This proposed research will develop the new methodology required to make a step-change in our ability to quantify fluvial flood risk at large scales, incorporating climate change. This will combine existing and emerging technologies, to provide national and regional estimates of flood risk based on gridded models for improved assessment of flood risk to recurrence intervals in excess of 50 years. Linking gridded rainfall, runoff, flood defence performance and flood inundation models will significantly improve our ability to assess flood risk from extreme events and explore the potential impacts of climate change, including new scenarios, as they become available from UKCIPnext. This will include a spatially and temporally consistent gridded rainfall model operating over large spatial domains, a high resolution gridded runoff and flow routing model capable of modelling at the national scale and a continuous system analysis of flood inundation, taking account of defence performance. As each of these models will be run continuously in time, a continuous, linked flood risk analysis system will be developed for the first time. Each model will also be able to use derived future changes in climate to produce predictions of future in flood risk.

Moreover there will be an assessment of the model and data uncertainties, as well as estimates of uncertainty due to climate change. These uncertainty assessments will include the propagation of uncertainty through the linked modelling system. The research will utilise many existing sources of data and build upon some established models and techniques, such as the Neyman-Scott Rectangular Pulses (NSRP) stochastic rainfall at the University of Newcastle, the CEH Grid-to-Grid (G2G) model, the RASP system models, and the use ensemble scenario sets to represent uncertainty. At the regional or large basin-scale analyses will include a grid-based (5km) rainfall model linked to a (1km) gridded runoff and routing model and associated knowledge of defence systems and new routines developed to translate rainfall to river levels. Such a modelling system is ultimately applicable at a national scale and this will be demonstrated for river flows. The precipitation for this demonstration will be sourced from observed rainfall datasets, or modelled time series, such as those available from Regional Climate Models (RCMs) driven with re-analysis data.

The impact of future changes in rainfall, runoff and river levels on flood risk will be assessed within an enhanced version of the HR Wallingford RASP HLMplus model. Scenarios of climate change will be derived from a range of both global (GCMs) and regional climate models (RCMs). There will also be an analysis of the application of multi-ensemble climate scenarios and the generation of probabilistic scenarios of change in future flood risk.

Project Duration: January 2007 - March 2011.

This project is funded by NERC - Grant Ref. NE/E002420/1 - through the Flood Risk for Extreme Events (FREE) NERC directed mode programme.

This project will develop a system to improve estimates of national and regional flood risk by linking gridded models of rainfall, runoff, flood defence performance and flood inundation. Many existing datasets already available at CEH and BADC will be used and build upon existing models and techniques. The model will produce long timescales of 1km grid hourly data. It is intended that model runs using UKCIP climate change scenarios for their study area of the Upper Severn will be conducted.

Output data and maps from notable model runs such as those based on UKCIP climate change scenarios and those used in publications will be archived in-house at the NERC Centre for Ecology and Hydrology (CEH).

The data from this project will be stored at NERC Centre for Ecology and Hydrology (CEH).

NERC Centre for Ecology and Hydrology (CEH) website - http://www.ceh.ac.uk

FREE Programme documentation:

• List of projects funded under the FREE programme.
• FREE Science Plan
• FREE Implementation Plan (January 2008)
• FREE Progress Report (May 2008)
• FREE Progress Report (Oct 2008)
• Data Inputs to FREE projects

This FREE project is headed by Mr Nick Reynard of the NERC Centre for Ecology and Hydrology (CEH), with co-investigators at CEH, Newcastle University and H R Wallingford Ltd.

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