Exploiting damage claim records of public insurance companies for buildings to Increase knowledge about the occurrence of overland flow in Switzerland

Daniel Benjamin Bernet, Rolf Weingartner and Volker Prasuhn

Overland flow is difficult to assess because direct data is missing. As Swiss public insurance companies for buildings cover overland flow along with other hazards, we exploited their records to investigate the occurrence of overland flow indirectly. With a novel classification scheme, it is possible for the first time, to distinguish claims related to overland flow from inundations caused by watercourses. We analyzed gapless data records from 1991 to 2013 of the cantons Neuchâtel, Fribourg, Nidwalden and Graubünden, each representing a different typical Swiss landscape. Altogether, roughly 40-50 % of the damage claims can be associated with overland flow, which account for 20-30 % of total loss in that period. However, the inter-cantonal differences are large and reflect the embedment of overland flow in the landscapeâs geographic setting. Finally, looking at averages per km2 and year, we found that pre-alpine Fribourg is affected most by overland flow. As an outlook, we are confident that the presented methodology can be used to start studying overland flow from a more process-oriented perspective.

2016/1 221-230