Storm Surge Study of the Hawaiian Islands Using the EST Method

Abstract

A hurricane-induced flood mapping study was conducted for the State of Hawaii encompassing the six major islands of Hawaii, Kauai, Lanai, Maui, Molokai, and Oahu shown in Figure 1. This paper briefly describes the storm selection process and application of the ADvanced CIRCulation (ADCIRC) hydrodynamic model to generate a database of storm-related tropical storm surges at a selected number of pre-defined transect points. The paper then concentrates on the theory and application of the Empirical Simulation Technique (EST), a statistical model to estimate frequency-related storm impacts. The Federal Emergency Management Agency (FEMA) specifically selected the EST approach because it uses historical events that have occurred at a location of interest, and these events serve as the basis of projecting the occurrence of future storm events. The results of the EST modeling were used to establish updated FEMA Flood Insurance Rate Maps (FIRMs) for the Hawaiian Islands with revised delineations of the 100-year and 500-year floodplains. BACKGROUND The hurricane-induced flood mapping study for the State of Hawaii encompassed the six major islands of Hawaii, Kauai, Lanai, Maui, Molokai, and Oahu shown in Figure 1. Selection of appropriate tropical storm events for the study area made use of the Eastern and Central North Pacific Basin HURDAT (HURricane DATabase) database of the National Hurricane Center. The database contains all hurricanes, tropical storms, and tropical depressions impacting the Hawaiian Islands from 1949 through 2005. For each event, the latitude, longitude, maximum wind speed, and, in many cases, the central pressure of the eye of the storm is given. Although the database contains 794 events, the majority of storms do not impact the Hawaiian Islands. Candidate events were required to pass within 200 miles of at least two of the islands with maximum winds at that point of at least 39 mph, corresponding to a tropical storm. This procedure resulted in the selection of just 11 historical events.