Hydraulic (HEC-RAS) model of the Lower San Saba River between Harkeyville and San Saba, TX, USA

Harris, Aubrey1 ; Cushway, Kiara2 ; Mitchell, Zachary3 ; Schwalb, Astrid4

Research facility: U.S. Army Engineer Research and Development Center

Published Aug 26, 2024 on Dryad. https://doi.org/10.5061/dryad.44j0zpcpq

Data files

Aug 26, 2024 version files 3.79 GB

Lower_San_Saba_Model.zip

3.79 GB
LowerSanSaba_HECRAS_Methods.docx

44.39 KB
README.md

9.24 KB

Abstract

This model is a two-dimensional (2D) hydraulic model created in the Hydraulic Engineering Center’s River Analysis System (HEC-RAS). The model was created for a segment of the San Saba River between Harkeyville and San Saba, TX, USA. The model’s geometry is based on United States Geological Survey 3D Elevation Program data collected in 2018, and the channel bathymetry was burned in using cross-sectional data collected by Texas State University researchers in 2018. The model was calibrated using water surface elevation and velocity measurements taken during field data collection.

README: Hydraulic model (HEC-RAS) of the Lower San Saba River between Harkeyville and San Saba, TX, USA

This hydraulic model was generated in the U.S. Army Corps of Engineers Hydrologic Engineering Center's River Analysis System (HEC-RAS), and consists of a 20 km segment of the lower San Saba River, a tributary of the Colorado River in Texas.

Software for accessing files

HEC-RAS produces several specialized file types that may require additional software to view and open. Many files are specific to HEC-RAS and may be opened with HEC-RAS v6.2 or later, which can be downloaded for free at https://www.hec.usace.army.mil/software/hec-ras/. Other files may be opened with the following free software:

HEC-RAS software can be used to open the file types with the following extensions:
- G01
- P01
- U01
- B01
- BCO01
- C01
- DSS
- IC.O01
- PRJ
- RASMAP
- X01
- Shapefiles (.cpg, .dbf, .prj, .sbn, .sbx, .shp, .shx)
- VRT
- RST
HDF (Hierarchical data format) files: HDF files can be opened with HDF software such as that provided by https://support.hdfgroup.org/products/java/hdfview/
DSS files can be viewed using HEC-DSS, freely available at https://www.hec.usace.army.mil/software/hec-dss/
GDAL virtual format files (.vrt) can be viewed with common GIS programs such as ArcGIS Pro, ArcMap, or QGIS.

Description of the data and file structure

By default, units are based on the imperial system (feet for depth or elevation, feet per second for velocity, and cubic feet per second for discharge). Note that files in series (e.g., .p01-.p15 or .b01-.b15) are files related to unsteady flow plans and are generated once per flow plan. Since flow plans are generated in numeric order, missing values in the series (e.g., there are files from .p01 to .p06 and .p08 but no .p07 file) are indications of unused or unnecessary flow plans/associated files not relevant to the calibration or validation of this HEC-RAS model that have hence been deleted from the current model version.

Backup.g01: HEC-RAS-generated backup geometry file for 2D geometry; associates terrain, landcover, and 2D model areas with one another.
Backup.p01: HEC-RAS-generated backup of the Plan file. Plan files provide information about simulation details used to run unsteady flow simulations (e.g., description, identifier, required files)
Backup.u01/Backup.u01.hdf: HEC-RAS-generated backup of the Unsteady Flow data and associated HDF file. Unsteady flow files contain information about flow hydrographs, initial flow conditions, and boundary conditions used to run HEC-RAS simulations
LowerSanSaba.b01-b15: Boundary conditions (inflow outflow) for the simulation, viewable from HEC-RAS interface. Boundary conditions identify internal or external flow conditions used to run flow simulations. There is one boundary condition file for each plan file.
LowerSanSaba.bco01-bco15: Unsteady flow log output files, viewable from the HEC-RAS interface. Provides details about potential convergence issues or errors during computation. One log file per unsteady flow simulation.
LowerSanSaba.c01: Geometric Pre-processor output file for the simulation geometry. Hydraulic properties, rating curves for hydraulic simulation that are computed in the background of the HEC-RAS interface. Decreases computation time for unsteady flow simulations.
LowerSanSaba.dss: Unsteady flow output as time series data for the unsteady simulation from HEC-RAS, viewable from any program that can read dss (data storage system) files, including HEC-DSS.
LowerSanSaba.g01: 2D Geometry file for the simulation, associates terrain, landcover, and 2D model areas with one another. Used for computation of unsteady flows.
LowerSanSaba.g01.hdf: 2D Geometry file for the simulation as an HDF file.
LowerSanSaba.g02: 1D Geometry file for the simulation, associates terrain, landcover, cross-sectional data, and 1D model areas with one another.
LowerSanaSaba.g02.hdf: 1D Geometry file for the simulation as an HDF file (Hierarchical Data Format).
LowerSanSaba.IC.O01-O15: Initial conditions (t=0) for the respective Unsteady flow simulations. Establish water surface elevation at beginning of simulations; set with restart file from a previous run (see hotstart files)
LowerSanSaba.p01-p15: Unsteady flow plans with associated input files and simulation options. HDF versions may be opened with the HDF software. Plan files provide information about simulation details used to run unsteady flow simulations (e.g., description, identifier, required files). Number after "p" represents plan number.
LowerSanSaba.p08.06SEP2008 2400.rst: Restart file used for the initial flow distribution in each unsteady flow simulation (hotstart that fills channel); sets initial water surface elevation in initial conditions files.
LowerSanSaba.prj: The project file, which when opened by HEC-RAS, collates all other files in this folder to be navigated in the HEC-RAS user interface. Contains information about project title, units, and defaults.
LowerSanSaba.rasmap and rasmap.backup: RASMAP is the spatial GUI in HEC-RAS, and these files contain symbology and settings for this interface.
LowerSanSaba.u01-u15: Unsteady flow input file which contains hydrographs, initial conditions, and unsteady flow file setting accessible from the HEC-RAS user interface. HDF versions may be opened with the HDF software.
LowerSanSaba.x01: Run file for unsteady flow, created by HEC-RAS so that unsteady flow may be simulated/computed. Generated during simulation and includes information needed for computations for each plan.
LowerSanSaba.x03: Run file for unsteady flow, created by HEC-RAS so that unsteady flow may be simulated/computed. Generated during simulation and includes information needed for computations for each plan. == Reference: HEC-RAS file types by Chris Goodell, 2013: https://www.kleinschmidtgroup.com/ras-post/hec-ras-file-types/

12cfs_Cal-40cfs_Cal folders:

HEC-RAS-generated post-processing HDF files for calibration flows (12cfs, 16cfs, 20cfs, 26cfs, 34cfs, 40cfs; cfs=cubic feet per second). Calibration flows were used to match field-measured flows to modeled results by adjusting Manning's N roughness. See attached report for more in-depth details about calibration of the HEC-RAS model. Post-processing files calculate hydraulic information for specific times during an unsteady flow simulation.

12.5cfs_Val-1600cfs_Val folders:

HEC-RAS-generated post-processing HDF files for validation flows (12.5cfs, 22cfs,54cfs, 86cfs, 241cfs, 1600cfs). Stream width of modeled results for validation flows were compared to stream width in aerial imagery from the National Agriculture Imagery Program (NAIP). See attached report for details about validation of the HEC-RAS model.

12cfs_hotstart folder:

HEC-RAS-generated post-processing HDF files for hotstart flow used to fill channel as a restart file for other flows.

Land Classification folder:

LandCover Shapefile sub-folder: Contains shapefile of delineated land cover based on NAIP imagery used to create LandCover file in HEC-RAS; see attached report for details about land cover classes
LandCover.hdf: Contains the landcover used for the simulation.
LandCover.tiff: Landcover for the simulation in a raster format.

Terrain folder:

Terrain.hdf: Contains the terrain used for the simulation; bathymetry was "burned" in and computed via Inverse Distance Weighted method described in the attached report. Terrain elevation is in feet.
Terrain.Terrain21524.terrain_21524.tiff: Terrain for the simulation in a raster format.
Terrain.vrt: Terrain for the simulation as a GDAL virtual format (vrt) as terrains can sometimes be composed of multiple raster datasets (not in this case).
Texas_Central_State_Plane_Projection.prj: HEC-RAS project file used to define the projected coordinate system of the HEC-RAS interface. Set to Texas Central State Planes (feet).

Sharing/Access information

Data was derived from the following sources:

Merrick-Surdex. Lidar Mapping Report. 2018. Prepared for United States Geological Survey contract G16PC0029.
Mitchell, Z.A., Cottenie, K., Schwalb, A.N. (2023). Trait-based and multi-scale approach provides insight on responses of freshwater mussels to environmental heterogeneity. Ecosphere 14(7): e4533. https://doi.org/10.1002/ecs2.4533
Mitchell, Z.A. The role of life history strategies and drying events in shaping mussel communities: a multiscale approach [dissertation]. San Marcos (TX): Texas State University. 2020.
United States Department of Agriculture (USDA). Texas NAIP Imagery, 2004–2018. Web. 2024-01-18.
United States Geological Survey (USGS). 2016. National Water Information System data available on the World Wide Web (USGS Water Data for the Nation), accessed Jan. 18th, 2024, at URL https://waterdata.usgs.gov/monitoring-location/08146000/#parameterCode=00065&period=P7D&showMedian=false.

Methods

Available data:

Researchers from Texas State University collected depth, flow velocity, and wetted width data at 200 cross-sections spaced approximately 350 ft apart using the equipment listed in Table 1.

Table 1. Equipment used and their accuracy for Texas State University data collection. Table from Harris et al. (2023).

Parameter	Equipment	Unit Accuracy
Location	GPSMap 64 Handheld GPS	10-50 feet
Velocity	Hach Velocity Meter (Model FH950.1)	0.1 feet/second
Depth	An adjustable “ruler” stick with feet as units	0.1 feet
Wetted Width	Laser Technology Inc. TruPulse 360r	3 feet to nonideal (natural) target

Data was collected between June 4^th and June 27^th, 2018. During this time period, USGS gage 08146000 (San Saba, TX) recorded discharges ranging from 11.9 to 396 cfs, with an average discharge of 20 cfs.

USGS 3DEP 1 m resolution data collected between February 14^th and April 22^nd, 2018, was used to create the HEC-RAS terrain (Merrick-Surdex 2018). Discharge at USGS gage 08146000 ranged from 40.5 to 966 cfs during this time period. For much of the time period, the discharge was approximately 60 cfs.

Bathymetric areas:

The 3DEP data was imported as a terrain in HEC-RAS v.6.2, and field-collected cross sections were burned into the channel following methods from Harris et al. (2023). The 95 most upstream sites in the segment were associated with a single depth measurement in the center of the channel, whereas the remaining 105 cross sections were associated with three depth measurements collected in the center of the channel and on the left and right, although the position of measurements were not recorded. For cross sections that had three depth measurements, if the standard deviation of the depth exceeded 0.25 ft, all three measurements were used to delineate the cross section in HEC-RAS. For all other cross sections, a single depth was used to delineate the cross section (either the single available depth measurement or the average depth based on three measurements; Harris et al., 2023). A final bathymetric/topographic surface was generated following Harris et al. (2023) using inverse distance weighted interpolation with the field-collected cross sections to estimate channel bathymetry.

Landcover was delineated using aerial photography (USDA 2018) and associated Manning’s N roughness values were determined following Chow (1959) and Harris et al. (2023) (Table 2).

Table 2. Selected Manning’s N roughness values based on delineated landcover. Adapted from Harris et al. (2023).

*Landcover Description*	*Chow 1959 Description, which has minimum/normal/maximum ranges (Manning's n Values (orst.edu)***)	*Selected Roughness*
Channel	(Main channel or Mountain Streams)
Channel	Sluggish reaches, weedy, deep pools (normal)	0.07
Channel2	clean, winding, some pools and shoals, some weeds and more stones (maximum)	0.05
Channel3	Clean, straight, full stage, no rifts or deep pools (minimum)	0.025
Cobbly3	No vegetation in channel, banks usually steep, trees and brush along banks submerged at high stages, bottom: gravel, cobbles, and few boulders (minimum)	0.03
Ineffective Sec2	Sluggish reaches, weedy, deep pools (maximum)	0.08
Ineffective Sec3	Very weedy reaches, deep pools, or floodways with heavy stand of timber and underbrush (normal)	0.1
Ineffective Sec4	Very weedy reaches, deep pools, or floodways with heavy stand of timber and underbrush (maximum)	0.15
Intermediate Zone	(Floodplains)
Grassy Floodway	Scattered brush/heavy weeds (maximum) or light brush and trees in summer (between normal and maximum)	0.07
Floodplain	(Floodplains)
Dense Woody	Dense willows, summer straight (minimum) or heavy stand of timber, downed trees, little undergrowth (normal)	0.1
Dense Woody2	Dense willows, summer straight (normal)	0.2
Sparse Shrub	Light to dense brush (Various definitions, ranges from minimum to maximum)	0.08
NoData	Scattered brush, heavy weeds (between normal and maximum)	0.06

A 2-D HECRAS mesh was created following Harris et al. (2023) with a mesh size of 40 square feet and a breakline with cell size of 20 feet located in the center of the channel.

A 12 cfs unsteady flow simulation was run as a “hot-start” to fill the modeled channel and subsequently used as the initial conditions for additional flows simulated for the segment. Because the discharge recorded at USGS gage 08146000 varied during the field sampling period, different sections of the segment were calibrated to different discharges to match field conditions at the time of data collection (Table 3).

Table 3. Discharges used to calibrate 2-D HEC-RAS model based on discharges recorded at USGS gage 08146000 during field collection dates in 2018.

Calibration discharge (cfs)	Average field discharge (cfs)	Range of field discharges (cfs)	Dates (2018)	Cross section
12	12.5	9.7-15.6	6/25; 6/27	29370-20044; 8279-467
16	15.9	13.5-17.4	6/21; 6/26	19597-8667
20	20	16.8-22.4	6/13-6/14; 6/20	49011-29699
26	26.5	21.1-30.3	6/12	56420-49340
34	33.8	30.3-36.5	6/11	63009-56840
40	40.3	20.6-114	6/4	72209-63766

Calibration was conducted in accordance with methods from Harris et al. (2023), with an initial channel roughness of 0.07 adjusted on a case-by-case basis throughout the segment based on comparisons of field-measured and modeled depth and velocity at cross sections. In addition, modeled channel widths were compared to aerial imagery for select discharges, and floodplain roughness was adjusted as needed in an attempt to match channel width from imagery (USDA, 2004-2018; Table 4).

Table 4. Average discharge recorded at USGS gage 08146000 on select dates when aerial imagery from the National Agricultural Inventory Program (NAIP) was available (USDA, 2004-2018), used for comparison of imagery channel width with modeled channel width.

Discharge (cfs)	Imagery	Imagery date
12.5	NAIP	August 16^th, 2006
22	NAIP	July 12^th, 2014
54	NAIP	July 31^st, 2010
86	NAIP	August 3^rd, 2016
241	NAIP	December 12^th, 2004
1600	NAIP	October 26^th, 2018

The final overall root mean-squared error of the model after calibration was 0.31 ft s^-1 for velocity and 0.34 ft for depth. Error at individual cross sections was also recorded for reference purposes.

Summary of assumptions:

This HEC-RAS model has assumptions matching those of Harris et al. (2023). Discharge data from 2018 at USGS gage 08146000 (San Saba, TX) have been approved by USGS.

Usage notes:

HEC-RAS 6.2 is a free hydraulic analysis software available for download from the U.S. Army Corps of Engineers.

References:

Chow VT. Open-channel hydraulics: New York: McGraw-Hill; 1959.

Harris A, Wiest S, Cushway KC, Mitchell ZA, Schwalb AN. Hydraulic model (HEC-RAS) of the Upper San Saba River between For McKavett and Menard, TX [Dataset]. Dryad Data Repository; 2023. https://doi.org/10.5061/dryad.pc866t1tt.

Merrick-Surdex. Lidar Mapping Report. 2018. Prepared for United States Geological Survey contract G16PC0029.

Mitchell ZA. The role of life history strategies and drying events in shaping mussel communities: a multiscale approach [dissertation]. San Marcos (TX): Texas State University. 2020.

Mitchell ZA, Cottenie K, Schwalb AN. Trait-based and multi-scale approach provides insight on responses of freshwater mussels to environmental heterogeneity. Ecosphere. 2023; 14(7):e4533. https://doi.org/10.1002/ecs2.4533.

Mitchell ZA, Schwalb AN, Cottenie K. Trait-based and multi-scale approach provides insight on responses of freshwater mussels to environmental heterogeneity [Dataset]. Dryad Data Repository; 2023. https://doi.org/10.5061/dryad.msbcc2g3d.

United States Department of Agriculture (USDA). Texas NAIP Imagery, 2018. Web. 2022-03-09.