Stormwater Attenuation and Filtration
Stormwater is the rainwater that runs off roofs, car parks, roads, pavements and yards. It can be surprisingly polluting due to contamination by petrol and diesel spills and drips, grit, mud, soiling by cats, dogs and birds, and spilled food and other material. The flow from paved surfaces is also much less even and consistent than from woods or farmland. By using constructed wetlands and flow buffering ponds, the water can be filtered to a high quality and is also discharged at a more even rate; helping to prevent floods and droughts further down the stream or river catchment.
Natural wetlands act as sponges in the water environment, soaking up surplus rain during wet weather and releasing it slowly during dry weather. This is the principle behind wetlands used in Sustained Urban Drainage Systems (SUDS), which are designed to counteract the rapid runoff from paved surfaces in towns and new developments. In this way, purpose built constructed wetlands for stormwater treatment can be designed to prevent small streams near new housing estates, roads or yard areas from being overwhelmed during downpours and drying out during prolonged dry spells.
Stormwater control is often required by the city and county councils as part of new developments. FH Wetland Systems have worked on many such developments to introduce pond and wetland areas that are attractive to local wildlife as well as satisfying the necessary planning requirements of water filtration and flow buffering.
Stormwater Links:UK SuDS design tools; includes Ireland in the geographical area covered.
Dublin City Council background on SuDS and list of further links to related sites.
Britis Geological Survey info on SuDS.
SusDrain overview of different SuDS components, linked here to their swales page. Good summary of pros and cons of different systems.
The following images are taken from a small urban stormwater area in northern Denmark. Note that this isn't one of our wetland projects - just an example of elegant, low-tech design for illustration purposes here.
FH Wetland Systems website content on this page by Féidhlim Harty is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.