Numerical Modeling of Storm Surges in Chesapeake Bay

Abstract

This paper presents the methodology, procedures, and results of numerically modeled high water levels from selected historical tropical and extratropical storms in Chesapeake Bay. The study is a part of the effort of life-cycle storm flooding analyses to compute mean frequency relationships with standard deviation error estimates (Scheffner et al. 1999, Melby et al 2005). A regional scale hydrodynamic model ADCIRC (Luettich et al. 1992; Luettich and Westerink 2003) is used to calculate water levels under high surface winds and low atmospheric pressure associated with the passage of storms. These estimates include astronomical tides. The numerical modeling considered 86 historical tropical and extratropical storms to simulate water-surface elevations throughout Chesapeake Bay. For tropical storms, surface wind and pressure fields were generated with the Planetary Boundary Layer (PBL) model (Cardone 1977; Cardone et al. 1992), and storm tracks were from the North Atlantic tropical storm track list (http://weather.unisys.com/hurricane). For extra-tropical storms, wind fields were extracted from the long-term wind hindcast database by the Meteorological Service of Canada, formerly Atmospheric Environment Service, AES (Swail et al. 2000) and the reanalysis project database (Kalnay et al. 1996) by the U.S. National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR). The pressure fields were obtained from NCEP/NCAR database. Validation of PBL, AES, NCEP/NCAR winds, and model water levels was performed by comparing to data available at 12 NOAA meteorological stations along the perimeter of the bay. Model results show a good agreement with measured wind and water levels. A key to the successful modeling was representation of the topography of river tributaries, which flooded during the storm to contain large water storage at peak surge. Higher ground associated with major roads and highways was included in the model to protect dry plains during high water level events.