Utilizing the State of Art Technologies to Assess and Address Urban Flooding

Abstract

Today, 55% of the world’s population lives in urban area, a proportion that is expected to increase to 60% by 2050. Projections show that urbanization, the gradual shift in residence of the human population from rural to urban areas, combined with the overall growth of the world’s population could add another 2.5 billion people to urban areas by 2050. With growing opportunities, there are great challenges. One of the challenges that urban communities are facing is the increasing flood risks. In U.S., over the past decade, extreme storm events have wreaked havoc on many urban areas. Aging and inadequate infrastructure, coupled with rapid land development, increased the amount of storm runoff to already stressed drainage systems, creating pockets of flooding in poorly equipped and vulnerable neighborhoods. However, with many new technology developments happening every second, it is our mission to understand how we can utilize these resources to assess and address urban flooding. In this dissertation, the urban flooding issues were investigated through three perspective: 1). To find a proper method to capture the rapid change of the land development and surface, and further contribute to hydrologic modeling or digital elevation model generation; 2). To conduct a flood inundation analysis for a highly urbanized watershed and evaluate a flood relief project effect using extreme rainfall coupled with storm surge; 3). To review the evolvement of an operational flood warning system in Houston and its performance during serval major storms, especially Hurricane Harvey. In the first phase, the unmanned aerial vehicles (UAVs) was utilized to derive digital elevation models (DEM) for an urban landscape through Structure-from-Motion (SfM) photogrammetry method. The accuracy of this method is impacted by many variables. One of the most important aspects is the ground control points (GCPs). The density and spatial distribution pattern were further evaluated in this study and the resulted DEMs are compared against the traditional survey and LIDAR DEM. In the second phase, the flood inundation modeling was conducted for a highly urbanized watershed in Harris County, Texas, which is one of the most flood prone areas in the world. The analysis was to evaluate the flood mitigation and relief project after Tropical Storm Allison. Extreme rainfall events (100-year and 500-year) was applied to test the pre and post construction effect. Storm surge levels was also considered and coupled with the design storm criteria. In the third phase, the performance of the Flood Alert System (FAS) 4th Generation was recapitulated and reviewed through three major storms since 2015 with a focus of its performance during Hurricane Harvey. This dissertation culminates with a longitudinal assessment of the different state of art technologies to assess and help to solve urban flooding issues. Utilizing the methods presented in this dissertation, a comprehensive view of assessing or solving urban floods should be complete, including: data acquisition (DEM with UAVs), method and modeling (flood mitigation project and flood inundation modeling), and applications (flood warning system, its long time development and its performance during extreme storms).