Benefits of investments in dikes worldwide known

Published: 31 July 2017

The economic benefits of building dikes to reduce flood damage far outweigh the costs at the global scale. In many parts of the world, it is even possible to reduce the economic damage from river floods in the future to below today’s levels, even when climate change, growing populations, and urbanization are taken into account.

This is according to a study led by Philip Ward of the Institute for Environmental Studies, Vrije Universiteit Amsterdam, Deltares (experts Hessel Winsemius, Jaap Kwadijk and Jarl Kind), other partners in the Netherlands, UK and USA. The research appears in the paper ‘A global framework for future costs and benefits of river-flood protection in urban areas’ in Nature Climate Change.

Benefits outweigh costs

In a first of its kind study of the costs and benefits of taking measures to reduce flood risk at the global scale, the authors assessed how much flood damage could be avoided in the future per state, if new dikes are constructed or dikes that are already in place are heightened. They then assessed how much it would cost to build and maintain these dikes, and whether the benefits would outweigh the costs. To do this, they used a cascade of global hydrological and economic models by Deltares, known as GLOFRIS.

Ward: “The model for simulating flood maps has been developed over the past years by Deltares, By combining these flood maps with our socioeconomic models, we were able to assess the costs and benefits of dikes. It is well-known that economic damages from floods are expected to increase over the coming decades due to climate change and an increase in population and assets in flood prone areas. However, in this study we show that flood damages in the year 2080 can actually be reduced to below today’s level, if we effectively invest in flood protection measures. This is important information for policy-makers; the results help to identify those regions where we could efficiently invest in flood protection, and also highlight those regions in which other adaptation strategies may be needed, like creating more room for rivers and constructing flood resistant buildings”.

Effectively address flood risk

The research will allow for more informed dialogue on flood risk management at the international level. Whilst past studies have shown that flood risk will increase in the future, this is the first study at the global scale to examine how we can effectively address this. The results and methods will be integrated in the Aqueduct Global Flood Analyzer, a tool developed by the World Resources Institute in Washington DC, together with Vrije Universiteit Amsterdam, Deltares, the World Bank, Utrecht University, and PBL Netherlands Environmental Assessment Agency.

Charles Iceland, Aqueduct Director at WRI states that “In order to develop sound flood prevention strategies, decision-makers need reliable estimates of the costs of building flood protection infrastructure and the benefits of that infrastructure in preventing future damages. We are in the process of working with the World Bank to incorporate these new cost and benefit estimates into the next version of the Aqueduct Global Flood Analyzer. The World Bank will use the resulting cost-benefit assessment tool to inform strategic dialogues with developing countries facing significant flood risk”.