An improved empirical equation for storm surge hydrographs in the Gulf of Mexico, U.S.A

• Analyze the limit of existing equation for storm surge.
• Present an enhanced equation for storm surge.
• Validate the equation by comparing to observations.

Traditional storm surge hydrograph equations are practically unable to fit well with the falling limb of the observed storm surge hydrograph. This study has investigated storm surge hydrographs induced by Categories 3 and 4 hurricanes at several NOAA coastal stations in the Gulf of Mexico. Five observed storm surge hydrographs for Category-3 hurricanes and four observed hydrographs for Category 4 hurricanes are chosen accordingly in the investigation. The observed storm surge hydrographs are obtained by subtracting tidal harmonic signals from the observed water level hydrographs. Comparisons of the average observations and the existing synthetic hydrograph show that the Categories 3 and  4 storm surge hydrographs do not follow the same trend. Existing synthetic empirical equations are found unable to fit well with the observed storm surge hydrographs. Due to the simple parameterization of the existing synthetic hydrograph equations, an improved empirical equation for general storm surge hydrograph is proposed in this study. Based on the observed data, a full set of parameters of the proposed equation for Categories 3 and 4 hurricanes is estimated. The improved empirical equation fits well with the observations of the storm surge hydrographs on both rising and falling limbs.