Assessing the Benefits of Flood Warning Phase 3 (October 2008 – June 2009)
September 2009


Project funders/partners: SNIFFER, SEPA, the Environment Agency, the Scottish Government, Glasgow City Council, and the Rivers Agency of Northern Ireland.

Background to research
This project has been commissioned by SNIFFER on behalf of the Scottish Environment Protection Agency (SEPA) and the Environment Agency. It takes forward the recommendations from the SNIFFER Assessing the Benefits of Flood Warning: Scoping Study Phase 2 report (UKCC10A, completed by Halcrow in March 2008) and builds on the principles outlined in the Phase 1 report (UKCC10, completed by HR Wallingford in September 2006). The Phase 1 report reviewed current practice in the assessment of benefits of flood warning in the UK and internationally. It gave recommendations on the components that could be used in future methodologies and proposed the use of Multicriteria Analysis (MCA) as the most appropriate assessment method. The Phase 2 report developed an MCA assessment methodology, and applied it to nine pilot study areas across Scotland, England and Wales. At the conclusion of Phase 2, several recommendations were made to improve the consideration of critical infrastructure within the MCA methodology, and to increase the variety of catchments types and scales using the method.

Objectives of research
This report summarises the adopted methodology and findings of the two key tasks defined in the initial project brief. Task 1 comprises a feasibility assessment of the inclusion of critical national infrastructure in future benefit assessments, through desk-based study and consultation with key infrastructure stakeholders. Task 2 comprises the application of the previously developed Flood Warning System benefit assessment methodology to a further five Scottish application areas and one application in Northern Ireland, taking into account both tangible and intangible benefits.

Task 1: Critical Infrastructure Scoping Study

The flooding experience across England and Wales during the summer of 2007 brought the vulnerability of UK infrastructure to the attention of the government, public and media. Society today is highly dependent on the function of many infrastructures, and the consequences of failure could be catastrophic, in terms of the economy, public health and safety. It was recognised that the assessment of the potential flood warning benefits associated with protection of Critical National Infrastructure (CNI) was not as simple as other flood warning benefits, therefore a key element of the Phase 3 project is a scoping study into the feasibility of inclusion.
After consultation with the steering group, key infrastructure stakeholders and Scottish Government advisors, it has been concluded that it is not possible to include critical national infrastructure in future flood warning benefits assessments using the MCA tool developed during Phase 2, due to the sensitivity and security implications of the processes and data involved. However through the investigation undertaken during Phase 3, it has been established that the flood risk and potential flood warning benefits to CNI will be assessed separately at a UK government level. Local infrastructure, such as schools, community centres etc. has been identified as being of key importance to communities, and as such may warrant further
consideration for inclusion into the MCA tool in order to capture the intangible benefits of flood warning on these facilities.

Task 2: Additional Application Areas

Five additional Scottish pilot sites identified by SEPA have been assessed using the MCA tool and methodology. In each of these cases, the relevant Local Authority (LA) had registered an interest in flood warning with SEPA prior to the commencement of Phase 3; however contrary to some of the previous study areas, no flood defence or flood warning schemes were fully in place. The five additional application areas assessed are: The Firth of Tay, Loch Linnhe, The River Forth; The River Garnock, and; Loch Lomond and the River Leven. One additional site in Northern Ireland has also been assessed: the Sixmile Water catchment.
Each of these sites has been assessed using the Multi-Criteria Analysis (MCA) tool and methodology developed during Phase 2, capturing both the tangible and intangible benefits of flood warning, across a range of categories:
These categories are assessed using MCA techniques to assign a benefit score to each area. These scores can then be compared with other assessed areas in order to compare the relative benefits of separate schemes. The assessment has involved four key phases:
The completion of these additional application areas significantly increases the databank of assessed catchments, therefore the calibration and scoring thresholds of each category has been revisited in light of the increased dataset. All areas from Phases 2 and 3 have been re-assessed using the updated calibration parameters.

Recalibration of the tool has resulted in a greater resolution of results between moderate to high scoring catchments, making it a more effective resource in aiding comparative decision making between scheme options. Increasing the dataset used for calibration has a positive impact on the robustness of the tool, as a wide representative sample of catchment types has been included in the analysis.

Application of the methodology to the Sixmile Water catchment in Northern Ireland has shown the MCA tool to be suitable for use with the available Northern Ireland national datasets and therefore the methodology can be considered to be applicable UK-wide, with successful applications having now been carried out in Scotland, England, Wales and Northern Ireland.

The key benefit score drivers identified during Phase 2 are supported by the results from the Phase 3 additional application areas: Scale, i.e. the number of people and properties within the floodplain; The number of return periods used in the assessment, where the inclusion of additional lower return periods more accurately represents the benefit profile for that location; Presence of operational flood defences by formalised defence schemes or individual actions;

Vulnerability of people in the floodplain, and; Presence of key infrastructure within the floodplain.

As a joint outcome of both Tasks 1 and 2, further investigation into the potential benefits associated with flood warning to key local infrastructure has the potential to further enhance the assessment capabilities and provide an additional measure of differentiation between similarly scored catchments.

Copies of this report are available from the Foundation, in electronic format on CDRom at 20.00 + VAT or hard copy at 25.00, less 20% to FWR members.

N.B. The report is available for download from the SNIFFER Website