Présentations Colloques

    Oral Presentation
    Session 7.02: Urban Hydrogeology
    Butcher Andrew S
    Investigating the Impact of Sustainable Drainage Systems on Groundwater
    Since April 2015, in the UK, lead local flood authorities have been expected to ensure that sustainable drainage systems are incorporated into the design of housing and commercial developments. By mimicking natural drainage regimes, the application of infiltration Sustainable Drainage systems (SuDS) aims to reduce surface water flooding and improve water quality, although the impact of enhanced recharge on groundwater quality and level, are poorly understood. A SuDS Observatory has been established where a permeable pavement car park was constructed in 2005. The car park is made up of permeable block paving at the surface, with graded gravel layers and a geotextile below for bio-attenuation. The underlying geology of the area is made ground and river terrace sand and gravel, underlain by glauconitic marl. The Observatory has been upgraded and now contains a number of different types of soil moisture sensors at different depths within the SuDS and the adjacent natural grassland. Within the SuDS, the upper sensors are in the fine gravel layer above the geotextile and the lower sensors are in coarser gravel below the geotextile, in an effort to investigate the flux of water through the unsaturated zone. A raingauge is also now used to trigger higher frequency measurements during rainfall periods. The preliminary data from the sensors highlight that in the grassland, water is stored even after rainfall events+ the SuDS act effectively by holding very little water and completely draining at certain points. Groundwater levels also appear to impact on the efficiency of these systems+ an increase in hydrostatic pressure can slow down drainage from the SuDS, even though groundwater levels may still be below the system. An understanding of the surface and subsurface (vadose and water table) components can greatly improve an assessment of the efficiency of these SuDS.
    United Kingdom


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