Multidisciplinary Studies on the Social and Health Implications of Stormwater Management and Flash Flooding

Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Engineering and Applied Science

First Advisor

Bell, Michelle

Abstract

Research on stormwater management and flash flooding is of the upmost importance given the increase in severity of storm events from climate change and the rising installation of impervious surfaces from urbanization. This dissertation presents three studies that reveal social and health implications of stormwater management and flash flooding. Stormwater control measures (SCMs) (i.e., green infrastructure) are advantageous methods of stormwater management. However, studies suggest that urban greening may be associated with gentrification, displacing racially/ethnically minoritized groups due to increased housing costs and loss of feelings of belonging. For the first study presented in this dissertation, I analyzed whether there was displacement of racially/ethnically minoritized groups after SCM installation in Washington, DC. I compared the change in percentage of persons in racial/ethnic groups at the Census block group level with varying levels of SCM installation (i.e., area-weighted SCM count at 300 m buffer). I stratified findings by SCM type, pre-installation income, and SCM size. DC installed a higher density of SCMs in areas with a higher percentage of Black and/or Hispanic/Latino residents. Nonetheless, findings suggest SCM installation is associated with displacement of Black residents. The percentage of residents who are Black decreased by 2.2% [95% Confidence Interval: 1.7, 2.7] and 4.1% [95% Confidence Interval: 3.4, 4.8] after low and high levels of SCM installation, respectively. In turn, the change in percentage of residents who are White increased with increasing levels of SCM installation. Compared to ecological studies on SCMs, studies about social impacts are scarce. This study intends to help optimize SCM installations so more residents can enjoy their health, economic, and ecological benefits. Mosquito borne diseases are increasingly problematic as climate change continues to alter patterns of precipitation, flooding, and temperatures that may favor mosquito habitats. SCMs, ecologically sustainable methods of stormwater management, may have varying impacts on Culex mosquitoes, such as in areas with CSOs. For the second study in this dissertation, I studied spatial and temporal associations of SCMs and Culex mosquito counts surrounding the SCMs, stratifying the examination amongst those that do/do not use pooling and/or vegetation, as well as surrounding CSO outfalls after heavy rainfall (≥95th percentile) during summer 2018. Results indicate Culex mosquito counts after heavy rainfall were not significantly different at SCMs that use vegetation and/or ponding from at those that do not. I also found a 35.5% reduction in the increase of Culex mosquitoes the day of, and 77.0% reduction 7–8 days after, heavy rainfall at CSO outfalls treated with medium SCM density compared to those without SCMs. The results suggest that SCMs may be associated with a reduction in the increase of Culex mosquitoes at the CSO outfalls after heavy rainfall. More research is needed to study how the impacts of SCMs on mosquito populations may affect human health. Ellicott City, MD was devasted by a flash flood in 2016 and another in 2018. A lack of qualitative research has been conducted on topics related to sense of place and flash flooding, especially within the United States. For the third study presented in this dissertation, I reveal the reasons why some who experienced flash flooding in Ellicott City continued to stay in Ellicott City’s flood zone and why some leave. I utilized a phenomenological approach to answer these research questions. Data were generated through in-depth interviews with 19 participants from the Historic District and adjacent neighborhoods in Ellicott City, MD. The most common reasons that participants stayed were: (1) Community Impact, (2) Historical Land, and (3) Financial Burden. The most common reasons that participants left included: (1) Emotional Exhaustion and Frustration, (2) Fear/Anxiety, and (3) Financial Burden. The results of the study indicate that the reasons why individuals who experience flash flooding stay, or leave are a complex nexus that includes sociocultural, environmental, emotional, and economic factors. This reveals the complexity of relocation and sense of place after natural/environmental disasters. This chapter does not intend to encourage individuals who experience flash flooding to stay nor leave the flood zone, but instead, I aim to identify burdens and inform understanding of flood victims’ decisions, so individuals who experience flash flooding are neither forced to stay nor forced to leave against their wills.

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