Flooding & Flood Control


Prince William County has taken steps to help protect people and property against flood concerns. The first step was to create Resource Protection Areas (RPA) and Resource Management Areas (RMA).

RPAs are areas along streams where floodplains exist. The County has several square miles of RPAs. Vegetative buffers are required within RPAs to help:

  • maximize infiltration, which reduces storm water runoff into streams and the potential for flash flooding
  • protect streams from development impact, which improves water quality

RMAs include floodplains, highly eroded soils and other sensitive areas. Our entire County is considered an RMA. Developers and builders working in an RMA are required to use best management practices, which are steps to minimize erosion, control runoff and prevent pollution. Many Prince William developers build storm water management facilities. These facilities incorporate the best management practices and help provide flood control.

Is your property in a floodplain?

You can view the County Mapper to determine if your property is located within a floodplain.

Before buying a property, you can also take these steps to learn more about floodplain issues:

  • Ask the real estate agent if the property is in a floodplain, if it has ever flooded and if it is subject to any other hazards, such as sewer backup or subsidence.
  • Ask the seller and the neighbors if the property is in a floodplain, how long they have lived there, if the property has ever been flooded and if it subject to any other hazards.
  • Call Watershed Management for assistance at 703-792-7070 (TTY: 711).

If you live in a floodplain, there are restrictions on building on your property. You can learn more about requirements and restrictions in the Environmental Systems Section 700 of the Design and Construction Standards Manual.

Learn more about Protecting Your Family & Property from Flooding

100 Year Floodplain Hazard

Prince William County has experienced 100 year floods. Today, more than ever before, there are more controls such as storm water management ponds and drainage systems in place to protect people and property. However, you should monitor weather reports and heed emergency warnings during major storms.

A History of Floods in Prince William County

Prince William County has experienced major floods in 1937, 1942 and 1972. By far, Hurricane Agnes in 1972 was the largest flood and exceeded any predicted 100-year floods.

According to newspaper reports, the storm caused severe damage in the Manassas area. Major flood damage occurred to businesses, homes, boats and automobiles.

Mobile homes were literally washed away. Water washed over numerous bridges, including the one across Bull Run. Currents broke up the roads, and road damage was intensified by stopped up culverts and other drainage ways. As the water rose, 700 people were forced to abandon their homes.

In the Occoquan River watershed, the storm wreaked havoc and caused $8.7 million in damage. Most of the damage was to residential property ($2.2 million) and to transportation facilities ($3.5 million). Three deaths were attributed to the storm.

Flood hazards pose serious threats to life and property. Take the steps to safeguard yourself, your family, your home and your property. If you have questions about whether you live in a floodplain, or for more information, please call the Department of Public Works at 703-792-7070 (TTY: 711).