Date of Award

1-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Huan Feng

Committee Member

Clement Alo

Committee Member

Yang Deng

Committee Member

Trueba Jorge

Committee Member

Yuewei Lin

Abstract

This dissertation presents a holistic framework for stormwater management in the Bound Brook River Basin, an urban watershed in central New Jersey that faces chronic nutrient enrichment and climate-driven hydrologic changes. The research integrates water-quality trend analysis, hydrologic modeling, and low-impact development (LID) optimization to assess current and projected watershed responses. By combining empirical monitoring data with downscaled climate simulations and spatial prioritization, the study utilizes a holistic approach for stormwater management planning. The first objective was to characterize nutrient dynamics and hydrologic transport pathways for nitrogen, phosphorus, and total suspended solids (TSS) from 2004 to 2019. Using bi-monthly monitoring data from the New Jersey Harbor Dischargers Group Station 25 and U.S. Geological Survey (USGS) discharge records, nutrient fluxes were calculated following the GESAMP (1987) method and partitioned into baseflow and stormflow using the Lyne–Hollick digital filter. Results showed that total phosphorus (TP) consistently exceeded New Jersey Department of Environmental Protection (NJDEP) freshwater standards (0.1 mg/L), with baseflow contributing approximately 49% more TP and 58% more orthophosphate (OP) than stormflow. Nitrogen, primarily as nitrate (NO3N), remained below regulatory limits but was also baseflow dominated, reflecting strong subsurface contributions likely tied to legacy nutrient storage in soils and shallow groundwater. In contrast, TSS was 92% stormflow-driven, indicating surface erosion and impervious runoff as major contributors. These findings demonstrate that the Bound Brook River exhibits dual nutrient transport mechanisms: groundwater-mediated nitrogen and phosphorus during baseflow, and particulate-bound TSS during stormflow. This highlights the need for management strategies that address both subsurface and surface pathways. The second objective was to quantify current and projected stormwater runoff under changing climate conditions. The Curve Number (CN) method (NRCS TR-55) was calibrated using observed discharge data to account for local soil hydrologic group, slope, and land-use variability across Hydrologic Response Units (HRUs). Calibrated CNs were then applied to daily precipitation derived from five LOCA v2–downscaled CMIP6 general circulation models (ACCESS-ESM1-5, CanESM5, MIROC6, GFDL-ESM4, and CNRM-CM6-1) under multiple Shared Socioeconomic Pathways (SSPs 245, 370, and 585). Modeled projections indicate a rise in annual runoff depth and event intensity throughout the years 2025-2065, particularly under SSP370 and SSP585 scenarios. HRU-level outputs revealed the highest projected runoff volumes in densely urbanized zones with compacted soils and steep slopes, emphasizing the need for targeted mitigation in high-CN areas. By coupling downscaled precipitation with empirically calibrated CNs, this chapter provides a climate-informed runoff model that captures temporal variability and localized hydrologic responses. The third objective was to identify and prioritize optimal locations for Low-Impact Development (LID) to reduce projected runoff. Using outputs from the runoff model, HRUs were evaluated for their suitability for LID practices such as bioretention systems, permeable pavements, and green roofs. Feasibility weighting was based on slope, soil hydrologic group, and land-use constraints, while runoff-reduction efficiency was derived from literature-based CN adjustments for each LID type. Results indicate that implementing feasible LID retrofits across high-runoff HRUs could reduce future (2025-2065) runoff up to 14.6%, with bioretention systems with no underdrains and permeable pavements contributing the greatest volumetric reductions. Collectively, the dissertation demonstrates that stormwater management in mixed-flow urban watersheds must be multi-dimensional, combining hydro-chemical data analysis, climate projections, and spatially explicit planning. The findings highlight that phosphorus exceedances are sustained by legacy baseflow inputs, while projected rainfall intensification will exacerbate stormflow-driven runoff and sediment transport. These results highlight the need for adaptive management that incorporates both groundwater remediation and distributed LID. Future work should integrate existing LID performance data into CN calibration, incorporate projected land-cover change, and validate runoff simulations with field monitoring. This dissertation provides a framework for regional stormwater management planning under climate uncertainty and water quality impacts.

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