Where does the rainwater go?

Technical Director of our partners centremapslive.com and this week’s guest blogger, Andrew Terry reports on the topic of rainwater and the SuDS legislation.

Over the last few months, I’ve been watching a new housing development being built near my home. It’s always interesting to see new communities appearing in previously open land and in this case, close to wetland areas and flood plains around Tewkesbury.

While I admire the civil engineering techniques used to create the housing infrastructure, it prompts me to think about the impact of surface water on this development, especially as it is overlooking the floodplain.

We’ve all seen news stories showing the damage that flash flooding can have on homes and roads due to a rapid run-off after heavy rain. However, there is now a recognition that new or redeveloped land should not exacerbate this and ideally should help to reduce the impact.

New housing development.

Here at CentremapsLive, we have seen a significant increase in clients facing queries from local authorities on their development plans. They’re being asked about the flood risk for a proposed (re)development, but also to ensure there will be no increase in contribution to peak flows (the highest rate of water flow following a rainfall event). To reduce any potential risks to a property or life, the Government introduced the new legislation Sustainable Drainage Systems (SuDS) to mitigate the impacts of surface water flooding.

Since 6 April 2015, SuDS has been a requirement in the planning process for all new developments in England. This is namely in areas affected by flooding or within CDAs (Critical Drainage Areas) as well as any major developments.

A SuDS strategy, especially if considered early in the project, not only works towards satisfying planning conditions but can also enhance the development through integration with open areas. It could potentially prevent high maintenance civil engineering by encouraging water to infiltrate ground water on site, or at the very least delay the release to surface water or drains. Even an existing site of buildings can use “blue roof” (storage for rainfall water on flat roof areas) strategies to reduce immediacy of run-off, costing less than building subterranean tanks. Things to consider include:

  • Flood risk – site susceptibility to surface or groundwater flooding which may impede drainage strategies.
  • Topography – the geography of the ground influencing drainage direction for drainage and natural depressions in the land.
  • Contamination – ground contaminants could gain a pathway to reach surface water bodies or protected groundwater resources.
  • Ground stability – improper loading of the ground could result in ground stability issues relating both to slope stability or sub-surface cavities.
  • Permeability – superficial and bedrock implications on the permeability of the surface may affect absorption of water.
  • Existing infrastructure – the presence of storm drains and other public

With the ever-increasing need for new and denser developments on green fields and existing sites, SuDS provides an opportunity to avoid compounding the risk of flooding. Whether you are a private investor, work for a local authority or are building your own home, it is worth considering a SuDS report from us. Our online portal delivers instant access to a wide range of data alongside environmental and flood risk reports. We have even recently added GeoSmart’s SuDSmart range which, for the first time, provides a cost-effective report to evaluate SuDS potential at an earlier stage of a project than ever before.

Visit our SuDS introduction to find out more about this service.

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