Publicly available lidar in Vermont, March 2015. USGS, from the U.S. Interagency Elevation Inventory.
Why elevation data matters
In Vermont, elevation data matter most for hazard mitigation and geologic assessment, conservation, agriculture, flood risk management and infrastructure. Federal, state, tribal and local agencies work together to replace older lidar and fill gaps, aiming for consistent statewide coverage.
By the numbers
| Expected annual benefits | $1.63 million |
| Estimated total cost | $3.21 million |
| Payback | 2.0 years |
| Benefit/cost ratio (8 years) | 4.1 to 1 |
| Cost to buy up to quality level 1 | $2.04 million |
About 83% of the identified needs fall in geologic hazards, conservation, agriculture and flood risk management; since not every benefit had a dollar value, the true total is likely higher.
| Rank | Business use | Annual benefits (thousands) |
|---|---|---|
| 1 | Geologic resource assessment and hazard mitigation | $417 |
| 2 | Natural resources conservation | 378 |
| 3 | Agriculture and precision farming | 326 |
| 4 | Flood risk management | 236 |
| 5 | Infrastructure and construction management | 84 |
| 6 | Forest resources management | 83 |
| 7 | Water supply and quality | 69 |
| 8 | Aviation navigation and safety | 29 |
| 9 | River and stream resource management | 4 |
| 10 | Renewable energy resources | 3 |
| Other | 6 | |
| Total | 1,635 |
How lidar helps Vermont
Landslides and aquifers. Detailed lidar improves surficial geologic mapping, used to find landslides and to assess resources such as sand and gravel aquifers. As a headwater state, Vermont has landslides in every part of it — the fact sheet shows one on Great Brook in Plainfield threatening a house and garage. As of 2015, statewide landslide data came mostly from old, coarse topographic maps; lidar reveals landslide-prone areas they missed.
Conservation. With statewide high-quality lidar, public and private groups could plan and engineer more from the desk, with less fieldwork, for conservation ponds, grassed waterways, pipelines, terracing, runoff estimates, finding drained historic wetlands and wetland restoration.
After Irene. Following Tropical Storm Irene, lidar is critical for setting new baseline elevations to manage flooding and stream erosion, supporting infrastructure planning, hazard mitigation and, sometimes, emergency response.
About 3DEP
The National Enhanced Elevation Assessment (Dewberry, 2011) found the best return from quality level 2 lidar for the conterminous United States and quality level 5 radar (ifsar) for Alaska, refreshed every 6 to 10 years; 3DEP chose an 8-year cycle. The USGS runs it as the federal lead for land elevation data.
| Quality level | Pulse spacing | Vertical error (RMSEz) |
|---|---|---|
| QL1 | 0.35 m | 10 cm |
| QL2 | 0.7 m | 10 cm |
| QL3 | 1.4 m | 20 cm |
| QL4 | — | 139 cm |
| QL5 (radar, Alaska) | — | 185 cm |
- Goal: complete national coverage by the end of 2022, depending on funding and partners.
- Value: conservatively $1.2 billion a year nationally, with the potential for $13 billion a year.
- Why a national program: larger purchases cut costs by 25%; buying high quality once avoids paying to "buy up" later; consistent data across state and watershed lines; more federal money reduces state and local shares; and ready contracts and specifications simplify buying.
Sources
Based on William J. Carswell, Jr., "3D Elevation Program: summary for Vermont," U.S. Geological Survey Fact Sheet 2015–3002, version 1.1 (2015); a work of the United States government in the public domain. The map and tables are taken from the fact sheet's PDF; its landslide photograph, courtesy of Norwich University, is not reproduced. Benefit figures come from Dewberry's National Enhanced Elevation Assessment (2011, revised 2012).
许可协议： CC0 1.0（公有领域） · 改编自 pubs.usgs.gov
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