Investigating green infrastructure to improve stormwater management on a historical site using the PCSWMM model

Rapid urbanization and climate change are intensifying stormwater challenges, particularly in flood-prone areas. Traditional “gray” infrastructure, though effective in conveying stormwater, often aggravates flooding and degrades water quality. In response, modern stormwater management emphasizes green infrastructure (GI) as a sustainable alternative solution that mimics natural hydrological processes, enhancing infiltration and reducing runoff. This thesis investigates the effectiveness of GI practices in managing stormwater, using Washington School in Stillwater, Oklahoma, an area prone to flooding due to its location within a floodplain, as a case study. The three objectives were to (1) develop a decision tree framework for selecting GI practices for a historical site using published literature and design guides, (2) determine the rainfall pattern by analyzing 30 years of local rainfall data, and (3) assess the impact of GI practices for stormwater resilience by applying the Personal Computer Storm Water Management Model (PCSWMM). Using a combination of literature review and data analysis, a decision tree was constructed to guide the selection of suitable GI practices, considering site-specific parameters such as drainage area, slope, and groundwater level. Subsequently, hydrological modeling with PCSWMM was conducted to evaluate various GI configurations, including bioretention cells, infiltration trench, rain gardens, and vegetative swales. The modeling results illustrate that GI practices can substantially mitigate runoffs and reduce peak flows especially for frequent, smaller storm events. The findings demonstrate the viability of GI as a flood mitigation strategy and highlight the importance of integrating GI with gray infrastructure to manage both small and large storm events. The decision tree framework and hydrological model developed in this study offer practical tools for selecting and designing GI practices tailored to specific site conditions. This research contributes to a broader understanding of sustainable stormwater management, providing a pathway for future studies.