HR Wallingford has been working with Japan’s largest utility company, J-Power, to apply the new UK reservoir risk assessment approach to two large dams in Japan, and assess the potential impacts of their failure on nearby communities.

The methodology, the Risk Assessment for Reservoir Safety (RARS), was developed by an HR Wallingford-led team of international experts in reservoir safety and risk management. The work in Japan is one of the first applications of this methodology in an international context.

Dr Yuichi Kitamura, Technical Director at J-Power, said: "The application of the new UK risk assessment methodology to our dams in Japan exceeded our highest expectations. HR Wallingford’s expertise in breach, flood and emergency response modelling has allowed us to make significant improvements in our understanding of the behaviour of our assets and our safe and efficient management of them for the future."

The findings will help to inform future emergency action planning and incident response.

Craig Goff, the project lead at HR Wallingford, said: "This fascinating project allowed us to work with an extremely well informed client to understand the risks of dam failure and the impact on the communities downstream in two areas in Japan. This job involved several of the niche areas which enthuse us – breach development, flood modelling and emergency planning. Weaving these services together in a seamless way allowed us all to understand the whole picture more thoroughly, right from the causes of a breach through to impacts on a community."

The approach includes use of the EMBREA software to model breach mechanisms, the 2D InfoWorks ICM model to calculate flood inundation extents, and the Life Safety Model to determine the consequences of this flood on the population. These modelling tools allow the estimation of the breach hydrograph and time, flood extents, flood depth, velocities, flow directions, and the population at risk.

The RARS method was published in 2013, and the guide has been designed to allow users to assess reservoir safety risks either qualitatively or quantitatively, depending on the level of detail required. It supersedes the Interim Guide to Quantitative Risk Assessment for UK Reservoirs, which has been the most commonly used method in the UK in recent years.