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Science for Environment Policy: Flooding

Science for Environment Policy: Flooding

The importance of managing flood risk

Flooding can bring profound and lasting effects on citizens, businesses and agriculture. According to the Centre for Research on the Epidemiology of Disasters' (CRED)1 global statistics on natural hazards, the 416 flood events in Europe from 1980 and 2009 which are classified as 'significant' affected 8.9 million people, caused 2,546 fatalities and incurred economic damages of over EUR75 billion.
This Thematic Issue brings together recent research that gives us insight into changes in European flood risk policy, which could help policymakers deal with the projected increases in flood risk.
'Flood risk' is defined as the likelihood of a flood occurring (from any source) combined with its associated effects on people, commerce and the environment. The risk can be altered by anything that changes the probability of flooding and/or its consequences. For example, flood risk can be affected by changes in the way a river responds to rainfall, or by socio-economic change, such as changes in agricultural practice. Thus flood risk is not static but responds to social, economic and environmental changes, such as the changes in precipitation identified in the IPCC Fourth Assessment report, which suggest that there will be an overall increase in flood risk in most scenarios of future climate, although the risk will vary considerably, depending on the region.
The greater risk of floods means that flood risk management has become a major challenge, both in engineering and societal terms. Flood risk management schemes aim to decrease the probability and impact of floods - taking into account factors that include the avoidance of development in areas likely to flood, to ensuring that local populations are informed and know what to do in the event of a flood. Thus flood risk management needs a holistic approach which takes into account the problems of rainfall, rivers and flooding, in addition to the problems of societal planning and administration. During the last two decades, many Member States have used this holistic and proactive approach in their flood risk management programmes.2
Managing residual risks has become a priority, with a focus placed on enhancing the resilience of individuals, businesses and communities to flooding. Residual flood risks are those which remain even after flood risk management measures have been put in place. For example, when a large flood causes damage by overcoming a flood bank which is designed for smaller flooding events.
The importance of flood risk management in EU policy is encapsulated in the 2007 Floods Directive3. The Directive, which has been adopted in every Member State of the EU, sets out a framework for managing and reducing risks. Under the Directive, the first round of preliminary flood risk assessment, flood risk mapping and production of Member States' flood risk management plans is underway, with a completion date of December 2015.
Two articles in this issue address flood risk at the European scale. 'New estimates of climate change's economic and physical consequences in Europe' covers aspects of the recent Projection of Economic impacts of climate change in Sectors of the European Union (PESETA)4 project. Findings from this project suggest that, by 2100, climate change could lead to annual damages from river flooding for the EU that cost EUR14 to EUR21.5 billion a year. 'A European scale assessment of river flood risk', indicates that the average annual damage from river flooding is highest in Europe for many Eastern countries, Scandinavia, Austria and the UK, as well as some areas of France and Italy.
The European Flood Alert System (EFAS), which generates twice-daily forecasts of river floods up to 10 days in advance of each event, has not been fully integrated into Member States flood risk management programmes. 'Improving use of the European Flood Alert System' identifies the effects of cultural and institutional barriers (such as persuading institutions to make use of EFAS's medium-term flood forecasts, rather than short-term warning systems) to integrating EFAS into national flood warning systems.
Flash floods are challenging to observe and conventional networks to measure rainfall and river flow are not always sufficiently dense to be in the right place to monitor such events. 'Flash floods in Europe characterised' describes how an improved understanding of flash flooding, and therefore an improved flood risk management, could be achieved through post-flood observations, a re-examination of weather radar data and through the use of combined weather and hydrological modelling.
The connection between land use, land management and flooding is complex, but action on these may also form part of flood risk management plans. 'Land use change and land management influence floods in small catchments', presents a study which investigated how land cover changes in Slovakia in recent decades have affected the frequency of flood events in small catchments. The management of forest activities such as logging, and activities that reduced rainfall absorption, seemed to have influenced the frequency of flooding. 'Steps to improve flood resilience on the ground' highlights three case studies that provide insight into how resilience is put into practice. Two of the case studies (Flanders in Belgium and Niedersachsen in Germany) suffer from lowland river flooding, while the third, Calabria, in Italy, experiences flash floods. Findings showed that, although flood management tools were in place, they were sometimes unused and often poorly understood by local residents.
Emergency flood plans in England and Wales, France and the Netherlands are reviewed in the article, 'How well do flood emergency plans meet management needs?' The essential information needed for effective flood emergency plans is identified in the article. This includes details on plan activation (i.e. triggers, such as flood levels that lead to action), details on flood hazard and impacts and evaluation.
Most respondents to a recent, large-scale European survey, claimed not to have prepared themselves for floods, even though they knew that their property was at risk of flooding. Some key results of this survey are presented in the article 'Communicating flood risk: public awareness does not ensure public preparedness'. The survey findings indicate that fear-inducing communication campaigns aimed at increasing public awareness of floods are inadvisable, given that, for most people, being worried about a potential hazard does not mean they will be more prepared.
The economics of flood risk management should be evaluated in terms of efficiency, that is, the sum of a project's costs and benefits over its lifetime. 'Multi-criteria analysis - the better way to evaluate flood management' describes how this approach captures the overall value of non-structural measures, such as warning and evacuation systems, that are effective in meeting specific standards of flood protection.
New research summarised in 'The Floods Directive: lessons from Germany for effective implementation' suggests that management decisions at the catchment scale should be discussed with stakeholders, such as local water boards, at sub-catchment levels, who play a central role in flood risk management. Although an essential part of the process, experts should not be the sole decision makers. The findings of scientific studies, such as those highlighted in this issue, can prove essential to the design of effective flood risk management strategies. However, the recent FLOODrisk 2012 conference5 highlighted some important barriers between science and policy, such as the tendency for scientists to only share their findings within their scientific community. As a result of these discussions, actions to improve flood risk management through a better science-policy interface, such as setting up a professional body for flood risk management, are in preparation.
Dr Paul Samuels

Technical Director, HR Wallingford, UK

New estimates of the physical and economic consequences in Europe of climate change
Research into future climate scenarios suggest that by 2100, climate change could lead to annual damages in the EU from river flooding alone of EUR14 billion to EUR21.5 billion, with more people affected than today, and a reduction in household welfare.
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A European scale assessment of river flood risk
Researchers have created a simple tool to analyse the risk of river flooding across almost all of Europe, and to estimate the associated economic losses. They found that Eastern Europe, Scandinavia, Austria and the UK are the regions and countries most at threat.
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Improving use of the European Flood Alert System
Cultural and institutional barriers, coupled with a lack of confidence about whether and how to use it, mean that the European Flood Awareness System (EFAS) has yet to be fully integrated into national flood warning systems, according to a recent study.
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Flash floods in Europe characterised
Improved understanding of flash flooding could be achieved through post-flood observations, re-examination of weather radar data and the use of combined weather and hydrological modelling, according to the recent HYDRATE research project. This information can be used to improve flash flood forecasting.
Download article (PDF)
Land use change and land management influence floods in small catchments
Research from Slovakia suggests that the total area of change in land cover, as well as land management practices, are more important in generating floods than the type of land cover change, such as deforestation.
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Steps to improve flood resilience on the ground
Modern flood risk management is placing more emphasis on improving the resilience of communities prone to flooding. By examining three case studies, a recent investigation has provided insight into how resilience is put into practice, suggesting that clearer identification between the roles of different actors and better communication to the public is needed for successful implementation.
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How well do flood emergency plans meet management needs?
The importance of comprehensive flood emergency plans is becoming increasingly recognised. A new study has evaluated plans in England and Wales, France and the Netherlands. It was found that, although plans perform well in terms of organisation and communication, they are lacking in more technical aspects, such as the provision of flood hazard maps and evacuation plans.
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Communicating flood risk: public awareness does not ensure public preparedness
The majority of respondents to a recent, large-scale European survey claim not to have prepared themselves for floods, even though they know their property is at risk of flooding and they are worried about the effects. A set of key recommendations for flood communications wrer developed from the survey's findings, intended to improve community preparedness as part of effective flood management plans.
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Multi-criteria analysis - the better way to evaluate flood management
According to a recent study, flood risk management projects should be economically evaluated in terms of their efficiency, i.e. the sum of the costs and benefits of a project over its lifetime. This would capture more fully the value of non-structural measures, such as warning and evacuation systems, that are better in terms of effectiveness related to hydrological protection standards.
Download article (PDF)
The Floods Directive: lessons from Germany for effective implementation
The European Directive on the assessment and management of flood risks1 (the Floods Directive) represents a shift towards holistic and catchment-oriented management of flood risk and is likely to prompt changes to policy in many Member States. New research from Germany suggests that effective implementation of the Floods Directive is likely to be greatly aided by the participation of stakeholders and communication between groups.
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