Hydrography for The Lower Rio Grande Valley A Comparison of Mapped versus Synthetic Streams By Jean Parcher GIS in Water Resources December 4, 2001

Purpose of Project To use the ArcHydro Geodatabase model to compare the NHD and EDNA datasets for two watersheds in the Lower Rio Grande valley: density of stream networks validity of flow networks ease of transferring unique attribute codes between the two datasets for international applications ease of transferring flow statistics and catchment basins between the datasets and to play with the Geodatabase model

Lower Rio Grande Valley Study Area Dendritic and anastomotic drainage patterns in a low relief landscape From Falcon Reservoir To Brownsville

EDNA Synthetic Streams HUCs Falcon Reservoir and Los Olmos Derived from the NED 30 meter resolution data in Texas and 100 meter DTEDs in Mexico Processed by NWS for Flash flood monitoring program Includes flow direction and flow accumulation grids, Pfafstetter codes, and vector synthetic stream network

NHD Data Sources National Hydrography Dataset HUCS for Falcon and Los Olmos watersheds 1:100,000-scale (river reach 3 files) 1:24,000-scale (matches streams on DOQs) NHD 24K – revised to the 1995 DOQ

Loading the EDNA Synthetic Streams into the Geodatabase ArcGIS hydro Load: Need a clean network Use the streams datafile for hydroedge Use the NHD waterbody file (set grid size to 1) In the schema add all fields that don’t match join files streams_match with streams for access to reach codes NED Derived threshold set to match 100K NHD 39 different files (vector and grids) one stream per catchment basin

Falcon HUC - EDNA Streams andTopography RESULTS Falcon HUC - EDNA Streams andTopography Shaded relief and EDNA streams, NHD waterbody (Falcon Reservoir) NWS Flash flood catchment Basins with EDNA streams And hydro junctions

Pfafstetter and Reach codes RESULTS Pfafstetter and Reach codes By joining together the streams and streams_match tables, using the STREAMS_ID field, can link both Pfafstetter and Reach codes to the same feature.

Application of Hydro Vector tools to find EDNA problems RESULTS Application of Hydro Vector tools to find EDNA problems Flow direction With two sinks Red – NHD Blue - EDNA

Loading the NHD into the Geodatabase ArcGIS Hydro Load: Need a clean network - use route.drain vector file instead of route.reach to create networks In the schema, add all fields that don’t match Change the grid size for Waterbodies from 1000 to 1 In ArcMap: relate route.drain to route.reach to get access to reach codes

100K and 24K NHD and EDNA Catchment Basins RESULTS 100K and 24K NHD and EDNA Catchment Basins 100K NHD – some basins With no stream network 24K NHD – some basins with Multiple streams

Use of Hydrology Modeling Tool to Improve Catchments for 24K NHD Hydro Modeling tool Minimum # of cells - 2500 RESULTS EDNA catchments

Acknowledgements Kris Verdin – USGS EROS data center (EDNA data) – TWDB Stratmap (1:24K NHD) – UT CRWR for ArcGIS Hydro data model exercise – UT CRWR for answering my questions – USGS RMMC (NHD geodatabase model) Kris Verdin Erika Boghici Reem Zoun Dr. Maidment Paul Wiese

Questions?