Prince William Conservation Alliance

A Wetlands Overview

by Larry Johnson

Wetlands occur throughout Prince William County, as well as all other Counties in Virginia. Virginia has approximately one million acres of wetlands. Of these, approximately one-fourth are tidal, and three-fourths are nontidal. Forested wetlands are the most common type of wetlands in Virginia, while the shores of the Chesapeake Bay have extensive estuarine wetlands. Approximately 42 percent of Virginia's wetlands are estimated to have been destroyed since the 1870's as a result of development for agricultural, urban, industrial and recreational uses (USGS Water supply Paper 2425). In fact, all of the original 48 states of the Union have lost massive areas (over 50 percent) of the original wetlands as a result of land use and development since colonization by the early European settlers.

Many areas of wetlands in the United States were destroyed as a result of draining agricultural lands for crop production through the practices of land tiling and stream channelization. Extensive soil erosion from agricultural lands also destroyed many wetlands along stream valleys. Major losses of wetlands occurred, and in some cases continue to occur, as a result of channelization of rivers for the benefit of commercial shipping interests. Some of the activities that destroyed wetlands were previously encouraged and subsidized by the United States Government through activities of agencies such as the Soil Conservation Service (SCS, now NRCS) and United States Corps of Engineers (COE) well into the latter half of the 20th Century. These two agencies, along with the Environmental Protection Agency (EPA), are now extensively involved in interpreting and enforcing wetland protection measures enacted by congress, as well as promoting education of the public about wetland issues.

In 1972, the Federal Water Pollution Control Act, which became known as the Clean Water Act in 1977, was amended to include Section 404 which provided recognition of the immense value of the remaining wetlands in maintaining the integrity of the waters of the United States and the need to control discharge of dredged or fill material into the aquatic ecosystem. Section 404 established a program to regulate the discharge of dredged and fill materials into waters of the United States, including wetlands. The EPA and COE were given responsibility for administering the program. The COE administers the permitting process for activities in wetlands which included filling, ditching, levee construction, land disturbance, road and dam construction. The COE also regulates wetlands associated with navigable waters in tidal areas in accordance with section 10 of the Rivers and Harbors Act of 1899.

Why should you care? The reasons are that wetlands provide many values to society in maintaining a clean environment, supporting an economic and recreational base, aiding in flood control, supporting a viable ecosystem, and providing aesthetic values. Wetlands absorb sediment and other pollutants in storm water runoff, thereby stopping the pollutants from reaching local stream waters, the Potomac River and the Chesapeake Bay. Healthy wetlands provide nutrients and safe spawning areas for fish and other aquatic life essential for maintaining commercial and recreational fish and shellfish industries. Wetlands also provide a wealth of plants and animals specifically adapted to wet environments. Wetlands frequently act as detention areas for floodwaters, thereby dampening the downstream impact of floods. Wetlands provide environmental habitat essential for the birth, feeding, and shelter of many species of waterfowl, as well as animals.

Healthy wetlands provide a sanctuary and moment of solace for those tuned into enjoyment of life's smallest treasures. For example, the next time you hear the chorus of the first spring frogs, the reclusive spring peeper (Pseudacris crucifer), you can be rather sure that it is setting up housekeeping in a nearby, perhaps quite small, wetland area. You will not regret a visit to a wetland park, such as Huntley Meadows Park in Fairfax County.

Wetlands typically occur where water accumulates naturally in the landscape as a result of rainfall, groundwater seepage, or flooding. These areas are often located in low-lying areas along drainage ways and flood plains, but also occur in upland areas where ponding occurs or the surface drainage is restricted. Wetlands may occur as large areas several hundred acres in size along tidal estuaries or, at the other extreme, as small apparently isolated pockets less than one-half acre in size.

A definition of wetlands that has been used by the US Corps of Engineers (COE) and Environmental Protection Agency (EPA) for regulatory purposes is as follows: " Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas".

In practice, jurisdictional wetlands (those subject to regulation) are identified by the concurrent presence of three indicators: a predominance of hydrophytic vegetation, hydric soils, and wetland hydrology. Hydrophytic vegetation consists of trees, shrubs, vines, and herbaceous plants that are adapted to, and thrive in, wet areas. Nearly 5000 species of plants in the United States may occur in wetlands (EPA). Hydric soils typically have dark organic surfaces and gray subsoils as result of long periods of saturation. In addition, approximately 2000 classified soil types in the United States may occur in wetlands. In Prince William County, approximately 8 percent of the County is encompassed by soil mapping units denoted as hydric soils (Prince William County Soil Survey). The total extent of wetlands is less because all three indicators must be present for jurisdictional wetlands to occur, however, hydric soils are powerful indicators as to where wetlands will occur.

Wetland hydrology may occur in areas of frequent flooding, where water ponds for long periods of time, where the water table is near the surface, or where natural springs occur. While many wetland features and areas are apparent to the casual observer (for example, the wetlands in tidal portions of Powell's Creek adjoining the Potomac River), many other areas are not at all obvious, especially during dry periods of the year. Individuals employed in identifying and delineating wetlands (including COE field staff who must make final wetland determinations for regulatory purposes) undergo special training to become proficient in wetland identification. A well-qualified wetland scientist must have a good working knowledge of wetland plants, hydric soils, and wetland hydrology.

The current wetland laws enforced by the COE became effective on June 7, 2000. At that time, the COE issued 5 new Nationwide Permits (NWPs) and modified 6 NWPs. In addition, the COE modified 9 NWP general conditions and added 2 new NWP general conditions. In brief, the maximum allowable acreage impact to wetlands from most of the new and modified NWPs is one-half acre and most require notification of the COE of any impact greater than one-tenth acre. The new NWP general conditions limit activities in designated critical resource waters and fills in waters of the United States within 100-year floodplains. For filling and excavation of streambeds, the COE has imposed a limit of 300 feet for certain impacts. Any impacts greater than those identified above will require a permit known as an individual permit. Individual wetland permits require more extensive analysis and project justification.

Wetlands of Prince William County
Prince William Conservation Alliance