Where rainfall lands on a surface, you can use source control sustainable drainage system (SUDS) techniques to control run-off at, or close to, the source. This includes permeable or porous surfaces such as permeable paving, swales and filter strips.
To deal with heavy or persistent rain which produces more run-off, you can use site control SUDS, which are downstream of source controls, to manage the surface water run-off from larger areas, such as:
- parts of housing estates
- major roads
- business parks
You can use detention basins to store run-off from large areas. Water usually runs into these from conventional drainage systems or from upstream SUDS.
Detention basins let run-off spread across a wide floor area and only fill after heavy rainfall, when they will hold large volumes of water. This lets pollutants settle out before the water soaks away or discharges slowly downstream.
Ponds and wetlands
If you want to store water for longer, you can use ponds instead of detention basins. This allows natural processes, using bacteria and sunlight, to break down pollutants before the water eventually flows into downstream watercourses. Ponds can also be a welcome addition to urban areas, encouraging plants and wildlife.
You should never use existing ponds or wetlands to treat run-off. Always create new ponds to avoid damaging or disturbing the wildlife that is already in the area.
You can also connect a number of ponds, or include wetland areas in tackling run-off from large areas. Wetlands contain a larger amount of vegetation and are more suitable for treating contaminated run-off. Newly created ponds and wetland areas are ideal for treating lightly contaminated water from farmyards and farm roads.