Framework and Tools for Local Flood Risk Assessment

The opportunities for fully informed and professional Flood Risk Assessment is taking a giant stride with the publication of the final Environment Agency Final Report on a framework and Tools for Local Flood Risk Assessment. The output from this project could lead to a greater understanding of flood risk & improved and informed flood management.

The new roles and statutory responsibilities for flood risk management in England and Wales are set out in the Flood and Water Management Act 2010 and Flood Risk Regulations 2009. Lead Local Flood Authorities (LLFAs) now have the duty to lead on local flood risk (flooding from surface runoff, groundwater and ordinary watercourses). They are supported by the Environment Agency, who has a strategic overview of all sources of flooding in England and a similar strategic oversight role for Resource Wales. A key and important part of this strategic role is providing guidance and tools to LLFAs to help them meet their new responsibilities.

The assessment of risk is the first stage in the planning and management of flooding. Already, risk assessment approaches are well established for rivers and the sea using the Environment Agency’s hierarchy of Risk Assessment for System Planning methods used in the national flood risk assessment) and are emerging for local flood risk through the Department for Environment, Food and Rural Affair‘s (Defra) Surface Water Management Plan Technical Guidance and the referenced sources in the report.

The report describes the methods and software tools have been developed to meet a number of basic requirements that emerged from consultation with LLFA-led flood risk management partnerships, such as:

Be simple to understand and efficient to apply

• Be implemented by LLFAs
• Use the best available information wherever possible
• Be highly visual and GIS-based
• Be independent of spatial scale and flood probability/scenario
• Be able to investigate the impacts of changes to the physical system
• Add to the evidence base to support balanced local decision-making
• Help LLFAs to meet their legislative requirements.

This project sets out to meet these requirements by generating the final project report, which describes methods for local flood risk assessment presented in terms of the level of knowledge, models and data required for their use. This is supported by prototype software tools to demonstrate the functional implementation of the risk assessment methods. The prototype software can potentially be used by anyone, such as the Environment Agency, local authorities, water companies, or any other professional partner/risk management authority, with access to ArcGIS 9.3 (and the Spatial Analyst extension).

The software uses the flood outlines produced by other Environment Agency projects and places them over the National Receptor Dataset to quantify the risk of flooding at a specific location. This process can be repeated with other data sources such as the Environment Agency flood maps, outputs from hydraulic models, or from other local information. It then allows users to weight different sources of flooding differently to reflect priorities. The risk from different sources can then be added together to give a single flood risk for a location. The results can then be presented in a table or on a map, and can be displayed quickly to deliver an interactive presentation.

The output from the project and the use of the software will add to existing evidence on flood risk assessment and will help support local authorities in their roles as LLFAs.

A copy of the final Project Report, its Summary and the Software User Guide can be found at http://bit.ly/1knfJoh

A download of the software is freely available at http://bit.ly/S4jXFz for those interested in further development of the software.