Impacts of urbanization on flood inundation during Hurricane Harvey

Abstract:

Hurricane Harvey caused substantial loss of lives and damages over the Houston area in 2017, despite the flood countermeasures that have been continually implemented and developed. Recent studies have examined the role of urbanization on the flooding in Houston and found that both the storm and flooding magnitudes were exacerbated by the land cover changes to impervious surfaces. Nonetheless, the impact of urbanization on flood inundation has not yet been explicitly quantified. In this study, we develop a runoff-rainfall ratio regression model that includes impervious surface area as one of the independent variables. Additional variables that helped explain the variance in changes in runoff ratio included the aridity index, soil moisture, soil temperature, and basin area. Using this simple statistical model we are able to predict the runoff (and hence streamflow) generated by rainfall during Harvey for different snapshots of impervious surface area. These streamflow predictions are then used as inputs to a benchmark hydrodynamic model (LISFLOOD-FP) that has been validated against observed flood extents during Harvey. These sensitivity simulations reveal the spatial patterns of flooding that can be attributed to urbanization, and can help elucidate the potential compounding effect of land use changes to climate-driven extreme events.