Project Need
Flood hazard
reduction improvements are needed to reduce or prevent flood damages to the
low-lying areas of McCully, Mō‘ili‘ili, and Waikīkī that may result from
insufficient channel capacities. Ecosystem restoration actions are needed
to restore aquatic and riparian habitats to a more natural state capable of
supporting the native species that previously existed there.
Flood Hazard Reduction:
The Ala Wai Canal has been found to have only marginal capacity
to accommodate the
10-year frequent flood event, and definitely could not handle the
100-year flood event. Current Canal bank-full capacity has been
estimated at 6,500 cubic feet per second (cfs), while the peak discharge
rate for the 100-year flood flow event was estimated to be 22,900 cfs.
Since
its construction, the Ala Wai Canal has overflowed and flooded the
surrounding neighborhoods at least three times. The flood of November, 1965
resulted from high intensity rainfall from what would be considered a
25-year event. Parts of Waikīkī were reported to have been submerged under
two feet of water. The flood of December, 1967 again caused the Canal to
overflow, this time also inundating the elementary school on the mauka bank
under 6-12 inches of water. Additionally, the passing of Hurricane ‘Iniki
in 1992 caused overtopping of the Canal banks and flooding in Waikīkī.
Failure to
implement flood improvements to the Canal area would result primarily in
damages to private property, and to commercial, recreational, and resort
uses. The three most affected areas of McCully, Mō‘ili‘ili, and Waikīkī are
all high density neighborhoods, with Waikīkī also being the resort and
commercial center of the State’s primary industry, tourism. Additionally,
these areas provide a variety of recreational opportunities to thousands of
residents and visitors on a daily basis.
The total
inundation damage for structure and contents
alone under without-project conditions is expected to cost $110,815,000 for
the 25-year flood, and $174,869,000 for the 100-year flood event. These
figures do not include impacts to automobiles, yard and outside properties,
emergency response, National Flood Insurance Program, travel delay
reduction, and business activities. Fifty percent of all visitor
expenditures in the State are believed to occur in Waikīkī, which hosts
60,000 to 70,000 visitors a day and provides jobs to 37,500 employees.
Generalized calculations suggest that roughly $5 billion was spent in Waikīkī in 1999, demonstrating the value of reducing the duration and
intensity of potential flooding in that area. (Back to
Project Need)
