USING TERRESTRIAL LIDAR FOR HYDRAULIC MODELING

Terrestrial LiDAR, also known as T-LIDAR, tripod-based LiDAR, or Terrestrial Laser Scanning, greatly increases the rate of data collection and the spatial resolution of three-dimensional topography, which is a key input for hydraulic studies of aqueous flows. In addition to topography, T-LIDAR collects the geometry and position of roughness elements in the field, such as trees, boulders, and constrictions, as well as laser intensity and photographic data that can be used to distinguish these roughness elements from one another. Using present-day examples from the Elwha River dam removals, WA, the Merced River in Yosemite National Park, CA, and the San Joaquin River, CA, we present results from 2D hydraulic models that were developed from topography and roughness derived from T-LiDAR data. The spatial distribution of roughness can be estimated from T-LiDAR data using either traditional roughness relationships for drag by individual roughness elements, or by T-LiDAR specific parameters, such as point-density. In contrast to other hydraulic studies, we utilize both topography and roughness from T-LiDAR, making field data-collection highly efficient, as well as using a unique roughness estimation using a spherical approach that is particularly well-suited for T-LiDAR data. Using T-LiDAR data for the development of 2D hydraulic models opens potential new avenues for hydraulic investigations because of its objective estimation of hydraulic roughness and its highly accurate topographic measurements. At present, this approach is limited to streams and rivers or their parts that are above water but it can be combined with bathymetric measurements in inundated channels. The development of T-LiDAR-derived hydraulic models has a number of applications including estimating discharge for past high-flow events, such as floods, flash floods, and paleofloods.