Understanding and Managing Stormwater Runoff in Two Types of Developed Land Uses: Urban Areas and Solar Farms
Restricted (Penn State Only)
- Author:
- Yavari Bajehbaj, Rouhangiz
- Graduate Program:
- Civil Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 10, 2024
- Committee Members:
- Farshad Rajabipour, Program Head/Chair
Cibin Raj, Major Field Member
Lauren McPhillips, Chair & Dissertation Advisor
Jonathan Duncan, Outside Unit & Field Member
CHRISTINE KIRCHHOFF, Major Field Member - Keywords:
- Stormwater management
Ground-mounted solar
Renewable energy
Sustainable solar development
Green infrastructure
Multicriteria model
Spatial analysis - Abstract:
- This dissertation explores the impacts of two types of land development on stormwater patterns. The second chapter focuses on stormwater management in urban areas, by emphasizing green stormwater infrastructure (GSI) and the multiple benefits that it could provide for the communities. We present a planning algorithm that leverages available spatial data, along with a community survey of siting criteria preferences, to hone in on ‘sweet spots’ of GSI implementation that are hydrologically optimal, feasible, and provide more equitable access to the benefits of GSI. We apply this approach in Lancaster, a city in Pennsylvania, US, with multiple stormwater-related challenges. indicated a preference for prioritizing the hydrology and sewer system criteria. Sweet spots for GSI implementation under each scenario were mapped based on the 90th percentile of the final combined key criteria layers. Despite being demonstrated in a specific city, this relatively simple approach leveraging widely available spatial data can be applied and customized elsewhere and help improve future GSI siting methods. The next chapters focus on the hydrology in solar farms as another land use type which adds impervious surfaces to the landscape. As solar energy becomes an increasingly cheap source of renewable energy, major utility-scale ground solar panel installations, often called 'solar farms', are rapidly growing. With these solar farms often covering hundreds of acres, there is the potential for impacts on natural hydrologic processes, including runoff generation and erosion. In the third chapter of this dissertation, we review the current state of scientific research on the hydrology and water quality impacts of solar farms, as well as management recommendations for minimizing any impacts. This review indicates very limited existing field research on solar farms, and very little modeling efforts customized for the unique landscape of solar farms. With regards to land and the stormwater management associated with solar farms, most US states currently do not have solar farm-specific recommendations and instead defer to standard stormwater management permits and guidance. In general, existing literature indicates that solar farms can be designed to minimize the impact on landscape ecohydrological processes, but more research is needed to determine whether current recommendations are adequate. In the fourth chapter, we present the results of a field investigation of soil moisture patterns, evapotranspiration, and vegetation at two solar farms in central Pennsylvania, USA that are representative of the complex terrain in the region (e.g., high or variable slopes). Both solar farms also included engineered infiltration basins or trenches that were investigated. Analysis of soil moisture patterns reveals redistribution of water relative to panels. There are also the greatest periods of saturation and runoff generation at the panel driplines. However, an open interspace between panel rows and existing infiltration basins and trenches are playing a critical role in managing runoff. Micrometeorological monitoring indicates reduced evapotranspiration (ET) under panels. However, a survey of vegetation revealed almost complete ground coverage under panels, which is critical for supporting infiltration and reducing erosion. This work demonstrates that healthy vegetation and well-draining soils can help manage runoff on solar farms; where necessary on more challenging landscapes, engineered stormwater controls can manage any unmitigated runoff. In the fifth chapter, a modeling framework is designed for simulating hydrologic dynamics within solar farms leveraging OpenHydroQual software, an open-source, component- based model capable of representing unsaturated zone hydrology. This study focuses on one solar farm investigated in Chapter 4. A model was created to represent the current condition in the solar farm, and was calibrated and validated using one year of soil moisture data. The model was also run for different sized design storm events. Comparison of the solar farm model with a model representing pre-development conditions indicates redistribution of soil moisture and increased runoff and peak flow rates. Additional scenarios performed to explore implications of different management options indicated that increasing the interspace width from 3 m to 4 m led to a slight reduction in runoff, while a decrease in Manning’s roughness (representing decreased vegetation height) had almost no impact. The findings of our research improve our ability to predict runoff and soil moisture patterns within solar farms and thus better design stormwater management practices. Overall, the work presented in this dissertation helps guide improved management of stormwater in urban areas and solar farms, helping support more sustainable land development practices.