456003002

457003010

457003001

457003003

457002001

457003999

4580

0200

1

457003002

457003011

7473

7271

7069

6867

6665

6463

6261

6024559

00mN

2457500m

N

7473

7271

7069

6867

6665

6463

6261

6024

5590

0mN

2457

500m

N

442800mE 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 6564 66 67 68 446900mE

442800mE 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 6564 66 67 68 446900mE

30'' 20" 159o31'00'' W10"40''159o32'00'' W 50"

30'' 20" 159o31'00'' W10"40''159o32'00'' W 50"

50"40"

22o13' N

22o12' 30" N

10"22

o13' 20" N50

"40

"22

o 13'

N22

o 12'

30"

N10

"22

o 13'

20"

N

HISTORICAL SHORELINES

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.

May

MayNov

1987

19501963

May 1975

1930 T-sheet

AprJulMar

1988199920022006Sept

0

0 10km

10mi

Kauai

LumahaiavaLumahai, Kauai, Hawaii

Contract C25514 Contract 7249

Charles Fletcher, Matthew Barbee, Siang-Chyn Lim,Matt Dyer and Ayesha Genz University 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.

Latitude/Longitude coordinatesUTM coordinates

159o32'00" W2455900mN

400 300200

1200 900600

100

3000

0100

300

Scale 1:3000Meters

Feet N

0

5

10

15

20

25

30

35

40

45

5052

55 5658

Kuhio Highway MakahoaPoint

KolokoloPoint

Lum

ahai

Riv

er

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.

AREA DESCRIPTIONThe Lumahai study area (transects 0 – 58) is located on the north shore of Kauai. The area is bounded by Kolokolo Point to the west and Makahoa Point to the east. Lumahai River flows through the westernmost portion of the area. The area is exposed to large seasonal swell during the winter months while strong tradewinds drive alongshore currents that transport sediment during the summer months. The sandy shoreline is composed of carbonate sand and fine grained terrigenous sediment.

Lumahai Beach is highly variable. Changes in the shoreline positions indicate an average summer-winter difference of 176 ft with a maximum of 300 ft (transect 47). Overall, Lumahai Beach is experiencing erosion at an average rate -0.4 ft/yr. The eastern portion of the area (transects 29 – 58) is eroding at an average rate of -0.6 ft/yr while the western portion (transects 0 – 28) is experiencing mild erosion at an average rate of -0.1 ft/yr. Previous studies1 did not analyze the Lumahai Beach 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.

20

25

30

35

40

45

50

5558

5256

-2

-1

0

1

2

-2

-1

0

1

2

0

5

1015

Shoreline Change Rate (ft/yr)