Why elevation data matter
Accurate elevation data support forestry, wildlife, national security, recreation and much more. In Delaware they are critical for agriculture and precision farming, river and stream management, conservation, flood risk, coastal zone management, geologic hazards and other business uses. Today lidar (light detection and ranging) is the main source, and federal, state, tribal and local agencies partner to replace old, lower-quality data and fill gaps with consistent, public, statewide coverage.
The 3D Elevation Program
The National Enhanced Elevation Assessment (NEEA) found the best benefit/cost from quality level 2 lidar for the conterminous United States (and quality level 5 radar for Alaska) on a 6- to 10-year cycle. The USGS-led 3D Elevation Program (3DEP) chose an 8-year cycle, aiming for national coverage by 2022, depending on funding and partners.
| Quality level | Pulse spacing (m) | Vertical error (cm) |
|---|---|---|
| 1 | 0.35 | 10 |
| 2 | 0.7 | 10 |
| 3 | 1.4 | 20 |
| 4 (radar) | n/a | 139 |
| 5 (radar) | n/a | 185 |
Nationally, 3DEP could conservatively bring $1.2 billion a year in new benefits, and potentially $13 billion, from better government services, fewer crop and flood losses, more efficient vehicle routing and more. A funded national program brings:
- economies of scale — about 25 percent lower costs over larger areas;
- a systematic plan that cuts the cost of "buying up" to higher quality;
- consistent national data across state and watershed lines;
- more federal contribution and less from state and local partners;
- ready contracts and published specifications.
What it means for Delaware
| Expected annual benefits | $680 thousand |
| Estimated total cost | $671 thousand |
| Payback | 1.0 year |
| Benefit/cost ratio over 8 years | 8.1 to 1 |
| Quality level 1 buy-up | $427 thousand |
Since not every benefit was given a dollar figure, the true total is likely much higher. About 80 percent of requirements come from four uses:
| Rank | Business use | Annual benefits (thousands) |
|---|---|---|
| 1 | Agriculture and precision farming | $209.3 |
| 2 | River and stream resource management | 148.7 |
| 3 | Natural resources conservation | 93.7 |
| 4 | Flood risk management | 92.7 |
| 5 | Coastal zone management | 42.8 |
| 6 | Sea level rise and subsidence | 42.3 |
| 7 | Infrastructure and construction management | 18.0 |
| 8 | Water supply and quality | 9.5 |
| 9 | Aviation navigation and safety | 7.2 |
| 10 | Forest resources management | 6.6 |
| Other | 8.9 | |
| Total | 679.7 |
Publicly available lidar in Delaware: the whole state has quality level 2 or better. USGS, from the U.S. Interagency Elevation Inventory (June 2014).
Current coverage: lidar for all three counties was collected in early 2014, paid for with Hurricane Sandy relief funds.
Examples
- Flood risk: statewide lidar cuts field-survey costs and supports detailed modeling of flooding from storms and coastal storm surge. The Delaware Coastal Flood Monitoring System relies on the elevation model to show real-time inundation, helping plan evacuation routes.
- Farming: about 41 percent of Delaware's land is agricultural. Better terrain data improve precision farming — higher yields, less soil loss and less chemical runoff.
Next steps: more partnerships among governments, acquisitions over larger areas to 3DEP specifications, and wider awareness and support. More: nationalmap.gov/3DEP.
Sources
Based on William J. Carswell, Jr., "The 3D Elevation Program—Summary for Delaware," U.S. Geological Survey fact sheet; a work of the United States government in the public domain. The map and tables are taken from the fact sheet's PDF; its screenshot of the Delaware Coastal Flood Monitoring System, from the Delaware Geological Survey, is left out.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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