The 3D Elevation Program: summary for North Carolina

Introduction

Elevation data are essential to a broad range of applications, including forest resources management, wildlife and habitat management, national security, and recreation. For the State of North Carolina, elevation data are critical for flood risk management, natural resources conservation, agriculture and precision farming, infrastructure and construction management, forest resources management, and other business uses. Today, high-density light detection and ranging (lidar) data are the primary sources for deriving elevation models and other datasets. Federal, State, Tribal, and local agencies work in partnership to (1) replace data that are older and of lower quality and (2) provide coverage where publicly accessible data do not exist. A joint goal of State and Federal partners is to acquire consistent, statewide coverage to support existing and emerging applications enabled by lidar data.

The National Enhanced Elevation Assessment (NEEA; Dewberry, 2011) evaluated multiple elevation data acquisition options to determine the optimal data quality and data replacement cycle relative to cost to meet the identified requirements of the user community. The evaluation demonstrated that lidar acquisition at quality level 2 (table 1) for the conterminous United States and quality level 5 interferometric synthetic aperture radar (ifsar) data (table 1) for Alaska with a 6- to 10-year acquisition cycle provided the highest benefit/cost ratios. The 3D Elevation Program (3DEP) initiative (Snyder, 2012a,b) selected an 8-year acquisition cycle for the respective quality levels. 3DEP, managed by the U.S. Geological Survey (USGS), the Office of Management and Budget Circular A–16 lead agency for terrestrial elevation data, responds to the growing need for high-quality topographic data and a wide range of other 3D representations of the Nation’s natural and constructed features.

Figure 1. Existing and planned publicly available lidar in North Carolina, June 2014. U.S. Geological Survey, from the U.S. Interagency Elevation Inventory.

3D Elevation Program Benefits for North Carolina

The top 10 North Carolina business uses for 3D elevation data, which are based on the estimated annual conservative benefits of the 3DEP initiative, are shown in table 2. The NEEA survey respondents, consisting of Federal, State, selected local and Tribal governments, and private and nongovernmental users in the State of North Carolina, estimated that the national 3DEP initiative would result in at least $69.1 million in new benefits annually to the State. The cost for such a program in North Carolina is approximately $16.5 million, resulting in a payback period of 0.2 year and a benefit/cost ratio of 33.5 to 1 over an 8-year period. Because monetary estimates were not provided for all reported benefits, the total benefits of the 3DEP to North Carolina are likely much higher. On the basis of the NEEA survey results, all levels of government and many organizations in North Carolina could benefit from access to statewide high-resolution elevation data.

For North Carolina, approximately 91 percent of the identified business use requirements will be met in flood risk management uses, as shown in table 2. The status of publicly available lidar data in North Carolina is shown in figure 1. By enhancing coordination between 3DEP and various government and private organizations in North Carolina, it may be possible to realize more than the cited conservative benefits and attain the higher potential benefits for many business uses.

3DEP is a national program managed by the USGS to acquire high-resolution elevation data. The initiative is backed by a comprehensive assessment of requirements (Dewberry, 2011) and is in the early stages of implementation. 3DEP will improve data accuracy and provide more current data than is available in the National Elevation Dataset (NED). The goal of this high-priority cooperative program is to be operational by January 2015, and to have complete coverage of the United States by the end of 2022, depending on funding and partnerships. 3DEP can conservatively provide new benefits of $1.2 billion/year and has the potential to generate $13 billion/year in new benefits through improved government services, reductions in crop and homeowner losses resulting from floods, more efficient routing of vehicles, and a host of other government, corporate, and citizen activities (Dewberry, 2011). A shared, common elevation dataset would foster cooperation and improve decisionmaking among all levels of government and other stakeholders.

Benefits of a Funded National Program

• Economy of scale—Acquisition of data covering larger areas reduces costs by 25 percent.
• A systematic plan—Acquisition of data at a higher quality level reduces the cost of “buying up” to the highest levels needed by State and local governments.
• Higher quality data and national coverage—Ensure consistency for applications that span State and watershed boundaries and meet more needs, which results in increased benefits to citizens.
• Increase in Federal agency contributions—Reduces State and local partner contributions.
• Acquisition assistance—Provided through readily available contracts and published acquisition specifications. The following examples highlight

how 3DEP data can support business uses in North Carolina: (1) Lidar data provide high-quality terrain information as input for more accurate and less expensive hydrologic and hydraulic modeling for flood studies; for design of structures (bridges and culverts) to accommodate runoff and flooding from large rain events; and for retention dam design, dam breach studies, and stormwater management and engineering. Lidar data also aid the identification of vulnerable properties within a floodplain, facilitating better floodplainmanagement decisions and education of the public on true flood risks (fig. 2). Dynamic 3D models using lidar data show the potential impact of flooding as a result of large storm events and coastal overland storm surges. With an enhanced ability to predict surfacewater movement along high-risk coastal areas, emergency planners have the ability to design improved evacuation routes to better protect the public should a disaster strike. (2) The statewide orthoimagery program, funded by the NC 911 Board, is dependent on current high-resolution elevation data to develop a high-quality product for emergency response. The orthoimagery program is leveraging the Federal and State contributions toward lidar to produce a 6-inch-resolution statewide imagery product that saves time locating and responding to emergencies and

that provides online map services (available to the public) for a myriad of uses. (3) The North Carolina Geographic Information Coordinating Council endorsed lidar-derived data as the source of high-accuracy elevation data for North Carolina and formally adopted the “North Carolina Technical Specifications for LiDAR Base Mapping” report, based on the USGS lidar base specification in 2013. The North Carolina specifications will enhance USGS efforts to collect and develop a nationally consistent elevation program.

References Cited

Dewberry, 2011, Final report of the National Enhanced Elevation Assessment (revised 2012): Fairfax, Va., Dewberry, 84 p. plus appendixes, http://www.dewberry.com/Consultants/GeospatialMapping/FinalReport-NationalEnhancedElevation Assessment.

Snyder, G.I., 2012a, National Enhanced Elevation Assessment at a glance: U.S. Geological Survey Fact Sheet 2012–3088, 2 p., http://pubs.usgs.gov/fs/2012/3088/.

Snyder, G.I., 2012b, The 3D Elevation Program—Summary of program direction: U.S. Geological Survey Fact Sheet 2012–3089, 2 p., http://pubs.usgs.gov/fs/2012/3089/.

3D Elevation Program—Continued

The USGS and its partners will acquire quality level 2 or better (table 1) 3D lidar data over the conterminous United States, Hawaii, and the U.S. territories. Interferometric synthetic aperture radar (ifsar) data are being collected at quality level 5 (table 1) in Alaska. The data will be acquired over an 8-year period and will be made available to the public. By using this acquisition scenario, a number of high-quality elevation-data products can be created to serve a wide range of business uses in government and the private sector.

Next Steps for Implementing 3DEP

For Further Information:

Director, USGS National Geospatial Program 12201 Sunrise Valley Drive, MS 511 Reston, VA 20192 Email: 3dep@usgs.gov

Gary L. Merrill, USGS Geospatial Liaison 720 Gracern Road, MS 509 Columbia, SC 29210 Email: glmerrill@usgs.gov http://nationalmap.gov/3DEP/

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