One Meter Topobathymetric Digital Elevation Model for Majuro Atoll, Republic of the Marshall Islands, 1944-2016.

Located in the western Pacific Ocean, Majuro is a large coral atoll consisting of a large, central narrow land mass and remote islands that are part of the Republic of the Marshall Islands. The waters surrounding the Majuro Atoll land areas are relatively shallow with poorly mapped bathymetry. However, the Pacific Ocean on the exterior of the coral atoll and the lagoon within its interior consist of deep bathymetry with steep elevation gradients. Thus, the low-lying Majuro Atoll is extremely vulnerable to sea-level rise, tsunamis, storm surge, coastal flooding, and climate change that could impact the sustainability of the infrastructure, groundwater, and ecosystems. The highest elevation of the Majuro Atoll is estimated at only 3-meters above sea level, which is the island community of Laura located on the western part of the atoll. At the eastern edge of the atoll lies the capital city of Majuro with the island community of Djarrit located in the northeast part of the atoll. To support the modeling of storm- and tide-induced flooding, the USGS Coastal National Elevation Database (CoNED) Applications Project has created an integrated 1-meter topobathymetric digital elevation model (TBDEM) for the Majuro Atoll, Republic of the Marshall Islands. High-resolution coastal elevation data are required to identify flood, hurricane, and sea-level rise inundation hazard zones and for other earth science applications, such as storm-surge models. The new Majuro TBDEM consists of the best available multi-source topographic and bathymetric elevation data for the Majuro Atoll onshore and offshore areas. The Majuro TBDEM integrates nine different data sources, including unmanned aircraft systems (UAS) imagery, Structure from Motion (SfM) derived topography, real-time kinematic (RTK) GNSS survey points, Satellite-Derived Bathymetry (SDB) using USGS Landsat 8 (L8) and DigitalGlobe WorldView-3 (WV-3) imagery, South Pacific Applied Geoscience Commission (SOPAC) bathymetry, hydrographic surveys, single-beam acoustic surveys, multi-beam acoustic surveys, and chart soundings obtained from the National Geospatial Intelligence Agency (NGA) and the Naval Oceanographic Office. The topographic and bathymetry surveys were sorted and prioritized based on survey date, accuracy, spatial distribution, and point density to develop a TBDEM model based on the best available elevation data. Because bathymetric data are typically referenced to Mean Low Water Springs or Mean Low Water, all bathymetric heights were adjusted to Local Mean Sea Level. The grid spacing is 1 meter and includes the Majuro Atoll, exclusive of some northern islands, extending offshore to a depth of at least 71 meters in the lagoon. The temporal range of the input topography and bathymetry is 1944 to 2016. Additional information regarding the CoNED Applications Project is located at https://topotools.cr.usgs.gov/coned/index.php.