Theses and Dissertations


Issuing Body

Mississippi State University


Parajuli, Prem

Committee Member

To, Filip

Committee Member

Dash, Padmanava

Committee Member

Linhoss, Anna

Date of Degree


Document Type

Dissertation - Campus Access Only


Biosystems Engineering

Degree Name

Doctor of Philosophy (Ph.D)


James Worth Bagley College of Engineering


Department of Agricultural and Biological Engineering


Coastal regions are at risk of environmental threats. Flooding in coastal rivers is the result of intense precipitation which is triggered by climate change. Coastal watersheds are prone to losing significant amounts of sediment and nutrients because of the shorter transport pathway that drains directly into the coastal water. In this study, the hydrology, flood frequency, and water quality assessment of two coastal watersheds, Wolf River watershed (WRW) and Jourdan River watershed (JRW), were conducted using the Soil and Water Assessment Tool (SWAT). Since WRW and JRW are the main tributaries to fetch freshwater to Saint Louis Bay (SLB) of Western Mississippi Sound, an integrated approach to assess the influence of freshwater influx into the coastal water is also performed by coupling SWAT with hydrodynamic visual Environment Fluid Dynamics Code (v-EFDC). An auto-calibration tool, SWAT Calibration and Uncertainty Programs (SWAT-CUP) was used to calibrate and validate the flow, total suspended solids and mineral phosphorous for obtaining satisfactory statistical results. While comparing the flood frequency of historical, baseline and projected scenario in both watersheds, the results illustrated that using annual maximum series, 1% exceedance probability was the highest for WRW baseline scenario, whereas for JRW, 1% exceedance probability was the highest for projected scenario. The water quality assessment study of WRW and JRW suggested that ponds and wetlands were more effective in reducing TSS and riparian buffers were more effective in reducing MinP at the outlet of both the watersheds. The integrated approach of coupling SWAT-vEFDC model result indicated that major impact on water quality was observed at the location where the freshwater inflow into the SLB, and the impact was diminished while moving further along the Western Mississippi Sound. Overall, this study gives an insight for integrated coastal watershed management which includes prediction of future flood frequency, the application of best management practices for reducing sediment and nutrient load, and estimation of upstream watershed pollutant load draining along with runoff including its effect on the coastal water quality.