Sealed surfaces cause flood risk. A 2020 study from John Hopkins University reveals that every time a city increases coverage of absorbent surfaces with roads, housing or parking lots by 1%, the annual flood magnitude in the nearby watercourse increases by 3.3%.
Flooding isn’t the only issue. With sealed surfaces comes pollution. A 2017 study reveals that 5-10% of microplastics in our oceans can be specifically attributed to tyre wear and tear (Kole et. al). Sadly, it is not only microplastics that cause harm, hydrocarbon and other pollutants often flow directly into nearby watercourses.
With this twin challenge in mind, the Trent Rivers Trust embarked on a pioneering project in Measham near the River Mease. Addressing the issue of surface water run-off from the nearby roads we worked on public land, near a housing estate to provide a Sustainable Drainage scheme that would prevent road run-off from running directly into the SSSI- and SAC-designated river.
This retrofitting project acts as a flagship for what Trent Rivers Trust wants to see as a standard – water-sensitive planning decisions in urban and rural settings. The earlier Sustainable Drainage systems are embedded in the planning process- the better.
Funded by the Trent Regional Flood and Coastal Committee, this scheme has transformed a previously plain bit of amenity grassland to provide multiple benefits, for the river as well as the local people.
Previously, all the surface water from Wigeon Drive flowed directly into the River Mease. As surface water from roads traditionally flows through gully pots, into pipes, then discharges into the local river through some sort of engineered structure. With no natural filter in place, toxins enter the watercourse directly.
By putting a filter in the form of nature-based interventions in place, the water is slowed and filtered before it enters the Mease. Flood risk decreases and the reduction in harmful chemicals and overload in nutrient and sediments helps meet SSSI and SAC favourable condition, as well as, the Water Framework Directive target of a ‘good’ ecological status.
As a public space on a housing estate, our thinking went beyond ecological benefits. Safety was paramount. Hence, the basins were designed to hold a maximum depth of 100mm of water whilst still functioning for storage.
The project was delivered locally in reducing pollution pressure from urban pollution. As the nature-based solution involved a boost in vegetation, residents also benefitted from a greener, more attractive environment around their estate.
The scheme not only slows and stores the road runoff to delay its passage to the river, but the new SUDS features also allow the microplastics and hydrocarbons to settle out on the land before they get to the river.
More importantly, the work has had a wider halo effect. It demonstrated that nature-based solutions have a place in the planning process and equipped Trent Rivers Trust with the expertise to navigate an often multi-layered planning process.
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