Bureau of Economic Geology, University of Texas at Austin Vegetation Removal from LIDAR X, Y, Z Data Sets for Use in Hydrologic Modeling of Waller Creek in Austin, Texas Rebecca C. Smyth Bureau of Economic Geology, University of Texas at Austin April 24, 2001

Procedure Start with 6.0GB LIDAR file of first and last pulse x, y, z points falling within coordinates (4 x 9 km area) of Waller Creek watershed provided by City of Austin Edit out first pulse and intensity data and x, y points with long or short ranges (resulting file size: ~1GB). Editing files from 6 to 1 GB must be done in UNIX Vary veg-removal parameters in 5 different scenarios - each scenario takes 7 to 9 hours to run on a dual-620MHz processor NT workstation

Procedure (cont.) Extract 150m x 315m sub-areas on UT campus for vegetation removal evaluation using awk scripts and UWIN program on NT work station Generate 1m DEM and point coverage plots for each scenario in Surfer Digitize cross section in Surfer and extract points 5m either side of section using Fortran program Plot cross sections in Grapher to aid in evaluation of parameters

Variations in Vegetation Removal Parameters

Surfer 1meter DEMs

Selected LIDAR Points After Vegetation Removal

Cross Section Selection

Vegetation and Veg-removal Options 1, 2, and 3

Vegetation and Veg-removal Options 4 and 5

Vegetation Removal Options 1, 2, and 4

Problems with Bridges on Waller Creek

Bridge Removal in Tegucigalpa, Honduras