The Future of Bull Run Watershed: An Overview

The Future of the Bull Run Watershed: An Overview

By

Stephen Bendele

Bull Run Watershed

Bull Run is perennial tributary that originates from the spring located at 630 feet above sea-level on Bull Run Mountain and flows 150,000 liner feet east to the Occoquan River 121 feet above sea level totaling a 509 feet change in elevation.

Bull Run Watershed is part of the Middle Potomac-Anacostia-Occoquan (MPAO) watershed and includes five subwatersheds (Cub Run, Little Bull Run, Lower Bull Run, Middle Bull Run, and Upper Bull Run) totaling a watershed area of 50,059 hectares.

One major benefits of streams is the removal of stormwater, however during storm events rivers, streams and even small tributaries can flood their banks and damage infrastructure and buildings. Federal Emergency Management Agency (FEMA) flood maps in order to identify areas pron to flooding and determine if land use decisions are properly considering flood risks.

FEMA is an agency of the United States Department of Homeland Security tasked with coordinating the response to a disaster that has occurred in the United States and that overwhelms the resources of local and state authorities. FEMA established the National Flood Insurance Program (NFIP) is a Federal program enabling property owners in participating communities to purchase flood insurance as protection against flood losses, while requiring State and local governments to enforce floodplain management regulations that reduce future flood damages. FEMA has thus created numerous productive models most notably the 100 year flood plain map. The 100-year flood plain map an attempt to map the the area impacted by a flood that statistically has a 1-percent chance of occurring in any given year. The storm event that create a 100-year flood is considered a 100-year storm. Areas within flood plains must be managed and development within these areas must evaluate the risk of doing so. 

The Bull Run Watershed has two major areas of extensive flooding rick one in located north west of the Manassas Park city and the other in west Fairfax county along Cub Run. The area of Bull Run that has a major area of only estimated (orange) 100 year flood plan is located in the Bull Run Regional Park and in the Bull Run National Battlefield. These two parks consist of primary greens spaces including fields, forested, and pasture. The low presence of development means that few areas are at risk of flood damage. The areas south near Flat Branch are at a greater rick of receiving damaging floods. The area in Fairfax County along Cub Run is more developed with fewer buffer spaces like parks and more impermeable surfaces. Fairfax is Virginia's most populated county and dense development has led to frequent flooding of stream banks.  

Land Use

The Bull Run watershed is a vast patch work of farmland, rural, suburban, metropolitan residences, major Airports, industrial parks, national and state protected areas, and numerous county and state parks. Forested areas are dominated by a diverse group of deciduous broadleaf trees. The Climate of the Bull Run watershed is temperate with hot summers and cool winters (annual average temperature of about 85℉. Annual precipitation is about 42 inches a year with slightly wetter winters and dryer summers.

A major issue facing the Bull Run watershed and the Virginia/D.C. metropolitan area is the high density of urban development and the water resource issues that development creates. Bull Run and its tributaries flow through a wide verity of land use/ land cover types. Bull Run flows through majority permeable surfaces (i.e. forest, pasture, agriculture, ect...). These areas have been protected under the Chesapeake Bay Act, and our often set aside of Resource Protection Areas (RPA). RPAs are development buffers that extend 100 feet landward from RPA components (i.e. perennial streams and adjacent wetland, and other specific feature called out by counties.  

Northern Virginia (NOVA) is subgroup of counties in Virginia that includes Fairfax, Prince William, and Loudoun Counties, and are often considered part of the Washington District of Colombia's metropolitan surroundings. These three counties along with a handful of cities such as Manassas, Reston, Arlington, and Alexandria account for roughly a half of Virginia's 8 million people according to the 2010 census. 

The area’s population has increased since 2010 and the need to house and accommodate the rising population has resulted in increased development in all counties and cities. The area surrounding Bull Run has experienced large growth with current estimates indicating a 15.9% increase in county population and a 16.5% and a 9.5% increase in Manassas City Park, and Manassas city respectively. The primary problem with the large and rapid population growth is the dramatic loss of green spaces and permeable surfaces resulting in increased storm-water runoff and pollution reducing in stream habitat and water quality. Negatively impacted impact waterways see a loss of aquatic and terrestrial wildlife. Ultimately, rapid over development results in the loss of natural resources and results in the loss of ecstatic, ecological, and economical benefits they provide for humans.       

Google Earth satellite Imagery of Bull Run 1989. 

Google Earth satellite Imagery of Bull Run 2016.

The pressure of population growth and development on watersheds and water features such as wetlands and streams will require innovative solutions. Wetland and stream mitigation with the goal of no net loss can help reduce the anthropogenic impacts to wetland systems and retain ecosystem functions. The ecosystem services provided by these wetlands becomes more essential as urban development increases. Failure to protect wetlands and streams can lead increased pollution, flooding, erosion and sedimentation, loss of biologic functions and more.

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