Map data showing concentration of landslides caused by Hurricane Maria in Puerto Rico

On September 20, 2017, Hurricane Maria hit the U.S. territory of Puerto Rico as a category 4 storm. Heavy rainfall caused landslides in mountainous regions throughout the territory. This data release presents geospatial data describing the concentration of landslides generated by Hurricane Maria in Puerto Rico. We used post-hurricane satellite and aerial imagery collected between September 26, 2017 and October 8, 2017 to visually estimate the concentration of landslides over nearly the whole territory. This was done by dividing the territory into a grid with 4 square km cells (2 km x 2 km). Each 4 square km grid cell was classified as either containing no landslides, fewer than 25 landslides/ square km or more than 25 landslides/ square km. We used 12 WorldView satellite images (~0.5 m-resolution) available from Digital Globe, Inc. and ~0.15 m-resolution aerial imagery collected by Sanborn and QuantumSpatial (http://www.arcgis.com/home/item.html?id=b1949283c1084b0daf2987d896392ac2). We identified landslides by locating areas with exposed soil or rock and morphology typical of landslides. Because leaves were stripped from much of the vegetation, landslide scars were readily visible in both sources of imagery. We assume that the majority of landslides were triggered by rainfall from Hurricane Maria, but rainfall from Hurricane Irma during the first week of September and rainfall from thunderstorms after Hurricane Maria may have also initiated landslides.

During this investigation, we visually examined a total area of 8103 square km, which encompassed most of the territory and nearly all the mountainous areas. Approximately 846 square km of the land area of the territory was not examined because either 1) imagery was unavailable or 2) the area was obscured by cloud cover. Approximately 61% of the examined area was unaffected by landslides. Landslides were observed in the remaining 39% of the examined area, but, for the most part, the landslide concentration was less than 25 landslides/ square km (37% of the examined area). Landslide concentration was greater than 25 landslides/ square km in about 2% of the examined area (156 square km), which includes parts of the Aasco, Mayagez, Las Maras, Maricao, Lares, Utuado, Adjuntas, and Jayuya municipalities. Based on visual examination of imagery, the municipality of Utuado appears to have been the most severely impacted, with about 40% of the municipality having a concentration of landslides greater than 25 landslides/ square km. This preliminary assessment serves to inform response and recovery efforts and as a basis for more detailed studies on the impacts of landslides in Puerto Rico caused by Hurricane Maria.

The data included in this release are: 1) a polygon shapefile (.shp) that classifies each 2 km x 2 km grid cell based on landslide concentration, and 2) a layer file (.lyr) that can be used to display the landslide concentration data. We also included a map showing the landslide concentration grid and the legal municipalities of Puerto Rico. A list of the municipality abbreviations used on the map and the corresponding municipality names are included in the attached Excel file. This data release only includes landslide concentrations mapped from satellite and aerial imagery, not the imagery itself.