Quantifying flood damage: A case-study in Kumasi, Ghana

In this research, the flood damage caused by heavy rain and plastic blockage in the neighbourhood of Atonsu, Kumasi is quantified. Rapid urbanisation and poor waste management result in floods with an increasing impact in Kumasi, the fastest growing city of Ghana. This rapid growth of the city results in uncontrolled urbanisation of the floodplains and induces damage to homes during a flood event. Furthermore, due to a poor waste management system around thirty percent of the waste produced in Kumasi gets dumped in the streets and forms blockage of the water flow in the river. Moreover, the river is used as a dump not only by citizens but also by factories, which results in contaminated river water. As this research aims to give a first insight into the actual flood damage in Kumasi, simplified methods are applied, as they do not require a lot of data. To quantify the tangible damage, expressed in monetary values, depth-damage curves are constructed for different types of land use in the study area, to show the relation between the inundation depth or inundated area and the monetary damage. Besides that the intangible damage is quantified in the form of the number of lives lost and people exposed to waterborne diseases, both depending on the total number of people affected. The damage is quantified for floods induced by four different rain events, all with different peak precipitation, duration and frequency. The results indicate that the larger the rain event, the more damage it causes. It is furthermore estimated that plastic blockage of the flow of the river results in an increase of monetary damage of up to 5.7 percent and the number of people that are affected by the flood increases with up to 17.4 percent. Finally, the results of this research show the magnitude of flood damage in Kumasi and could be used to show the urge of measures that need to be taken to reduce the flood damage.TWIGAAfrican Water Corridor (AWC) projec