHI ScoreOverall StabilityIncision

Ratio

Vertical

StabilityLateral Stability

9

Reach 1

Under natural discharge and sediment supply

conditions, a valley such as this would likely support

stable meandering channel processes and the

adjacent seep-fed riparian wetlands. However,

under the current dynamic flow and sediment

discharge regime, this reach varies from an incised

over-widened unstable channel upstream to a

recovering stable channel downstream.

The lower portion of Reach 1 is actively aggrading

due to excessive sediment supply and backwater

conditions at the adjacent confluence with the

receiving Jabez Branch 2 and nearby Severn River.

As a result, an incised channel has established within

the previously developed wide and shallow channel

with access to an active floodplain as evidenced by

overbank deposition. In general, the lower Reach 1

is stable, based on a low NBS, and currently functions

to somewhat reduce sediment

contributions from Jabez 3 into the Severn

River.

The upper portion of Reach 1 exhibits

some aggradation and isolated point bar

development, but because of the

degree of incision, may never reconnect

with the relic floodplain and associated

seep-fed wetlands. As a result, this reach

is at risk of reduced physical function;

wetlands face potential dewatering, the

stream faces reduced baseflow, and the

system faces further degradation of aquatic and riparian ecological function. Overall,

upper Reach 1 exhibits local instability, but is trending toward greater instability.

Reach 2

Reach 2 is similar to upper Reach 1, but shows stronger signs of active degradation.

High to moderately high BEHI and NBS results support this assessment. Historic soil has

been undermined as evidenced by soil layers in the stream bank. Further vertical

incision is prevented by accumulation of larger sediment moved to the bottom of the

channel.

Photograph 2: Typical section of upstream Reach 1.

Photograph 1: Typical section of

downstream Reach 1

10

The existing channel through Reach 2 lacks

access to an active floodplain. For this

reason, Reach 2 will continue to confine

peaks much larger than the 2-year event.

Confining large these larger storms will

increase sediment competency and

capacity, thereby perpetuating the down-

cutting and overwidening process until the

relic floodplain is inaccessible.

Reach 2 is also at risk of reduced physical

and ecological function. Overall, Reach 2

exhibits widespread instability with the apparent likelihood of continued degradation

unless active management measures are

taken.

UT 1

This tributary may have originally been

a spring/seep fed drain located at the

valley toe and has since enlarged in

response to changes in the flow and

sediment discharge regime. In its

current state, this channel appears

incised for much of the entire reach

length. However at the location that UT 1 joins Reach 2 the main channel of Jabez

Branch 3 is only moderately incised.

Therefore, the confluence is much more

stable and tends to demonstrate that

this tributary has a strong potential to

recover on its own.

UT 2

This tributary exists largely as an

intermittent/ephemeral channel that

responds primarily to larger storm

events. This channel forms at the

stormwater outfall near Jabez Run

Road, where erosion is high. However,

not far below the outfall, flows disperse

and the channel becomes

indistinguishable. UT 2 appears in a

stable condition until its confluence with

Reach 2. Because Reach 2 is deeply Photograph 6: Typical section along UT 2

Photograph 5: Typical stable section of UT 1

Photograph 4: Headcut at the confluence of UT 1 and

Reach 2

Photograph 3: Typical vertical incision along Reach 2

11

incised to an elevation lower than UT 2 at this confluence, a short and very steep

headcut has formed at this location.

Reach 3

Reach 3 begins downstream as a single threaded

channel upstream of Reach 2. Continuing upstream the

channel diverges into multiple channels, then

converges, and diverges again. Just below the crossing

under Hog Head Road, as a single threaded channel,

Reach 3 begins.

Beginning from the downstream portion of Reach 3 the

channel exhibits widespread instability due to active

degradation. It is apparent that degradation will

continue unless active management measures are

taken. As the assessment moves upstream, various

features of note should be considered.

A convergence of multiple channels into one channel is

located upstream. This section of Reach 3 has one low

to moderate BEHI and NBS. However, continued degradation is observed in Reach 3

where the seep channels reconnect the Jabez Branch 3.

The primary active headcut that had previously led to

degradation further downstream is currently located

above the relic abandoned convergence. This headcut

is characterized by a

series of five (5) 1-ft steps

over a distance of about

50 feet (~10% slope)

where the typical channel

slope was approximated

on the order of 1%. The

effect of this headcut is

most visible immediately downstream and suggests strong

potential for additional upstream migration and

associated degradation.

Photograph7: Typical diverged

channel section in Reach 3

Photograph 8: Typical braided

channels in Reach 3

Photograph 9: Typical headcut

seen in Reach 3

12

The first braided portion of Reach 3 is characterized by two

principal channels. The left channel appears to be actively

aggrading, with regular overbank events contributing to

flows to adjacent riparian wetlands and floodplain pools.

This left channel should potentially be avoided as

disturbance could be destructive to sensitive aquatic and

riparian habitats. While apparently undersized in

comparison to a similar single threaded channel (refer to

regional curves), the right channel through this portion of

Reach 3 appears incised and actively degrading from a

meandering channel to a

more entrenched, less

sinuous channel. As the

right channel continues to

degrade, upstream

hydrologic connections to the left channels will likely be

threatened. In general, the left channel is stable, and

the right channel exhibits localized instability

throughout.

In between the two

braided portions of

Reach 3, a very short single-threaded reach serves as

the primary low flow conveyance, and appears to flow

out of bank more often than bankfull. This reach is

characterized by expansive adjacent overbank

wetlands with a well-defined headcut initiated at the

upstream of this single-threaded reach moving upward

into the next braided stream section.

The upper portion of Reach 3 has a braided stream

channel that is also characterized by two principal

channels. Alternatively, these channels appear to be

actively aggrading, with regular overbank events

contributing to flows to adjacent riparian wetlands and

floodplain pools. The low flow velocity found in the

braided stream section allows sediments carried from

upstream areas to be deposited in the overbank areas along this section of Reach 3. This

will persist until the downstream headcut migrates and promotes more confined flow.

Photograph 12: Typical stable

section of Reach 3

Photograph 10: Converging

channels in Reach 3

Convergence

Photograph 11: Typical upstream

section of Reach 3

13

Upstream of the first flow divergence, a single threaded channel conveys flow from the

culvert outfall, downstream to the end of Reach 3. With stable floodplain access and

historic alluvial contributions from two nearby tributaries (UT 3 and UT 4), this section of

Reach 3 currently shows signs that is has previously been incised and has since aggraded.

UT 3

This tributary exists largely as an

intermittent/ephemeral channel in a more

confined valley that responds primarily to larger

storm events. It is also very likely that seasonal

seeps and springs also contribute to base flow.

The headwater of this channel is on private

property, but the observable reach appeared

stable. UT 3 appears that through hydrologic and

sediment inputs, it supports riparian wetlands along

the overbank of Reach 3.

UT 4

Reach UT 4 is a stable intermittent/ephemeral

channel that responds primarily to seasonal storm

events and may maintain base flow through

groundwater contributions. This reach has a steeper

slope than the main channel of Jabez Branch 3. The

headwater of this channel is on private property,

but the observable

reach appeared

stable. It appears that

through hydrologic and sediment inputs, UT 4 supports

riparian wetlands along the overbank of Reach 3.

Reach 4

Located between Route 32/I-97 and I-97, Reach 4 is

generally the most incised and unstable portion of

Jabez Branch 3 within the assessed study area. This

channel appears to have been historically modified,

possibly straightened and/or deepened. While the

valley is slightly narrower than that of the downstream

Reach 3, the degree of incision and lateral erosion is

greater than anywhere on the entire stretch of Jabez

Branch 3 or its tributaries. BEHI and NBS ratings indicated

higher erosion in Reach 4 than anywhere else. This

active incision is likely caused by upstream confined

Photograph 13: Typical channel in UT 3

Photograph 15: Representative

channel in Upper Reach 4.

4presentative

Photograph 14: Typical channel in UT

4

14

flow. Giving the stream access to historic floodplains will help restore the stream to more

natural process and prevent future channel incision.

Because of active headcut migration and

the associated increased capacity and

competency, the upstream portion of

Reach 4 exhibits the most degradation in

the Jabez Branch 3 study area. With

Extreme/Very High BEHI/NBS scores and

Bank Height Ratio, which validate an

observed incised channel, this reach may

be responsible for the bulk of downstream

sediment contributions to the receiving

Severn River.

Further downstream, the middle Reach 4 exhibits clear indicators of a relatively wide and

entrenched channel. The middle of Reach 4 is somewhat of a transition between the

upper and lower reaches. Although active deposition appears to promote development

of a less entrenched, more sinuous channel, there are no indicators of stability. It is very

likely that this material will only wash further downstream as larger storm flows (10 year

return period and greater) remain confined. This promotes excessive erosion and forces

the stream to transport greater volumes of sediment than it otherwise would.

While the predominant process of this reach has been

degradational, the downstream portion of Reach 4

exhibits active deposition and transitions from an

entrenched wide channel toward a less entrenched

more sinuous stream type.

UT 5

This reach begins at the culvert crossing outlet below

Morris Tongue Drive for approximately 500 linear feet.

This channel is relatively stable due to prior channel

stabilization, which consisted of a series of step-pool

structures. Prior to stabilization, this channel may have

been a major source of sediment to the downstream

portions of Reach 4. However, it should be noted that

some of the structures may be at risk and subsequent

failure may yield excess sediment contribution to the

middle and downstream ends of Reach 4.

Photograph 16: Representative channel in middle of

Reach 4.

Photograph 17: Channel Stabilization

in Reach UT 5

15

UT 6

At the time of the field verification and

data collection effort, Reach UT 6 was

not approved for access and therefore

no evaluation was performed. Please

see map entitled Private Parcels with

No Access Permitted in Appendix 2 for

locations of all properties where access

was not permitted.

Reach 5

Reach 5 begins at the outlet of an unconfirmed BMP

and continues to the culvert crossing inlet under I-97

South Bound (SB). The BMP is unconfirmed because

access to the property was not granted for this

assessment. The BMP is suspected to be some sort of

manmade modification adjacent the channel.

Observations from adjacent properties with access

granted indicates that this BMP is offline. In general, this

reach consistently demonstrates extreme BEHI/NBS and

is overall unstable.

UT 7

This reach appears to consist of an ephemeral /

intermittent channel that discharges into Reach 5 below the unconfirmed BMP

described above. No data was collected because it was located mostly on a

property that did not provide access. However, it

was observed from

outside the property

that the reach is stable

but at risk due to the

unstable nature of the

downstream receiving

Reach 5.

Reach 6

Reach 6 is an

ephemeral/intermittent stable channel, located

between Mallet Hill Lane and Millersville Road that has

been restored by the County. The channel connecting

Reach 7 to Reach 6 is a swale with a concrete “V”

shaped bottom structure. Despite being historically

straightened, the vegetation and regular access to a

Photograph 19: Headcut at BMP

outlet in Reach 5.

Photograph 21: Typical stable

channel in Reach 6.

Photograph 20: Typical channel in

Reach UT 7

Photograph 18: Typical channel in the upper section

of Reach 5.

16

floodplain has enabled stability within the channel. While the channel is stable, the

associated habitat could be improved through minor channel modification.

Reach 7

Reach 7 is an ephemeral channel that extends

upstream from Kathy Ann Lane through a constructed

wetland/wet pond and beneath Isabella Court where

there is no longer a discernable channel. Reach 7 is the

most upstream reach in the watershed and the

subwatershed that drains to this reach is not heavily

developed. The riparian area around the discernable

channel is heavily wooded; because of this, reach 7

experiences low flow rates and is in stable condition.

Photograph 22: Typical wooded

channel in Reach 7

17

Habitat Assessment Results A visual assessment of habitat and biota was conducted at the same time as the stream

assessment. This visual assessment was to be compared with ongoing Maryland Biological

Stream Survey (MBSS) data. However the latest MBSS data for Jabez Creek was

completed in 2003 and included a larger watershed than just Jabez Branch 3. Therefore

other sources were sought for a habitat assessment comparison. According to the 2003

report, 1.57 miles of stream had habitat assessments conducted on Jabez Branch 3. The

overall stream length weighted MPHI score was 55.58 and the FHS score was 50.63. Both

of these ratings fall in the fair range. 22.7% of the assessed area fell in the good range for

both the MPHI and FHS score (KCI Technologies, Inc, 2003).

During the visual stream assessment, good habitat was observed in stable reaches of

Jabez Branch 3. Poor habitat also was observed but primarily confined to areas with

severe channel incision. Observed stream channels where aggradation was observed

also exhibited poor habitat quality as deposition of sediment on top of natural channel

material eliminates the roughness needed for aquatic insects and fish to hide. Overall,

the visual habitat assessment agrees with the results of the 2003 assessment; a majority of

the stream in poor or fair conditions with some good areas along Jabez Branch 3.

18

Forest Resources During the initial review of the Jabez Branch 3 watershed, GIS analysts performed a

desktop review of the existing forest and tree resources within the watershed. This analysis

utilized existing base data provided by Anne Arundel County, MD Department of Natural

Resources (DNR), MD SHA, and high-resolution aerial imagery provided by the State of

Maryland. The overall purpose of the assessment of forest resources was to identify

potential opportunities to expand forest cover in the watershed which in turn will help to

improve water quality. The opportunities for forest expansion will be discussed in detail in

the “Proposed Conditions Report-Restoration Plan,” to be provided later.

The first step towards addressing this goal was to validate the base data and the extents

of forest cover that were indicated in the GIS datasets. Using the Anne Arundel County

layer “Treeline,” GIS analysts reviewed every existing feature within the watershed and

compared those features against the high-resolution imagery. The Treeline features were

edited to reflect the approximate boundaries of forests and tree canopies as indicated

in the imagery. The resulting dataset was spot checked by field teams for accuracy. Any

revisions identified were then incorporated into the final dataset.

The results of this analysis indicate the relative forest and tree cover within the watershed.

Currently, the desktop evaluation identified approximately 390.01 acres of forest and tree

cover within the Jabez Watershed. This represents approximately 51.9% of the total land

area in the watershed. Of this area, 64.52 acres of forest occur within existing SHA Right

of Way. Approximately 30.71 acres of forest occur on lands considered to be “public.”

This includes parks, government parcels, and state and federal lands.

A discrepancy can be noted between the 390.1 acres of tree cover derived from the

desktop analysis and the 255.8 acres of forest noted in the land use summary table found

in the report’s introduction (Table 1). The land use/land cover dataset summarized in

Table 1 is based on automated photo-interpretation and will differ significantly from what

the field review indicates. This Maryland Department of Planning (MDP) generated

dataset under-represents the tree cover in the watershed because it applies its land use

codes more generally. For example, a parcel that may be coded as residential by MDP

may still contain a substantial amount of tree cover. Additionally, residential tree cover is

not typically labeled/considered forest unless it meets DNR requirements.

19

20

Jabez Branch 3 Watershed Pollutant Loading The estimates of annual pollutant loading in the Jabez Branch 3 watershed are 4,816

lbs/year of Nitrogen, 355 lbs/year of Phosphorus, and 71,004 lbs/year of sediment. These

estimates are a baseline that does not incorporate the impact of existing BMP facilities

found in the study area. The loading rates with existing BMPs can be found below.

Table 4: Pollutant Loading Rates for Jabez Branch 3 Watershed

Nitrogen (lbs/year)

Phosphorus

(lbs/year)

Sediments

(lbs/year)

Baseline (no

existing BMPs) 4,816 lbs/year 355 lbs/year 71,004 lbs/year

Pollutant Reduction

from Existing BMPs 140 lbs/year 27 lbs/year 7,842 lbs/year

Resulting Pollutant

Loads 4,676 lbs/year 328 lbs/year 63,162 lbs/year

Loading rates were determined using the Chesapeake Bay Facility Assessment Scenario

Tool (BayFAST) – a web-based nitrogen, phosphorus and sediment load estimator.

Although SHA currently uses the modeling program MAST for their BMP planning efforts, it

was determined that BayFAST will yield more watershed – and subwatershed – specific

results compared to MAST. As per BayFAST’s documentation regarding the differences

between BayFAST and MAST:

“BayFAST allows users to define the boundaries of a parcel and the land use areas

within that parcel, and then to build scenarios for those user-defined parcels. The

CAST family of tools requires users to select land areas for scenarios based on land-

river segments within the Bay watershed and to use the land use areas defined by

the Chesapeake Bay Program… The load calculations performed by all tools are

identical.”

Because the land area occupied by the Jabez Branch 3 watershed is much smaller than

the land-river segments used to characterize land use in the MAST model, a user defined

parcel boundary representing the boundary of the drainage area will yield a more

accurate representation of the study area’s land use breakdown.

Calculating baseline pollutant loads for the entire Jabez Branch 3 watershed was

achieved by manually entering a facility representing the watershed’s drainage area

into BayFAST (note: the watershed’s drainage area was initially created in GIS using

detailed topographic data and existing stormwater systems). A facility represents a land

area where decision makers seek to develop a plan for meeting a load allocation.

Following facility entry, a scenario was generated through the BayFAST interface in which

no BMPs were applied to the watershed. Baseline pollutant loads were then generated

for the entire watershed.

21

Once a baseline of pollutant loads for the Jabez Branch 3 watershed was created, the

impacts of the existing BMP facilities could be considered. The drainage area of each

existing BMP was entered into the BayFAST model as a unique facility to determine its

impact on nutrient and sediment removal. BMP drainage areas were initially digitized on-

site during field investigations before being manually entered into BayFAST. The BayFAST

program does not support the uploading of these detailed drainage areas from GIS.

BayFAST will automatically associate land use data to the drawn polygon for each

drainage area. Review of BayFAST land use data revealed some discrepancies when

compared to field verification and land use data obtained from Anne Arundel County

Office of Information Technology. For example, the drainage area of BMP facility 2 was

field verified to have 3.00 acres of impervious area, but the BayFAST model listed the

impervious area as 0.92 acres. To correct for this and other possible errors, the Anne

Arundel County Impervious surfaces and land cover shapefiles from 2011 were used to

more accurately calculate the components of land use area for entry into the BayFAST

model. Land use was divided into four categories: impervious (entered into BayFAST as

regulated impervious developed), non-forested pervious (entered as regulated pervious

developed), forested (entered as forest), and water (entered as water). All other land

use types were zeroed out.

A second component of the BayFAST model called scenarios were used to compute

nutrient load reductions from the existing BMPs. Comparative scenarios for baseline

pollutant loading and loads following reductions from existing BMPs were created. The

baseline scenario was created using a facility with no modeled BMP facilities (discussed

previously). Scenarios modeling the pollutant loads with existing BMPs in place were

modeled and pollutant loads recorded.

BMPs within the study area included infiltration trenches, infiltration basins, bioswales, wet

ponds, and raingardens. Table 5 outlines the BayFAST equivalent BMPs that were used for

these BMP types.

Table 5: Equivalent BMP Types BMP type observed

in-field BayFAST BMP type used in model

Infiltration trench Infiltration Practice w/o Sand, Veg. – A/B soils, no underdrain

Infiltration basin Infiltration Practice w/ Sand, Veg. – A/B soils, no underdrain

Bioswale Vegetate Open Channels – A/B soils, no underdrain

Wet pond Wet Ponds and Wetlands

Raingardens Bioretention/raingardens – A/B soils, underdrain

Calculations based on Maryland Department of Environment’s Environmental Site Design

(ESD) process were completed for existing BMPs. Several ESD design components were

computed for existing BMPs based on drainage area delineated in the field by the

22

project team. BMP measurements were also taken to calculate the Storm Water

Management (SWM) volume provided by each BMP. If BMP measurements were not

available in as-built plans, engineering judgment was used to determine BMP dimensions

and SWM volume. Once the SWM volume was computed the potential treatment area

was computed for each BMP. The potential treatment area (acres treated) was the value

input into BayFAST to determine the nutrient and sediment reduction for each existing

BMP. A summary of all existing BMPs, the SWM volumes, and nutrient and sediment

reductions can be found in Appendix 1.

Baseline scenarios and scenarios accounting for the presence of existing BMPs were then

compared for each created BMP facility. Table 4 (above) shows baseline annual

pollutant loading for the overall Jabez Branch 3 watershed, and the pollutant loading

reductions provides by the currently existing BMPs in the subwatershed.

23

BMP Assessment and Subwatershed Summary To better characterize the entire Jabez Branch 3 watershed, it was divided into 10 sub-

watersheds. Map 1, included in the report’s introduction, entitled Jabez Branch 3

Watershed and Stream Reaches, shows the boundaries of the subwatersheds. Several of

these subwatersheds align closely with the drainage area divides for many of the stream

reaches, and can be used in tandem with stream reach condition results.

Subwatersheds 7-10 were developed by Anne Arundel County Department of Public

Works watershed engineers using a DEM derived from 2011 LiDAR with 3-foot resolution

(available from Eastern Short Regional GIS Cooperative – ESRGC), and stormwater

management infrastructure data available through the County. Subwatersheds 1-6 were

developed using the same data sets as the County engineering team and field

delineated drainage areas. Subwatershed boundaries digitally modeled by largely

agreed with coinciding boundaries of the County-produced subwatersheds. Where

computer modeled subwatershed boundaries differed from the field-verified datasets,

the field delineated boundaries were used.

Through mapping analysis, more informed decisions can be made when proposing

projects to better manage and treat stormwater. Specific projects will be provided in the

“Proposed Conditions Report – Restoration Plan”, to be produced at a later phase in this

watershed planning effort.

A summary table of the subwatershed assessment can be found below.

Table 6: Subwatershed Summary Table

Subwatershed

Total Subwatershed Area (Acres)

Total Impervious

Areas (Acres)

Untreated Impervious

Area (Acres)

Percent Impervious Untreated

Impervious Owned by

SHA (Percent)

Impervious Owned by

County (Percent)

Impervious Privately Owned

(Percent)

1 39.04 0.53 0.53 1.4 0 1 0

2 52.68 10.70 7.70 14.6 24.4 75.5 0.1

3 48.57 20.62 20.43 29.7 52.2 47.8 0

4 54.95 5.54 5.54 10.1 9.0 72.0 19.0

5 69.32 17.44 17.26 24.9 91.2 5.8 3.0

6 98.74 11.08 9.41 9.5 60.8 35.6 3.5

7 4.56 0.40 0.40 8.8 0 100 0

8 65.53 11.14 9.90 15.1 82.4 8.3 9.3

9 37.21 6.92 6.92 18.6 98.8 1.2 0

10 299.30 37.62 23.46 7.8 4.8 64.6 30.6

24

Existing BMPs There are several existing BMPs in the watershed. They vary in type, size, ownership and

date of construction. All of the recently built BMPs meet current water quality standards

and are beneficial to the health of the watershed. Older BMPs that were built to lower

standards can help the watershed by reducing peak flows from developed areas with

large amounts of impervious surfaces. These BMPs can be improved via retrofits to satisfy

current water quality treatment standards. Map 3: Existing BMP Locations (below), shows

the existing BMPs within each subwatershed.

The map entitled Percent Impervious per Subwatershed in Appendix 2, shows the percent

of each subwatershed currently covered by impervious surfaces where runoff is

untreated. These numbers take into account the treatment capacities of existing BMPs.

All treated acres were removed from impervious acreage totals. The percentages

displayed in the mapping reflect this consideration.

Descriptions of each subwatershed and their associated BMPs are provided below. A

summary of subwatershed data is also found in Table 6, above.

25

26

Subwatershed 1:

This subwatershed drains the northernmost portion of the Jabez Branch 3 subwatershed.

Runoff flows to Reach 2 and then Reach 1. Although Reach 2’s condition is severely

degraded, it transitions quickly to a stable condition in Reach 1.

Subwatershed 1 has 0.53 acres of impervious – all of which is privately owned. It also has

the lowest relative amount of impervious cover compared to the other subwatersheds

within the overall Jabez Branch 3 watershed (1.4%). There are no existing BMPs in this

subwatershed.

Subwatershed 2:

This subwatershed drains a northwestern portion of the Jabez Branch 3 subwatershed.

The subwatershed is divided by I-97 with drainage from the area lying east of the highway

being piped under the roadway and outletting into UT 2. The larger portion of the

subwatershed on the western side of I-97 is composed of mainly privately held land; its

most notable landmarks being Strayer University and the adjacent small business park

comprised of three large buildings. All runoff from these properties flows to Reach 3.

Reach 3’s condition is moderately degraded. Reach 2, which begins at the confluence

point of UT 2 and Reach 3, is in severely degraded condition. This may reflect a

compounding effect of high flows in Reach 3 converging with high runoff volumes

originating from the eastern portion of subwatershed 2.

Subwatershed 2 has 10.7 acres of impervious land cover. Privately held land accounts for

most of the impervious (8.08 acres). SHA owns the remaining 2.6 acres of impervious. This

subwatershed is further characterized by having 14.6% of its area occupied by impervious

cover after accounting for the impervious land area treated by the subwatershed’s

existing BMPs. This ranks fifth relative to the other subwatersheds in terms of percent

impervious cover.

Wakefield Business Park and Strayer University (BMP #2)

This BMP is located at 1518 Jabez Run. It

was field verified as a wet pond. Current

Anne Arundel County and MDE records

incorrectly list this BMP as an extended

detention dry structure. Records should

be updated to reflect the correct

existing condition. Original plans were

not located, but an Anne Arundel

County Infrastructure and Environmental

Programs Inspection Report was found

for this facility. The property is

commercial.

Photograph 23: BMP # 2 – Wet pond

27

Subwatershed 3:

This subwatershed drains a northeastern portion of the Jabez Branch 3 watershed,

centered on the I-97 overpasses over the service road connecting Routes 3 North and

South. All runoff flows to Reach 3, entering the channel near the point where Reach 3

confluences with UT 3. Reach 3’s condition is moderately degraded downstream from

where subwatershed 6 drains into the stream.

Subwatershed 3 has 21.31 acres of impervious land cover. Roughly half is owned by SHA,

with the other half owned by the County (11.94 and 11.37 acres respectively). This

subwatershed has the highest percentage of impervious cover relative to the other

subwatersheds within the overall Jabez Branch 3 watershed (29.7%) after accounting for

the impervious land area treated by the subwatershed’s existing BMPs (BMP #3, 7, 8, 9,

10, 11, 12, 14). Despite the high number of BMPs within this subwatershed, current

cumulative treatment capacity seems undersized for the amount of impervious cover in

this drainage area.

There are 14.43 acres of untreated impervious surface in subwatershed 3. BMP #12 is an

SHA infiltration basin that has the capacity to treat 11.69 acres of impervious, but only

treats 1.06 acres. This sizeable BMP was also placed upstream of 7.2 acres of impervious

land owned by SHA, with no additional existing BMPs constructed downstream of BMP

#12 in this subwatershed. Although adequate capacity exists to manage much of the

currently untreated runoff, the BMP’s hydrologic position within the subwatershed

prevents it from being a viable option to treat much of the untreated SHA impervious.

SHA owns 52% of the impervious land in this subwatershed.

Classic Collision Repair (BMP #3)

This BMP is located at 8796 Generals

Highway (Classic Collision Repair). It is an

infiltration trench with original plans

dated 2007. The facility is included in

MDE and Anne Arundel County records.

The trench also provides rooftop runoff

disconnect for 50% of the rooftop area

(observed during field verification). This

site is classified as a “redevelopment”

project according to Anne Arundel

County. The 2007 plans that included the infiltration trench also indicate a reduction of

the then existing impervious area by 31.5%, therefore meeting the water quality

requirement. Subsequent interviews with the property owner revealed that previously

undeveloped land was built on in 2007 to construct the current property at 8796 Generals

Highway. The Anne Arundel County records indicating that this was a redevelopment

appears to be inaccurate and should be updated to reflect the accurate site condition.

Photograph 24: BMP 3 – Infiltration trench

28

According to Anne Arundel County records, the infiltration trench has a 104 cf capacity.

The property is commercial.

730 Generals Highway (BMP #7)

There is a BMP located at 730 Generals Highway. Anne Arundel County records indicate

that there is an infiltration basin at this location. Original plans could not be located and

the property owner would not allow access to investigate this facility. Examination of

recent satellite imagery shows a feature resembling an infiltration basin at this location.

The basin’s dimensions and stormwater capacity were estimated from the aerial imagery

and standard sizing values found in the 2000 Maryland Stormwater Design Manual. The

property is commercial.

Canterbury Square (BMP #8-11)

There are several BMPs located in the

Canterbury Square shopping center (760

Generals Highway). They are four (4)

infiltration tanks with original plans dated

1989. Each tank is located under the

paved parking surface of Canterbury

Square with an inlet located at both the

upstream and downstream ends of each

tank. Anne Arundel County has records of

these four (4) facilities. Available design

plans are not in good condition and were

difficult to read when attempting to ascertain the sizing of each facility. The property is

commercial.

BMPs in median between 97 NB and 3 EB

(BMP #12)

There is a BMP located along the outside

of the northbound I-97, between I-97 and

MD Route 3, just west of the I-97 overpass.

It is an infiltration basin that has original

plans dated 1988. The infiltration basin

accommodates drainage from I-97

northbound and Route 3 eastbound. It is

also located hydrologically downstream

of Canterbury Square and Opportunity

Builders (see below) and can receive excess runoff and overflow from these sites. This

BMP and associated design plans are included in SHA records, however, no as-built plans

could be found. It is owned by SHA.

Photograph 25: BMP 10 – Infiltration tank

Photograph 26: BMP 12 – Infiltration basin

29

Opportunity Builders (BMP #14)

This BMP is located at Opportunities

Builders at 8855 Veterans Highway. It is a

dry detention pond that has original

plans dated 2007. Existence of the BMP

was field-verified. Original design plans

indicate that the drainage area of the

dry pond encompasses 10.04 of the 14.57

acres of the 8855 Veterans Highway

property. Records of this facility can be

found with both MDE and Anne Arundel

County, however, these records have

the BMP listed as a wet pond. These records should be updated to reflect the facility’s

dry pond status. The property is commercial.

Subwatershed 4

Subwatershed 4 lies mostly outside of the SHA ROW and falls mainly on privately held land

with little impervious cover. All runoff in this subwatershed flows into UT 4 and the upstream

portions of Reach 3. The upper portions of Reach 3 show signs of aggrading while UT 4

remains mostly stable.

The subwatershed has 5.5 acres of impervious land cover. Of this 3.99 acres of impervious

is on land held by private landowners, 1.05 acres falls within County ROW, and 0.5 acres

is SHA owned impervious. This subwatershed is further characterized by having 10.1% of

its area occupied by impervious cover after accounting for the impervious land area

treated by the subwatershed’s existing BMPs. This ranks sixth relative to the other

subwatersheds in terms of percent impervious cover. No BMPs have been built within this

drainage area.

Subwatershed 5

This subwatershed drains an area along I-97 north of Route 3. Conveyance through the

subwatershed is mainly achieved through stormwater infrastructure. Runoff is collected

and ultimately conveyed to the culvert running northeast under Route 3 and I-97,

outfalling into Reach 4.

Subwatershed 5 has 17.44 acres of impervious land cover. This predominately falls on SHA

owned land (15.9 acres). This subwatershed is further characterized by having 24.9% of its

area occupied by impervious cover after accounting for the impervious land area

treated by the subwatershed’s existing BMPs. This ranks second highest relative to the

other subwatersheds in terms of percent impervious cover.

Photograph 27: BMP 14 – Dry detention pond

30

BMP at 97 Southbound (BMP #27)

This BMP is a swale along the west side of the I-97 Southbound lane. Due to the slope of

the roadway only a small area of impervious area from I-97 drains to this BMP. There is

another ditch to the west of this BMP that prevents offsite drainage from getting to this

BMP as well.

Subwatersheds 6 & 7:

Subwatersheds 6 and 7 have been combined into one subsection of the existing

conditions report. Justification includes both subwatersheds draining into a common

reach (Reach 4), both are characterized by similar percentages of impervious land cover

(9.5% and 8.8%, respectively), and subwatershed 7 (delineated by Anne Arundel County

watershed engineers) was much smaller than any of the other nine (9) subwatersheds.

This combined subwatershed drains an area along I-97 just after the highway turns sharply

eastward, splitting away from Route 32 and orienting parallel with Route 3. All runoff in

this subwatershed flows into UT 5, UT 6 and Reach 4. This subwatershed ultimately

discharges to the large culvert that runs northeast under Route 3 and I-97. UT 5 is in stable

condition and UT 6 is moderately degraded.

Combined subwatershed 6 and 7 has 11.48 acres of impervious land cover. Of this, 6.74

acres fall on SHA owned land, 4.35 acres are on privately-held land, and 0.39 acres are

on County owned. This subwatershed ranks third/fourth lowest relative to the other

subwatersheds in terms of percent impervious cover.

BMP at Route 3 to Route 32 (BMP# 26)

This BMP is a large basin structure along the ramp from Route 3 North to Route 32

westbound. Preliminary SHA plans were obtained for this BMP. The plans show a large

basin with an outlet pipe size of 24 inches. A corrugated metal riser structure was found

during field verification; however, the outfall could not be located due to heavy growth

of multiflora rose. The principal pipe runs under adjacent ramp and discharges to the

north to a roadside ditch along I-97 southbound.

Subwatershed 8:

This subwatershed drains an area along I-97 just south of its junction with Route 32. All

runoff flowing out of this drainage area enters the upstream end of Reach 4 at

approximately the same location as the outlets from Subwatersheds 10 and 9.

Subwatershed 8 has 11.14 acres of impervious land cover. This predominately falls on SHA

owned land (9.18 acres). Approximately one (1.0) acre of impervious lies on both

privately held parcels and County owned ROW. This subwatershed is further

characterized by having 15.1% of its area occupied by impervious cover after

accounting for the impervious land area treated by the subwatershed’s existing BMPs.

31

This ranks fourth highest relative to the other

subwatersheds in terms of percent

impervious cover.

BMP at 97 ramp to 32 west (BMP #16)

This BMP is located on the north side of the

ramp from I-97 to Westbound Route 32. This

is a dry pond with plans dated 1988.

However, recent construction has just been

completed in the ponds basin to update this

BMP. The updates include regrading of the

basin side slopes and rock check dams in

the bottom of the basin. No changes or

updates were made to the existing outlet

structure.

Subwatershed 9:

This subwatershed drains an area along

Routes 3 and 32 just north of 32’s junction

with I-97. The southernmost cloverleaf of the three highway interchange (97, 32, and 3)

also falls within this subwatershed. All runoff from this area outfalls into the upstream end

of Reach 4. Flows from the culvert draining subwatershed 1 enters into Reach 4 at this

point as well. Reach 4 is in severely degraded condition, likely caused by the high

volumes of runoff received from the surrounding largely impervious subwatershed (i.e.

subwatersheds 8 and 9), and the large culvert conveying water from subwatershed 10,

which was constructed below natural grade to encourage fish passage.

Nearly all (99%) of the impervious area that exists within the subwatershed in owned by

SHA (6.8 acres). No BMPs have been built within this drainage area.

Subwatershed 10:

This subwatershed drains the southernmost portion of the Jabez Branch 3 watershed.

Runoff collected in this subwatershed flows to Reaches 7, 6, 5 and UT 7. Reach 5 outlets

from BMP #17 (wet pond) and is in severely degraded condition. All runoff flows out of

this subwatershed by a culvert passing under the I-97 and Route 32 junction which outfalls

to Reach 4.

Subwatershed 10 has 37.62 acres of impervious land cover. This predominately falls on

private landowner property (24.29 acres). Only 1.8 acres of impervious within this

drainage area is owned by SHA. This subwatershed is also characterized by having the

second lowest percentage of impervious cover relative to the other subwatersheds within

the subwatershed (7.8%) after accounting for the impervious land area treated by the

subwatershed’s existing BMPs.

Photgraph 28: BMP 16- Infiltration Basin

32

BMP at Route 3 to 32 East (BMP #17)

This BMP is located on the south side of the ramp from Route 3 North to Route 32 East. This

pond was designed as a wet pond BMP that has original plans dated 1986 and was built

in 1988. This BMP is adjacent to Jabez Branch 3, Reach 5, but is offline from the channel.

Severn Run Evangelical Presbyterian Church (BMP #22)

This BMP is an infiltration basin that is located on the northwest side of the parking lot at

Severn Run Evangelical Presbyterian Church. This facility had design approval in 1998 and

was built in 2000. The water quality computations for this basin provide enough volume

to treat the first half (0.5) inch of rainfall.

Devonshire BMP (BMP #18)

The BMP is located just northeast of the cul-

de-sac on Isabella Court. This BMP was

designed in 1992 and built in July 1993. The

outlet structure for this BMP is a concrete V

shaped weir. This wetland/wet pond and

outlet was designed to attenuate the 2, 10

and 100-yr storm events. Available design

plans shows this BMP combined with BMP #20

(below), which together have a drainage

area of approximately 117 acres. Alone, BMP

#18 has the largest drainage area of any in

the watershed, with approximately 100 acres

draining to this facility. The outlet structure is

still in good condition at this facility however

much of the planting that was originally

planned for this pond area has not been

maintained.

Overlea Farms Pond (BMP #20)

This BMP is a wet pond located just west of

the intersection of Nichols Court and Kathy

Ann Lane. This facility was approved in 1995

and built in 2001. This pond is fed by two (2)

pipes and discharges through an 8 inch PVC

pipe. This pond and outlet were designed to

attenuate the 2, 10 and 100-yr storm events.

This pond discharges to the Devonshire BMP

basin.

Photograph 29: BMP 18- Constructed

Wetland/Pond

Photgraph 30: BMP 20-Wet Pond

33

BMPs without Detailed Analysis Completed:

A small number of BMPs found in SHA, Anne Arundel County, and MDE records were

unable to be located during field verification, or were found to not lie within the Jabez

Branch 3 subwatershed boundary. The following is a summary of these BMPs and the

project team’s field findings.

1700 Charles Road (BMP #25)

This BMP is shown in the County GIS shapefiles. Field verification could not locate this BMP,

which may be located underground. Field verification did show a buried vertical pipe in

the location of the BMP. The drainage area that would be treated by this BMP is actually

part of a larger drainage area that ends at the BMP #18 (Devonshire). Therefore this BMP

was not considered in the existing conditions analysis but the drainage area for this BMP

was included the Devonshire drainage area.

Millersville Elementary School Parking Lot (BMP #24)

This BMP is a County owned and operated facility located at Millersville Elementary

School. The system includes a bioswale located in the upgraded parking lot area and

also a dry pond with a forebay to treat runoff from other areas of the site. Given the

standards that this system was designed for and also the age of the system this is a very

high functioning BMP structure. Field investigation revealed that this BMP drains outside

of the Jabez Branch 3 watershed. Therefore this BMP will not be included in any existing

conditions analysis.

1357 Coleus Drive (BMP #23)

This BMP is a system of five (5) raingardens at a private residence located at 1357 Coleus

Drive. This facility had planning approved in 2006 and was built in 2011. This system of

raingardens addresses the follow storm water management criteria: Water Quality

Volume, Recharge Volume, Channel Protection Volume, Overbank Flood Protection

Volume, Extreme Flood Volume. Given the standards that this system was designed for

and also the age of the system this is a very high functioning BMP structure within the

watershed.

Overlea Farms Trench (BMP #21)

According to GIS databases this was built in 2001 at the southernmost end of Kathy Ann

Lane. However, there were no as-built plans available for this facility. Attempts to field

verify this facility were also unsuccessful.

Cecil Avenue South (BMP #19)

The BMP is located on the southwest corner of the property owned by Maryland Central

Korean Baptist Church, which was once the Providence Baptist Church off of Cecil

Avenue. The BMP is an infiltration basin that had a final design approved in 1987 and built

in 1993. From the plans for this BMP is appears that this facility was designed only for the

10 year storm event. Larger storm events may overflow the infiltration pond and

34

discharge outside of Jabez watershed. However, a sediment trap basin was approved in

1998 and built in 1999 to account for additional site improvements. Field investigation

revealed that this BMP actually discharges outside of the Jabez Branch 3 watershed.

Therefore detailed calculations were not computed for this BMP.

Cecil Avenue North (BMP #15)

According to MDE records, there is a BMP facility located at 633 Cecil Avenue. The

structure type is listed as complete exfiltration. It has a listed total BMP drainage area of

0.70 acres and it was built in 1985. The property owner chose not to allow property access

for the field investigation. Due to the lack of availability of original plans and

maintenance records, and due to the age of the BMP facility, this BMP was not factored

into the subwatershed’s existing condition pollutant loading removal.

1526 Jabez Run (BMP #13)

There are no BMPs located at 1526 Jabez Run. Anne Arundel County records indicate

that there are two BMPs at this location – an infiltration trench type BMP and a separate

10,000 gallon storage tank. Original plans dated 1993 were found for these facilities, but

no BMPs were found at this location. The 1993 plans list the infiltration tank’s dimensions

to be 25 feet wide x 70 feet long x 13 feet deep and filled with #2 stone. The property is

commercial.

733 Generals Highway (BMP #6)

There is no BMP located at 733 Generals Highway. Anne Arundel County and MDE

records indicate that there is an infiltration

trench type BMP at this location. Original

plans could not be located and no signs of

an infiltration trench or other type of BMP

facility could be found at this location

during field investigation. The property is

commercial.

Lonergan’s Charter Services (BMP # 4-5)

There are two (2) BMPs located at 8797

Generals Highway (Lonergran’s Charter

Services). One is an infiltration basin and

the other is a bioswale type BMP. Original

plans could not be located. The two (2)

facilities are located on either side of the

entry drive where it meets Generals

Highway. Two drainage inlets along

Generals Highway deliver runoff to each of

the facilities. The property is commercial.

During field investigation, standing water

Photograph 31: BMP 4 Infiltration Basin

Photograph 32: BMP 5 - Bioswale

35

was noted in the infiltration basin, and both facilities were found to be supporting various

hydric wetland plant species. The infiltration basin (BMP 4) had a considerably larger

drainage area, receiving runoff from a large adjacent paved parking lot. The bioswale

(BMP 5) received drainage from a smaller area comprised mainly of the paved entry

drive on the property.

609 N Cecil Avenue (BMP #1)

There are a number of small-scale residential BMPs located at 609 N Cecil Avenue

according to Anne Arundel County records. These are four (4) dry wells and two (2)

microbioretention facilities that have plans dated 2012. The BMPs were built to manage

stormwater from 4,440 square feet of new impervious resulting from new home

construction. The property is residential. Due to the limited capacity of these BMPs and

the property’s position at the edge of the watershed (i.e. significant portions of the

property drain away from Jabez Branch 3), these BMPs were not factored into the

subwatershed’s existing condition pollutant loading removal.

36

Summary The current conditions of the Jabez Branch 3 watershed are mixed, both in terms of the

Branch’s reaches and the upland subwatershed areas. The various stream reaches range

in condition from stable to severely degraded. Reach 4 is in the poorest condition and is

in need of restorative measures to prevent further degradation to the stream. However,

other segments such as Reach 6 and a number of unnamed tributaries to the main

channel are in relatively good health and exhibit stable conditions.

Analysis of the ten (10) subwatersheds that make up the overall Jabez Branch 3

watershed also display a wide range of potential stormwater runoff impacts to Jabez

Branch 3. Comparison of subwatersheds 10 and 3 demonstrates the extremes of this

range. Subwatershed 10 is characterized by having the second lowest percentage of

impervious land cover compared to the other subwatersheds. The reaches that this

subwatershed drains to were primarily in stable condition (i.e. Reaches 6 and 7).

Conversely, subwatershed 3, which has the highest percentage of impervious land cover,

drains to a Reach 3 found to be in degraded condition.

Detailed forest analyses have revealed a major discrepancy between planning level

land use polygons available from state and County sources and actual conditions.

Detailed land use data helps to better analyze the condition of the watershed.

One step to help improve stream conditions is to actively manage stormwater runoff.

Several existing BMP facilities currently treat and prevent a portion of stormwater runoff

volumes from further degrading the stream. Using the BayFAST model, the project team

has determined that the existing BMPs remove over 140 lbs. of nitrogen, over 27 lbs. of

phosphorous and over 7,840 lbs. of sediment that would normally enter the Jabez Branch

3 channel every year. Retrofitting existing BMPs and constructing additional facilities to

properly manage stormwater, along with well-designed stream restoration projects,

should continue to help this watershed.

When planning future BMP and watershed restoration projects, the following points

should be noted. First, subwatersheds with a high percent cover of impervious land area

should receive high consideration. Second, the condition of the Jabez reaches within

and immediately downstream of the subwatershed should be considered. The condition

of the stream will be associated with the quality and quantity of runoff flowing into it. A

good starting point for examination would be to consider subwatersheds 2, 3, 5, 8, and

9. These five (5) subwatersheds have high percentages of their land cover as impervious,

and all drain to reaches that are in moderate to severely degraded condition.

37

Next Steps The next phase of the Jabez Branch 3 Watershed Restoration Plan is the development of

a proposed conditions evaluation (i.e. Phase II of the project scope). This existing

conditions report is a preliminary planning level evaluation of the system. This document

will inform the forthcoming proposed conditions report. The proposed condition report

will include specific recommendations for projects such as new BMPs, retrofits, and stream

restoration efforts.

A master list of potential projects and a corresponding prioritization schema are the next

items to be developed in order to identify and prioritize restoration needs and activities.

The existing conditions report and corresponding analysis mapping will help stakeholders

make more informed decisions as potential projects are rated.

The prioritization schema will further expand upon the land use, land ownership and

existing infrastructure landscape and infrastructure factors explored in the existing

conditions report (i.e. subwatersheds where BMP treatment is lacking, areas with a high

degree of untreated impervious, Jabez Branch 3 reaches in degraded condition, areas

generating high pollutant loads, etc.) Socio-cultural and economic factors and their

impact on the watershed’s diverse stakeholder population must also be taken into

consideration. These factors will be explored during prioritization schema development

as well. Using the existing conditions report and a stakeholder-driven prioritization schema

will allow for the most informed recommendations with the greatest stakeholder support

for proposed projects in the Jabez Branch 3 Restoration Plan.

38

References:

Anne Arundel County. (accessed 2014). Anne Arundel County GIS data download.

County, A. A. (accessed 2014). Anne Arundel County GIS data download.

KCI Technologies, Inc. (2003). Severn River Watershed Management Master Plan. Annapolis, MD .

The Jabez Branch: A Unique and Fragile Coastal Plain Stream. (n.d.). Retrieved November 2014, from

Anne Arundel County: http://www.aacounty.org/SevernRiver/jabez.cfm

Appendix 1- Existing BMP Summary Table

Appendix 2- Jabez Branch 3 Subwatershed Mapping