Evaluation of Techniques for Numerical Calculation of Storm Surges

Abstract

Two numerical models are employed to describe the water motion in a coastal region associated with the passage of a hurricane or severe storm. The first is two-dimensional, employs the vertically integrated or "tidal" equations of motion and utilizes a finite-difference scheme. The second is also two-dimensional, also employs the vertically integrated conservation of mass and momentum equations and utilizes a finite element solution scheme. Model results are compared and evaluated through various parametric studies such as computer time and accuracy. Boundary condition sensitivity is investigated. In application, storm surge heights are computed for various hurricane systems at the Atlantic Generating Station site using both models. Results are also compared to bathystrophic calculations. It is concluded that under certain instances of storm size and speed the bathystrophic approach may be non-conservative due to the ignoring of inertial terms and two-dimensional effects. The resulting storm surge calculations indicate no significant advantage in using the finite element method over the finite difference method or vice versa, although the same may not be true for other hydrodynamic applications. Other results include maximum surge heights as a function of forward velocity and angle of incidence, as well as historical verification studies for the hurricane of September 14, 1974.