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PACIFIC SCIENCE, Vol. XVII, July 1963 
fronts beyond the straits partially filled the area 
leeward of the islands. Locally, complex inter- 
ference patterns resulted from crossing of wave 
trains from different straits. In general, however, 
the leeward sides of the islands had only low 
waves of the 7-sec period. Southwest of Oahu 
a third train of 7-sec waves was observed mov- 
ing northward; it is of unknown origin. 
The waves of about 1-sec period were too 
short to have been produced by other than local 
winds. However, their round crests and large 
angle with the wind slicks indicate that these 
waves were not being formed during the time 
of the survey. Possibly the ones northeast of 
the island chain and southeast of Hawaii re- 
mained from a local wind which blew just prior 
to the survey; these areas were surveyed only 
during 31 August. The waves southwest of the 
chain were more irregular in pattern and may 
have owed their origin to cold air masses flowing 
down the slopes of several islands. 
EFFECTS ON SHORES 
During a study of beachrock in the Hawaiian 
Islands by Emery and Cox (1956) the shores 
of most of the islands were examined in detail. 
Others were viewed from the air during the 
wave survey. These shores can be classified as 
follows : rocky ( irregular and commonly rugged, 
with sea cliffs and only narrow beaches or pocket 
beaches), sandy (long, broad sand beaches), and 
muddy (mangroves, narrow beaches or none, 
locally with lagoons or artificial fish ponds). 
Ignoring transitional forms, the shore types of 
the islands are illustrated by Figure 4. A re- 
lationship of the shore type to the chief wave 
pattern, that from a generally easterly direction, 
can readily be observed. High storm waves from 
any direction (Arthur, 1948) also can control 
the shore types, but infrequency of the storms 
and inconstancy in direction of their waves 
reduces their importance. 
Rocky shores characterize the sides of the 
islands most exposed to direct wave attack, 
except at Kaneohe Bay (east side of Oahu) 
where a wide offshore reef protects the shore. 
In some areas, such as almost the entire circum- 
ference of Hawaii, rocky shores dominate, re- 
gardless of exposure direction, probably because 
of the recency of vol can ism. Longshore currents 
developed by a diagonal approach of waves to 
the shore have caused much of the sediment 
produced by wave attack of the rocky shores or 
of adjoining reefs to be carried beyond the 
areas of greatest exposure to waves. Some of 
Fig. 2. Results of aerial observation of wind at sea surface on 31 August and 1 September 1961. Wind 
flow lines (wide lines) are based upon wind slicks observed at each position (note weather-vane line at each 
position). Wind speeds are based upon condition of sea surface expressed in Beaufort scale (indicated by 
narrow numbered lines). 
