Sea Level Rise and Beach Erosion

Saving structures in balance with protecting the environment

Sea levels are rising, with a 3.2-foot increase on Maui shores projected by 2100. The 304-page “Sea Level Rise Vulnerability & Adaptation Report,” released in December 2017 by the state Office of Conservation and Coastal Lands, identified West Maui, Waihee, Hana and Kihei as communities most susceptible to rising ocean waters, resulting in flooding, submerged lands, coastal erosion and new wetlands.

Residents in vulnerable areas are already dealing with ocean waves lapping at their doorstep, including the Kahana area of West Maui.  It often results in conflicts between saving structures and protecting the environment. Following is one property’s example. However, beach erosion crosses property lines, so a community approach is often the key to successful shore protection.

When the multistory Hololani condominium buildings in Kahana began facing threats from erosion, the condominium association started putting up shoreline hardening measures during the winter of 2006-07. According to recent court documents, the Department of Land and Natural Resources gave the Hololani association emergency authorization to install geotextile sandbags and erosion blankets for three years. The emergency permit has been reauthorized three times as of May 2014, and the structure remains today.

In the meantime, the Hololani association began work on a more permanent solution, including a 400-foot seawall, which received approval from the Maui Planning Commission in June 2014. According to Michele McLean from the Maui County Planning Department, plan was for a revetment, or a sloped wall with a toe that extended into the ocean, backed by sheet piles. This article’s photo shows and example of sheet piles topped by a cement seawall (not in Hawaii).

Because the seawall would encroach onto the state-owned shoreline, the Hololani association was required to obtain an easement, which called for approval by the state Legislature, but the Legislature did not act on the request. Holoani’s association was able to obtain approval from the Maui Planning department for a modified plan, moving the sheet pile portion of the structure 7 feet inland off State property and abandon the seawall while keeping existing sandbags in place. The project was approved, but not without lawsuits from environmental groups.

Solid structures in shoreline hardening efforts, including sheet piles, are a concern to the environment because they cause erosion; harm reef ecosystems, fisheries and monk seals; and actually destroy beaches leading to loss of access. The area most impacted by shore erosion control measures is the intertidal zone, located between high and low tide. Habitat, food and cover for many species of fish and wildlife are the products of the intertidal zone.

The current efforts at Hololani are still only temporary measures in the wave of rising tides. The group is working with neighboring properties on a a beach nourishment program. Selecting non-structural shore erosion control methods, such as plantings and sand replacement, provides greater environmental benefits than structural control methods and could provide an opportunity for a better balance between the concerns brought forth by environmental groups and homeowners.

 Read the full sea level rise report here.

2018-09-25T18:44:42+00:00