Coastal inundation in the Marshall Islands forebodes the future of extreme events

On Tuesday, waves inundated the southern part of Majuro, the capital of the Republic of the Marshall Islands (RMI), flooding homes and causing extensive damage to property. The waves reached two and a half meters high, according to Majuro Weather Service meteorologist Reggie White, who serves on Pacific RISA’s Advisory Committee. The flooding caused the Majuro airport to close for the day, after the runway seawall crumbled under the weight of the waves, and a United Airlines flight bound for Majuro was redirected. High swells could persist for several days, so residents are doing what they can to prepare for further inundation possible through Thursday.

Many parts of Majuro atoll are less than one meter above sea level and are therefore vulnerable to flooding during very high tides. This week’s events can be attributed to local weather (a storm produced high ocean swells), coinciding with an unusually high tide (a result of the recent supermoon); yet, such events are very likely to increase in frequency and severity as sea-level continues to rise.  Whether or not future storm patterns change over the next century, the impact that rising average water levels will have on such extreme events is well recognized.  A study focusing on Australian sea-level stations estimated that an increase of 10 cm (about 4 inches) in average water level corresponds to a threefold increase in the frequency of extreme events on average (Hunter, 2012).  Thus, an increase of 20 cm (about 8 inches) will mean that what is currently a 100-year inundation event will become a 10-year event on average. The picture is clear—cities and villages on low-lying islands such as the Marshalls will be at heightened risk for severe flooding in the future.

Majuro residents will tell you that the increasing frequency of these situations and the effects of sea-level rise are already visible. In places where the coastline is eroding, trees and plants are removed as a result, and the waves have an easier time coming up. Coastal erosion is a natural long-term, dynamic process; however, sea-level rise is increasing the rate of erosion in many places, and loss of land at the shoreline is evident. As infrastructure becomes threatened, more and more structures to protect land from the ocean (seawalls, rubble mounds, etc.) are being built on Majuro, and seawalls now cover nearly the entire coastline of Majuro city and the eastern part of the atoll. While seawalls can protect against more minor high tide events, they may be overtopped by waves in more extreme events, as they were on Tuesday.  Seawalls, in fact, can accelerate erosion of nearby beaches by disturbing natural coastal processes that transport beach sediment along the shoreline and by increasing the force of waves due to wave reflection off the seawall.  Thus, there are obvious limits to this kind of protective structure as a long-term solution.

As low-lying islands face a wide range of impacts due to increased water levels and the possibility of more frequent extreme inundation events, places like RMI will require assistance from other governments and the international community in order to appropriately address the near-term and long-term threats.  The U.S. Congress is currently debating an immigration reform bill, and Senator Brian Schatz of the State of Hawai‘i has proposed an amendment that would give a legal status to people displaced by climate change.  The amendment would allow the U.S. government to designate individuals or groups of individuals displaced permanently by climate change as stateless persons, identifying climate change, like war, as a potential major cause of homelessness in the world.  This move both signifies the severity of the problem that island countries are facing, and recognizes that now is the time for Pacific Islands together with other governments to put in place measures to prepare for a possibly not-so-distant future when such legal structures, as well as broader adaptation policies, will be needed.

References

Huang, T. and Rapp, H. (2010). Coastal Erosion on Majuro Atoll : Marshall Islands with Special Regard to Sea-Level Rise (Master thesis). Available from Division of Water Resources Engineering, Department of Building and Environmental Technology, Lund University, http://www.lunduniversity.lu.se/o.o.i.s?id=24965&postid=1670491

Hunter, J. (2012). A simple technique for estimating an allowance for uncertain sea-level rise. Climate Change, 113(2), 239-252. doi:10.1007/s10584-011-0332-1

Johnson, G. (2013, June 26). Marshalls capital inundated by high tide. Marianas Variety, Regional News, Palau/Pacific News. Retrieved from http://www.mvariety.com/index.php/regional-news/palaupacific-news/56955-marshalls-capital-inundated-by-high-tide

Keener, V.W., Marra, J.J., Finucane, M.L., Spooner, D., & Smith, M.H. (Eds.). (2012).  Climate Change and Pacific Islands:  Indicators and Impacts.  Report for the 2012 Pacific Islands Regional Climate Assessment.  (Chapter  3: Sea Level and Coastal Inundation on Pacific Islands.) Washington, DC: Island Press. Available from www.PacificRISA.org/projects/PIRCA.

Leber, R. (2013, June 20). Amendment Would Give Legal Status To People Displaced By Climate Change. Message posted to http://thinkprogress.org/immigration/2013/06/20/2187831/climate-refugee-immigration-bill/?mobile=nc

Pope, T. (2013, June 25). Marshall Islands bracing for more destructive seas. Australia Network News. Retrieved from http://www.abc.net.au/news/2013-06-25/an-marshall-islands-braced-for-more-flooding/4779164