Drainage swales are an environmentally sensitive means of providing roadside drainage that is promoted by the Florida Department of Environmental Protection (FDEP) through the issuance of swale exemptions to General Stormwater Permit requirements. Nearly all subdivisions constructed during the last 10 years have used swales to convey runoff from the subdivision roads to retention basins and outfalls.
In addition to conveying stormwater, the intention of a swale is to provide stormwater treatment by allowing some portion of the runoff water to infiltrate into the ground versus completely running off to an outfall. The infiltration process cleans the runoff water and provides a natural recharge to the ground water. The FDEP swale requirements allow the stormwater 72 hours to infiltrate into the ground.
Frequent problems with drainage swales are that they are filled in by residential landscaping efforts or the flow line to an outfall is blocked by a driveway without a culvert. Another frequent problem is the high water table found in many areas of Bay County. The water table will not allow the stormwater to infiltrate into the ground and the swales stay "wet" all the time.