HR: 0800h
AN: H41B-0507    [Abstracts]
TI: PX and PXT: New Methods for Calculating Shoreline Change Rates
AU: * Genz, A S
EM: agenz@hawaii.edu
AF: University of Hawaii, School of Ocean and Earth Science and Technology 1680 East West Rd, Honolulu, HI 96822, United States
AU: Frazer, L N
EM: neil@soest.hawaii.edu
AF: University of Hawaii, School of Ocean and Earth Science and Technology 1680 East West Rd, Honolulu, HI 96822, United States
AU: Fletcher, C H
EM: fletcher@soest.hawaii.edu
AF: University of Hawaii, School of Ocean and Earth Science and Technology 1680 East West Rd, Honolulu, HI 96822, United States
AU: Romine, B M
EM: romine@hawaii.edu
AF: University of Hawaii, School of Ocean and Earth Science and Technology 1680 East West Rd, Honolulu, HI 96822, United States
AU: Barbee, M M
EM: mbarbee@hawaii.edu
AF: University of Hawaii, School of Ocean and Earth Science and Technology 1680 East West Rd, Honolulu, HI 96822, United States
AU: Lim, S
EM: siangl@hawaii.edu
AF: University of Hawaii, School of Ocean and Earth Science and Technology 1680 East West Rd, Honolulu, HI 96822, United States
AU: Dyer, M
EM: mdyer@hawaii.edu
AF: University of Hawaii, School of Ocean and Earth Science and Technology 1680 East West Rd, Honolulu, HI 96822, United States
AB: It is imperative that coastal erosion studies produce valid erosion rates and erosion hazard predictions to aid in the development of public policy and protect coastal resources. Currently, the Single-Transect method is the most common shoreline change model, which calculates a rate at each shore-normal transect without regard to influences of data from adjacent transects along a beach. Improving on Single-Transect, the University of Hawaii Coastal Geology Group has developed the PX (Polynomial in distance X) and PXT (Polynomial in distance X and Time) shoreline change rate calculation methods, which model all the shoreline positions within a beach simultaneously using polynomial techniques. PX is a special case of PXT that models shoreline change rates spatially along a beach. PXT not only models the shoreline change spatially, but it lets the rate change with time (acceleration). This is an important advance, as beaches may not erode or accrete at a constant (linear) rate. A linear sum of basis functions characterizes the shoreline change rate for both PX and PXT. These methods are an improvement on previous methods as they produce more meaningful, i.e., statistically significant rates and erosion hazard predictions. To date, PX and PXT improve the significance in the rate by 25% on Maui. We use an information criterion (gMDL) to (1) identify the number of coefficients of the basis functions that are needed to describe shoreline change in PX and PXT, and (2) compare different methods to determine which method best describes shoreline change. We present an overview of the PX and PXT methods and results from a shoreline change study of the beaches of southeast Oahu, Hawaii, utilizing these rate calculation methods.
DE: 4200 OCEANOGRAPHY: GENERAL
DE: 4217 Coastal processes
DE: 4299 General or miscellaneous
SC: Hydrology [H]
MN: 2007 Fall Meeting