|Timeline:||October 2014 - 30 September 2018|
Urban growth is a factor known to intensify local flooding. By orienting urban development, land use planning may contribute to reduce flood risk through better regulation and infrastructure investment. Two case studies were developed to determine the extent to which such strategy could be effective: Kigali, Rwanda (where land use regulations are stringently applied) and Kampala, Uganda (with much less effective institutions but important infrastructure investments over the last decade). Both cities are mid-sized (one to two million inhabitants); they share a physical context of hilly terrain and low-lying flood prone valleys, but with divergent policy and institutional organizations.
For each case, geo-information technologies are deployed to develop data models of land cover, drainage systems, and soil infiltration. The case studies present a good opportunity to leverage the available data from Earth Observation, in the face of systematic data scarcity of even basic parameters, such as rainfall, soil maps, and land cover. These data models, in turn, are used to design and calibrate cellular automata-based urban growth models, and to calibrate the openLISEM flood model for each city. Monte Carlo methods, the Particle filter and the Metropolis-Hastings algorithm, are applied to calibrate the cellular automata models of Kampala (2001-2016) and Kigali (2000-2015), specifying the relative importance of spatial factors hypothesized to determine the location of urban growth (accessibility, slope, wetland areas, and informal settlements) as well as the size of the neighborhood effect of the cellular automata. The cellular automata model is then integrated with the flood model, such that scenarios of future land cover can be assessed in terms of hydrological outcomes (e.g. total flow at outpour points) and spatially explicit flood maps (of depth, velocity, duration). This intersection of flood and urban growth patterns can now be used to understand the exposure of built-up land cover to flooding.