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Publicly available lidar in Arizona, June 2014. Quality level 2 or better meets 3DEP's requirements. USGS, from the U.S. Interagency Elevation Inventory.
In 2014, almost none of Arizona had public, high-quality lidar — the laser-scanned elevation data now used to build terrain models. The USGS 3D Elevation Program (3DEP) aims to change that.
By the numbers
| Expected annual benefits | $12.56 million |
| Estimated total cost | $38.14 million |
| Payback | 3.0 years |
| Benefit/cost ratio (8 years) | 2.6 to 1 |
| Cost to buy up to quality level 1 | $24.27 million |
About 88% of the identified needs fall in infrastructure, conservation and flood risk management. Not every benefit had a dollar value, so the true total is likely much higher.
| Rank | Business use | Annual benefits (millions) |
|---|---|---|
| 1 | Infrastructure and construction management | $6.11 |
| 2 | Natural resources conservation | 3.23 |
| 3 | Flood risk management | 1.75 |
| 4 | Geologic resource assessment and hazard mitigation | 0.49 |
| 5 | Agriculture and precision farming | 0.33 |
| 6 | Forest resources management | 0.31 |
| 7 | Renewable energy resources | 0.11 |
| 8 | Aviation navigation and safety | 0.10 |
| 9 | Water supply and quality | 0.06 |
| 10 | River and stream resource management | 0.05 |
| Other | 0.02 | |
| Total | 12.56 |
How lidar helps Arizona
- Conservation. Better terrain data would let state, regional and local governments plan grade stabilization, dam safety, habitat easements, pipelines, terracing and wetland restoration with less fieldwork, at lower cost to the public.
- Floods. Lidar makes hydrologic and hydraulic models more accurate and cheaper — for flood studies, for sizing bridges and culverts, for retention dams, dam-breach studies and stormwater engineering — and helps identify vulnerable properties in floodplains.
The Hassayampa River in flood near Morristown, February 10, 2005, with water moving faster than 19 feet per second. USGS photo by Michael Sanders.
- Wildfire. After several years of record fires, lidar can help decide where to focus planning, community education and fuel treatments, and improve fire behavior modeling, response, and assessments of slope instability and debris flows after fires.
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, managed by the USGS, chose an 8-year cycle: lidar over the conterminous states, Hawaii and the territories, radar over Alaska, all made public.
| Quality level | Pulse spacing | Vertical error (RMSEz) |
|---|---|---|
| QL1 | 0.35 m | 10 cm |
| QL2 | 0.7 m | 10 cm |
| QL3 | 2.0 m | 20 cm |
| QL4 | — | 139 cm |
| QL5 (radar, Alaska) | — | 185 cm |
- Goal: operational by January 2015, 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; data stay consistent across state and watershed lines; federal money reduces state and local shares; and ready contracts and specifications simplify buying.
- What it depends on: more partnerships among federal, state, tribal and local governments, larger project areas built to the program's specifications, and wider awareness and support.
Sources
Based on William J. Carswell, Jr., "The 3D Elevation Program: summary for Arizona," U.S. Geological Survey Fact Sheet 2014–3085; a work of the United States government in the public domain. The map, photograph and tables are taken from the fact sheet's PDF. Benefit figures come from Dewberry's National Enhanced Elevation Assessment (2011, revised 2012).
Licenza: CC0 1.0 (pubblico dominio) · Tratto da pubs.usgs.gov
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