Water Depth – Damage functions for flood direct tangible damage evaluation in built-up areas in Sardinia (Italy)

Flash floods occurring in the Mediterranean area lead to investigate on relevant damages caused by floods in Sardinian territory (Italy). The Flood Directive 2007/60/EC, requiring a cost-benefit analysis for the definition of mitigation measures, should be supported by appraisals of flood damages. Actual study background recognises the use of water depth-damage functions as key elements in decision-making evaluation of authorities. Flood damage functions are still not available for Italy and should be developed considering the regional territory. This paper revises the Joint Research Centre Model approach (Huizinga H.J., 2007) for Sardinian region and provides water depth-damage functions for direct tangible damage assessment. Historical data on flood damages were collected considering two recent events. The first event occurred the 22nd October 2008 in Capoterra town, in the South-East of the region, where it caused damages in structures of residential and touristic area for millions of Euros, and 4 victims; the second event occurred the 18th November 2013 in the North-East area determining damages in multi-storey buildings in Olbia town and 13 victims. The collected data were statistically studied considering the possibility of fitting relations between water depth and expected damage data using a Pearson III probability distribution. The water depth-damage functions show different trends due to building types in the two studied areas. The procedure was subsequently implemented considering synthetically generated flood events in order to estimate the expected mean annual damage values due to flooding in prone areas and to verify economic efficiency of planned mitigation measures.