Abstract
Majuro Atoll in the central Pacific has high coastal vulnerability due to low-lying islands, rising sea level, high wave events, eroding shorelines, a dense population center, and limited freshwater resources. Land elevation is the primary geophysical variable that determines exposure to inundation in coastal settings. Accordingly, coastal elevation data (with accuracy information) are critical for assessments of inundation exposure. Previous research has demonstrated the importance of using high-accuracy elevation data and rigorously accounting for uncertainty in inundation assessments. A quantitative analysis of inundation exposure was conducted for Majuro Atoll, including accounting for the cumulative vertical uncertainty from the input digital elevation model (DEM) and datum transformation. The project employed a recently produced and validated DEM derived from structure-from-motion processing of very-high-resolution aerial imagery. Areas subject to marine inundation (direct hydrologic connection to the ocean) and low-lying lands (disconnected hydrologically from the ocean) were mapped and characterized for three inundation levels using deterministic and probabilistic methods. At the highest water level modeled (3.75 ft, or 1.143 m), more than 34% of the atoll study area is likely to be exposed to inundation (68% chance or greater), while more than 20% of the atoll is extremely likely to be exposed (95% chance or greater). The study demonstrates the substantial value of a high-accuracy DEM for assessing inundation exposure of low-relief islands and the enhanced information from accounting for vertical uncertainty.
Highlights
IntroductionLow-lying islands are vulnerable to inundation (coastal flooding), whether the increased water levels are from episodic events (storm surge, wave run-up, king tides) or from chronic conditions (long-term sea-level rise)
Low-lying islands are vulnerable to inundation, whether the increased water levels are from episodic events or from chronic conditions
The vertical uncertainty of the local geoid model is estimated at 0.061 m [64], which is the standard deviation of the differences between the predicted point values and the actual point values derived from cross validation of the results of empirical Bayesian kriging used to generate the geoid surface [13]
Summary
Low-lying islands are vulnerable to inundation (coastal flooding), whether the increased water levels are from episodic events (storm surge, wave run-up, king tides) or from chronic conditions (long-term sea-level rise). Atolls are vulnerable to the effects of sea-level rise in the form of. Atolls are vulnerable to the effects of sea-level rise in the 2foorf m20 of shoreline erosion, inundation, and saltwater intrusion into fresh groundwater [1]. Coastal vulnerability is inherently spatial, and this geographic dependence requires that risk assessments of places, people, and assets be llooccaattion ssppeecciifificc [[1111]]. For such aassessments, mapping and characterization of physical hazards are critical, and the need is great for ddeettailed, localized analyses rather than more general coarse-scale assessments [6]. Detailed knowledge of the topography is essential for assessing coastal inundation exposure, especially on low-lyiinngg llaannddss,, and the lack of suitable elevation data has been notedd [[1,,1122––1144]]
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