Sustainable drainage for the Thames catchment

In urban environments where many surfaces are sealed by buildings and paving, natural infiltration of water into the ground is limited. Instead water drains to pipes and culverts, which channel surface water into local ditches and water courses. During intense and extreme rainfall events the drainage network is overwhelmed leading to flooding and deterioration in river water quality as foul sewers exceed capacity. To overcome this problem more sustainable drainage systems (SuDS) are being installed for new developments and retro-fitted to existing urban areas.

The role of infiltration SuDS

Flow of water through sustainable drainage systems into the subsurface

BGS has developed the national infiltration SuDS map, which gives a preliminary indication of the suitability of the ground to receive water from infiltration SuDS for those involved in the planning and design of SuDS and for those who approve SuDS planning applications. We are using the national infiltration SuDS map in combination with the London 3D geology model to generate a more local assessment of SuDS-focussed hydrodomains for the Thames catchment near Reading. Our aim is to couple our understanding of the complex geological sequence and the infiltration SuDS suitability with our hydrological models of the Thames basin to assess the role that infiltration SuDS can play in dampening the effects of extreme weather at the catchment scale.

SuDS observatory

SuDS observatory at an Environment Agency car park in Oxfordshire.

BGS has established a SuDS observatory at an Environment Agency car park in Oxfordshire that uses permeable pavement to promote the infiltration of surface water to the ground. The car park is made up of permeable paving stone at the surface, with a sand and gravel layer and a geotextile underneath to attenuate any pollutants arising from the car park, preventing the contamination of groundwater. The aim of the observatory is to assess how well the permeable pavement performs during heavy rainfall events, how water moves through the shallow unsaturated zone beneath the paving and whether the design of the pavement is successful in limiting pollutants.

Find out more about SuDS.

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