HR: 13:55h
AN: H33L-02    [Abstracts]
TI: Determining littoral sediment transport paths adjacent to an eroding carbonate beach through net sediment grain-size trend analysis: Lanikai Beach, Hawaii.
AU: * Bochicchio, C J
EM: bochicch@hawaii.edu
AF: University of Hawaii Coastal Geology Group, University of Hawaii at Manoa Dept. of Geology and Geophysics 1680 East West Rd POST 721, Honolulu, HI 96822, United States
AU: Fletcher, C
EM: fletcher@soest.hawaii.edu
AF: University of Hawaii Coastal Geology Group, University of Hawaii at Manoa Dept. of Geology and Geophysics 1680 East West Rd POST 721, Honolulu, HI 96822, United States
AU: Vitousek, S
EM: seanfkv@hawaii.edu
AF: University of Hawaii Coastal Geology Group, University of Hawaii at Manoa Dept. of Geology and Geophysics 1680 East West Rd POST 721, Honolulu, HI 96822, United States
AU: Romine, B
EM: romine@hawaii.edu
AF: University of Hawaii Coastal Geology Group, University of Hawaii at Manoa Dept. of Geology and Geophysics 1680 East West Rd POST 721, Honolulu, HI 96822, United States
AU: Smith, T
EM: Thomas.D.Smith@poh01.usace.army.mil
AF: US Army Corps of Engineers Honolulu District, US ARMY CORPS OF ENGINEERS HONOLULU DISTRICT ATTN: Thomas D. Smith (CEPOH-EC-T) Building T223, Ft. Shafter, HI 96858, United States
AB: Identifying long-term trends of sediment transport in coastal environments is a fundamental goal shared by coastal scientists, engineers, and resource managers. Historical photographic analysis and predictive computer models have served as the primary approaches to charactering long-term trends in sediment flux. Net sediment grain-size trend analysis is an empirical, sedimentologically based technique that uses physical sediment samples to identify long-term sediment transport pathways. Originally developed by McLaren and Bowles (1985), net sediment grain-size trend analysis identifies progressive trends in grain-size parameters (mean size, sorting, and skewness) in sediment samples. Ultimately, the results give an indication of long-shore sediment transport, a visualization of individual littoral cells, and a better understanding of sediment processes in the near- shore region. We applied two methodologies put forth by Gao and Collins (1992) and Roux (1994) to 214 samples collected off Lanikai Beach, Hawaii; an excellent example of a coastal environment with chronic beach erosion. The Gao methodology searches point-to-point search for the two trend types used by McLaren. The Roux methodology simultaneously searches between five adjacent points for four trend types. Despite significant differences, similar trends dominate in both sets of results. The Gao methodology produces generalized trends while the Roux methodology shows finer details of sediment transport. Long-shore transport direction is shown to be northward for the majority of the study area, implying a sediment supply to the south. Therefore erosion is instigated if the sediment supply south of Lanikai Beach is cut off. A strong onshore sediment transport trend fails to accrete a beach in an armored section of the southern Lanikai coastline, demonstrating the erosive effect of increased wave refraction from coastal armoring. Results of the sediment trend analyses agree well with tidal current models produced in Delph3D and directional current velocity data for the area.
DE: 1815 Erosion
DE: 1834 Human impacts
DE: 1862 Sediment transport (4558)
DE: 9355 Pacific Ocean
DE: 9820 Techniques applicable in three or more fields
SC: Hydrology [H]
MN: 2007 Fall Meeting