166 
PACIFIC SCIENCE, Vol. XXII, April 1968 
TABLE 4 
Beach Sand Reservoirs, Miscellaneous 
Coastal Zones, Kauai 
SUMMATION 
AVERAGE 
OF BEACH 
SAND 
LENGTHS 
VOLUMEf 
COASTAL ZONE* 
(yards) 
10 3 yd 3 
Lae o Kaweonui— 
Kalihiwai 
4000 
160.0 
Kalihiwai-Moloaa 
5765 
691.8 
Moloaa 
700 
84.0 
Moloaa-Anahola 
1965 
78.6 
Anahola-Kealia 
1700 
102.0 
Kealia 
1100 
220.0 
North Kapaa 
1000 
20.0 
South Kapaa 
1210 
24.2 
South Kapaa-Wailua 
1925 
38.5 
Wailua— Hanamaulu 
4450 
267.0 
Hanamaulu 
500 
30.0 
Nawiliwili-Poipu 
4820 
289.2 
Waiohai 
450 
18.0 
Poipu-Hanapepe 
2080 
83.2 
Hanapepe— Makaweli 
950 
38.0 
Makaweli 
1340 
53.6 
Makaweli-Waimea 
Waimea (Pier-Boat 
2815 
112.6 
Harbor) 
2580 
103.2 
Kekaha 
2300 
230.0 
Kekaha-Bonham 
8750 
1750.0 
Na Pali 
4700 
188.0 
Ka Lae o Kailio 
350 
14.0 
Ka Lae o Kailio-Haena 
1650 
66.0 
Maninihola-Kepuhi 
2665 
799.5 
Kepuhi 
420 
12.6 
Wainiha 
450 
67.5 
Middle Lumahai 
250 
25.0 
Makahoa-Waioli Stream 
Hanalei River-Lae o 
1335 
560.7 
Kaweonui 
1380 
82.8 
* Listed clockwise from northern coast of island, 
f Volumes obtained from a single set of profiles in 1963, 
supplemented by aerial photographs and maps. 
yearly, or otherwise, in response to waves and 
currents. An intimate and complex relationship 
exists between the various nearshore sand 
reservoirs and the beach reservoir; in some 
cases it can be shown that increases in the 
beach sand volumes are accompanied by de- 
creases in the offshore reef channel reservoirs 
and vice versa. 
The actual volume of the various reef chan- 
nel reservoirs varies greatly. Surge channels 
extending up across the front of the reef may 
have a thickness of from 1 to 4 ft of sand and 
individual channels may contain several hun- 
dreds of cubic yards. Accurate volume measure- 
ments involving subsurface probing have shown 
that the summation of sand channel volumes 
along the entire front of a typical, small, Ha- 
waiian reef between the depth ranges of — 40 
to — 5 ft mllw amounts to a sand reservoir 
of somewhat more than 50,000 cubic yards per 
linear mile of reef. On a large reef this volume 
may be nearer 200,000 cubic yards per linear 
mile. 
The largest channels across the reef, some 
of which are ancient river courses, contain 
reservoirs of sand that are measured in millions 
of cubic yards. For example, the sand reservoir 
of the Halekulani Channel crossing Waikiki 
Reef, Oahu, has been measured and found to 
contain nearly l/ 2 million cubic yards of sand 
within the depth range of 0-30 ft mllw. Ac- 
curate measurements including subsurface prob- 
ings of the sand channel reservoir in Pokai 
Bay, Oahu, indicate a reservoir volume of be- 
tween 1 and 2 million cubic yards out to a 
water depth of 30 ft mllw. 
Reef Flat. There exist numerous shallow de- 
pressions on the reef flats surrounding the Ha- 
waiian Islands. Many of these are measured in 
hundreds or in thousands of square yards, and 
quite a few are measured in hundreds of thou- 
sands of square yards. Most of the sand pro- 
duced on the reef flat is transported onto the 
beach by being moved in a series of steps from 
one of these depressions, or sand pockets, to 
another. Consequently, the reef flat reservoirs 
also play an important role in the littoral sand 
budget. 
Most of the sand reservoirs on the reef flat 
are shallow, sand thickness being measured in 
feet; individual sand pockets may contain only 
a few hundred or a few thousand cubic yards 
of sand. But when the sand pocket volumes 
are summed over an extensive reef, such as the 
Sprecklesville Reef, Maui, or the Waimanalo 
Reef, Oahu, the total indicates a reservoir of 
several millions of cubic yards of sand per 
square mile of reef. 
These large volumes of sand located near 
shore and generally in water depths of less 
than 12 ft are very susceptible to varying wave 
and current conditions. Under certain wave 
conditions the rapid rates of accretion of the 
Hawaiian beaches is entirely due to the avail- 
