The Role of Wetlands

Wetlands are low-lying areas that are at least periodically saturated or inundated with water and have specific types of soils and vegetation consistent with these moist or wet conditions. Wetlands provide unique habitats that support a wide variety of wildlife and they provide wonderful opportunities for observing nature.

Although wetlands are sometimes blamed for mosquito problems, a healthy wetland actually has a balanced relationship between mosquitoes and their predators which results in natural mosquito control.

Wetlands serve a vital role in protecting surface water quality by filtering sediment, nutrients, metals, and other pollutants from stormwater runoff - in fact, sometimes they are equated to kidneys for their filtering capability.


Erosion & Flooding

Wetlands also help prevent erosion and flooding by acting as sponges that absorb and detain runoff as well as recharging groundwater. Historically, wetlands were often drained or filled to accommodate agriculture and urban development. Impacts to wetlands now require Federal and State permits and if the proposed impacts exceed established thresholds, they must be mitigated by creating new replacement wetlands.

Loss of Wetlands

Even with these protections, an estimated loss of 13 acres of wetlands and 20,000 feet of streams occurs annually within the county. Part of this net loss occurred because some of the wetlands that were established to replace those lost in Loudoun County were created in other counties. Federal and state laws only require that wetlands be replaced in the same large drainage area in which they were impacted and these large drainage areas often include multiple counties.

Environmental staff in the Department of Building and Development worked to modify the application and review process so that more replacement wetlands are now being built in Loudoun County.

Stream & Wetland Mitigation Banking

Staff also worked with the Wetland Workgroup, an ad-hoc group of environmental consultants and stream and wetland mitigation bank owners, to develop a map of all of the approved and proposed stream and wetland mitigation banks in the county and an associated contact list (PDF). Developers looking for mitigation credits and property owners interested in pursuing potential mitigation opportunities on their property are encouraged to refer to the contact list for additional information.