Master Plan
The Pelekane Bay Watershed Restoration Project has been in the planning stages for more than a decade and is truly “shovel-ready,” both in terms of environmental compliance and public support.
This journey began over ten years ago when the Mauna Kea Soil and Water Conservation District conducted a baseline survey of the watershed. This study was the beginning of a long process of identifying particular areas and elements of concern. In May 2005, a comprehensive management plan for the watershed was drafted, which addressed threats including erosion and fire and recommended remedial actions like prescribed grazing and native plant restoration. The NOAA grant is enabling KWP to implement key elements of the 2005 management plan.
As a result of NOAA funding, three jobs were retained and fifteen new jobs have been created. The new jobs include on-the-job training in a Conservation Corps-type program. KWP employees will learn skills that are applicable to future work in the conservation and habitat restoration fields in Hawai‘i and beyond. Restoration crew activities include the construction of ungulate-proof fences on lava rock substrates, construction of sediment check dams, invasive plant control, native plant identification, seed collection, propagation and outplanting, and feral animal control.
The first step in the restoration effort is construction of fences along the two stream corridors of Waiakamali and Luahine. Since grazing cattle will remain in the area and feral herds of goats continually roam the lower elevations, fencing is the only option available to protect the project’s native out-plantings.
Since all the plants needed are being propagated and grown by our restoration crew, they will simultaneously begin to source seeds and cuttings. There are 40 species identified as geographically appropriate to this watershed and a total of 100,000 plants are needed to adequately restore the riparian areas of the two streams. Some of the seeds are available from mature plants on-site, while others are coming from sites around the island. KWP will not be collecting seeds from off-island.
The Department of Land and Natural Resources (DLNR) is allowing us to use their baseyard at the Kamuela State Tree Nursery for all of our nursery operations. We are also partnering with their staff to develop a crop of pili grass (Heteropogon contortus), a native bunch grass, both for our site and as material for future KWP projects and wider community projects.
Additionally, we will conduct quarterly plant surveys to document the location and health of existing and rare plant populations. As our plantings mature, ripe fruits and seeds will be collected, propagated, and then reintroduced back to the watershed.
The restoration crew is also constructing sediment check dams at over 100 sites identified as “critically eroded.” The dams, specifically designed for this project, are small barriers constructed of rock found on-site, hog wire, and woven, polypropylene groundcloth. These are placed across a swale, ditch, or gully, reducing the effective slope of the channel. This in turn reduces the velocity of flowing water, allowing sediment to settle and thus reducing erosion. Sediment dams in the lower part of the Pelekane Bay Watershed will be installed in head-cutting gullies to trap stored sediments and any remaining sediment which is carried downslope in runoff. Following each storm event (there may be none or several in any given year), accumulated sediment will be measured and removed from behind the check dams.
With annual rainfall averaging between 5 to 30 inches, initial irrigation is crucial to keep newly installed plants alive. Because we are working on land that Parker Ranch leases for their cattle operation, there are existing water tanks that we have been given permission to amend and tap off of. Before significant planting begins, we are building two over-flow tanks, fed from existing tanks, to use the excess rainfall rather than depleting water that Parker Ranch needs for its cattle.
Once the fences and irrigation are in place, planting will begin. Native trees will be planted along and between the two streams to reduce erosion, increase infiltration of rain, and to provide for the protection of the stream bed from wind and sun. This will directly improve the quality and decrease the quantity of water in the streams, thereby decreasing the sediment load into Pelekane Bay. Communities of shrubs and ground covers will also be introduced, to shade the ground, add organic matter to depleted soils, and hold the soil in place during storm run off.
Research shows that using mulch around new plantings dramatically increases the plants’ ability to survive and thrive. To that end and when appropriate, eradicated invasive plant material will be reused as mulch. Our pili grass project is expected to provide significant quantities of seed-laden material that will be used both as mulch and as a source for regeneration.
Data will be collected by field technicians on the number of plants and survivorship of each native species, the total area and number of trees planted, and the total length of stream corridors protected. Additionally, efficacy of invasive plant control will be monitored and reported.
In the bay itself, regular monthly monitoring of nearshore water quality will occur. Water samples will be collected during or soon after any storm event. Coral health surveys will also be conducted quarterly to document changes in the benthic habitat. Storm water runoff collection bottles will be installed downstream of the check dams to gauge the dams’ effectiveness at removing suspended sediment. Auto-samplers at Makeahua Gulch and Waiakamali Gulch will also sample storm events to allow the comparison of load reductions in the lower watershed with load reductions in the upper watershed.
