Hydrography for The Lower Rio Grande Valley

A Comparison of Mapped versus Synthetic Streams

By Jean ParcherGIS 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

From Falcon Reservoir To Brownsville

Dendritic and anastomoticdrainage patterns in a low relief landscape

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

Shaded relief and EDNA streams, NHD waterbody (Falcon Reservoir)

NWS Flash flood catchmentBasins with EDNA streamsAnd hydro junctions

RESULTS

Pfafstetter and Reach codes

By joining together the streams andstreams_match tables, using the STREAMS_ID field, can link bothPfafstetter and Reach codes to the same feature.

RESULTS

Application of Hydro Vector tools to find EDNA problems

Red – NHDBlue - EDNA

Flow directionWith two sinks

RESULTS

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

100K NHD – some basinsWith no stream network

24K NHD – some basins withMultiple streams

RESULTS

Use of Hydrology Modeling Tool

to Improve Catchments for 24K

NHD

Hydro Modeling toolMinimum # of cells - 2500

EDNA catchments

RESULTS

Acknowledgements

– 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)

Questions?