Abstract
Abstract. When floods hit inhabited areas, great losses are usually registered in terms of both impacts on people (i.e., fatalities and injuries) and economic impacts on urban areas, commercial and productive sites, infrastructures, and agriculture. To properly assess these, several parameters are needed, among which flood depth is one of the most important as it governs the models used to compute damages in economic terms. This paper presents a simple yet effective semiautomatic approach for deriving very precise inundation depth. First, precise flood extent is derived employing a change detection approach based on the normalized difference flood index computed from high-resolution synthetic aperture radar imagery. Second, by means of a high-resolution lidar digital elevation model, water surface elevation is estimated through a statistical analysis of terrain elevation along the boundary lines of the identified flooded areas. Experimental results and quality assessment are given for the flood that occurred in the Veneto region, northeastern Italy, in 2010. In particular, the method proved fast and robust and, compared to hydrodynamic models, it requires sensibly less input information.
Highlights
Climate science foresees a future in which extreme weather events could happen with increased frequency and strength as a consequence of anthropogenic activities
If the resulting polygon extent does not match with the observed flooded polygon, we manually look for the elevation value that best approximated the flood extent and set it as the water elevation
By means of the adaptive threshold starting from the 95th percentile, the method is able to estimate the elevation of the water surface looking for a plateau on the distribution
Summary
Climate science foresees a future in which extreme weather events could happen with increased frequency and strength as a consequence of anthropogenic activities. Flood risk and impacts are not sufficiently understood and documented and need to be monitored systematically with improved precision as underlined by the European Union Floods Directive (European Commission, 2007). This is important to support climate change adaptation policies as well as to develop robust public disaster relief funds, risk profiles for financial institutes, risk portfolios for reinsurance companies, and profiles of risk in supply chain for multinational companies (Mysiak, 2013; Desai et al, 2015). Flood depth is important since it governs the damage functions (or vulnerability curves or loss functions), which define the expected loss given a certain flood depth (Mojtahed, 2013; Scorzini, 2017)
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