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SCIENCE-POLICY BRIEF No. 3

ADAPTIVE FLOOD RISK MANAGEMENT IN EUROPEAN

AND ASIAN CITIES

KEY MESSAGES

• The CORFU project has had wide ranging policy impacts at the Supranational, National, and

local scales

• We have provided guidance and practical examples on how to implement the requirements

of the European Floods Directive.

• The Project has led to real policy changes in the way floods are managed in cities. New

national guidelines have been developed for China.

• The DPSIR (Drivers-Pressures-States-Impacts-Response) framework has proved its value as

an approach to evaluate the effectiveness of different flood management strategies.

• Effective flood risk management needs to extend beyond economic damage and consider

other key consequences, such as the health impacts.

Introduction

Flooding is one of the most damaging natural hazards, with negative impacts to society, the

economy, and the environment. Cities are especially prone to flooding because of their high

population density, the concentration of economic activity, and the proliferation of hard surfaces

through which water cannot infiltrate. The world is becoming increasingly urbanised with many cites

growing rapidly. Infrastructure can fail to keep pace with this economic growth. In many developed

cities, drainage and flood defence infrastructure systems are ageing, and may be inadequate to cope

with the increases in rainfall and river flow that may result from global and local climate change.

These developments present a number of key challenges in flood risk management that cities have

to face. The CORFU (Collaborative Research on Flood Resilience in Urban Areas) project was

established to lead to a more scientifically sound management of flood risk, through the

investigation and evaluation of state-of-the-art strategies.

This brief explains how CORFU has been able to support current policies related to water and flood

management, influenced new policies, and how the results have identified new policy gaps. The

CORFU results have had implications for policy on a range of scales from the municipal to the

supranational scale.

The project

The CORFU project was funded under the European Union's 7th

Framework Programme and was

implemented by 17 project partner institutions from 11 countries. The aim of the project was to

enable partners to learn from each other through the investigation, development, implementation,

and dissemination of strategies to enable a more scientifically sound management of urban flooding.

Seven case study cities were selected that represent a diversity of situations and challenges:

Barcelona (Spain), Beijing (China), Dhaka (Bangladesh), Hamburg (Germany), Mumbai (India), Nice

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(France), and Taipei (Taiwan). A unique aspect of the project was the focus on European and Asian

cities.

The project used a Drivers-Pressures-States-Impact-Response framework to organise the

investigation into the existing flood risk in the cities, how these risks may change, and what

responses and strategies are both feasible and effective (Figure 1).

Figure 1. The Drivers-Pressures-States-Impacts-Response (DPSIR) framework as applied to flood risk

management in the CORFU project case study cities

Policy context

Flood risk management policy is created and enforced at a number of governmental and

administrative scales. At the highest level, there are supragovernmental policies that are developed

by international bodies, including the European Union. National policies in the EU Member States

are affected by these policies, who must develop their own policies to meet these larger policies. In

Asia, no such overarching organisation exists, and nations independently develop their own policies

and regulations. Finally, policies can be developed also at the regional or municipal level.

Policy at the Supranational level

Within the European Union, the overarching policy mechanism for flood risk management is the

Floods Directive (2007/60/EC). The Directive requires Member States to assess if water courses and

coast lines are at risk from flooding, to map the flood extent, and assets and humans at risk in these

areas, and to take adequate and coordinated measures to reduce these flood risks. The Floods

Directive (Directive 2000/60/EC) should be implemented in conjunction with the Water Framework

Drivers/Pressures

State

Impact

Response

DPSIR Logical Framework

Drivers – the social and economic

developments, such as population

change, lead to environmental

Pressures. These pressures lead to

changes in the environmental State,

which lead to Impacts on society

and the environment. These impacts

can be mitigated through planned

Responses

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Directive, which requires member states to develop River Basin Managements plans to ensure good

ecological status.

The Floods Directive has two key requirements, and the CORFU project was able to provide guidance

on how these could be achieved.

• The preparation of flood hazard and risk mapping (Article 6)

• Preparation of flood risk management plans (Article 7)

Preparation of flood hazard and flood risk maps

First, to support the requirements of Article 6, a consistent framework was developed for the

analysis of urban flood modelling and flood hazard mapping. This framework takes into account the

availability and quality of data, the nature of the investigation, the scale of the study site, and the

human, financial, and technical resources available. This was supplemented by guidance on the

development of procedures for the calibration of urban flood models.

This framework allowed the production of flood hazard and risk maps for all seven case study cities,

covering floods with low, medium, and high probabilities, as required by the Floods Directive. One

key advance is the development of methods to model flood risk for entire mega-cities, using a multi-

cell technique. This was highlighted on 21 July 2012, when large parts of Beijing were seriously

flooded, causing 57 casualties. The multi-cell model was applied in Beijing (area more than 1000

km2), and it was able to reproduce the observed flood extents (Figure 2) (Hénonin et al, 2013).

Flood hazard maps have been produced for all case study cities, to cover floods with low, medium,

and high probabilities, as required by the Floods Directive.

Figure 2. A zoom into the flood map produced for all of Beijing showing flood testimonials (the red spots)

and flood depths modelled by the multi-cell model

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Article 6 stipulates that flood risk maps should show the potential adverse consequences of flooding,

including those on “human health and life, the environment, cultural heritage, economic activity and

infrastructure associated with floods”. The CORFU project has led to significant advances in the way

these consequences are modelled.

First, the state-of-the-art in flood impact assessment was reviewed, and a model was developed. In

many of these cities, information was collected for the very first time on the exposure of assets and

the damage that could be expected (through the development of flood damage functions). The

methodology used here can be transferred to other locations.

A GIS-based flood impact assessment tool was developed and applied in all case study cities. The key

advantages of this tool are its ease of use, and its flexibility, as it can work with different data

formats on range of scales. This tool was used in all the case study cities, to produce flood damage

estimates.

Figure 3. Flood impact assessment for Raval District in Barcelona for 1, 10 and 100-years storms.

An innovative development is the assessment of the health impacts of flooding, that follow from

human contact with flood water contaminated with pathogens. A hydro-dynamic model was

developed and applied in Dhaka. This work was bolstered by the collection of water quality data at

several sites (Mark et al, 2014).

Improvements in the visualization of flood hazard maps was made through the development of an

open GIS-based flood risk mapping tool for stakeholders. Flood hazard maps for all of the case study

cities are available on line, and viewers can ‘swipe’ between the existing state, and possible future

states with and without mitigation measures. This will aid stakeholder engagement who will be

consulted on the development of adaptation strategies and risk mitigation measures (Article 10 (2)).

Preparation of flood risk management plans

The Floods Directive requires that Member States produce flood risk management plans at the river

basin level. These plans should “address all aspects of flood risk management focusing on

prevention, protection, preparedness, including flood forecasts and early warning systems … Flood

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risk management plans may also include the promotion of sustainable land use practices”.

Furthermore, these flood management plans should “take into account relevant aspects such as

costs and benefits” (Article 7, Paragraph 3).

For the case study areas, a set of measures formulated in different adaptation strategies, focusing on

prevention, protection and preparedness (Article 7 (14)) have been developed. The proposed

adaptation strategies or flood risk management plans have been analysed in their efficiency and cost

effectiveness. The CORFU project investigated the potential for real-time warning systems to be

used in the cities. In Barcelona and Dhaka, systems have been developed and implemented.

CORFU also explored the potential future risks that may occur due to the climate change (Article 7,

(14)), considering the plausible climate futures when developing future scenarios in the case study

cities.

Apart from implementing the elements of the Floods Directive, CORFU went beyond its

requirements, which can be reflected in the following aspects:

- In addition to the aspects of climate change, CORFU demonstrated that other drivers of

future development such as urban and economic growth can have a considerable impact on

the future flood risks and as such should be more prominently included in the policy.

- The relevance of addressing different dimensions of resilience, that go beyond the economic

ones (i.e. cost benefit analysis), has been demonstrated in European and Asian case study

cities. In that sense, any resilient planning for future should include a wider scope rather

than merely addressing costs and direct/economic benefits.

- The work undoubtedly demonstrated that extreme rainfall combined with limited drainage

network capacity represents one of the major flood sources in cities, which is not reflected

in the Floods Directive (Article 2), even stating that it ‘may exclude floods from sewerage

systems. This is a significant limitation of the Directive.

The relevance of this flood typology has also been acknowledged by a number of responsible

Agencies (e.g. in Copenhagen, Barcelona and Hamburg).

Contribution to National Policy

The approach adopted in the CORFU project has led one of the project partners, the China Academy

of Urban Planning and Design, to produce two national guideline documents: Notification on the

Enhancement of the Construction of Urban Drainage and Urban Flooding-protective Facilities from

the General Office of the State Council of the People’s Republic of China, and, a Technical Guidance

for the Formulation of Integrated Urban Storm Water Drainage Engineering System (Minor Drainage

system) and Urban Pluvial Flood Mitigation Engineering (Major Drainage system) Planning.

The first document sets out a number of tasks for cities with regards to their urban drainage

planning. Some of the identified key tasks include:

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• Comprehensively investigating the potential for flood risk, using Geographical Information

Systems, and updating information on extreme rainfall events;

• Determining the standard of the design on the basis of flood risks. In megacities such as

Beijing, design standards should be increased.

• Formulating new versions of integrated Urban Storm Water Drainage and Flood Mitigation

Planning in all the cities.

• Increasing investment and accelerating the programme for the renovation and construction

of improved urban drainage, including low impact development solutions, such as

permeable surfaces.

• Improving flood warning systems which are used by relevant organizations to better prepare

for extreme flood events.

The second document presents guidelines on how to formulate integrated Urban Storm Water

Drainage and Flood Mitigation Planning. Key steps include:

• Investigating the physical (climate, geological) and socio-economic situation of the city.

• Determining the existing flood risk in the city through modelling and surveys of key

infrastructure, as well as investigating the historical flood record.

• Undertaking flood risk assessment and risk mapping.

• Considering a range of mitigation measures

Our research in Beijing has practically demonstrated how these steps could be implemented, and

this knowledge is being transferred to other cities in China.

Contribution to policy at local level

All the CORFU case study cities have municipal governments who have a strong influence on flood

risk management, and the outputs of the project have influenced these municipalities. Nice (France)

presents an excellent example of this. Flood management planning in Nice is regulated by Risk

Prevention Plans or “Plans de Prévention des Risques” (PPR) and Local Development Plan “Plan Local

d’Urbanisme” (PLU) policy. Each plan includes hazard areas as well as building restrictions. Climate

scenarios are not considered in the current plans, and data on the flood extents reflect the greatest

observed event, and are classified as being exceptional, frequent or very frequent, without any

reference to any estimated probability or likelihood.

The outputs of the CORFU project are used by the Nice Cote d’Azur Métropole (NCA) to:

• Develop a new flood management strategy, and updating the flood master plan. CORFU

produced the first ever pluvial flood simulation over the whole central district;

• CORFU has led to the improvement of the real time system, which will cover the entire

city area of Nice (about 100 km2). The forecasts are supported by new river gauging

stations, and will be provided to the public through a website.

• The flood maps (10, 50 and 100 years return periods) and a Flood Resilience Index for

each parcel of Nice was been produced and will be made publicly available. This

represents a significant improvement of the flood management procedures in Nice.

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Figure 4. Assessment of Flood Resilience Index Maps for Nice, France

Addressing and involving key local stakeholders (also referred to as the end users) in the case study

cities was a key component of the project. The stakeholder workshops in all cities represent a step in

presenting the project outcomes to the key policy makers. The final CORFU workshops were

attended by over 300 people in the cities, mainly end users and local policy makers, who intensively

discussed the potential of the CORFU methods, tools and results to be adopted in the local planning

policy. Furthermore, there was significant media interest in these workshops, which included

national television channels and print media.

As a general rule, the development and implementation of local policies have timelines that exceed

the lifetimes of research projects and require a range of regulatory activities and internal and

external iterations of expert judgment procedures. In particular, this practice applies to the

European countries. Consequently, the practical implementation of CORFU outcomes into the local

policy is hardly achievable during the project lifetime. The accomplishment of CORFU is however

perceived in the adoption of the methods, tools and results by the responsible agencies, which in the

next phase can be included in policy documents and standards.

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REFERENCES

Djordjević, S., Butler, D., Gourbesville, P., Mark, O. and Pasche, E.

(2011) New Policies to Deal with Climate Change and Other Drivers

Impacting on Resilience to Flooding in Urban Areas: The CORFU

Approach. Environmental Science & Policy, 14 (7), 864-873.

EC, European Commission (2007) EU Directive of the European

Parliament and of the European Council on the estimation and

management of flood risks. 2007/60/EC. Brussels.

EC, European Commission (2010) World and European Sustainable

Cities. Ref: EUR 24353. Brussels.

Hénonin, J., Ma, H., Yang, Z. Y., Hartnack, J., Havnø, K., Gourbesville,

P., & Mark, O. (2013). Citywide multi-grid urban flood modelling:

the July 2012 flood in Beijing. Urban Water Journal,

http://dx.doi.org/10.1080/1573062X.2013.851710.

IBRD/WB (2009) Climate Resilient Cities. International Bank for

Reconstruction and Development/The World Bank, Washington.

Mark, O., Jørgensen, C., Hammond, M., Khan, D., Tjener, R.,

Erichsen, A., Helwigh, B., Albretchsen, H.-J., 2014. A new

methodology for modelling of health risk from urban flooding

exemplified by cholera - Case Dhaka, Bangladesh, Journal of Flood

Risk Management, submitted.

Further Information on the CORFU Project

Start / End Date of Project:

1st

April 2010 to 30th

June 2104

Participating institutions

University of Exeter, UK (Coordinator)

Hamburg University of Technology, Germany

DHI, Denmark

University of Nice - Sophia Antipolis, France

Indian Institute of Technology in Bombay,

India

AREP Group, France

Institute of Water Modelling, Bangladesh

Beijing University of Technology, China

China Academy of Urban Planning Design,

China

Beijing Municipal Institute of City Planning

and Design, China

CETaqua, Spain

Hydrometeorological Innovative Solutions,

Spain

Cranfield University, UK

Dura Vermeer Business Development,

Netherlands

Hamburg Institute of International

Economics, Germany

Programme:

The CORFU project received funding from

the European Union through the 7th

Framework Programme, Grant Agreement

Number 244047.

Disclaimer:

This publication reflects only the authors’

views and the European Union is not liable

for any use that may be made of the

information contained herein.

Web-link:

www.corfu7.eu