Detailed Elevation Data for Puerto Rico: The 3D Elevation Program

Elevation data serve a huge range of uses: forestry, wildlife and habitat management, research, national security, recreation and many more. For Puerto Rico they are critical for flood risk management, landslide mitigation, conservation, sea-level rise and subsidence, coastal zone management, and infrastructure and construction. Today, dense lidar (light detection and ranging) data are the main source for elevation models, and federal, state, Tribal, territorial and local agencies work together to replace old, lower-quality data and cover places with no public data, aiming for consistent, island-wide coverage.

The 3D Elevation Program

The National Enhanced Elevation Assessment (NEEA, Dewberry, 2011) weighed data quality and replacement cycles against cost. The best benefit-to-cost ratio came from lidar at quality level 2 for the conterminous United States, Hawaii and selected U.S. territories, and radar (IfSAR) at quality level 5 for Alaska, renewed every 6 to 10 years. The 3D Elevation Program (3DEP), managed by the U.S. Geological Survey, the lead federal agency for land elevation data, chose an 8-year cycle, and aims to cover the country with quality level 2 or better data, made public, to serve government and private uses alike.

Nationally, 3DEP could conservatively bring new benefits of $1.2 billion a year, and potentially $13 billion, through better government services, fewer crop and home losses from floods, more efficient vehicle routing and much else. Its goal was complete U.S. coverage by the end of 2022, depending on funding and partners. A funded national programme brings economies of scale (larger areas cut costs by 25 percent), a systematic plan that avoids costly "buy-ups" to higher quality, consistent data across boundaries, larger federal contributions, and ready-made contracts and specifications.

Benefits for Puerto Rico

NEEA respondents in Puerto Rico estimated at least $0.53 million a year in new benefits; because several major benefits were not given a money value, the real total is probably much higher. About 84 percent of the identified needs fall in four uses: flood risk management, natural resources conservation, sea-level rise and subsidence, and coastal zone management.

Existing and planned-with-funding public lidar for Puerto Rico, fall 2015; about 95 percent of the quality level 2 data was planned with funding. Source: United States Interagency Elevation Inventory. USGS.

Lidar with planned funding will be collected at quality level 2 where current airborne technology allows; dense vegetation may reduce accuracy in parts of the islands.

How the data help

• Hazards. Accurate bare-earth elevation models support modelling of water resources, sea-level rise and storm surge, and the vulnerability of shallow tidal habitats to climate change, and let agencies plan for the risks that hurricanes, tsunamis, storm runoff, sea-level rise, landslides, debris flows and storm surge pose to coastal resources, buildings, transport and cultural sites.
• Beaches. Better assessment of beach shape and sand volume could reveal shrinking sand budgets that bring more erosion and put infrastructure, property and lives at risk.
• Coast. Elevation data on the current vertical datum (NAVD 88, GEOID 12B) would allow seamless bathymetry-to-topography coverage of the coast, for modelling sea-level rise, storm surge and wave run-up.

Tracks of a sample of hurricanes that affected Puerto Rico between 1852 and 1998, coloured by Saffir-Simpson category from blue (category 1) to red (category 5); arrowheads show direction. Large storms can reshape the land. Graphic by Sheila Murphy, USGS, from NOAA Coastal Services Center data.

Next steps

Reaching national coverage in 8 years depends on more partnerships among federal, state, Tribal, territorial and local governments; partnerships that buy data to program specifications over larger areas; wider awareness of the program; and support from government and other stakeholders.

Sources

• William J. Carswell, Jr., The 3D Elevation Program—Summary for Puerto Rico, USGS Fact Sheet 2015–3088, February 2016. https://doi.org/10.3133/fs20153088
• Dewberry, Final Report of the National Enhanced Elevation Assessment (2011, revised 2012); G. I. Snyder, National Enhanced Elevation Assessment at a Glance and The 3D Elevation Program—Summary of Program Direction, USGS Fact Sheets 2012–3088 and 2012–3089.
• The maps and tables are taken from the fact sheet's PDF.