haena, kauai, hawaii - soest | school of ocean and earth science

Click here to load reader

Post on 12-Sep-2021

1 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

85 84
83 24586
00m N
24565 00m
N 66
67 68
69 70
82 71
72 73
74 75
76 77
78 79
80 81
96 97 98 99 4400 01 02 03 04 05 06 07 08 09 10 11 12 13 14 1615 17 18 19439500mE 20 21 22 23 442400mE
96 97 98 99 4400 01 02 03 04 05 06 07 08 09 10 11 12 13 14 1615 17 18 19439500mE 20 21 22 23 442400mE 66
67 68
69 70
71 72
73 74
24 58
60 0m
N 75
76 77
78 79
80 81
82 83
84 85
24 56
50 0m
N
50"40" 30" 10"20" 159o34' W 159o33'40" W50" 159o35'10" W 159o35' W
50"40" 30" 10"20" 159o34' W 40"50" 159o35'10" W 159o35' W
10 "
Contract C25514 Contract 7249
Charles Fletcher, Matthew Barbee, Siang-Chyn Lim, Matt Dyer, Craig Senter and Ayesha Genz University of Hawaii Coastal Geology Group School of Ocean and Earth Sciences and Technology 1680 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.
Kuhio Highway
Kuhio Highway
Kuhio Highway
Kailio Point
Haena Point
Erosion rate measurement locations (shore-normal transects)
Historical beach positions, color coded by year, are determined using orthorectified and georefer- enced aerial photographs and National Ocean Survey (NOS) topographic survey charts. The low water mark is used as the historical shore- line, or shoreline change reference feature (SCRF).
Movement of the SCRF along shore-normal transects (spaced every 66 ft) is used to calcu- late erosion rates.
T-sheet 1927
Feb 2002
Nov
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.
The Haena study area (transects 0 – 156) is located on the north shore of Kauai. The area is bounded by the steep ridges of the Na Pali coast to the west and Haena Point to the east. The shoreline is composed of carbonate sand, exposed beach rock, and basalt boulders deposited by the several streams that interrupt the beach. An extensive fringing reef lies offshore resulting in varying wave approach directions at the shoreline1. The coast in this area is exposed to large seasonal swell during the winter months.
Overall, the Haena study area is experiencing erosion at an average rate of -1.0 ft/yr. The study area is divided into three areas. Haena Beach Park is located in the eastern portion of the area (transects 101 – 156) and is eroding at an average rate of -1.3 ft/yr. The central portion of the area (transects 18 – 100) is eroding at an average rate of -1.0 ft/yr. The western portion of the area (transects 0 – 17), which covers Haena State Park and Kee Beach, is eroding at an average rate of -0.5 ft/yr.
Study results generally agree with Sea Engineering (1992) 1 for this portion of coast except at Haena State Park where the vegetation line is difficult to identify with accuracy on the selected photography.
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.
-2
-1
0
-2
-1
0
0
5
10
-2
-1
0
-2
-1
0
Shoreline Change Rate (ft/yr) 25 40 45 5030 35 55 60 65 70 75 80 85 90 95 10018 20
-2 -1
/yr)
110
120
125
130
135
140
145
150
155
115
156
101
105
0
5
10
15
20
25
30
35
40