Light Detection and Ranging technology that uses laser pulses to create highly accurate 3D point clouds of terrain and objects. LiDAR-derived elevation data are essential for high-resolution floodplain mapping and hydraulic modeling.
LiDAR (Light Detection and Ranging) is an active remote sensing technology that emits rapid laser pulses (typically 100,000-500,000+ pulses per second) and measures the time for each pulse to return after reflecting off the Earth's surface and objects above it. Airborne LiDAR systems, mounted on aircraft or drones, produce dense 3D point clouds that can be classified into ground returns (bare earth) and non-ground returns (vegetation, buildings). In hydrology, LiDAR-derived DEMs at 1-3 m resolution have transformed floodplain mapping, enabling FEMA to produce more accurate flood insurance rate maps. Bathymetric LiDAR uses green-wavelength lasers that penetrate water to map submerged channel geometry, critical for hydraulic modeling. The vertical accuracy of airborne LiDAR (typically 5-15 cm RMSE) far exceeds satellite-based DEMs, making it indispensable for urban stormwater modeling and levee certification. The USGS 3D Elevation Program (3DEP) aims to provide nationwide LiDAR coverage for the United States. Terrestrial and mobile LiDAR systems are increasingly used for stream bank erosion monitoring, bridge scour assessment, and infrastructure inspection along waterways.