lualualei flood mitigation studylualualei flood mitigation study october 11, 2016 3 • overview of...

1

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


• 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


Pa‘akea Road and Ili‘ili Road Intersection Looking Southeast


Pa‘akea Road and Ili‘ili Road Intersection Looking Makai


“Pa‘akea Dip” Pa‘akea Road Adjacent to Navy RTF Looking

Northwest


“Pa‘akea Dip” Pa‘akea Road adjacent to Navy RTF Looking

Northwest


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.


To Mā‘ili Stream

To Ulehawa Stream


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)


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


1906


1914


1953


1983


2014


1953

Ulehawa

Stream

No Mā'ili

Stream Yet

Flow

Unimpeded

Flow

Unimpeded


1983

Mā'ili Stream

Constructed

Ulehawa

Stream

Development

Starting to

Block Flow

Development

Starting to

Block Flow


2014

Mā'ili Stream

Ulehawa

Stream

Development

Completely

Blocking Flow

Development

Completely

Blocking Flow


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


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


Short-Term Flood Mitigation

These are BMPs

•Community Volunteer Work

•Private Maintenance

•Low Cost


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


Short-Term Flood Mitigation• Stream Clearing -- Remove excess

vegetation and accumulated sediment• Streams are private (Requires ROE)

Mā'ili'ili Stream


Short-Term Flood Mitigation• Stream Clearing -- Remove excess

vegetation and accumulated sediment• Streams are private (requires ROE)

Ulehawa Stream


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


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


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


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


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


Mahalo!!David Brotchie, P.E., LEED AP

[email protected](808) 554-0526

lualualei flood mitigation studylualualei flood mitigation study october 11, 2016 3 • overview of...

Documents