The problem, they say, is the sediment buildup before Manoa Stream runs under Woodlawn Ave.
The problem, they say, is the size — or lack thereof — of the bridge there.
The Army Corps of Engineers released their revised plan recently. In the 16 years since heavy flooding from the stream sent three cars into a tree, and caused heavy damage to the University of Hawaii at Manoa campus, there have been some changes made. Mostly, though, it has been plan, then no reaction, then a last-second rebuttal, and the process repeats.
August, 2020: https://www.westhawaiitoday.com/2020/08/20/hawaii-news/army-corps-releases-updated-honolulu-flooding-control-plan/
This revised plan one doesn't call for the outright takeover of residential properties in upper Palolo Valley. There are still several basins in the plan for Manoa and Palolo Valleys, as well as Ala Wai Golf Course, Kanewai Field and Hausten Ditch, a.k.a. Alanaio Auwai.
That explains all the work going on at Ala Wai Canal. From one drawn-up version of the basins, walls will be built around Hausten Ditch to contain flood waters. That's not a large stream at all, and it originates only a few blocks mauka, but the basin will help.
Over at Ala Wai Golf Course, there's plenty of room for containment. That whole area, including Kapahulu Ave., was once a big part of the waterways. sweeping down from Manoa and Palolo. The natural contour is into Ala Wai Golf Course, according to century-old maps, so a basin there makes all the sense in the world.
I wonder if they considered simply digging deeper at Manoa Stream near Woodlawn. One report said a slope would be built up to increase flow and lessen the buildup of sedimentation.
From what I saw today, the area should be cleared. There's a lot of foliage, mostly the result of sedimentation. As wide as the channel is, it really should've been deeper. The precipitation in the Koolaus above Manoa Valley are some of the heaviest in Honolulu. The '04 flood, it has been stated, was worsened because the thunderstorm halted above the area and simply gushed rainwater into the area. A 2-percent chance of anything that catastrophic, and it happened that year.
Rewind
Nov., 2004: Lingle declares disaster. http://archives.starbulletin.com/2004/11/01/news/index.html
> The damage. http://the.honoluluadvertiser.com/article/2004/Nov/02/ln/ln27p.html
2007: A study of the 2004 flood. http://www.soest.hawaii.edu/GG/FACULTY/aly/flood.html
May, 2010: Lessons not learned. http://www.hawaiireporter.com/manoa-flood-lessons-not-learned/
Sept., 2015: Aesthetics of walls. https://www.civilbeat.org/2015/09/ala-wai-canal-flood-control-the-high-cost-of-protecting-waikiki/
May, 2018: The makeover begins. https://www.hawaiinewsnow.com/story/38135356/state-to-begin-major-makeover-of-manoa-stream-near-woodlawn-bridge/
> Dredging issues. https://www.kitv.com/story/38136025/councilmember-kobayashi-plans-to-prevent-another-manoa-stream-flood
May, 2018: The makeover is halted. https://www.khon2.com/news/state-pauses-manoa-stream-project-in-light-of-residents-concerns/
Be Ready Manoa: A Disaster Preparedness Plan. http://bereadymanoa.org/wp-content/uploads/2017/12/BRM-Disaster-Preparedness-Plan-v2.2.pdf
Manoa Stream at Woodlawn Ave., ewa view
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