Stormwater Wetlands

Constructed stormwater wetlands treat runoff the way natural marshes treat floodwater: shallow pools and vegetated benches slow the water, settle solids, and let plants and microbes work on nutrients and metals. The group includes shallow marsh systems, extended detention wetlands, pond/wetland combinations and pocket wetlands. Wetlands want the same drainage area and baseflow security as ponds — a marsh that dries out loses both its vegetation and its treatment — but they reward the extra design care with strong sediment and bacteria removal and the highest habitat value of any practice group. Their footprint is the largest in the toolbox, which is why they appear most often on larger sites, regional facilities and retrofit opportunities where land is available. These fact sheets cover marsh grading, the pondscaping plan that establishes wetland vegetation, sizing rules and the maintenance routine of a living treatment system.