Sea-level Rise Vulnerability of Contiguous U.S. Coastal Beaches

by Lis Fano

This web map visualizes the relative susceptibility of coastal beaches to sea-level rise through the use of a coastal vulnerability index (CVI). The initial classification used in the CVI is based upon the following variables: geomorphology, regional coastal slope, tide range, wave height, relative sea-level rise and shoreline erosion and accretion rates. The combination of these variables and the association of these variables to each other furnish a broad overview of beaches where physical changes are likely to occur due to sea-level rise. Additional CVI information can be found at the National Assessment of Coastal Change Hazards website.

Data Sources

Data for this project were obtained from the USGS Coastal Change Hazards Portal and the U.S. Board on Geographic Names GNIS.

Data Processing Steps

• Using Node.js to filter the beach data from the rest of the GNIS data: process-beaches.js

• Buffer PACIFIC.shp, ATLANTIC.shp, and GULF.shp polylines to polygons:

ogr2ogr -f "ESRI Shapefile" -dialect SQLite -sql "select SEA_LEVEL, SLOPE, TIDES, WAVES, EROSION, GEOMORPH, CVI, ID_COAST, ST_Buffer(geometry, .05) from PACIFIC" PAC-buffer.shp PACIFIC.shp

ogr2ogr -f "ESRI Shapefile" -dialect SQLite -sql "select SEA_LEVEL, SLOPE, TIDES, WAVES, EROSION, GEOMORPH, CVI, ID_COAST, ST_Buffer(geometry, .05) from ATLANTIC" ATL-buffer.shp ATLANTIC.shp

ogr2ogr -f "ESRI Shapefile" -dialect SQLite -sql "select SEA_LEVEL, SLOPE, TIDES, WAVES, EROSION, GEOMORPH, CVI, ID_COAST, ST_Buffer(geometry, .05) from GULF" GULF-buffer.shp GULF.shp

• Combine/merge the three shapefiles:

mapshaper -i PAC-buffer.shp ATL-buffer.shp GULF-buffer.shp combine-files -merge-layers -o CVI-merge.shp

• Convert the US-beaches.json to shapefile to perform a spatial join with the merged CVI polygons:

ogr2ogr -f "ESRI Shapefile" US-beaches.shp US-beaches.json  

• Perform the spatial join by location (point in polygon):

mapshaper US-beaches.shp -join CVI-merge.shp -o US-beaches-join.shp

• Remove the non-coastal beach points where join is null:

ogr2ogr -f "ESRI Shapefile" -where "CVI is not null" all-beaches.shp US-beaches-join.shp

• Convert the shapefile to json:

mapshaper all-beaches.shp -o precision=.00001 format=geojson all-beaches.json

• Build the web map using the all-beaches.json file.