Assessing the Benefits of Flood
Warning: A Scoping Study
UKCC10
August 2006
Background to research
Flood warning is the provision of advance warning of conditions that
are likely to cause flooding to property and a potential risk to
life. The main purpose of flood warning is to save life by
allowing people, support and emergency services time to prepare for
flooding. The secondary purpose is to reduce the effects and damage of
flooding (Defra, 2004).
The benefits associated with flood forecasting and warning are
inextricably linked with the effectiveness of the warning dissemination
programmes and the activities of the public and supporting agencies
(both voluntary and official) in their response. The total benefits can
be defined as ‘the reduction in losses (tangible and
intangible) resulting from the provision of a warning when compared to
the situation prior to the operation of the warning system’.
Tangible losses are the cost of the damage arising as a consequence of
the physical contact of floodwater with property (direct losses), and
the losses which are consequent upon direct flood damage (indirect
losses). Flood warning systems can provide a reduction in
direct losses through:
- the timely operation of flood control structures (e.g.
gates, temporary flood defences) preventing inundation of property and
land;
- Pre-event maintenance operations to ensure free channel
conveyance;
- the installation of flood resilience measures (e.g.
sandbags, property flood barriers);
- the removal of property to somewhere above the flood level
or out of the flood plain.
Intangible losses include loss of life and injury, and the damage
caused to human health and long-term well-being. Such losses are
extremely difficult to quantify in economic terms, but are important
considerations when evaluating the benefits of any flood management
scheme, particularly flood warning where significant impacts can be
made through facilitation of timely evacuation of those at risk.
Organisations represented by the PSG have recognised that a revised
flood warning system benefit assessment methodology is required that
takes appropriate account of both tangible and intangible
benefits. This report documents a scoping study undertaken by
HR Wallingford, John Chatterton (J Chatterton Associates), and Maureen
Fordham (Northumbria University) of the range of approaches adopted to
date, and recommends potential components and characteristics that
could be used within the development of future methodologies.
Objectives of research
This report delivers Phase 1 of a research project to develop a new
method that improves on SEPA’s existing cost benefit
assessment technique, considers tangible and intangible benefits, and
takes full account of the current legislative framework in Scotland.
This first phase of the research reviewed current practice in the
assessment of the benefits of flood warning in the UK and
internationally. The objectives of the review were:
- To identify the key characteristics of the different
approaches (including data requirements);
- To characterize the extent and type of benefits assessed;
- To understand the main advantages and limitations of each
approach;
- To consider the appropriateness of the methods for
assessing the benefit of flood warning in Scotland, given the
legislative nature of flood warning and dissemination;
- To develop a preliminary recommended method.
Key findings and
recommendations
- The over-riding justification for implementation of flood
warning systems is mitigating risks to life or serious injury, and any
future flood warning system benefit assessment methodology should
reflect this.
- There is a need for any tangible benefit assessment
methodology for flood warning scheme justification to move from a
largely uni-directional focus on the movement of possessions, to a
holistic approach incorporating the benefits from operational and
resilience activities. For an economic quantification
approach, damage datasets and flood damage avoided factors used in
England and Wales would require validation for Scotland. The
dependence of benefit levels on a range of catchment
characteristics also requires evaluation through future pilot
study work.
- It has only been very recently that there has been any
agreement on indicative figures for the intangible impacts of flooding
and that research has been confined to England and Wales. There is
still a lack of clear guidance on the quantification of intangible
flood warning benefits in any part of the UK. This calls for a minimum
of further research to understand what effects warnings have on
people's health and wellbeing and therefore what value warning systems
have in benefit appraisals.
- It would be possible to undertake an economic valuation of
the tangible benefits of flood warning by adapting and validating the
new Multi-Coloured Manual (MCM, 2005) model and associated datasets for
application in Scotland, and enhancing these with any potential
operational and resilience benefits that might be realised as a result
of flood warning system implementation. However, research to
date has demonstrated the high likely level of uncertainties and
variability of both potential flood damage datasets and the factors
used to convert potential to actual savings attributable to a flood
warning scheme.
- The Project Steering Group (PSG) therefore believe that a
multi-criteria scoring approach is the most appropriate benefit
assessment model for SEPA at present which will allow strategic
prioritisation of schemes nationally, based on an understanding of the
score achieved by a proposed scheme across a range of benefit
components.
- A multi-criteria approach will require strict validation
via ground truthing to indicate the relative weights of each component
and sub-component. The influence of catchment and community
characteristics on scores and weights will also require evaluation.
Pilot study work including expert opinion surveys, interviews, focus
groups, and key stakeholder consultation will be required to support
the development of a robust scoring methodology.
- A Decision Support System is recommended to support a
structured approach to decision making and to facilitate sensitivity
testing. A GIS-based approach, similar to the MDSF system
(developed and used by the Environment Agency to implement Catchment
Flood Management Plans) would:
- allow the mapping of each of the benefit scores and the
visualization of
- zones and levels of benefits;
- allow a benefit assessment framework to be coded into
the
tool; and
- allow systematic sensitivity testing.
Key words:
flood warning, benefit, economic, tangible, intangible
Copies of this report are available from the Foundation, in electronic
format on CDRom at £20.00 + VAT or hard copy at
£35.00, less 20% to FWR members
N.B.
The report is available for download from the SNIFFER Website