Stormwater management systems within the Lake Worth Drainage District (LWDD) area are required to provide both flood control and water quality mediation. There are two general types of stormwater systems that perform these functions – retention and detention. Both systems depend on proper grading of the land to successfully keep homes from flooding and ensure water quality. The relationship between land and stormwater management is inseparable.
A retention stormwater system is designed so the grading or slope of the land helps to collect water in low lying areas. This helps to prevent flooding in undesirable areas and allows the water to slowly seep into the shallow groundwater aquifer. As the stormwater seeps into the ground, the grasses, sand, soils and rocks help filter out contaminants thus providing water quality treatment. The retention stormwater system can be man-made or a naturally occurring depression. There is no discharge to another water body such as a pond, lake or canal. This type of drainage system is often found in rural areas or large undeveloped areas.
A detention stormwater system is used by most modern-day residential communities. The design directs and contains stormwater onsite in a pond. It is designed to allow pollutants in the water to settle to the bottom of the pond leaving cleaner water on top. Again, the grading of the landscape is vital to the success of the system as the water must flow toward and into the detention system. The detention system consists of pipes and catch basins to collect and direct the stormwater. Water moves away from homes via an overland drainage flow. Front, side, and back yards typically utilize overland drainage. Stormwater flows through the front or back yards and may cross four to five lots until it reaches a catch basin. The catch basin is connected to underground pipes that discharge the water to the community pond for storage and cleaning.
After a rainstorm, the water in the pond will rise and if the elevation is high enough, the cleaner water at the top will drain from the pond through an outflow structure and eventually into a LWDD canal. The overland flow of stormwater over a LWDD canal bank and into the channel is not allowed. The untreated stormwater can impact water quality and dangerous washouts in the bank can occur.
The LWDD designs its canal banks and rights-of-way to prevent stormwater runoff from directly entering the canal system. A typical LWDD canal right-of-way is graded so the canal berm is higher than the surrounding land and stormwater will flow away from the canal. Due to the regular maintenance activities of the LWDD like mowing, as well as the natural settling of the soils, regrading of the right-of-way is one of the important flood control operations performed by the LWDD.
Over time, property owners may also have to regrade their front, side and back yards to match their original drainage design. Settling of the soils or enhancements such as landscaping materials or installation of fences may impede the overland drainage flow. This disruption can cause soggy areas in yards and standing water during heavy rain events. In severe cases, patios, garages and homes can be adversely affected. Property owners should be aware that it is their responsibility to ensure the overland drainage flow is maintained to the design condition.
Development activities that effect how much rain can soak into the ground, how much water leaves a property, and where it will go are regulated by the South Florida Water Management District. Community drainage system permits and plans may be obtained through this agency at www.sfwmd.gov. Additionally, permits for the crossing and use of the LWDD canal right-of-way for the installation of drainage infrastructure such as culverts and outlets can be obtained by visiting LWDD’s online permit system at www.lwdd.net/right-of-way/permitting.