Many countries in Asia and the Pacific are exposed to flood risks from typhoons, flash floods, riverine flooding, storm surges and coastal flooding. Flood risk compromises sustainable economic growth and prosperity, which will be further impacted by rapid urbanization and climate change.
The Asian Development Bank (ADB) promotes and adopts an integrated and risk-based framework for flood management. Integrated flood risk management (IFRM) is a framework that promotes sustainable, long-term flood resilience by combining social, economic, financial, environmental, and institutional solutions, as well as those involving engineering, disaster preparedness, insurance, and emergency response.
The overarching concept is to manage the risk posed by floods to an acceptable and affordable level, rather than control the physical waters or fully protect communities against floods of all magnitudes.
Flood risk management plans or projects require an understanding of both the technical nature of the flood as well as the way in which it interacts with land, the communities that occupy it, and development plans. Sound analysis based on quantitative data helps in understanding the physical attributes of a flood, while interaction with stakeholders aids understanding of land use and affected communities’ exposure and vulnerability.
The objective of IFRM is to cost-effectively manage the risks posed by floods across landscapes, considering existing and future scenarios, and to improve flood resilience by:
- minimizing economic damages and loss of life, and limiting potential negative impacts to health, well-being, and economic development;
- maximizing sustainable economic benefits of land use; and
- improving or maintaining floodplain ecosystems dependent on flood inundation.
The approach has the advantages of being robust, flexible, and adaptable, as well as comprehensive. It encompasses wider benefits than could be provided by any single solution.
Flood risk management is rarely entirely about flooding. Often flood issues cannot be separated from broad economic and social development issues, as well as land and environmental management. Adopting a holistic, risk-based integrated approach allows for comprehensive solutions and linkages to other opportunities.
Flood risk is normally described as a function of three components: hazard, exposure, and vulnerability.
Source: Asian Development Bank. Strengthening Integrated Flood Risk Management: A Practical Guide to Integrated Flood Risk Management. Consultant’s report. Manila (TA 9634-REG).
- A flood hazard is a flood event that is potentially damaging and has three main characteristics: source, magnitude (depth, velocity, and duration that causes damage), and location or extent. The magnitude of the flood hazard is usually described using the term annual exceedance probability (AEP) or return period.
- Exposure refers to people, property, assets, systems, or other elements present in flood hazard areas that are thereby subject to potential loss and damage. Since a dominating factor is the density of population and infrastructure, exposure will increase with population growth and rural-to-urban migration. Furthermore, as the quality of life increases in developing countries, so does the relative value of assets exposed and their potential loss.
- Vulnerability refers to the characteristics and circumstances of a community, system or asset that make it susceptible to the damaging effects of a hazard. High vulnerability can create large losses from even moderate hazards. In poor and highly vulnerable areas, the frequent small- or medium-scale floods can have a significant cumulative effect.
Flood risk will be exacerbated by climate change. Sea-level rise by 2100 strongly depends on future emissions, predicted to reach about 0.40 m for very low emissions (global warming close to 1.5 °C), about 0.8 m for very high emissions (global warming above 4 °C), and 1 m more if ice-sheet instability processes associated with deep uncertainty are triggered. Due to relative sea-level rise, extreme sea-level events are projected to occur more frequently.
Climate change is also expected to significantly increase the intensity of extreme rainfall and droughts in some areas. Further, more frequent extreme typhoon and storm surge events are projected that will increase the likelihood and rate of coastal flooding and coastal erosion. The impact of climate change will depend on actions for managing and mitigating risk, and guiding socioeconomic dynamics.
Identifying risk with data and decision-making tools is necessary for risk-informed structural and non-structural measures and land use development. Risk-informed spatial planning is a key tool for managing exposure for fixed assets, such as houses, factories, and other infrastructure. Appropriate land use planning for new development should ensure separation between flood-prone areas and fixed assets. Structural measures help mitigate the impact of natural shocks on people, reduce disruptions, and improve living standards. Nature-based solutions can complement the protective function of structural measures, while also contributing to improved livelihoods. Even with effective risk reduction systems in place, there is a chance of experiencing flood impacts. Emergency response, relief and recovery plans are key for managing residual risks. Flood preparedness can be enhanced with flood forecasting and early warning systems, and, at the local level, improved knowledge can ensure better responses for flood-proofing or evacuation. Institutional strengthening should target coordination, communication, and decision-making systems. Social protection systems, disaster risk financing strategies, and insurance can also help manage residual risk.
ADB have been supporting the Asia and Pacific region address flood risks by project/program investments and technical assistance, by creating knowledge and by building the capacity of local governments and institutions managing flood risk. Click on the resources below to learn more.