Spatial dependence of floods shaped by extreme rainfall under the influence of urbanization

Abstract

Weather system are spatially and temporally dependent, and these dependencies can result in flood events with similar behaviors. While it is well known that urbanization profoundly impacts the flood generation process, much less is known about the impacts of urbanization on the spatial dependence of floods, a major determinant of flood risk severity. To this end, a scheme was proposed to detect the flood dependence variations influenced by urbanization. Based on the scheme, we found that 1) the flood dependence can be weakened with extreme rainfall increasing from a short return period to a long return period; 2) The flood dependencies can be amplified in slightly urbanized regions and mitigated in highly urbanized regions due to intensifying urbanization. In addition, the change characteristics of the flood dependencies influenced by urbanization are first identified from the perspective of network structure. We found that urbanization can significantly affect the network structure (i.e., hub and connectivity) of flood dependence, especially in highly urbanized regions. The catchments with high hub and connectivity are prone to widespread floods and should be given more attention in flood warning and control management work, which can contribute to helping defend against floods in hazard-prone areas.

Keywords: Extreme rainfall; Flood dependence; Functional data analysis; Network analysis; Urbanization.