Large-scale and High-resolution Flood Risk Model for Japan

Abstract

Japan has experienced several catastrophic flood events causing extensive damage to property and the national economy due to its topography, geography, and climate. Steep and short rivers, frequent typhoons and torrential rains, extremely high concentration of people and assets in flood-prone areas, and intensive human intervention subject the country to frequent flood disasters. Risk Management Solutions (RMS) has developed a stochastic inland flood model as part of its Japan Typhoon Model to assess flood risk due to typhoon for the (re)insurance industry. The RMS flood risk model consists of i) a precipitation-driven flood hazard module, ii) a building-level exposure module, iii) a component-based vulnerability module and iv) a financial module. The flood model is driven by 105,000 years of continuously simulated precipitation accounting for typhoon and non-typhoon precipitation. Rainfall-runoff and routing models, fluvial- and pluvial-inundation models, and probabilistic defence failures are included in the flood hazard module to obtain a realistic view of flood risk. By combining a large, country-level stochastic dataset with a high-resolution grid (~40m) for flood inundation modeling, and building level exposure data and hundreds of unique component-based vulnerability types, a comprehensive view of flood risk is provided on both local and aggregate levels, The financial module accounts for insured risk from different financial contracts.