San Francisco District planning team applies nature-based solutions to Roi-Namur recovery efforts

Second largest island of the Kwajalein Atoll devastated earlier this year by large waves

USACE San Francisco District
Published Oct. 29, 2024
This is a computerized graphic of an island with numerous types of trees and bushes on it in front of a gabion (rock wall) and a concrete seawall in front of the ocean.

This is one design solution to mitigate damage to facilities from overwashing waves at Roi-Namur, the second largest island of the Kwajalein Atoll in the western central Pacific Ocean. On Jan. 20, 2024, a high water-level and wave event struck the island of Roi-Namur causing significant damage to infrastructure from direct wave impacts and inundation flooding. During the six-hour event, waves periodically washed overland, striking buildings and pushing tens of thousands of cubic meters of water onto the island. Debris such as sand, gravel, corals, large rocks and chunks of concrete that was previously located on the offshore reef and shoreline was pushed by waves hundreds of feet inland.

U.S. Army Corps of Engineers San Francisco District’s knowledge of and push for Engineering with Nature principles and designs reached a new high as the district’s EWN expertise jumped an ocean all the way to Roi-Namur, the second largest island of the Kwajalein Atoll in the western central Pacific Ocean. It’s part of the Republic of the Marshall Islands, and it lies 2,100 nautical miles southwest of Honolulu and about 4,200 nautical miles southwest of San Francisco.

On Oct. 11, a San Francisco District project development team submitted its preliminary EWN and non-EWN design plans to protect facilities against large waves to the USACE Honolulu District to present to the U.S. Army Garrison – Kwajalein Atoll and U.S. Army Space and Missile Defense Command.

The Kwajalein Atoll falls under the Honolulu District, and it is a high priority Department of Defense site with multiple stakeholders calling it home such as Missile Defense Agency, Defense Logistics Agency, U.S. Army Space and Missile Defense Command and U.S. Army Garrison – Kwajalein Atoll.  Kwajalein and Roi-Namur have more than 1,250 residents, which are comprised of military personnel, Army civilians, contractor employees and family members.

On Jan. 20, 2024, a high water-level and wave event struck the island of Roi-Namur causing significant damage to infrastructure from direct wave impacts and inundation flooding. During the six-hour event, waves periodically washed overland, striking buildings and pushing tens of thousands of cubic meters of water onto the island. Debris such as sand, gravel, corals, large rocks and chunks of concrete that was previously located on the offshore reef and shoreline was pushed by waves hundreds of feet inland.  

Dr. Jin Yang from the Honolulu District is the technical lead of the team working on formulating solutions to mitigate damage to facilities from overwashing waves and drainage system improvements to mitigate inundation flood waters if such an event were to happen again.  The protection is designed to a service life of at least 10 years with the understanding that designs for longer term solutions are in development.

A Honolulu District coastal engineer, Dr. Jack Davis, who worked on the project noted that “while experts were reviewing aerial imagery from before and after the event, they observed that areas with dense stands of vegetation appeared to mitigate the flooding or at least the vegetation appeared to trap debris and prevent it from moving inland.”

Yang added, “We brought the observations to the customer’s attention during a working meeting, and they showed interest in moving this further with the design. Because of this, I reached out to Julie Beagle at San Francisco District.”

Yang used to work here in San Francisco District, and he wanted the District to do the EWN designs as he said, “they are known for EWN and Environmental Justice.”

San Francisco’s Julie Beagle is the chief of Environmental Services Branch and is a practice lead for the district’s EWN program.

In early June, Beagle brought San Francisco District, and other practice leads, Elizabeth Godsey from Mobile and Michelle Viera from Jacksonville District, into the phase of the project that included getting the project designs to 35 percent.

“We worked with the team to move the alignments of the grey infrastructure further back away from the shoreline and include the vegetation buffer,” she said. “Sometimes EWN is all about giving shorelines space - it increases habitat area, decreases pressure on the built infrastructure and reduces erosion. Nature-based solutions are based in nature so we are learning from what happened in the storm event, using plants that exist on the island and using those tools to increase resilience along the shoreline.”

Anna Kirsch, a San Francisco District civil engineering technician, added, “During the project meetings, there were concerns of the design not impacting Army operations, so we had to accommodate and work around their requests. Our plans give them the option to use either the EWN or non-EWN designs.”

“The biggest differences are the location of the coastal protection berm – EWN design has it further from the shore to allow for a bigger area to plant vegetation to serve as a natural barrier. Non-EWN has no vegetation area in the design.”

Kirsch added, “There are also other unique instances; the island has some World War II legacy structures and landmarks that needed to be preserved and other structures that we had to build around. Some buildings will have to be relocated or abandoned to build the new coastal berm and floodwall.”

She described the main design improvements as a new gabion (rock-filled bag) berm with setback floodwall, which will consist of either concrete blocks or stacked “eco-blocks.” The EWN design will have an additional planting area, and there is a new swale and culvert design for southwest of the airfield.

San Francisco District Environmental Manager Jade Ishii was also part of the project development team who worked with Kirsch to complete the designs.

“We recommended using plants native to and sourced from Roi-Namur to establish a resilient coastal forest at a low cost,” she said. “There are many naturally dense and complex patches of vegetation around the island, and the EWN team suggested strategically creating similar vegetation patches to enhance protection of critical structures.”

Ishii said that the numerous districts gave the U.S. Army Garrison – Kwajalein Atoll a number of choices, and Honolulu District is waiting to hear back from them.

“This was a big PDT, with members from Honolulu as the tech lead and project manager,” Kirsch said. “Here we had civil engineering and EWN; Sacramento brought in mechanical engineering; Detroit had structural and geotechnical engineering; and the Army Geospatial Center, Warfighter Support Directorate provided the lidar survey and aerial imagery.  There were lots of folks in different time zones, but we successfully completed our end of the designs.”

Davis added, “The project was a great representation of how USACE can reach across the lines of its districts and divisions to tap expertise and capacity needed for projects.”