Computer Model
The computer model is set up to input used defined wave, beach, and groundwater conditions and create a beach profile, surface water profile, and groundwater profile. The equations used for calculations are shown in the Approach section.
The module of the program that created the groundwater profile is an implicitly solved, finite element model. The beach cross section is divided into a 20 x 30 grid. The surface water profile, and the aquifer Dh serve as the boundary conditions for computing the flow (the bottom boundary is impervious).
The model works from the upper left corner of the grid to the lower right, where the head and flow in any given node is a function of the four elements surrounding it.
The model then reverses direction and works from the lower right to the upper left. This reversal step helps eliminate any biases in the results. These steps are repeated until the change in head from one pass to the next is sufficiently small.
Currently, the model assumes that the aquifer is both homogeneous and isotropic. Additionally, the time step in the model is large, and the permeability is high. These factors all allow the model to converge more quickly on the result, though the don't necessarily represent conditions that are experienced in the field.