180 
PACIFIC SCIENCE, Vol. XXII, April 1968 
per mile of coast for these two islands is 
1.2 X 10 5 cu yd and 0.8 X 10 5 cu yd, respec- 
tively. The island of Hawaii has the smallest 
total beach sand reservoir (1.6 X 16 6 cu yd) 
and the smallest volume per mile of coastline 
(5.5 X 103 cu yd). 
3. Large volumes of sand are found in the 
nearshore zone either on the reef flats in sand 
pockets and depressions, or in sand channels 
that cut across the reef, or in large sand deposits 
off the mouths of coastal streams and rivers. 
For a small reef area, measurements have been 
made showing that this nearshore sand reservoir 
out to a depth of -40 ft mllw is on the order of 
5 X 10 4 cu yd of sand per mile of coast. Within 
a similar depth range along coastal areas with 
large nearshore sand channels, volumes for the 
nearshore sand reservoir of 10 6 cu yd of sand 
per mile of coast have been measured. 
4. Seasonal fluctuations in the beach sand 
reservoir are very pronounced. Beach volume 
rates of change at several tens of cubic yards of 
sand per linear yard of coast per month have 
commonly been measured. Rates of change of 
up to 10 2 cu yd of sand per linear yard of coast 
per month are not uncommon. During 1962-63 
the highest beach volume rates of change oc- 
curred on the northern coast of Kauai, the west- 
ern coast of Oahu, and the western coast of 
Molokai. 
5. Fluctuations in the beach sand reservoir 
volume are particular for various sectors of the 
various islands, and are correlated with the 
amount and type of wave energy that reaches 
the beaches. Those beaches opening to westward 
are eroded upon the commencement of the 
westerly (winter) winds due to the arrival of 
the steep, high Kona waves commonly associated 
with those winds. During the summer period of 
northeasterly winds and waves, these beaches 
accrete. Beaches lying on the eastern or wind- 
ward sides of the Hawaiian Islands are com- 
pletely dependent upon the Northeast Trade 
Swell, and their beach sand volumes fluctuate 
accordingly. When the strength of the North- 
east Trade Swell diminishes, as during the de- 
velopment of westerly winds, the eastern beaches 
accrete. During steep Northeast Trade Swell or 
North Pacific Swell these same beaches undergo 
rapid erosion. 
6. The following data appear pertinent to 
the quantitative balancing of the littoral sand 
budget along the coasts of the Hawaiian Islands : 
a. littoral sand sources. An average sand 
contribution to an Hawaiian littoral cell may be 
2-5 X 10 3 cu yd per mile of coast per year. 
Depending upon the locality, the following 
rates are applicable: 
(1) Stream runoff. For Waimea, Kauai, 
perhaps 2.5 X 10 4 cu yd per year; for other 
Hawaiian streams, much less. 
(2) Biological activity. No direct measure- 
ments; from consideration of littoral transport 
rates, an average of 1-5 X 10 3 cu yd of sand 
per mile of coast per year for well-developed 
reef areas. 
(3) Coastal erosion. Locally, 10 2 -10 3 cu 
yd of sand per mile of coast per year. 
(4) Wind. Negligible. 
b. LITTORAL TRANSPORT RATES 
(1) Alongshore. Average: 2X 10 3 cu yd 
per year. Locally, possibly as high as 10 4 cu yd 
per year. 
(2) Normal to shore. Measured values of 
2 X 10 4 cu yd per mile of coast per month are 
common. Average is probably 5 X 10 3 cu yd 
per mile of coast per month. 
C. LITTORAL SAND LOSSES 
(1) Paralic sedimentation. 
(a) Nearshore. Average, perhaps 
2 X 10 3 cu yd yer mile of coast per year (attri- 
tional products of the beach sand: silt and very 
fine sand) . 
(b) Coastal pro gradation. Locally, 
5 X 10 3 cu yd per year; average, 10 3 cu yd per 
mile of coast per year. 
(2) Wind. Locally, high rates of loss, 
perhaps 2 X 10 3 cu yd per mile of coast per 
year. On the leeward side, loss negligible. 
(3) Beachrock formation. Small, perhaps 
10 2 cu yd per mile of coast per year. 
7. To balance the littoral sand budget, the 
estimated average sand contribution within each 
littoral cell of 2-5 X 10 3 cu yd of sand per 
mile of coast per year must be balanced by 
the yearly loss from the littoral cell due to 
paralic sedimentation, wind, or beachrock for- 
mation. Rates of alongshore transport may also 
equal these rates if the alongshore-transported 
sand is destined to be removed from the littoral 
