Wherever rainfall lands, it starts to flow into and through the landscape. The more we pave over the soil, converting open land into urban space, the greater the potential for flooding and pollution.
To address these twin issues redesign of stormwater is needed to ensure that no water should leave an impermeable surface without first being introduced to plants and having time to sit around and chat with them.
Examples of stormwater systems that allow this to happen include rain gardens, swales, stormwater wetlands and ponds, bioretention areas, tree pits and similar measures. These are all variations on a theme whereby plants, soil and soil organisms carry out the work of slowing the flow, filtering the pollutants and gradually reintroducing runoff back into streams again.
| What we offer: Water- and catchment-management plans for towns and villages, rivers and streams. Consultancy and advice Workshops, training and public talks Catchment management workshops in Lahinch, Co Clare. Note: FH Wetland Systems can offer design and consultancy for catchment scale projects where full community participation is available. Alternatively, individual, site-specific stream or river improvement projects can be carried out to improve the water quality of the catchment downstream of that point. These are useful where one landowner wishes to make positive changes without the challenges and time constraints of involving others. |
SUDS for 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 volume leaving paved surfaces is much less consistent than from woods or farmland. By using NBS-SUDS (nature based solutions for sustained urban drainage systems), water can be filtered to a high quality and discharged at more stable rates. This helps to prevent floods and droughts further down the stream or river catchment.
Natural wetlands (and indeed most intact natural habitat) 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 SUDS ponds, wetlands, swales etc.. These are designed to counteract the rapid runoff from paved surfaces in towns and new developments. In this way, purpose built stormwater systems can be designed to prevent small streams near new housing estates, roads or yard areas from flooding during downpours and drying out during prolonged dry spells.
Holistic Flood Management
SUDS aren’t the only way to reduce flooding and droughts. Other factors include ecosystem restoration work on upland areas, catching rainfall as it lands on high ground in areas of planted native woodland or blocking bog drains to retain the water storage value, carbon storage, habitat and soil integrity of these areas.
Further down the catchment, farm ponds, contour hedgerows and similar measures can help hold water in the farming landscape. This can play a valuable collaborative role with urban SUDS to reduce land runoff and ease the impact of both flooding and droughts.
Climate breakdown exacerbates flooding and drought conditions. When we adopt nature based solutions, many of the measures that create climate resilience on farms and in urban areas also provide carbon sequestration, habitat protection and ecosystem repair. All of these contribute to a virtuous cycle of steady, self-reinforcing effectiveness.
Water Flow & Filtration on a Catchment Scale
Improving our own wastewater and stormwater is important, but imagine the difference you could make if you took the whole valley into account to really improve the overall water quality in your river basin or catchment. Catchment management can be used to maximise the pollution reduction and environmental protection in the wider area for an integrated approach to improving waterway quality.
Reintroduction of wetlands within the river basin is one of the most straightforward ways to improve water quality and habitat value of streams and rivers, and is being increasingly practiced worldwide for flood control, pollution reduction and habitat enhancement. Introduction of other habitats such as woodlands, hedgerows and seasonally grazed grasslands can offer similar benefits. Buffer zones can be used on farmland and adjacent to any dispersed sources of pollution to offer further water filtration. Stormwater wetlands for runoff from roads and paved areas can also offer extra filtration, as can the use of effective sewage treatment within the whole area.
Further reading:
Sketch showing sample rain garden types: Rain Garden Measures