We developed satellite-derived bathymetry and benthic habitat and hydrodynamic roughness maps for Kwajalein Atoll in the Republic of the Marshall Islands. These products are supporting a modelling effort led by the U.S. Geological Survey (Pacific Coastal and Marine Science Center) to examine the impacts of sea level rise and climate change on Department of Defense installations on atolls in the Pacific Ocean.

Why We Care
In many areas throughout the world, reliable, up-to-date bathymetry, or submarine topography, is difficult or impossible to find. Even in developed countries like the United States, cost restrictions usually limit updating bathymetry to areas directly related to shipping. For areas not related to shipping, it is common to see bathymetric charts and data that have not been updated since the late 1800s. Improving satellite-derived bathymetry protocols can provide useable bathymetry for areas that cannot gain access to higher resolution bathymetry generated by technologies like multibeam sonar or airborne LIDAR.

The Department of Defense is charged with maintaining and protecting installations on atolls in the Pacific Ocean. Current maps of coastline and bathymetry are essential to this mandate. Satellite-derived bathymetry and benthic habitat and hydrodynamic roughness maps are crucial components of the U.S. Geological Survey’s geospatial models that provide new understanding of the potential effects of global sea level rise and climate change on these remote atoll and island states. The models can help identify which atolls and islands are most vulnerable to sea level rise.

What We Did

• During a field mission to Kwajalein Atoll in April 2014 we collected tide-corrected depth information to build the satellite-derived bathymetry and assess its accuracy and collected underwater video to aid in developing the benthic habitat map.
• We developed a satellite-derived bathymetry product, derived from imagery from the commercial WorldView-2 and -3 satellites, for the area around Roi-Namur, the northernmost tip of the Kwajalein Atoll.
• We developed a benthic habitat map for the Roi-Namur area using a combination of semi-automated and manual image processing techniques on the same WorldView-2 and -3 imagery.
• We developed a hydrodynamic roughness map by assigning friction coefficients derived from the literature to the individual classes from the benthic habitat map.

Next Steps
We are doing additional runs with the satellite-derived bathymetry models to try to determine the minimum field data required to produce reliable satellite-derived bathymetry products. Reducing field mission length will drastically lower costs of providing up-to-date bathymetry products for these remote locations.