Tsunami Inundation Zones

A geographic information system model was developed to estimate the extent to which coastal land is likely to be inundated by tsunamis. Based on a digital elevation model (SRTM data), water flow from the coastline inland was calculated iteratively using ArcGIS Spatial Analyst 9.1 application tools. Assuming tsunami heights of 5 meters, 10 meters, and 20 meters, tsunami inundation zones were modeled for most of the world’s coastlines. The hazard maps were developed for the risk management purposes of the insurance industry but could also be used by governments as a basis for land-use planning.

The satellite image shows northern Sumatra (map 1) in December 2004 when the Sumatra-Andaman earthquake created a massive tsunami that struck Indonesia and caused countless fatalities. In some areas, the tsunami peaked at over 20 meters and reached several kilometers inland, almost completely destroying the town of Banda Aceh. The modeled inundation depth for a 20-meter tsunami is indicated in shades of red. A high degree of agreement between the calculated inundation zone and the areas actually destroyed can be seen in the detailed maps (2A and 2B).

Using the model, future potential scenarios were also examined. For example, map 3 shows the modeled inundation zones of a 10-meter tsunami off the coast of Seattle in the event of a 9.1-magnitude earthquake along the Cascadian fault. The results of the scenario show that no residential areas would be affected, but the ports north and south of the city center would be hit.

Courtesy of Munich Re Group.