Date of Award

Fall 1981

Project Type

Dissertation

Program or Major

Engineering

Degree Name

Doctor of Philosophy

Abstract

An integrated numerical modeling methodology was developed for analysis of non-point contaminant production and water quality impacts in estuarine receiving waters. The methodology was calibrated against contaminant source observations and estuarine data.

Contaminant source loading is based on the runoff curve number technique combined with a partial contributing area approach. Sediment washoff is used as an indicator of contaminant quantities.

Hydrographs and contaminant load time series are introduced into a set of one-dimensional estuary models. Freshwater flow and tidal height are forcing functions for dynamic computation of velocity and water surface profiles. The effect of longitudinal salinity distribution is included through a closed form solution of governing differential equations.

Sensitivity of the models to key parameters was investigated through numerical experiments. Runoff volume and contaminant weight were greatest on impervious areas of the watershed. Hydrologic analysis could be calibrated by a single parameter. Contaminant load was primarily affected by sediment transport coefficients. Hydrodynamic model results demonstrated that the key components of the dynamic force balance are surface slope and acceleration of the water mass. Friction was an important but smaller component. The hierarchy of physical processes affecting contaminant dispersion was dominated by tidal currents. Density driven circulation is most significant in deep sections with a large longitudinal density gradient.

Calibration runs and application to analysis of non-point source water quality impacts in the Oyster River, New Hampshire, were performed. Both salinity and dye distributions were adequately simulated. Investigation of receiving water impacts in the Oyster River Estuary revealed that following major storm events, BOD concentration and dissolved oxygen deficit can be dominated by the effect of non-point source contaminants.

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