Introduction

DEFRA and the Environment Agency have recognised that to improve the performance of flood defences it is necessary to consider systems of defences rather then merely considering single defences in isolation. If a town is protected by several different defences then it is necessary to consider how this flood defence system functions as a whole in order to assess and manage the flood risk to the inhabitants and assets in the town. At present there is little useful guidance on assessing risk to large floodplain areas which depend on numerous, perhaps extensive and diverse, systems of defences such as embankments, walls, and moveable structures. With moves towards more integrated flood management, it is essential that risk managers have recourse to sound and practical tools and techniques for assessing the performance of whole systems in order to develop balanced, integrated risk management strategies. The aim of RASP is therefore to develop and demonstrate methods for dealing with systems of flood defences.

A tiered methodology

In any decision-making situation it is important to undertake an appropriate level of analysis, which is justified by the importance of the decision and its sensitivity to uncertainty. The appropriate level of analysis will be guided by the cost and time associated with collecting and analysing data about the flooding problem and the risks associated with any proposed flood management option. The notion of appropriate analysis is fundamental to RASP and is reflected in the tiered methodology that is proposed.

• The High Level Method will be based on nationally available datasets on flood defences, flood plains and land use. It will provide a methodology for updating national estimates of flood risk (for example to support the updating of the National Appraisal of Assets at Risk from flooding published by MAFF in 2000). Reliable national estimates of risk will enable changes in flood risk in England and Wales to be monitored and reviewed.
  
  
• The Intermediate Level Method will use measurements or model estimates of flood water levels, flood defence levels and ground elevation to generate better estimates of flood risk. It will be used to inform strategic decisions on flood risk management.
  
  
• The Detailed Level Method will use detailed information about the composition of defences to generate an improved estimate of their probability of failure by a number of different failure modes. Simulation methods will be used to estimate risks in a large number of flooding scenarios.
  

The RASP methodology will deliver

• an estimate of the flood risk associated with the failure of any single or combination of flood defences;
  
  
• an estimate of the total flood risk for identified impact zones in the flood plain;
  
  
• an indication of the contribution that each defence makes to the total risk in the floodplain.
  

These outputs will be compatible with standard Geographical Information Systems to support simple user visualisation. RASP will not be delivering new software but it will be inputting into current software development projects such as the Modelling Decision Support Framework being developed in the Broad Scale Modelling Theme.

RASP will also involve demonstration studies at pilot sites and production of written guidance to enable widespread application. Through a linked study, the RASP High Level Method will be applied to all of England and Wales in order to update the National Appraisal of Assets at Risk.
The RASP project began in January 2002 and will be completed in Spring 2004.

GIS image from RASP - for now simple one from Fabio

RASP can be used for

• national monitoring of risk from flooding;
  
  
• strategic prioritisation of investment in defence improvements or other flood management options (e.g. increased storage or diversion);
  
  
• targeting flood warning and emergency preparedness;
  
  
• highlighting priorities for monitoring and maintenance and justification of maintenance decisions;
  
  
• scheme design and optimisation.

Connections between RASP and other R&D and software projects, such as the MDSF and the NFCDD

• The Modelling and Decision Support Framework (MDSF) is being developed to support Catchment Flood Management Plans. MDSF and RASP are closely related and are being jointly developed. RASP is focussing on the flood defence systems aspects whilst MDSF is providing a standard GIS platform for visualisation and decision support.
  
  
• The National Flood and Coastal Defence Database (NFCDD) provides key information on defence types and conditions to be entered into RASP. RASP will provide an estimate of the contribution that each defence makes to flood risk, which will be linked to NFCDD.
  
  
• DEFRA/EA funded research on performance and reliability of individual structures and components will provide information on individual defence failure mechanisms which will be used in the RASP methodology.
  
  
• The National Appraisal of Assets at Risk from flooding will be updated in 2002 using the RASP High Level Method.

RASP's contribution to achieving DEFRA's High Level Targets

DEFRA's High Level Target 5A requires that the Environment Agency reports, on a national basis, on its assessment of the risk of flooding. The High Level Method in RASP will satisfy this requirement. RASP will also provide a basis for risk-based prioritisation of inspection and maintenance of flood defences.

Download leaflet (PDF)
Project Overview (PDF)
Programme