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

2. 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

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

4. 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

5. 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

6. 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

7. 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

8. 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.

9. 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

10. 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

11. 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

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

13. 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

14. Questions?