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Mana, Kauai, Hawaii · 412002013 412002001 412002026 417900mE 80 81 82 83 84 85 86 87 88 89 90 91...
Transcript of Mana, Kauai, Hawaii · 412002013 412002001 412002026 417900mE 80 81 82 83 84 85 86 87 88 89 90 91...
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159o47’40” W 20” 10” 159o47” W 50” 159o46’40” W30”
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Mana, Kauai, Hawaii
Contract C25514 Contract 7249
Charles Fletcher, Matthew Barbee, Siang-Chyn Lim,Matt Dyer, Michael Borger, and Ayesha GenzUniversity of Hawaii Coastal Geology GroupSchool of Ocean and Earth Sciences and Technology1680 East West Road, Honolulu, HI 96822, U.S.A.
The preparation of this poster was financed in part by the Coastal Zone Management Act of 1972, as amended, administered by the Office of Ocean and Coastal Resource Man-agement, National Ocean Service, National Oceanic and Atmospheric Administration, United States Department of Commerce, through the Office of Planning, State of Hawaii.
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HISTORICAL SHORELINES
1962MayMay
1966Apr 1975
Jul 1987Mar 1988Oct 1991
Erosion rate measurement locations(shore-normal transects)
1950NovMay 1927
Historical beach positions, color coded by year, are determined using orthorectified and georeferenced aerial photographs and National Ocean Survey (NOS) topographic survey charts. The low water mark is used as the historical shoreline, or shoreline change reference feature (SCRF).
Movement of the SCRF along shore-normal transects (spaced every 66 ft) is used to calculate erosion rates.
Sept 1992Nov 2006
Sept 1984
AREA DESCRIPTION
The Mana study area is located on the west coast of Kauai on the Mana Plain. The area includes the air strips of the Pacific Missile Range with Mana Point at the center of the area. The shoreline is characterized by ex-tensive beach rock backed by vegetated sand dunes and broken by carbon-ate sand beach. The study area is exposed to swell from the northwest and west during winter and spring months, swell from the west and southwest in the summer as well as persistent tradewinds.
The area is divided into three discrete sections for analysis and description purposes. The southernmost section (transects 0 – 15) is experiencing ero-sion at an average rate of -0.5 ft/yr. The next section to the north (transect 17) is eroding at a rate of -0.1 ft/yr. The northernmost section (transects 20 – 33) is eroding at an average rate of -2.4 ft/yr. Previous studies1 did not analyze the Mana study area shoreline.
1 Makai Ocean Engineering and Sea Engineering, 1991 Aerial Photograph Analysis of Coastal Erosion on the Islands of Kauai, Molokai, Lanai, Maui, and Hawaii. State of Hawaii Office of Coastal Zone Management Program.
Erosion RateAccretion Rate
SHORELINE CHANGE RATES
Historical shoreline positions are measured every 66 ft along the shoreline. These sites are denoted by yellow shore-perpendicular transects. Changes in the position of the shorelines through time are used to calculate shoreline change rates (ft/yr) at each transect location.
Annual shoreline change rates are shown on the shore-parallel graph. Red bars on the graph indicate a trend of beach erosion, while blue bars indicate a trend of accretion. Approximately every fifth transect and bar of the graph is numbered. Where necessary, transects have been purposely deleted to maintain consistent alongshore spacing. As a result transect numbering is not consecutive everywhere. The rates are smoothed alongshore using a 1-3-5-3-1 technique to normalize rate differences on adjacent transects.
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Mana
Mana Point
Kinikini
Kau
mua
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Pacific Missile Rangeair strip
Pacific Missile Rangeair strip