How Lidar Elevation Data Serve New Hampshire

This USGS fact sheet describes the program's status in New Hampshire as of May 2024.

New Hampshire's landscape runs from the coastal lowlands through the eastern New England upland to the White Mountains, and good elevation data help manage all of it. The state's short coastline, including the Great Bay estuary and the Hampton–Seabrook marshes, is worth a disproportionate amount to its tourism economy, and its exposure to sea-level rise calls for accurate elevation data on land near the shore and depth data offshore to protect fisheries, habitat and infrastructure. Assessing flood hazards, which means mapping flooding and sediment movement and estimating the costs, requires detailed knowledge of both land surface and river and lake bottoms. Geologic assessment, hazard mitigation, planning, construction and historic preservation all depend on elevation data too.

Much of that work relies on lidar (light detection and ranging), which produces a highly detailed three-dimensional (3D) model of the Earth's surface and the features on it.

The 3D Elevation Program

The U.S. Geological Survey (USGS) manages the 3D Elevation Program (3DEP) with federal, state, tribal, territorial and local partners. Its goal is the first national baseline of consistent, high-resolution elevation data from lidar (from radar in Alaska), both bare-earth elevation models and 3D point clouds. Baseline data must meet quality level 2 or better:

Products include every point collected and bare-earth elevation models at 1-meter resolution or better, all integrated into The National Map and free to use without restriction. Nationally, the program's benefits are conservatively estimated at $690 million a year, with the potential for $13 billion a year more across the economy.

New Hampshire's coverage

Quality level 2 lidar now covers all of New Hampshire. In 2019 the state, through a legislative capital budget appropriation combined with 3DEP funding, acquired quality level 1 data, the first regionally extensive dataset of that quality for the state.

Status of 3D Elevation Program baseline lidar data in New Hampshire, May 2024. USGS figure.

A national assessment conservatively estimated that lidar data would bring New Hampshire about $1.68 million a year in new benefits:

Three uses in detail

Flood risk. The New Hampshire Geological Survey and the Dam Bureau of the state Department of Environmental Services provide information and tools to help the public and businesses plan for and respond to floods, working through partnerships. Lidar terrain data make hydrologic and hydraulic models more accurate and cheaper for flood studies, dam design and dam-breach studies, and stormwater engineering. The results help identify vulnerable properties in floodplains, guide floodplain decisions, and show the public, with dynamic 3D models, what major storms could flood.

Conservation. Statewide lidar helps governments carry out conservation more effectively and at lower cost: planning and engineering conservation ponds, grassed waterways, pipelines and terraces with less fieldwork, calculating runoff accurately, finding wetlands that were drained in the past, and planning their restoration.

Forestry. The executive director of the New Hampshire Timberland Owners Association has said the state's forest products industry employs more than 7,200 people, supports another 5,500 related jobs, and generates $1.6 billion a year, making it vital to rural economies. Getting the most from it requires accurate estimates of biomass, tree species and habitat, along with mapping of wet areas and detection of changes in vegetation, all of which lidar elevation models and classified point clouds greatly improve.

Taking part

Federal, state, tribal, territorial and local governments and private companies can join 3DEP, including to buy higher-quality data. Partners can contribute funds to USGS-managed projects or receive cooperative funds to run their own, through an annual Data Collaboration Announcement, and can contribute existing data that meet program standards.

Sources

• U.S. Geological Survey, "The 3D Elevation Program—Supporting New Hampshire's economy," Fact Sheet 2024–3056. https://pubs.usgs.gov/publication/fs20243056/full
• The fact sheet cites the National Enhanced Elevation Assessment (Dewberry, 2012) for the benefit estimates, Heidemann (2012) and Sugarbaker and others (2014) for quality levels, and Foley (2020) for the forest industry figures.
• 3DEP lidar data: https://apps.nationalmap.gov/downloader/ and https://usgs.gov/NationalMap/LidarExplorer; how to participate: https://www.usgs.gov/3DEP/collaborate/
• The map is recovered from the fact sheet PDF; a lidar image credited to a non-federal source is not reproduced.