A Rapid Assessment of Kili Island - Sea Grant College Program

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Between April 2009 and August2011 a wave buoy deployedoff Delap point, Majuro 4 . Thisbuoy, deployed as part of aNational Science Foundationproject lead by the Universityof Hawai‘i provides real-timemeasurements of ocean waves.The buoy is directional, whichmeans not only does it measurethe height and period of thewaves, but also the directionthe waves are coming from.Calculations can also determineif waves from multipledirections are impacting thebuoy. For example a storm inthe north Pacific might generatea northerly swell with a periodof 15 seconds at the same timeFigure 9. Output of Wave Watch 3 wave model on 1/20/2011 18:00 showing moderate as locally generated wind wavesnorth north-westerly swell.coming from the east with adifferent period. The wave buoy provides a means for calculating the wave heights and transmitting thisinformation to the users on the internet.Between January 20 th and the 22 nd the wave conditions in Majuro (and assumed for Kili) werecharacterized by long-period swell waves approaching from the north (Figure 10). Wave heightswere not unusually high during the period of flooding, although Hs 5 peaked at over 2.0 m on severaloccasions.Figure 10. Wave height and peak period between 12:30 pm on 1/20/2011 and 12 pm on 1/22/2011. Wave conditions were characterizedby long period waves between 1.5 m and 2.0 m. Long period waves are generally generated from distant weather events and are morelikely to cause inundation than short period waves.5
SummaryThe sea level during the January 2011 inundation event was unusually high, probably amongst thehighest non-storm driven sea level encountered within the recent history of Kili. Seasonally highastronomical tides were further amplified by La Niña conditions. At the time of the inundation waveconditions were moderately energetic, while not an unusual or rare event, when all climate andoceanographic factors occur in unison sea level at Kili was elevated to a level that result in widespreadinundation.Physical Impacts of January 2011Inundation EventConsultations with the community suggest waves breached the low point in the island ridge on thenorthwestern section of the island and proceeded to inundate areas to the east extending as far as theairport runway. Historically, a low, swampy area existed in areas of the central core of the island, similarto that seen on other reef platform islands such as Jabat. It appears water entered through the breachand proceeded to raise the water level of the swamp which in turn flooded low-lying areas. The area ofoverwash is characterized by the deposit of sand gravel washed from the reef, beach and island ridge onto the island surface (Figures 11 and 12).No accurate quantitative measures of the vertical flood level or spatial extent of flooding were madeat the time of the event. However, community consultations indicate large areas of the island wereinundated as a result of salt water incursion through the swamp in the northwest section of Kili. InOctober, 2011 a follow up event assessment was undertaken using a community-based, scientificassessment to map the extent of the flooded area. Such an approach is quick, simple and utilizes thecollective experience of community to provide powerful information after an event.Figure 11. Large area of overwash on the NW side of Kili. Coral rubble and debris were washed as far as 60 m from the island ridge.This low point in the island is likely the historic channel between the swamp and the reef flat; as a result, it is a highly vulnerable tobreaching during high tides and wave events. Direction of flood water indicated by red arrow.MethodologyLarge satellite image prints of Kili were presented to small groups (2-5 people) of the communitymembers who were present on Kili during the January 2011 inundation event. Community memberswere instructed to shade the areas of the island they recalled were flooded during the January 2011event. Typically the groups discussed the event at length and appointed one member to draw on thesatellite image with the collective agreement of the group. In total 15 groups were interviewed for theassessment. Resultant outputs were photographed for later analysis (Figure 13A).6
Page 3 and 4: Executive SummaryKili is one of fiv
Page 5 and 6: Figure 2. Aerial photo of Kili, 194
Page 10 and 11: Photographs were then loaded within
Page 12 and 13: Figure 15. Location of elevation me
Page 14 and 15: Figure 17. Generalized contouring o
Page 16: Table 1. A generalized comparison o
Page 19 and 20: ANNEX 2A Simple Plan for Inundation
Page 22 and 23: References1Measured using the edge

A Rapid Assessment of Kili Island - Sea Grant College Program

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