existing conditions evaluation · 14, 2014. the planning level stream evaluation was based...
TRANSCRIPT
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.
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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
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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
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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