Cabin John Watershed

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The Cabin John Creek Watershed

The Cabin John watershed drains to the Potomac River where it discharges downstream of the Beltway above Lock 7 of the C&O Canal. The watershed has been significantly impacted by suburban development patterns centered around the County's main transportation corridors. The Interstate 495/270 corridor passes through the central part of the watershed, and commercial and high density residential development are common along this corridor, particularly affecting the eastern tributaries. Rockville Pike and the City of Rockville occupy the headwaters of Cabin John. In contrast, the western tributaries transition to lower density residential communities with far less commercial development. Like many downcounty watersheds, this area developed before environmental regulations for stream buffers and stormwater management went into effect, so on-site stormwater runoff controls are uncommon in Cabin John. The mainstem of Cabin John Creek is protected within the County's stream valley park system and, to some extent, the western tributaries also benefit from parkland buffers, particularly Buck Branch. Drainage from the highly impervious areas in these tributaries, however, has had a detrimental effect on habitat quality and stream conditions within the park.

Several regional stormwater control facilities are located in the watershed, including ponds controlling drainage from Montgomery Mall, the office parks at Democracy and I-270, and several headwater areas in the upper watershed. These ponds treat runoff from only a small part of the highly developed areas of the watershed.

Uncontrolled runoff in Cabin John has resulted in seriously impaired habitat throughout the watershed. Impacts have included accelerated stream channel downcutting and widening of channels which has undermined and toppled trees. Exposed sanitary sewer lines, in many cases originally buried 10 -20 feet below the bottom of stream channels, are a common occurrence in Cabin John, as in some other urban County watersheds. Booze Creek in particular has been adversely affected by stormflow impacts to the sewer system. Many problems can develop when sanitary sewer systems are exposed, including leakage of raw sewage into the streams. Repair of these systems is costly and requires temporary construction impacts to the stream system.

Despite the overall fair/poor quality of the stream conditions in Cabin John, there are still three remaining tributaries that maintain a good resource condition. These tributaries, Buck Branch, Ken Branch and the Congressional tributary, support a diverse community of insectivorous fish species. The presence of this fish community is reassuring evidence that polluted runoff has not become a chronic problem and that habitat still provides in-stream cover adequate to support the fish and benthic macroinvertebrate community.

Observant visitors to the lower Cabin John mainstem, where the fish community is influenced by proximity to the Potomac mainstem, may eventually be rewarded with sightings of large golden redhorse (a sucker species) resting quietly on the bottom of deep pools or swimming quickly through shallow areas. This species was identified in monitoring efforts during the summer of 1996 and added a new species to the overall County fish list.

To help address the chronic problems associated with urban stream degradation in Cabin John, development of a watershed restoration action plan is scheduled to begin in 1999 to identify goals and target capital improvement projects and stream restoration needs.

Cabin John Creek Biological Integrity, Habitat Conditions, and Management Category

Subwatershed/

Stream Condition
Habitat Conditions
Primary Factors Affecting Stream Condition
Unique Characteristics/Management Category Designation

DEP baseline monitoring of Cabin John was conducted in 1996

Upper Mainstem - FAIR (preliminary)
GOOD - (preliminary)
Uncontrolled stormwater runoff is affecting channel stability. In-stream habitat problems are limiting biological community.

City of Rockville

Bogley Branch - FAIR (preliminary)
FAIR - (preliminary)
High imperviousness and uncontrolled runoff are affecting channel stability, in-stream habitat. Riparian buffer provides inadequate protection.

Watershed Restoration Area (outside City of Rockville)

Upper Old Farm Branch - FAIR (preliminary)
GOOD - (preliminary)
Problems are similar to those in Upper Mainstem and Bogley Branch. All of these headwater areas are impacted by impervious conditions, inadequate buffers, and in-stream habitat problems.

Watershed Restoration Area (outside City of Rockville)

Lower Old Farm Branch - POOR
POOR
This section has been impacted by imperviousness form the I-270/I-495 spur

Watershed Restoration Area

Snakeden Branch

(Deborah Dr. Branch) - POOR
FAIR
Poor bank stability, embeddedness and sediment deposition are resulting from uncontrolled stormwater flows.

Concrete swales in this watershed create flashy hydrology.

Watershed Restoration Area

Middle Mainstem - FAIR
FAIR Overall
Channel alteration from road crossings and erosion control measures is common in this section. Embeddedness, and problems with bank stability and sediment deposition indicate impacts from stormwater flows.

Watershed Restoration Area

Buck Branch - GOOD

(preliminary)
GOOD - (preliminary)
This tributary is on the margin between good and fair.

Flow-related bank stability and sediment deposition problems are affecting in-stream habitat, particularly benthic habitat.
This stream currently supports the most diverse fish community of all the tributaries.

Watershed Protection Area - remedial

Beltway Branch - POOR
FAIR
This stream runs alongside I-495 and I-270 and has been altered by these roads.

Channel stability and embeddedness impact substrate.

Urban Watershed Management Area

Ken Branch - GOOD (preliminary in upper area)
FAIR (preliminary in upper area)
Sediment deposition, embeddedness and bank stability problems are impacting the benthic community.

Fish community is less impaired than elsewhere in Cabin John. Close observation of trend is important.
Frequent flooding problems occurring at Bradley Blvd.

Watershed Protection Area - remedial

Congressional Trib. - GOOD (preliminary)
FAIR (preliminary)
Good biological conditions were observed during a COG inventory, however, that assessment is based primarily on intolerant species collected above the golf course. COG rated bank stability as fair.

Watershed Protection Area - remedial

Upper Booze Creek - POOR (preliminary)
POOR to FAIR (preliminary)
Significant areas of the headwaters have been channelized or piped. Non-point source pollutants and chronic problems with leaking sewer lines are also sources of impairment to biological community.

Urban Watershed Management Area

Lower Booze Creek - POOR
FAIR to GOOD
Habitat is on the margin between fair and good, with impacts occurring from scouring, sediment deposition and channel widening.

Biological conditions, despite availability of habitat, are impaired by very flashy hydrology.

Watershed Restoration Area

Lower Mainstem - FAIR
GOOD Overall
Benthic community is impaired by impacts to substrate from scouring and embeddedness. Fish community remains good due to better fish habitat and access to the Potomac River.
Passes through Potomac River valley wall in steeply descending section of the Creek.

Watershed Restoration Area

Cabin John Creek Watershed Management Categories

Management of the stream resources in this watershed includes activities by the City of Rockville in the upper part of the watershed, and upcoming efforts to develop a watershed restoration action plan by Montgomery County DEP.

In addition, the Potomac Subregion Master Plan Study is currently underway, covering the Cabin John watershed west of the mainstem, which will include an examination of land use and stream condition relationships. Watershed management approaches will be updated in the CSPS as necessary to respond to land use recommendations.

Watershed Protection Areas

Remedial level of protection

The three tributaries in this management category, Buck Branch, Ken Branch, and Congressional Tributary, include the stream reaches that have good stream conditions although problems in the habitat condition are being observed in all three of these drainages as a result of uncontrolled stormflows and sediment deposition. Remedial actions, which include addressing accelerated stream bank erosion and preservation of refugia, are recommended as part of comprehensive efforts to restore the watershed, in order to avoid deterioration in overall conditions and maintain and improve biological function.

Watershed Management Strategy

Conduct additional biological monitoring to update preliminary assessments.
Study and implement remedial protection measures as part of a comprehensive watershed restoration action plan, to begin in FY99.
Further evaluate relationships between land use and stream conditions through the Potomac Subregion Master Plan Study.

Watershed Restoration Areas

The majority of the tributaries in the watershed fall into this category, including Upper Mainstem, Bogley Branch, Old Farm Branch, Snakeden Branch, Middle Mainstem, Lower Booze Creek, and the Lower Mainstem.

Watershed Management Strategy

Study and implement stormwater retrofit and stream restoration measures as part of a comprehensive watershed restoration action plan, to begin in FY99.
Ongoing application and enforcement of existing environmental regulations and guidelines.

Urban Stream Management Areas

Two tributaries in Cabin John are recommended for this management category - Beltway Branch and Upper Booze Creek. Streams in these areas have been highly altered by land use, and implementing water quality improvements and pollution prevention efforts will be the most effective management tools to ensure that impacts to downstream reaches are minimized. Limited areas of stream channel stabilization may be warranted to address specific erosion problems, but the likelihood of restoring highly functioning biological communities in these areas is unlikely.

Watershed Management Strategy

Identification and implementation of pollution prevention efforts and erosion control measures as part of the Cabin John Watershed Restoration Action Plan to begin in FY99.

Maps

Land Cover
Impervious Area
Stream Condition
Management Categories

Land Cover Graph

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