Quantitative Inundation Exposure Assessment for Majuro Atoll
Dates
Start Date
2018-03-07
End Date
2018-09-30
Release Date
2017
Summary
With an average elevation of just seven feet above sea level, the Republic of the Marshall Islands is acutely vulnerable to inundation from both episodic events such as storm surge and chronic conditions such as sea-level rise. Some projections estimate that future sea-level rise could exceed the average elevation of these islands by 2100. Already, residents are facing extreme high tides and 16 foot swells that flood the islands with saltwater, damaging homes and infrastructure and contaminating the freshwater supply. Land elevation is the primary factor that determines the vulnerability of coastal areas to inundation. This project builds on previous work in which a 1-meter resolution digital elevation model (DEM) was developed for [...]
Summary
With an average elevation of just seven feet above sea level, the Republic of the Marshall Islands is acutely vulnerable to inundation from both episodic events such as storm surge and chronic conditions such as sea-level rise. Some projections estimate that future sea-level rise could exceed the average elevation of these islands by 2100. Already, residents are facing extreme high tides and 16 foot swells that flood the islands with saltwater, damaging homes and infrastructure and contaminating the freshwater supply.
Land elevation is the primary factor that determines the vulnerability of coastal areas to inundation. This project builds on previous work in which a 1-meter resolution digital elevation model (DEM) was developed for Majuro Atoll, home to the capital and largest city in the Marshall Islands. Researchers will use this DEM to map areas of Majuro Atoll that are vulnerable to inundation, based on different water level scenarios. For example, these maps can be used to answer the question of which areas would flood should seas rise by 0.4, 0.8, or 1 meter, and will represent the first detailed assessment of sea-level rise vulnerability for Majuro.
The results of this project will support assessments of how future inundation events could impact ecosystems, infrastructure, the freshwater supply, and agroforestry on Majuro Atoll. This much-needed information will provide government authorities and local community groups with an improved understanding of the types of actions needed to prepare for future inundation and an estimated timeline for when these actions would best be implemented.
Low-lying island environments, such as Majuro Atoll in the Republic of the Marshall Islands, are particularly 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). Land elevation is the primary geophysical variable that determines exposure to inundation in coastal settings. Accordingly, coastal elevation data are a critical input for assessments of inundation exposure and vulnerability.
This work encompasses conducting a quantitative assessment of inundation exposure for Majuro Atoll. This effort will employ a recently produced and validated high-resolution, high-accuracy topobathymetric digital elevation model (TBDEM) covering Majuro Atoll (Palaseanu-Lovejoy et al., 2017). Established methods (Gesch, 2009; Gesch 2013) will be implemented to map and characterize areas subject to marine inundation and groundwater inundation (Rotzoll and Fletcher, 2013). Spatially explicit results of the exposure assessment will be displayed as graphics of locations under specific inundation (water level) scenarios. Statistics will be reported at specific confidence levels in recognition of the inherent uncertainty in such elevation-based analyses. Results derived from other less accurate elevation models will also be presented to demonstrate the substantial value of high-resolution, high-accuracy DEMs for assessing vulnerability of low-relief islands and their population, buildings, and infrastructure.
Project Extension
parts
type
Technical Summary
value
Low-lying island environments, such as Majuro Atoll in the Republic of the Marshall Islands, are particularly 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). Land elevation is the primary geophysical variable that determines exposure to inundation in coastal settings. Accordingly, coastal elevation data are a critical input for assessments of inundation exposure and vulnerability. Previous research has demonstrated that the quality of data used for elevation-based assessments must be well understood and applied to properly model potential impacts. The vertical uncertainty of the input elevation data controls to a large extent the increments of water level increase and planning horizons that can be effectively used in an assessment. Recent high-resolution elevation data along the coast exhibit high vertical accuracy, and thus have become indispensable for assessments, whether a simple inundation model is used or a more sophisticated process-based or probabilistic model is employed. When properly characterized, the vertical accuracy of the high-resolution, high-accuracy elevation data can be used to generate maps and report assessment results with the uncertainty stated in terms of a specific confidence level. This work encompasses conducting a quantitative assessment of inundation exposure for Majuro Atoll, including rigorous accounting for the cumulative vertical uncertainty in the input geospatial data (elevation model) and data processing (datum transformations). This effort will employ a recently produced and validated high-resolution, high-accuracy topobathymetric digital elevation model (TBDEM) covering Majuro Atoll (Palaseanu-Lovejoy et al., 2017). Established methods (Gesch, 2009; Gesch 2013) will be implemented to map and characterize areas subject to marine inundation and groundwater inundation (Rotzoll and Fletcher, 2013). Spatially explicit results of the exposure assessment will be displayed as graphics of locations under specific inundation (water level) scenarios. Statistics will be reported at specific confidence levels in recognition of the inherent uncertainty in such elevation-based analyses. Results derived from other less accurate elevation models will also be presented to demonstrate the substantial value of high-resolution, high-accuracy DEMs for assessing vulnerability of low-relief islands and their population, buildings, and infrastructure. Project results will be delivered as a USGS data release (for GIS datasets of inundation maps) and in a peer-reviewed journal publication.