Innovate UK: Improved probabilistic mapping and modelling of groundwater flooding in urban areas

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There is a need to better understand the role of groundwater in urban flooding - a quarter of claims following the most recent major flooding (winter 2013/14) were associated with flooding predominantly from a 'groundwater' mechanism. Additionally, existing groundwater mapping solutions, do not quantify the expected degree of impact of flooding expected for a given return period - rather a high/med/low classification. We will create a novel software tool that allows for the dynamic simulation of surface and groundwater flow, over a wide area. Currently such a tool which represents the entire water-system does not exist in a dynamic form (i.e. where the two layers react and change with one-another over time).There are two main types of groundwater flooding: Permeable Superficial Deposits (PSD) driven by surface water flooding and Clearwater flooding where the groundwater table cuts the groundwater surface. The former, PSD, occurs when superficial deposits transmit the flood wave and results in groundwater flooding outside that identified by traditional flood risk approaches. The latter can take the form of surface ponding as well as flowing features. These two distinct types of groundwater flooding require two different approaches:1. PSD - surface water levels in rivers, streams and drains will drive the groundwater head. Therefore a method needs to be developed that links the surface water heads to groundwater heads.2. Clearwater - Based on the method developed by Upton and Jackson (2011; http://nora.nerc.ac.uk/13501/) to produce a dynamic groundwater surface produced from groundwater point models (AquiMod). Once the appropriate groundwater heads are produced these can be combined with a DTM to produce a revised groundwater flood map. lumped parameter groundwater models for Permeable Superficial Deposits (PSD) and Clearwater flooding on the Chalk will be developed. The two suggested areas are Oxford for PSDs and Kenley/Croydon for Clearwater flooding. The former (PSD) will need to develop a linkage with Ambiental surface water models to drive the groundwater response and the latter can feed into flood extent models. Once the integrated system has been developed then the following will be undertaken: 1. Assessment of areas prone to flooding - this will take the form of using OpenData (BGS geological maps, Environment Agency groundwater level data, OS data) to develop risk maps for groundwater flooding.2. Regional assessment of PSD and Clearwater flooding - by extending the modelling approach applying this to the flood prone areas identified in (1). 3. Climate change impacts and changes to flood risk probability.