60
Haleiwa
T
he Haleiwa coastline is dominated by the embayments associated
with the confluence of the Kiikii and Paukauila streams and the
Anahulu River.A long and narrow beach, bordered in many places by dete-
riorated seawalls and revetments, extends from Mokuleia to Kaiaka Bay.
Rocky outcrops of limestone compose both Kaiaka and Puaena points. To
the northeast, the coast toward Kawailoa Beach consists mostly of inter-
spersed sand beaches and 3-6-ft rocky escarpments of basalt or limestone.
Broad wave abrasion platforms extend offshore of Mokuleia Beach, but
narrow toward Kawailoa Beach. This is a high wave-energy coastline that
receives some of the largest breaking waves in the state. In 1969, for exam-
ple, wave heights of between 30 and 35 ft were recorded offshore of
Haleiwa, and in 1998 as high as 50 ft. It is also a low-sloping coast, and near
the stream mouths wetlands and ponds are found. The only boat harbors
along the entire North Shore of Oahu are found inside Kaiaka and Waialua
Bays.
The moderate to high (5) to high (6) Overall Hazard Assessment
(OHA) for the Haleiwa coast is largely influenced by the low coastal slope
and a history of high wave energy and stream flooding.Additionally, where
erosion is ranked high along Mokuleia, and Alii Beach Park in Haleiwa, the
OHA is ranked high (6). The tsunamis of 1946, 1952, and 1957 generated
flood heights of 11, 17, and 17 ft, respectively, along the Haleiwa coastline.
In 1932, between 26 and 30 in of rain fell in a 24 hr period, resulting in
extensive local flooding. Because of this history and the low coastal slopes
found here, hazards due to tsunami, stream flooding, and high waves are
ranked high along this coast. The storm hazard along this coast is moder-
ately high, except northeast of Kawailoa Beach where the threat from hur-
ricanes is reduced because of higher slopes and local sheltering. Erosion is
high along the western segment of the Mokuleia shoreline and at the
Anahulu River mouth, and moderately high along the eastern portion of
Mokuleia and between Puaena Point and Kawailoa Beach. It is reduced to
moderately low and low at three sites in Mokuleia, where the wide offshore
reefs and scattered rocky carbonate outcrops onshore help buffer the
coastline from wave energy. Sea-level rise is ranked moderately low
throughout this region compared to Maui and the Big Island. The hazard
due to volcanism and seismicity is also ranked moderately low as it is
throughout the northern half of Oahu.
Haleiwa
Narrow beaches and
wide fringing reefs line
the Mokuleia and
Haleiwa coastal areas.
S
ome of the world’s best surf breaks are found along the Waimea Bay coastline, where
winter waves annually reach breaking heights of 20 to 25 ft. Small pocket beaches along
the Kawailoa Shoreline give way to a rocky basalt coast south of the beautiful wide beach and
stream mouth at Waimea Bay. Long, coarse-grained sand beaches extend between Sunset
Beach and Waialee. Isolated outcrops of basalt and reefrock harden the shoreline near
Pupukea, Sunset Point, and Waialee Point. The coastal slope is steeper near Waimea Bay, but
gradually decreases toward Sunset Beach where it coincides with a low coastal terrace that
reaches northeast to Kahuku (see Kahuku map). Fringing reefs (mostly fossil) cover most of
the offshore region of this coast.
The Overall Hazard Assessment (OHA) for the Waimea coast is moderate to high (5),
which is primarily a result of the susceptibility to high wave energy and stream flooding. In
1946, 1952, and 1957, tsunami runup of 19, 20, and 22 ft, respectively, inundated Waimea Bay.
Stream flooding, especially in the flash flood prone Waimea River Valley, historically has been
significant, and high wave events annually overwash the coastal road and cause damage to
coastal property. For these reasons, the hazard due to tsunami, stream flooding, and high
waves are ranked high. While storms like Hurricane Iwa have been known to produce 50-55
mph winds along this coast, the hazard due to storms is ranked moderately low relative to
other areas in Hawaii. Erosion is ranked moderately low in Waimea Bay and along hardened
coastlines, and moderately high for most of the long sandy beaches to either side of Waimea
and along Pupukea Beach to Sunset Beach. It is also ranked high at the sandy beaches along
the coastal terrace near Waialee. The hazard due to sea-level rise is ranked moderately low
here as it is for most of Oahu, which is experiencing only moderate rates of rise. The vol-
canic/seismic hazard is also ranked moderately low here in the northern half of Oahu.
61
Waimea Bay
Waimea Bay
The Waimea coast looking southwest toward Kawailoa.
62
Kahuku
R/B
frw
Bfr
e
Rfr
Hazar
d
Type:
G CS
T SF
W S E SL
V/S OHA
Bfr
Rfr
Bfr
e
R/B
frew
Rfr
Rfrw
R/Bfrw
R/B
frw
B
fre
Rfr
R/B
fr
no
data
1
4
4
2
2
2
2
2
4
Rfrw
Island of Oahu
Coastal Hazard Intensity
158°00'W
Hazard Intensity:
EXPLANATION
[For explanation of hazard types, see
Notes on Specific Hazards in the Introduction]
Overall Hazard Assessment (OHA)
G - Geology:
fr-fringing reef; br-barrier reef; e-embayed coast; w-wetland
B-Beach; S-Stream; R-Rocky; H-Headland; D-Developed
Low - 1 2 3 4 - High
<20% -1 2 3 - >45%
W - High Waves
SF - Stream Flooding
S - Storms
E - Erosion
SL - Sea Level
V/S - Volcanic/Seismic
- No Data
T - Tsunami
CS - Coastal Slope
1 2 3 4 5 6 7
Low
High
Base Credit: USGS 1:50,000 Kaena Point, Hawaii5321 II W733 Edition 1-DMA and USGS 1:50,000 Laie, Hawaii 5421 III W733 Edition 1-DMA
Prepared in cooperation with Hawaii Coastal Zone Management Program, Hawaii Office of Planning and the National Oceanic & Atmospheric Administration
K
ahuku
21°43'N
SCALE: 1:50,000
Contour Interval = 40 meters
0
0.5
1 mile
0
0.5
1.0
1.5 km
Cartography by Manoa Mapworks, Inc.
T
he northernmost tip of Oahu reaches around Kahuku Point where
low coastal terraces host one of the most extensive wetlands in the
state. Relict and modern dune fields lie seaward of mixed-use aquaculture
ponds and a wildlife sanctuary that provides habitat for birdlife. Rocky
limestone cliffs encircle the embayments at Kawela and Kuilima bays.
Lithified outcrops of eolianite along Kahuku and Makahoa points are
scoured by solution weathering, intertidal bioerosion, and the relentless
trade winds, creating a sharp and jagged surface that makes access to the
shoreline difficult. Extensive ridges of beachrock on the foreshore are
found along the entire area and are evidence of recent coastal erosion and
retreat. Spectacular wind-swept sand formations mark much of the wind-
ward coast and have left limestone outcrops and islets offshore. Sand
beaches are perched on benches of eolianite and old reefrock or beachrock
between Kahuku Point and Makahoa Point. Here some active dunes also
exist seaward of vegetated Holocene dunes. The fringing reefs widen east
of Kahuku Point due to the decreased wave energy away from the winter
swell of the north shore.
The Overall Hazard Assessment (OHA) is moderate to high (5) from
Waialee around Kahuku Point to just north of Kahuku town, while south to
Makahoa Point, where the wave energy is lower, it is reduced to moderate
(4). The tsunami and stream flooding hazards are ranked high along the
entire Kahuku coastline. During the 1946 and 1957 tsunamis, flood inun-
dation heights of 27 and 23 ft were recorded at Kahuku Point. The hazard
associated with high waves is ranked high around the entire Kahuku Point,
but is reduced to moderately low southeast of the Point where the coast is
partly sheltered from north swell. The storm threat is ranked moderately
low along the Kahuku coast because it is partly sheltered from the impact
of the majority of tropical storms that historically track to the west and
south of Oahu. Erosion is ranked moderately low for the small embay-
ments lining the western portion of Kahuku Point, except along the rocky
point immediately northeast of Kawela Bay beach where it is low.Along the
northeast side east of Kahuku Point there are no available data, except at
the town of Kahuku, where erosion is ranked high, but is then reduced to
low along Makahoa Point. The hazard due to sea-level rise here is moder-
ately low. The volcanic/seismic hazard here in the northern half of Oahu is
also ranked moderately low.
Kahuku
Sand dunes and
perched beaches
along Kahuku Point
are continuously
reshaped by the
persistent trade
winds.
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