Suburban Land Use, Stormwater Best Management Practices, and Receiving Stream Health

Suburban Land Use,

Stormwater Best Management Practices,

and Receiving Stream Health

Assessing Implementation of Management Practices

and Their Relation to Water Quality

Dianna Hogan1, Taylor Jarnagin2, Keith VanNess3, Jennifer St.John3, and Rachel Gauza3

1USGS Eastern Geographic Science Center2EPA Landscape Ecology Branch, Environmental Sciences Division

3Montgomery County Department of Environmental Protection

March 25, 2009

Clarksburg Special Protection Area (CSPA)

Presentation Overview

Definition (BMP)

Partnership and goals

Study site description

Selected methods and preliminary findings

Local level BMP database that maps development, BMP type

and placement, and landscape stormwater flow direction

Four Light Detection And Ranging (LiDAR) overflights

Monitoring of physical and biological parameters

Detention pond and

sand filter

Which Best Management Practices (BMPs)?

Suburban land management actions

above/below ground retention or infiltration, wet or dry ponds,

sand/gravel filters, constructed wetlands, vegetated buffer strips,

etc.

Designed to lessen impacts of suburban land use by treating

and/or retaining or detaining stormwater runoff

recharge trenchfiltration

detention basin

Splitter with vent


Partnership

Montgomery County Department of Environmental Protection (DEP)

Montgomery County Department of Permitting Services (DPS)

Maryland-National Capital Park and Planning Commission

University of Maryland College Park (UMDCP)

Virginia Polytechnic Institute and State University

USEPA Landscape Ecology Branch, Ecosystems Research Division, and Office of Water

US Geological Survey (USGS) Eastern Geographic Science Center (EGSC) and Water Resources Discipline (WRD)


Partnership Goals

Study the impacts of land use change

Agriculture / forest to suburban

Document how the changes in topography and imperviousness

affect the hydrology, biology, chemistry, and geomorphology of

receiving streams

Assess the effectiveness of local level BMP mitigation protocols

Goal: Better understand the potential pollutant retention of

specific BMP mitigation designs and promote the application of

this information across the Chesapeake Bay region


Study Site Description

Developing under SPA guidelines

Designed to protect high quality streams in developing areas

Advanced sediment and erosion controls, stormwater BMPs in series, interception of water further upstream

Before-after control study

5 subwatersheds (0.9 – 3.4 km2)

Undeveloped positive control on parkland

Developed negative control in Germantown (completely built out; pre-2000 criteria)

Three test areas

5 USGS stream gages (red dots)

Water quality (blue dots)

2 precipitation gages (near Sopers and Cabin Branch)


Methods and Preliminary Findings: BMP Database

Local level BMP database (GIS)

Pre- and post-development

Building footprints, roads

Stormwater management infrastructure and conveyance (pipes, swales, treatment trains)

BMP type, placement, DA, IC

Stormwater flow direction

Integrate land use and BMP information with chemical, biologic, and physical stream data

Study local level BMP protocols for water quality mitigation

Effect of BMP type, location, use in series or as individuals, and development patterns



Inclusive

retention or infiltration areas, wet ponds, extended detention ponds, sand filters, etc.

private BMPs - dry wells along the back side of houses by streams

Temporal

Sediment and erosion control during construction (settling for large volumes of sediment-laden runoff)

Stormwater management post-construction (quantity and quality control of stormwater runoff)

Adjacent sediment trap prior

to conversion to a detention

basin Clarksburg, MD 5/06

Sand filter

Clarksburg, MD 5/06

Dry well schematic

Dry well

Clarksburg, MD 9/05


Methods and Preliminary Findings: LiDAR

Four Light Detection And Ranging (LiDAR) overflights

2002, 2004, 2007, 2008

Optical remote sensing

Measures properties of scattered light to determine distance by measuring time delay between transmission and detection of the reflected signal

Map temporal changes in the landscape, stream morphology, watershed hydrology, infiltration conditions, and used for hydrological modeling Z

X

Y

After, Flood, 1997

Clarksburg Maryland Special Protection Area: Tributary 104 site

USGS Stream Gauge Site2002

Jarnagin 2008 EPA LEB



2005 post constr. BMP



Methods and Preliminary Findings: Monitoring

Monitoring of physical and biological parameters

Stream flow (USGS flow gages at each subwatershed)

Stream monitoring focusing on rapid habitat assessment, geomorphology, water temperature, sediment, and benthic macroinvertebrates

Precipitation gages (2)

Selected BMP monitoring

Integration of monitoring data with the BMP database

Preliminary findings in developing areas:

Stream conditions have declined

Flashier storm response

Altered stream geomorphology (bed aggradation during development then channel erosion postdevelopment)

Sinuosity ratio indicates channel straightening

Average Stream Conditions

(combined benthic macroinvertebrate and fish scores)


Methods and Preliminary Findings: Monitoring


Summary

Few studies have followed comparable small watersheds from pre-construction through build-out to evaluate various combinations of stormwater management mitigation

Development in the CSPA is ongoing - need to be further in the development process for trend analysis and determine if there will be recovery

Increasing targeted monitoring efforts – USGS postdoc and discussing sediment collection

We will continue to evaluate the effectiveness of different BMPs and water quality protection measures

20081998

Correlate changes in stream flow,

biological and chemical

parameters, and geomorphology

with development patterns and the

BMPs used to mitigate the impacts

of development

THANK YOU !Dianna [email protected]

Taylor Jarnagin

[email protected]

Keith VanNess

[email protected]

Jennifer [email protected]

Rachel Gauza

[email protected]

Hogan, D., Jarnagin, T., VanNess, K., St.John, J., Gauza, R., 2009, Suburban Land

Use, Stormwater Best Management Practices, and Receiving Stream Health [abs.]:

Ecosystem Based Management - The Chesapeake and Other Systems, p. D-45.

Suburban Land Use, Stormwater Best Management Practices, and Receiving Stream Health

Technology

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