The 3D Elevation Program in Connecticut: $4.4 Million a Year in Benefits

High-resolution elevation data could bring Connecticut at least $4.4 million a year in new benefits, according to users surveyed for the National Enhanced Elevation Assessment, for a statewide programme costing about $1.7 million: a payback period of 0.4 year and a benefit-cost ratio of 21 to 1 over 8 years.

Why elevation data

Elevation data serve forest and wildlife management, national security, recreation and much more. In Connecticut they are critical for coastal zone management, flood risk management, natural resources conservation, precision farming, sea level rise and subsidence, and other uses. High-density lidar (light detection and ranging) is now the main source of elevation models. Federal, state, tribal and local agencies work together to replace old, lower-quality data and fill gaps, aiming for consistent statewide coverage.

Publicly available lidar data in Connecticut (United States Interagency Elevation Inventory, June 2014, updated annually). Quality level 2 or better meets 3DEP requirements. USGS.

The national programme

The National Enhanced Elevation Assessment weighed options against cost and found that quality level 2 lidar for the conterminous United States and quality level 5 radar (ifsar) for Alaska, collected every 6 to 10 years, gave the best return. The USGS-managed 3D Elevation Program (3DEP) chose an 8-year cycle and aims to cover the whole country by the end of 2022, depending on funding and partners. Nationally it could conservatively bring $1.2 billion a year in new benefits, and potentially $13 billion, through better government services, fewer crop and flood losses, more efficient vehicle routing and more.

A funded national programme brings economies of scale (larger areas cut costs by 25 percent), cheaper "buy-ups" to the higher quality some states and localities need, consistent data across state and watershed lines, more federal funding in place of state and local shares, and ready contracts and specifications.

Benefits for Connecticut

About 83 percent of identified needs lie in coastal zone management. Better elevation data allow more accurate models of the risks of sea level rise and storm surge and of how vulnerable shallow tidal habitats are to climate change, helping plan for coastal resources, buildings, transport and cultural sites threatened by storm runoff, rising seas and surges. Better measurement of beaches and sand volume could also spot shrinking sand budgets that threaten erosion and endanger property and lives. Since not every benefit was given a dollar value, the true total is likely much higher.

Next steps

Reaching national coverage in 8 years depends on more partnerships among federal, state, tribal and local governments; partners acquiring data to the programme's standards over larger areas; better awareness of the programme's benefits; and support from governments and other stakeholders. More: nationalmap.gov/3DEP.

Sources

• William J. Carswell, Jr., The 3D Elevation Program—Summary for Connecticut, U.S. Geological Survey Fact Sheet 2015–3036. https://pubs.usgs.gov/publication/fs20153036
• A photograph from the Connecticut Department of Energy and Environmental Protection, of a house in Lyme overturned by erosion, is not reproduced here.