Assessing
the Benefits of Flood Warning Phase 3 (October 2008 – June 2009)
UKCC10B
September 2009
EXECUTIVE SUMMARY
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:
- Minimising the risk of death or serious injury
- Reducing the social impacts of flooding (including impacts on
vulnerable groups)
- Enabling householders to remove or protect property
- Enabling business and agriculture to remove or protect property
- Enabling Local Authority operation of flood defence assets or
carrying out other operations
- Reducing disruption to infrastructure
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:
- Data gathering
- Analysis of data using GIS software
- Consultation with relevant Local Authorities
- Tool Calibration and Scoring.
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