Introduction

The State of Tennessee has an area of approximately 42,100 square miles and includes six physiographic regions: Blue Ridge, Valley and Ridge, Appalachian Plateaus, Highland Rim, Nashville Basin, and the Gulf Coastal Plains. Up-to-date elevation data support key activities across the State, such as economic development, infrastructure and construction management, agriculture and precision farming, forest resources management, natural resources conservation, flood risk management, emergency management, and urban and regional planning. The State experiences frequent landslides affecting major roadways. High-resolution elevation data can help identify potential landslide-prone areas. Critical applications that meet the State’s management needs depend on light detection and ranging (lidar) data that provide a highly detailed three-dimensional (3D) model of the Earth’s surface and aboveground features.

The 3D Elevation Program (3DEP; refer to sidebar) is managed by the U.S. Geological Survey (USGS) in partnership with Federal, State, Tribal, U.S. territorial, and local agencies to acquire consistent lidar coverage at quality level 2 or better (table 1) to meet the many needs of the Nation and Tennessee. The status of available and in-progress 3DEP baseline lidar data in Tennessee is shown in figure 1. 3DEP baseline lidar data include quality level 2 or better, 1-meter or better digital elevation models, and lidar point clouds, and must meet the Lidar Base Specification version 1.2 (https://www.usgs.gov/3dep/lidarspec) or newer requirements. The National Enhanced Elevation Assessment (Dewberry, 2012) identified user requirements and conservatively estimated that availability of lidar data would result in at least $6.32 million in new benefits annually to the State. The top 10 Tennessee business uses for 3D elevation data, which are based on the estimated annual conservative benefits of 3DEP, are shown in table 2.

Status of 3DEP in Tennessee

Collection of quality level 2 3DEP lidar data is 100 percent complete in Tennessee. The success of this effort is due to strong coordination among Federal, State, and local government agencies. The Tennessee Valley Authority, U.S. Army Corps of Engineers, U.S. Department of Agriculture’s Natural Resources Conservation Service, U.S. Forest Service, and the USGS are the Federal partners. State agencies that have contributed to the USGS 3DEP effort include Transportation, Environment and Conservation, and Finance and Administration. At the local level, several counties, municipalities, utility districts, and electric co-operatives have contributed additional funding. In 2022, quality level 1 lidar data were acquired in Davidson County (Nashville area) through 3DEP to update existing quality level 2 data. The long-term plan is to update existing quality level 2 data to quality level 1 throughout the State as part of the USGS 3D Hydrography Program.

Agriculture and Precision Farming

Tennessee cash crop receipts for 2020 were $2.35 billion according to the Tennessee Department of Agriculture’s 2019–2020 Biennial Report (Tennessee Department of Agriculture, 2021). High-resolution elevation data can provide a more accurate depiction of terrain and significantly improve precision farming activities, which can help improve crop yields, prevent soil degradation, minimize groundwater usage, and reduce agricultural chemical runoff—factors that help farmers realize a larger return on their investments.

Natural Resources Conservation

High-quality elevation data enable State, Tribal, and local governments to more effectively implement natural resources conservation practices while providing additional cost savings to the public. Now that quality level 2 lidar data are available statewide, public and private organizations can expand their use of lidar for planning and site-level engineering to reduce fieldwork for conservation ponds, grassed waterways, pipelines, terracing, accurately calculating runoff, identifying historical wetlands (drained), and wetland restoration.

Flood Risk Management

The availability of more accurate statewide elevation data reduces onsite data collection costs and the amount of time required to complete flood risk project that help protect lives and property (fig. 2). The quality of analyses and study results are improved because of the more accurate elevation data. Overall, the project completion time and cost are reduced, and the savings can be applied to other priority flood risk projects.

Geologic Resource Assessment and Hazard Mitigation

The Tennessee Department of Environment and Conservation (2020) uses elevation data to conduct detailed mapping, analysis of geologic structures and stratigraphy, and assessment of mineral resources. The availability of high-quality elevation data allows for improved accuracy and detail in geologic maps and data that inform public policy and support Tennessee’s non-fuel mineral industry production, which totaled $1.46 billion in 2018.

Dense vegetation and woodlands can obscure hazardous areas. Lidar digital terrain (bare-earth) models can be used to (1) locate and assess abandoned mine lands, landscape changes related to oil and natural gas drilling, and active landslides and preexisting landslides that are susceptible to reactivation; and (2) detect sinkhole features in karst areas that have not been identified in previous elevation mapping programs. These lidar-derived data support public and environmental safety programs and the site-selection process for industry and commerce.