A GIS-based procedure for measuring the effects of the built environment on urban flash floods

Urban flooding has been a severe problem for many cities around the world as it remains one of the greatest threats to the property and safety of human communities. In Australia, it is seen as the most expensive natural hazard. However, urban areas that are impervious to rainwater have been sharply increasing owing to booming construction activities and rapid urbanisation. The change in the built environment may cause more frequent and longer duration of flooding in floodprone urban regions. Thus, the flood inundation issue associated with the effects of land uses needs to be explored and developed. This research constructs a framework for modelling urban flood inundation. Different rainfall events are then designed for examining the impact on flash floods generated by land-use changes. Measurement is formulated for changes of topographical features over a real time series. Geographic Information System (GIS) technologies are then utilised to visualise the effects of land-use changes on flood inundation under different types of storms. Based on a community-based case study, the results reveal that the built environment leads to varying degrees of aggravation of urban flash floods with different storm events and a few rainwater storage units may slightly mitigate flooding extents under different storm conditions. Hence, it is recommended that the outcomes of this study could be applied to flood assessment measures for urban development and the attained results could be utilised in government planning to raise awareness of flood hazard.