LIDAR Flood mapping for Brownsville and Matamoros Gueudet Pierre GIS in Water Resources University of Texas Austin Fall 2002

Particularity of the region:   Frequent Rainfalls (hurricanes + floods)   Very flat region (5 to 6 m above sea level)   A vast network for irrigation Bonsville/Matamoros

HEC-GeoRas Preprocessing Geometric data stream centerlines, riverbanks, floodplain boundaries, cross- sections along the streams HEC-GeoRas Postprocessing Flow data from HEC-HMS HEC-RAS steady state simulation Hydraulic modeling Hydrologic modeling Flood map visualization Import file ARCVIEW Terrain model processing LIDAR input data 1m grid DEM Procedure:

Terrain model processing I need to :  Collect LIDAR data  Build a Hydro Network  Build a TIN which rivers have a clean cross-sections (problem with bridges)

-Elevation accuracy : 10 to 25 cm - records first and last returns of individual pulses and intensity Applications in :  Flood mapping  Forest management  Land cover classification  Atmospheric pollution monitoring First Step: collecting LIDAR data

I don’t have the LIDAR data yet (not available before January) then:  I used less precise data (7 m resolution) from the Bureau of Economic Geology.  I just obtained LADAR data for a small part of Brownsville and I am going to work on it.

Second step: building an Hydro Network I tried to use Arc Hydro Terrain Processing. I got no useful results because of:  the flatness of the region  the precision of the data Streams obtained with Arc Hydro Terrain processing Flow direction

Second step: building an Hydro Network Rio Grande River => I am going to work only on the Rio Grande

Third step: terrain processing

Conclusion   Work in progress!   I am going to start working on HEC-GeoRas and HEC- HMS.   I want to use the LIDAR data to see if I can obtain interesting results with Arc Hydro Terrain Processing