Bank seepage occurs along natural streams bounded by an alluvial material when the passage of a flood wave produces a rise and fall in the stream stage. Owing to the difficulties of measuring flow rates in a porous medium, the quantity of bank seepage and its effect on the attenuation of a flood wave have not been determined from experimental observations. As an alternative for the purposes of this study, the equations of motion were used to describe flood flows in an idealized rectangular channel bounded by banks of a homogeneous, isotropic, porous medium in which the Boussinesq equation governs flow. The channel and the banks were assumed to be underlain by an impervious layer. Numerical simulation of a sinusoidal flood wave in the channel showed that bank seepage causes significant attenuation of the wave in narrow channels bounded by a relatively pervious material. This attenuation is characterized by a reduction in the hydrograph peak and sustenance of the flow during recession. In wide channels and in channels bounded by a relatively impervious material, no significant attenuation of the flood wave occurs.

A two-dimensional vertically well-mixed steady state intertidal model based upon the law of conservation of mass was developed to describe the distribution of chloride, nitrogen, biochemical oxygen demand, and dissolved oxygen within a geometrically complex estuary having interconnected tributaries and bayous. The model was verified against two sets of independent field data taken under different temperature and flow conditions within the Pascagoula River basin estuary. Application of the model under critical temperature and flow conditions was made to assess present water quality within the estuary and to predict the effect of alternate wastewater management methods on the water quality within the estuary.

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In predicting the tidal elevations in the Back Bay of Biloxi in Mississippi, the WaterQuality Analysis Simulation-S (WASP5) hydrodynamics model DYNHYD5 wasutilized. Model calibration of the tidal elevations was initially accomplishedutilizing historical data collected by the U.S. Geological Survey (USGS) during theperiod June 14-16, 1977 along with a second set of data collected by the U. S.Environmental Protection Agency (USEPA) during the period July 28-August 2,1972. Final model calibration was performed utilizing a set of field data acquiredon the Back Bay of Biloxi, during September 12-21, 1994 and during April 25 May2, 1995. Comparisons of the predicted and observed tidal data are madequalitatively by using temporal comparisons. The respon se of model predictioncalculations is consistent with trends of the observed data ranges, but not withabsolute values in all cases. The results indicate that the model can accuratelypredict the tidal elevations in the Bay under varying conditions of estuarine flow .