3. Beach Nourishment
Beach nourishment, a technique used to restore an eroding or lost beach or to create a new sandy shoreline, involves the placement of sand fill with or without supporting structures along the shoreline to widen the beach. It is the only management tool which serves the dual purpose of protecting coastal lands and preserving beach resources. Beach nourishment is a common management practice on the mainland (NATIONAL RESEARCH COUNCIL, 1995). Miami Beach, FL; Myrtle Beach, NC; Ocean City, MD; and several other locations have ongoing beach nourishment projects.
Although Maui has limited experience with beach nourishment, a few small-scale projects have successfully restored lost or eroding beaches (Figure 7). Most restoration projects that have taken place on Maui were privately funded and carried out without a thorough engineering study.
Beach nourishment requires large volumes of beach-quality sand. The initial nourishment project typically requires thousands of cubic meters of sand per kilometer of shoreline, and most beaches need periodic renourishment. Maui should take measures to more effectively manage its limited sources of readily available sand and should build its capacity to tap new, currently unavailable sources of sand.
Sand Sources for Beach Nourishment
Sand for nourishment projects is from a variety of environments. Terrestrial sources of sand include coastal dunes, coastal plains, and inland sand dunes. Offshore sources include dredge spoils from harbor maintenance, shallow-water sand fields, medium-depth sand channels, and deeper-water sand banks. Harbor spoils can be accessed from land with a clamshell dredge but comprise only a minor portion of Maui's sand resources. Larger sources of sand must be hydraulically dredged with a suction dredge. Currently, Maui lacks its own suction dredge and hence lacks the capacity to tap large offshore sand resources.
To date, most small-scale nourishment and coastal protection projects on Maui have used sand mined from inland dunes. The fine-grained nature of dune sand may not be compatible for high energy beaches that typically have coarser-grained sand. Because some sand dunes contain burial sites, sand should be acquired only from quarries designated free of cultural sites. Inland sand mines on Maui charge $10 to $18 per cubic yard, which is relatively inexpensive. In contrast, dune sand from Kaua'i for the creation of four pocket beaches at Ko'olina Lagoons on O'ahu cost $80/cubic yard in place. Nonetheless, terrestrial sources of sand are limited. Sand shipment off island-primarily for cement companies on O'ahu-has occurred for decades. This constitutes a loss of valuable Maui sand that could be used for local beach nourishment projects. The export of Maui's sand resources should be restricted, perhaps by introducing new legislation.
Maui should build its capacity to tap offshore sand resources. Potential offshore borrow sites should be identified, mapped, and sampled. Local scientists and consulting firms have mapped offshore sand resources for O'ahu (SEA ENGINEERING, INC., 1993). Although a similar study was done for Maui and Moloka'i in 1971 (CAMPBELL, ET AL., 1971), this study did not include extensive sampling and should be updated. Sampling is necessary because offshore sand may not be suitable for beach nourishment. A recent sand nourishment viability study on O'ahu found that offshore sand is often fined-grained and discolored for beach nourishment (SEA ENGINEERING, INC., 1993). Funding for
Figure 7. Beach Nourishment at Sugar Cove, Spreckelsville, Maui. Before and after small-scale beach nourishment project implemented entirely with private funding. Above photo taken June 1996; below photo taken October 1997.
the updated offshore sand resource study could be shared by Maui County, DLNR, the University of Hawaii, and the United States Army Corps of Engineers (USACOE).
Pilot Beach Nourishment Project
Beach nourishment is the only management tool that protects coastal development without degrading the beach. Preserving or restoring a sandy beach has direct, beneficial impacts on recreational opportunities and property values. Some homeowners associations-Sugar Cove Condominiums in Pa'ia, and Kana'i O Nalu in Ma'alaea, for example-have implemented small-scale, privately-funded beach nourishment projects. Both of these projects were deemed successes; it was worth the expense to restore the recreational use and value of the beach. The demand for beach nourishment on Maui as well as statewide has grown in recent years and will likely continue to grow. The County of Maui should anticipate this growing demand and take the lead in promoting and implementing beach nourishment.
A pilot project is very much needed. It would illustrate the engineering requirements of nourishment as well as surface all the environmental and permitting requirements, problems, and concerns. An action plan for a pilot beach nourishment project should be prepared based on guidelines from the Coastal Protection and Beach Nourishment Study. Site selection should consider erosion rates, geographical location, beach configuration, sand availability, cause of erosion, public use and access, and cost sharing. In order to better ensure a successful pilot beach nourishment project, a site-specific, coastal engineering study will likely be necessary.
Objective
3.1) To promote beach nourishment by more effectively managing the limited sources of readily available sand and building its capacity to tap new, currently unavailable (offshore) sources of sand
Recommendations
3.1a) Earmark beach-quality sand that is periodically removed from Maui's harbors for nourishment projects3.1b) Restrict the export of Maui's dune sand resources, perhaps by introducing new legislation
3.1c) Limit sand mining to quarries designated free of cultural sites
3.1d) Identify, map, and sample potential offshore borrow sites
3.1e) Consider acquiring a suction dredge to use to tap offshore sand resources, provided offshore borrow sites have sand of good quality, and dredging will not cause long-term environmental impacts
3.1f) Identify and implement one or more pilot beach nourishment projects
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