DOI: 10.5061/dryad.44j0zpcpq
title: Hydraulic (HEC-RAS) model of the Lower San Saba River between Harkeyville and San Saba, TX, USA

description: 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.
description: 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). 
 <strong>Parameter</strong> 
 <strong>Equipment</strong>
 <strong>Unit
 Accuracy</strong> 
 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<sup>th</sup> and
 June 27<sup>th</sup>, 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<sup>th</sup> and
 April 22<sup>nd</sup>, 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 <em>et al</em>. (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 <em>et
 al.</em>, 2023). A final bathymetric/topographic surface was
 generated following Harris <em>et al. </em>(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
 <em>et al. </em>(2023) (Table 2). Table 2.
 Selected Manning’s N roughness values based on delineated landcover.
 Adapted from Harris et al. (2023). 
 <strong><em>Landcover
 Description</em></strong> 
 <strong><em>Chow 1959 Description, which has
 minimum/normal/maximum ranges (</em></strong><strong><em>Manning's n Values (orst.edu)</em></strong><strong><em>)</em></strong> <strong><em>Selected Roughness</em></strong> <strong>Channel</strong> <strong>(Main channel or Mountain Streams)</strong>   Channel Sluggish reaches, weedy, deep pools (normal) 0.07 Channel2 clean, winding, some pools and shoals, some <br>weeds and more stones (maximum) 0.05 Channel3 Clean, straight, full stage, no rifts or deep pools <br>(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 <strong>Intermediate Zone</strong> <strong>(Floodplains)</strong>   Grassy Floodway Scattered brush/heavy weeds (maximum) or light <br>brush and trees in summer (between normal and maximum) 0.07 <strong>Floodplain</strong> <strong>(Floodplains)</strong> <strong> </strong> Dense Woody Dense willows, summer straight (minimum) or <br>heavy stand of timber, downed trees, little <br>undergrowth (normal) 0.1 Dense Woody2 Dense willows, summer straight (normal) 0.2 Sparse Shrub Light to dense brush (Various definitions, ranges <br>from minimum to maximum) 0.08 NoData Scattered brush, heavy weeds (between normal <br>and maximum) 0.06   A 2-D HECRAS mesh was created following Harris <em>et al. </em>(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. <strong>Calibration discharge (cfs)</strong> <strong>Average field discharge (cfs)</strong> <strong>Range of field discharges (cfs)</strong> <strong>Dates (2018)</strong> <strong>Cross section</strong> 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 <em>et al. </em>(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. <strong>Discharge (cfs)</strong> <strong>Imagery</strong> <strong>Imagery date</strong> 12.5 NAIP August 16<sup>th</sup>, 2006 22 NAIP July 12<sup>th</sup>, 2014 54 NAIP July 31<sup>st</sup>, 2010 86 NAIP August 3<sup>rd</sup>, 2016 241 NAIP December 12<sup>th</sup>, 2004 1600 NAIP October 26<sup>th</sup>, 2018   The final overall root mean-squared error of the model after calibration was 0.31 ft s<sup>-1</sup> 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 <em>et al</em>. (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.  
description: # 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/](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/](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](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](https://waterdata.usgs.gov/monitoring-location/08146000/#parameterCode=00065&period=P7D&showMedian=false).