New inland US flood model from AIR

New inland US flood model from AIR

Boston-based catastrophe modeller AIR Worldwide has released an Inland Flood model for the US. It said that the phisically-based probabilistic model would "provide insurers and other industry stakeholders with a comprehensive tool for assessing and managing inland flood risk at a high resolution for locations on and off the many and varied floodplans across the US".

Jayanta Guin, executive vice-president at AIR Worldwide, said that "until now, the industry has lacked the tools to effectively quantify flood risk in the US". He said that the new model was "a major step forward in helping the industry manage this compl;ex risk by better understanding the severity, frequency and location of potential flood events".

The model captures inland flood risk for all 18 hydrological regions across the contiguous US about 3m sq miles). The US has about 1.4m miles of rivers and 335,000 distinct drainage catchments. The model simulates both the weather systems and the flooding they cause. Damage is determined by calculating the inundation depth at each affected location, taking into account the country's extensive system of levees and their probability of failure, as well as regional differences in building codes and building practices.

AIR has also incorporated off-floodplain flooding, which can be caused by, among other factors, particularly intense rainfall and poor drainage.

The rainfall simulation model combines a global Community Atmospheric Model (CAM) with a regional Weather, Research, and Forecasting (WRF) model. AIR said that "a sophisticated downscaling technique" enabled the model to capture both large- and small-scale precipitation patterns. These included those bursts of extreme rainfall that contribute greatly to highly localized flooding.

A physically based hydraulic model calculates the extent of flooding and the depth of inundation at each location of interest on the floodplain.

Dr Guiin said that this model, "a game-changer", represented "one of the most challenging and innovative research development efforts in AIR's history".

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