Tide-Induced Groundwater Flow Properties Along Sloping Unconfined Coastal Aquifer

Abstract

Tidal attenuation on groundwater flow properties is a crucial aspect in understanding groundwater-surface water interaction along coastal beaches. In this article, an analytical model is developed for describing the flow in the sloping unconfined aquifer bounded by ocean water along one side. Closed form of the transient solution from the linearized Boussinesq equation is obtained with exponentially decreasing tidal boundary condition. Numerical solution of nonlinear hydrodynamic equation is derived to assess the validity of linearization method. In this regard, the Alternate Direction Implicit (ADI) Method is applied, which is further used to obtain the impact of recharge on groundwater flow from non-linear Advection-Convection equation. Sensitivity analysis for larger amplitudes over smaller mean depths of saturation is carried out to obtain the validity of linearization technique. For varying bed slopes, water table fluctuation is analyzed using various tidal components. The error statistics involving mean error and Relative Percentage Difference (RPD) show that both solutions are in good agreement with each other. The flow rate and volumetric exchange are discussed to elaborate the flow analysis of groundwater in the interaction. The bed slope is considered along the inland side and the results are discussed briefly with graphs. Similarly, the flow behavior along the coastal side is presented in tabular values.