Hamakua Wetlands Water Flow Restoration

A method to Restore Hamakua Wetlands’ Water Flow, even as Seasons and Climate Change. Click image once to enlarge:

Proposed Restoration/Management of Hamakua Wetlands' Water Flow
Historically, prior to Oneawa Canal and construction/revision of the Levee, Kawainui Wetlands (Marsh) discharged its water seaward through the Hamakua Wetlands, which was likewise served. Modern adjustable dams now allow manual fine-tuning of such water flows, to maximize the health and habitat in both Wetlands and waterways. Additional safety is provided in rapid manual response to rainfall and flood events.
Illustrated at left is the Kawainui Outlet into the Oneawa Canal, and the Primary Hamakua Inlet. At right are two possible Secondary Hamakua Inlets.

Background:  Kailua WaterwaysOceanit

4 thoughts on “Hamakua Wetlands Water Flow Restoration”

  1. The concept presented will literally require an act of Congress (honest) to implement because it involves modification to a USACE structure. In addition the local USACE has adamantly stated its objection to any modification to their structure. This is why the Oceanit report recommends making the connection between the marsh and the stream in a buried pipline around the southern end of the levee adjacent to, and within the right-of-way of Kailua Road. This solution would have the added benefit of feeding into the ITT wetland with the possibility of augmenting this pond and/or supplying water for taro patches proposed at this site by others.
    All three Oceanit reports on this topic can be downloaded from the BourkeEcology.com website.

    1. Mr. Bourke,

      The page at “Hamakua Wetlands Water Flow Restoration” on this website was and remains largely conceptual. The idea was to keep the conversation going about the reasons for increasing water flow, and to illustrate a mock-up of how it might be accomplished. We decided, e.g., to wait in posting a video because it had too much detail. As the community understands the rationale of the effort we can all start to consider the merits of more finished solutions.

      I will say the Obermeyer inflatable dams, though they’re clever and have had successful world-wide installations, are NOT a good application here. Flood control is of paramount importance in Kailua and these dams would have at least the perception of a failure which leads to an open dam. I doubt the community would accept that as a prudent design.

      The goal of transferring water from Kawainui to Hamakua Wetlands is, among others, to keep Hamakua and its down stream connection to the ocean cleaner and healthier. We’ve been in agreement with Oceanit from the outset. I’m glad that documentation is also available on your website. Our contribution is in support of that effort and we’d like to cooperate in its illustration and promotion.

      Here are a few observations which could be added to, or emphasized within, the evolving proposal:

      1- Water from Kawainui Wetland should be collected from near its surface to help avoid suspended solids.

      2- Any flow management system, to avoid down-stream flooding, must include a likely pressure operated mechanism to close automatically should flood conditions or failure occur.

      3- The system should also have a enough managed flow capacity to provide:
      3.1- fine-tuning of flow as conditions, e.g., annual seasons change, and
      3.2- an escape valve at the eastern corner of the wetland in the occurrence of a storm flood threatening to overtop the levee. Due to climate change future weather is a wild card. We should take this opportunity to build a system with enough capacity to help mitigate future flood events.

      4- Failure can occur due to power outages common in Kailua, especially during rain storms. Incorporating solar/battery backup into the design can meet this power requirement.

      5- A second type of failure is common in Hawaii. It can be due to poor design but more likely is the result of a lack of proper ongoing maintenance. Certainly governmental facility maintenance should be tasked with the scheduled accountable hands-on work. We suggest perhaps the scheduled testing of the mechanism be done under the final responsibility of the Fire Department. Its familiarity with the system could also allow it to be the agency of last resort to assure critical manual hydrologic adjustments are made to the system in an emergency.

      6- Perhaps some or all of this cost can be covered through the new Stormwater Utility.

      There are firms which have been for years in the business of designing and building to order automated (manual over-tide) types of pressure or water level dependent water management systems. Waterman Valve (watermanusa.com/products/) is one of many.

      Given the issues with power and maintenance the watchword needs to be simplicity.

      I’m glad Oceanit has over the years been involved in analysis and planning of the Kawainui Project. I hope the design team there will incorporate these suggestions into their future proposals, and we look forward to being their ally in providing all the advantages of a better managed Kawainui Stream and Hamakua Wetland.

      Robert Gratz

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