Stormwater Runoff and Pollution Transport: New Models for a Changing Urban Environment
In urban and suburban settings, complex flow paths make it difficult to identify the source of contaminants. Since the majority of urban landscapes are covered with paved surfaces, stormwater runoff, termed Hortonian overland flow, occurs when the rate of rainfall exceeds the surface’s infiltration rate. Therefore, expanding cities can anticipate increased Hortonian flow responses, and ultimately higher instances of pollution wash-off. In addition to Hortonian flow, saturated excess flow refers to the runoff produced when the soil is saturated. Variable source area (VSA) hydrology is a concept incorporating the spatial and temporal variation of saturation runoff production. Urban rain gardens are designed to alleviate excess runoff from nearby paved surfaces and may behave as a VSA if contributions from the surrounding landscape are not realized. Coupled Hortonian and VSA models will contribute substantially to our limited understanding of pollution flow paths in cities.
To date, several scientific models have been developed to explain the transport mechanisms of urban stormwater runoff and pollutants. Physically based models are classified by their depiction of spatial conditions (distributed, semi-distributed, lumped) and hydrological processes (Hortonian or VSA flows). In general, distributed models represent runoff production more precisely than lumped models. However, many distributed models rely solely on Hortonian flow processes. Due to our limited scientific understanding of urban runoff processes, my research objectives include (1) developing a coupled Hortonian and VSA runoff model, (2) evaluating the model through field studies, and (3) using virtual simulations to propose holistic community-based stormwater management strategies.
Unlike other runoff models, the Soil Moisture Distribution and Routing model (SMDR) is a grid based model that accurately represents VSA runoff and pollution spread over mixed urban landscapes (Easton et al. 2007). While Easton et al. (2007) applied the SMDR model to urban areas with a shallow groundwater table, I will extend the model’s application to urban areas with deep groundwater tables so it can be implemented more broadly. At Cornell University, I am implementing a model to predict the transport of agricultural pesticides into the groundwater via subsurface paths of least resistance, termed preferential flow pathways. The knowledge I have gained from this study is transferable to my proposed research and has inspired my interest in groundwater conservation. Urban runoff that is concentrated with pollutants will eventually make its way to the groundwater, where it is extremely difficult and costly to remediate.
Also, field studies assessing runoff quality from rain gardens and other strategies will be used to test model results and quantitatively measure the ability of alternative infiltration practices to reduce stormwater runoff and pollution loads. Furthermore, I will use the SMDR model to analyze the impact of population expansion and alternative stormwater management practices on the quality of urban runoff.
Lastly, I plan to incorporate the influence of human decisions on changing land cover over into the SMDR model. As a Bioengineering major at Binghamton University, I developed a solid foundation in mathematical modeling that is directly applicable my proposed research. Zellner et al. (2008) combine agent based models and game theory to predict the outcomes of zoning restrictions and policy incentives on land use change in Michigan. By adapting the approach of Zellner et al. (2008) to urban settings, optimal stormwater management strategies will be realized.
My research will assist urban policy makers as they work to safeguard groundwater and surface water resources from urban pollutants. I also plan to encourage the use of effective alternative stormwater management practices through public education initiatives. As a current Ithaca Sciencenter volunteer, I will collaborate with Sciencenter staff to create hands-on activities and demonstrations for children and their families. Through Cornell’s Expanding Your Horizons (EYH) program, I will use my research themes to actively engage middle school girls interested in science. In connection with Cornell’s Prisoner Education Program (CPEP), I will develop a college level course on hydrological processes and pollution transport for incarcerated men looking to obtain their Associates degree. Finally, I intend to publish my results in peer reviewed journals and present them at national (e.g. scientific conferences) and local (e.g. New York State Fair) events.
Our abilities to reduce the unintended consequences of urban expansion hinges on our scientific understanding of urban hydrological processes and our willingness to share this acquired knowledge with the public. As city populations continue to increase, holistic consideration for changing human and environmental responses must define stormwater management strategies. The research areas proposed here will lead to the development of accurate science based tools and facilitate effective public decision making as it pertains to improved urban water quality.
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