Assessing extreme typhoon-induced coastal flood risk in the Philippines

Client: Asian Development Bank          Partner: Landell Mills          Location: Philippines

Challenge

The Philippines is among the most at-risk countries in the world with respect to natural disasters. The risk associated with typhoon-induced coastal flooding was devastatingly illustrated by Tropical Cyclone Haiyan in 2013, which generated a storm surge of over 6m, and killed more than 6,000 people in Leyte and neighboring provinces. Despite this high level of risk posed by storm-surge, people were unaware of the severity of the potential impacts of Haiyan and thus were not prepared to take appropriate actions. Hence there is a need to design appropriate flood risk management measures to effectively protect people against coastal flooding.

Solution

Working closely with Landell Mills and the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), this project developed new Good Practice methodologies for the derivation of extreme sea-level estimates in the Philippines. The methodology was used initially to produce extreme sea level estimates for the mouth of Jalaur River and the nearby coastal city of Iloilo, with the immediate goal of informing on-going flood risk management schemes. However, the method was also developed in such a way that PAGASA and others can now use it to derive extreme sea-level estimates for other parts of the country. The approach involved:

  • The generation of a 10,000 year synthetic dataset of typhoons.
  • Hydrodynamic modelling of the storm surge that would result from a sub-set of the synthetic typhoons.
  • Estimation of the storm surge magnitude for the remaining typhoons using machine learning approaches.
  • Derivation of extreme sea-levels using the Skew Surge Joint Probability method.
  • Estimation of the impacts of sea-level rise.

Benefit

The key benefit of this project was the collaborative working between ourselves and PAGASA, and the associated capacity building and engagement. This collaborative working has helped to raise the profile of coastal flood risk in the Philippines and to embed skills locally which can now be used to inform future work nationally. Additionally, the work is specifically informing the Jalaur River flood risk management scheme.

Philippines collage

Want to know more?

Funding for this work is provided by the Urban Climate Change Resilience Trust Fund. This fund supports cities by improving urban planning, designing climate resilient infrastructure and investing in projects and people. The Rockefeller Foundation and the governments of Switzerland and the United Kingdom support the fund.

Email Fay Luxford for more information about coastal flood risk in the Philippines. Discover more of our projects on our International Development webpage.



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