Waves inundate Honoapiilani Highway at Olowalu. Other sections of the busy roadway are actively undermined by erosion and waves. A system to be developed by the Pacific Islands Ocean Observing System will provide wave run-up forecasts for various areas in West Maui. PHOTO COURTESY OF PACIOOS.

WEST MAUI – The National Oceanic and Atmospheric Administration’s Regional Coastal Resilience Grants Program will award the Pacific Islands Ocean Observing System (PacIOOS) with $500,000 to develop a high-resolution, real-time wave run-up forecast and notification system for West Maui’s coastline.

Fiona Langenberger, communications and program coordinator at PacIOOS at the University of Hawaii at Manoa, explained that while the impacts of waves and erosion are being experienced statewide, the challenges facing West Maui are particularly severe and warrant attention.

“Due to chronic shoreline erosion caused by a combination of rising sea levels, wave action and human interventions, there are several sites where high-density development and critical infrastructure are imminently threatened. The intention of this project is to apply the best available science to provide high-resolution and locally based tools and information for improved response and planning,” she noted in an e-mail.

Project data and information will be applicable from Lipoa Point at Honolua Bay at the north part of the region to Ukumehame at the south end.

In addition to the wave run-up forecast and notification system, PacIOOS will also model a suite of inundation planning scenarios that take rising sea levels and increasing wave energies into account.

According to PacIOOS, site-specific short- and long-term forecasts will strengthen West Maui’s coastal community and economy by enhancing preparedness and response operations, and by informing future land use planning.

Multiple components will be required to develop the real-time, site-specific wave run-up forecast for West Maui.

Pressure gauges and current meters will be deployed in three spots along the coastline in depths of two to 17 meters. The deployment periods will be during winter and summer (3-4 months each).

Data from the PacIOOS wave buoy will provide information on wave conditions.

“With the instrumentation, we will gain a very detailed time series of the sea levels, currents and waves in the West Maui area,” Langenberger explained.

All of the data that is collected through the instrumentation will be used to develop and validate the numerical model that can simulate the conditions in West Maui.

PacIOOS will divide the West Maui shoreline in about a dozen segments based on topography and other features. This will help make the wave run-up forecast very specific to each segment.

Impacts along the shoreline can vary significantly, and the model will factor in the differences within each segment.

Langenberger wrote, “What’s of most interest is how the model output translates to what we are actually seeing on the shoreline. If the model predicts a certain amount of wave run-up for a specific segment, what exactly does it look like on the shore?

“To establish different sets of ‘thresholds’ within the forecast, we will work with citizen scientists to help document certain events with photographic surveys.”

PacIOOS will also develop a suite of future inundation planning scenarios for long-term planning.

For those scenarios, researchers will use the validated model and change environmental conditions within the model to run possible future scenarios. For example, what would the different modeled segments look like if sea level is increased by a specific amount, or if wave energy is heightened?

All of the forecasts – short- and long-term – will be freely available online on the PacIOOS website.

The three-year project is expected to begin in October 2017. Project partners include the University of Hawaii School of Ocean and Earth Science and Technology, Hawaii Sea Grant, state Department of Land and Natural Resources and County of Maui.

Chronic (long-term) and episodic (event-based) erosion is an ongoing and worsening problem statewide. Methodologies and lessons learned in this project will be documented to enable communities with similar vulnerabilities to implement a similar framework.

The State of Hawaii has experienced an increase in wave plus tide-driven flooding in recent years. These events are expected to grow in numbers and duration due to sea level rise and changing wave energies.

“We are affected by chronic shoreline erosion in West Maui. Some of the properties that are built close to the shoreline are literally on the brink of falling into the ocean,” said co-investigator Tara Owens of the U.H. Sea Grant College Program.

“Flooding and wave inundation is also a major concern for our infrastructure, including Honoapiilani Highway, which is the only reliable access to this part of the island. These roughly 21 miles of coastline are extremely important for Maui’s economy, local businesses, homeowners and visitors, and yet they are extremely vulnerable to the impacts of rising sea levels and wave inundation.”

Co-investigator Dr. Douglas Luther of the Department of Oceanography at the U.H. School of Ocean and Earth Science and Technology (SOEST) explained, “West Maui is exposed to both large north and south swells that wrap into the coast in odd ways due to the ancient offshore reef topographies. While certain parts of the shoreline might not see any impacts, other sections can be appreciably flooded.

“Our model will incorporate relevant offshore and shoreline wave propagation characteristics to show the varying levels of vulnerability along the coast during each swell event.”

Principal Investigator Melissa Iwamoto of PacIOOS said the system and information will be user-friendly.

“We will work closely with coastal managers, emergency managers, property owners and local residents on Maui and around the state to ensure that data and tools are easy to understand and suitable for short- and long-term decision-making. The goal is to better understand site-specific risks and vulnerabilities, so that such stakeholders can integrate the information into community planning, policy-making and hazard-related ordinances,” she said.