Identifying Delta Regions Most Vulnerable for Flooding

A Multiple Land Use Flood Risk Assessment for Australia

Bachelor thesis (2015)

Authors

S.P.C. Suijkens Civil Engineering & Geosciences

Contributors

S. van Vuren (supervisor 1)
M. Kok (supervisor 1)
Faculty
Civil Engineering & Geosciences
Copyright: © 2015 Sven Suijkens
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Published Date

2015-6

Language

English

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Faculty

Civil Engineering & Geosciences

Abstract

The global economical losses caused by flooding have increased over the last 50 years (IPCC, 2014; UNISDR, 2013). Deltares and HKV are developing new methods to quantify flood risk on a global scale. A Flood Risk Assessment Tool (FIAT) is used to performcalculations. The definition of risk is hazard x exposure x vulnerability. FIAT is able to combine these elements and calculate the Expected Annual Damage (EAD) for each city.

Currently two methods are used on a global and continental scale. For Europe a flood risk analysis is performed based on five land uses categories and five depth-damage functions, this method is referred to as the Multiple land use method. On a global scale an analysis is performed based on one land use and one depthdamage function, this method is referred to as the Single land use method. Nootenboom (2015) investigated the difference between the two methods for Europe. He described a good correlation of 0.97. Deltares and
HKV want to extend the Multiple land use method to a global scale.

A flood risk assessment for Australia is performed with the Multiple land use method. Brisbane, Adelaide, Melbourne, Perth and Sydney are reviewed. Recently derived depth-damage functions by Huizinga (2015) were used. Australian functions are available for residential and commercial land use. For other land use classes European functions are used instead. As a source for flood hazard the PCR-GLOBWB hydrological model is used. Exposure maps for Australia are made with OpenStreetMap (OSM). Metadata from OSM was filtered and processed in such a way five land use classes were formed. A total coverage of 52% was achieved.
The areas where no data could be recovered was filled in with ratios of the retrieved data. A sixth layer, named the no-data layer is formed. Visual analysis shows that the assumptions made in the no-data layer are most accurate in densely populated areas.

When the results of the Multiple land use method are compared to the Single land use method a correlation of 0.99905 is found. For every city there was a decrease in flood risk. The depth-damage function for Australia is investigated. Typical for the Australian function is the steep shape compared to the European function. A sensitivity research shows that each city reacts different to changes in the depth-damage function. Especially for cities with low inundation depths the risk is strongly influenced by the use of Australian functions. Cities with high inundation depths, such as Brisbane, are far less susceptible for changes in the depth-damage function. The use of European functions for certain land uses classes is therefore acceptable in Brisbane, as long as the dominant residential and no-data layer have continent specific functions.