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Hale Ikena, Fort Shafter, Honolulu, Hawai‘i
October 12, 2016
Aloha 'auinala
Society of American Military EngineersOctober Luncheon
Lualualei Flood Mitigation Study
October 11, 2016Lualualei Flood Mitigation Study 2
Mahalo!
Hawai‘i Emergency
Management Agency
October 11, 2016Lualualei Flood Mitigation Study 3
• Overview of Lualualei
• Discuss the Flooding Problems in Lualualei
• Brief History of how Lualualei developed which resulted in flooding (Similar to many
location in Hawaii)
• Long-Term Flood Mitigations
• Short and Mid-Term Mitigations since funds for the Long-Term are unavailable
October 11, 2016Lualualei Flood Mitigation Study 4
October 11, 2016Lualualei Flood Mitigation Study 5
October 11, 2016Lualualei Flood Mitigation Study 6
Pa‘akea Road and Ili‘ili Road Intersection Looking Southeast
October 11, 2016Lualualei Flood Mitigation Study 7
Pa‘akea Road and Ili‘ili Road Intersection Looking Southeast
October 11, 2016Lualualei Flood Mitigation Study 8
Pa‘akea Road and Ili‘ili Road Intersection Looking Makai
October 11, 2016Lualualei Flood Mitigation Study 9
Pa‘akea Road and Ili‘ili Road Intersection Looking Makai
October 11, 2016Lualualei Flood Mitigation Study 10
“Pa‘akea Dip” Pa‘akea Road Adjacent to Navy RTF Looking
Northwest
October 11, 2016Lualualei Flood Mitigation Study 11
“Pa‘akea Dip” Pa‘akea Road adjacent to Navy RTF Looking
Northwest
October 11, 2016Lualualei Flood Mitigation Study 12
What’s going on?
• Like many other rural areas in Hawai‘i Lualualei developed at a time when there wasn’t infrastructure requirements.
• Roads inland were developed for agriculture (sugar cane and ranching). Makai development blocked drainage
• As the land was subdivided further and developed without a drainage master plan the PRIVATE roads were paved as is.
October 11, 2016Lualualei Flood Mitigation Study 13
To Mā‘ili Stream
To Ulehawa Stream
October 11, 2016Lualualei Flood Mitigation Study 14
1906 Map of SouthernLualualei
Mā'ili'ili Stream
The Beginnings
of Pa'akea Road
The Beginnings
of Ili'ili Road
Ulehawa Stream
Not Shown
Map: 1906 Donn Hawaii Territory Survey Map with Land Use (RM 2374) Graphic Credit to CSH (2015)
October 11, 2016Lualualei Flood Mitigation Study 15
1914 Map of SouthernLualualei
The Beginnings
of Pa'akea Road
The Beginnings
of Ili'ili Road
Mā'ili Stream
Ulehawa Stream
Map: 1914 Wall Map of Lualualei Homestead (HTS Plat 2026) Graphic Credit to CSH (2015)
Hakimo Road
October 11, 2016Lualualei Flood Mitigation Study 16
1906
October 11, 2016Lualualei Flood Mitigation Study 17
1914
October 11, 2016Lualualei Flood Mitigation Study 18
1953
October 11, 2016Lualualei Flood Mitigation Study 19
1983
October 11, 2016Lualualei Flood Mitigation Study 20
2014
October 11, 2016Lualualei Flood Mitigation Study 21
1953
Ulehawa
Stream
No Mā'ili
Stream Yet
Flow
Unimpeded
Flow
Unimpeded
October 11, 2016Lualualei Flood Mitigation Study 22
1983
Mā'ili Stream
Constructed
Ulehawa
Stream
Development
Starting to
Block Flow
Development
Starting to
Block Flow
October 11, 2016Lualualei Flood Mitigation Study 23
2014
Mā'ili Stream
Ulehawa
Stream
Development
Completely
Blocking Flow
Development
Completely
Blocking Flow
October 11, 2016Lualualei Flood Mitigation Study 24
USACE Flood Mitigation
• Developed in 2001 to address the 50 and 100-yr Flooding
• ~2001 CIP Budget $38M• Large concrete channels• Large box culverts• Road Bridges
• ~Escalated to 2020 it’s $100M
• Funding is difficult to obtain since most areas are privately owned. Therefor, Short and Mid-Term mitigation were developed
October 11, 2016Lualualei Flood Mitigation Study 25
Surveyors Hawaii
maintains base
station in Mililani,
rents equipment,
and trains operators
Survey
Grade GPS
(GNSS)
G70 EIT learned
how to operate the
equipment in one
morning allowing
us to quickly assess
drainage patterns,
and then transfer
that data to GIS
October 11, 2016Lualualei Flood Mitigation Study 26
October 11, 2016Lualualei Flood Mitigation Study 27
Short-Term Flood Mitigation
These are BMPs
•Community Volunteer Work
•Private Maintenance
•Low Cost
October 11, 2016Lualualei Flood Mitigation Study 28
Short-Term Flood Mitigation
• Community Clean Up Days • Photos below are from 2011 organized by the Navy and Community• 2012 Storm passed without major flooding
October 11, 2016Lualualei Flood Mitigation Study 29
Short-Term Flood Mitigation• Stream Clearing -- Remove excess
vegetation and accumulated sediment• Streams are private (Requires ROE)
Mā'ili'ili Stream
October 11, 2016Lualualei Flood Mitigation Study 30
Short-Term Flood Mitigation• Stream Clearing -- Remove excess
vegetation and accumulated sediment• Streams are private (requires ROE)
Ulehawa Stream
October 11, 2016Lualualei Flood Mitigation Study 31
Mid-Term Flood Mitigation
• Interim measures intended to alleviate flooding for small storm events up to the 10 year recurrence interval
• Interim measures will alleviate flooding, but will not fully comply with established drainage standards for flood control
• Interim measures will typically be lower in cost and will be prioritized
• Interim measures will include establishment of flow paths and drainage ways
October 11, 2016Lualualei Flood Mitigation Study 32
Mid-Term Flood Mitigation• Master Planned Infrastructure• 10-year Recurrence regardless of area• Ditches, culverts, limited catch basins
and pipe, and drivable swales
Drivable Swale
Culvert Road Crossing
Ditches Mā‘ili Stream
October 11, 2016Lualualei Flood Mitigation Study 33
Mid-Term Flood Mitigation• Master Planned Infrastructure• 10-year Recurrence regardless of area• Ditches, culverts, limited catch basins
and pipe, and drivable swales
Drivable Swale
Culvert Road Crossing
Ditches Ulehawa Stream
October 11, 2016Lualualei Flood Mitigation Study 34
2020 Cost Comparison
• Mā‘ili Stream Infrastructure from Pa'akea Road to Mā‘ili Stream• Long-Term Cost = ~$37M• Mid-Term Cost = ~$1.8M
• Ulehawa Stream Infrastructure from Ili‘ili Rd to Hakimo Rd• Long-Term Cost = ~$10M• Mid-Term Cost = ~$4M
• Mauka Hakimo Rd Infrastructure from Ili‘ili Rd to Hakimo Rd• Long-Term Cost = ~$10M• Mid-Term Cost = ~$4M
• Makai Hakimo Rd Infrastructure from Ili‘ili Rd to Hakimo Rd• Long-Term Cost = ~$3.5M• Mid-Term Cost = ~$100k
October 11, 2016Lualualei Flood Mitigation Study 35
Conclusion
• Typical flood control mitigation is not feasible due to size and cost of projects to manage 50 year and 100 year events
• Interim measures must be developed to create defined drainage ways and conveyances and alleviate localized flooding for smaller more frequent storm events
• Interim measures may include a variety of short term and mid term projects focused on:
• Outreach• Best practices• Maintenance• Establishment of drainage courses• Smaller scale drainage improvements
October 11, 2016Lualualei Flood Mitigation Study 36
Mahalo!!David Brotchie, P.E., LEED AP
[email protected](808) 554-0526