Title: Towards a more comprehensive assessment of flood risk: Mapping flood susceptibility and social vulnerability
Authors: Hemal Dey, Wanyun Shao – The University of Alabama
Abstract: The frequency and intensity of floods have dramatically increased due to climate change. The innate social inequality has been exposed and even exacerbated by increasing flooding. To mitigate the social impact of flooding, it is imperative to assess flood risk in a comprehensive manner, accounting for both physical exposure and social vulnerability. Harris County in Texas, U.S., is selected as the study area as it has experienced a few devastating floods in recent history, with Hurricane Harvey (2017) being the most impactful. This study generates a flood susceptibility map (FSM) by applying Random Forest (RF) algorithm on remotely sensed data. It further combines this FSM with social vulnerability map (SVM) to produce a flood risk map (FRM) of Harris County. Specifically, a total of 500 flood inventory points are extracted from different sources and randomly divided into training (70%) and testing (30%) samples. A total of 12 flood conditioning factors including elevation, slope, aspect, curvature, topographic wetness index, stream power index, precipitation, land cover, distance to rivers, NDVI, drainage density, and soil texture, are used as predictors in the RF model. The ROC-AUC value of the RF model prediction is 0.92 for the flood susceptibility analysis, indicating high accuracy. The results from RF analysis show that elevation, distance to rivers, precipitation and LULC are the major contributing factors to flooding in Harris county. Furthermore, this study finds that 9.06% of the area has high flood susceptibility. Principal component analysis (PCA) is used to condense sociodemographic data to produce a social vulnerability index and 1.45% of the area is found to have very high social vulnerability. Combining both flood susceptibility and social vulnerability, this study reveals that 5.59% of the total area in Harris County has a very high risk for flooding. The findings of this study can be useful to policymakers to identify the spatial distribution of flood risk zones and assist flood mitigation for Harris County.