DOI: 10.5061/dryad.pc866t1tt
title: Hydraulic model (HEC-RAS) of the Upper San Saba River between Fort McKavett and Menard, TX

description: This is a 2D Hydraulic model (HEC-RAS) for the Upper San Saba River
 between Fort McKavett and Menard, TX. Model geometry is based on USGS 3DEP
 data (2018), with underwater bathymetry “burned” in using cross-sections
 sampled in the field in 2018. The model was calibrated based on water
 surface and velocities measured during data collection.
description: The following is a summary of
 available data utilized for developing a bathymetric terrain for 2D
 hydraulic modeling using HEC-RAS. Data available for model calibration and
 validation is also discussed. Available Data Cross-section data was collected at
 approximately 350-foot increments with the following devices:
 Table 1. Equipment used and
 their accuracy for field data collection. <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 The data was collected from July 10 to 26, 2018. The USGS Gage on the San Saba River at Menard, TX (08144500) shows discharges varied from 8 to 18 cfs during the time period. USGS 3DEP data was used in the HEC-RAS terrain. These data were collected at a 1-meter resolution over a period of two months (February 14 to April 22, 2018) over a range of discharges from 16 to 25 cfs. Bathymetric Areas 3DEP represents areas where the terrain is inundated as a hydro-flattened surface (hydrosurface). These flat areas are apparent relative to the surrounding terrain. The 3DEP terrain was imported into HEC-RAS 6.2. The field data collection featured 200 cross-sections. HEC-RAS was utilized to create a bathymetric surface by interpolating 1-D cross-sections. The field data were projected as a shapefile and brought into HEC-RAS for cross-section placement. Cross-sections were drawn from the field-measured location. Given that the 3DEP data collection was at a similar discharge, wetted widths at the field-measured location were compared to the width of the hydrosurface areas by the following procedure: Hydrosurface areas are delineated with a shapefile. 1D XS from the HEC-RAS are exported to ArcMap. The 1D XS are “clipped” to the hydrosurface extent using the hydrosurface shapefile. The 1D XS lengths are calculated using the Geometry Calculator. Wetted widths are compared to the clipped 1D XS lengths. 1D XS placement was shifted downstream or upstream from the field-measured location to try to conform to the wetted widths measured in the field. At the first iteration, 80% of the XS were able to be placed within 5 feet of the field-measured wetted width. Locations that diverge greater than 5-feet from the field-measured data were flagged for further inspection. For the field-measured cross-sections, three depths and a mid-channel velocity were measured in the field. Given that the discharges and the wetted depths for the 3DEP data and the field-measured data collection are similar, a first iteration of bathymetric data formulation assumed measured depths were equivalent to the distance from the hydro-flattened surface on the 3D to the channel bed. Three depths were measured in the field per cross-section, on channel left, right and mid-channel. The exact locations of these depth measurements were not recorded. Cross-section depths within 0.25 feet of each other, and average depth was used for the 1D cross-section formulation in these locations. For areas where the standard deviation of measurements per cross-section exceeded 0.25 feet, all three depths were used in delineating the cross-section. Once the 1D cross-sections were processed, bank stations were shifted toward the center of the channel. This reduces high ridges during channel interpolation and ensures all channel points are beneath the hydrosurface. A TIF was created using HEC-RAS 6.2 from bank to bank (Channel-only option). The TIF was exported as a 3-foot resolution raster. The 1D interpolation captures channel centerline between measured cross-sections, but meanders and channel widening may not be covered by the interpolated channel. The channel raster was exploded in ArcMap using the Raster to Point tool. The points were then interpolated using the Inverse-Distance-Weighted interpolation tool (IDW). This creates a much wider-coverage terrain while maintaining fidelity to the points/channel-only raster, while also covering meanders and pools that conform to the energy grade between cross-sections. The IDW surface is clipped to the hydrosurfaced area, and then mosaicked with the original 3DEP terrain to create a seamless bathymetric/topographic surface. Landcover was delineated using aerial photography. (4) types of landcover were identified: Dense woody vegetation, sparse shrub, channel areas, and grasslands.  Normal Manning’s n values, based on Chow 1959, were selected. The 2D HEC-RAS mesh was set to 40-feet square, with a breakline with 25-foot cell-spacing at the channel center. The discharge event simulated for this segment was 15 cfs. A 1D computation of 15 cfs was used as a “hot-start” to fill the river channel, and then 15-cfs unsteady state simulation was run. The outlet boundary was observed for 15 cfs flow. The depth and velocity results for the timestep associated with 15 cfs were exported to ArcMap. The statistics (mean, minimum, maximum) for each 1D cross-section were pulled from the raster results using the Zonal Statistics as Table Tool. The Table of 2D model simulation results was compared to the field-measured mid-channel velocities and average channel depth. If the field-measurement was within the range of the Zonal Statistics, then a 0 [unit] RMSE error was assumed. RMSE for the 2D model table was computed based on whether the model results were ‘High’ or ‘Low’ from the field-measurement. Then the error was computed from the Maximum and Minimum results respectively. 15 cfs is within the channel banks, this was also the dataset with most field-measured information. The Manning’s n for the channel was adjusted as a single roughness and then improved by adding more roughness types. Modification of the roughness type was dictated by 1) bed material recorded during the field survey, to justify the use of “Cobbly” bed roughness; 2) inspection of aerial photography and confirmation via site visits to justify areas as being “weedy and ineffective flow”. The 3DEP data is available for areas of inundation calibration for low flows. The uncertainty of the areas of inundation may be quantified by delineating inundated areas from aerial photography (or from the 3DEP terrain). A discharge of around 120 cfs was captured with aerial photography in November 2018; a discharge around 45 cfs was captured with aerial photography in September 2020. These inundated areas can be used to calibrate/validate flows of a similar discharge magnitude. Inundated areas in the aerial photography were delineated with a shapefile polygon. Differences between the modeled inundated area at a similar discharge were inspected for corrections in landcover roughness and breakline delineations in the mesh for proper numerical computation. Following calibration, the model has overall RMSE error in velocity of 0.26 ft/s and 0.56-ft depth error. Error per cross-section communicates the magnitude of possible error in specific areas of the reach. <em>Landcover Description</em> <em>Chow 1959 Description, which has minimum/normal/maximum ranges (</em><em>Manning's n Values (orst.edu)</em><em>)</em> <em>Selected Roughness</em> <strong>Channel</strong> <strong>(Main Channel or Mountain Streams)</strong> <strong> </strong> Channel sluggish reaches, weedy, deep pools (normal) 0.07 Channel2 clean, winding, some pools and shoals, some weeds and more stones (maximum) 0.05 Cobbly no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stages no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stages (maximum) 0.07 Cobbly2 sluggish reaches, weedy, deep pools (maximum) 0.08 Ineffective Sec sluggish reaches, weedy, deep pools (normal) 0.07 Ineffective Sec2 sluggish reaches, weedy, deep pools (maximum) 0.08 Ineffective Sec3 very weedy reaches, deep pools, or floodways<br>  with heavy stand of timber and underbrush (normal) 0.1 Weedy Reach very weedy reaches, deep pools, or floodways<br>  with heavy stand of timber and underbrush (between normal and maximum) 0.12 <strong>Intermediate Zone</strong> <strong>(Floodplains)</strong>   Grassy Floodway Scattered brush/heavy weeds (maximum) or light brush and trees in summer (between normal and maximum) 0.07 Grassy Floodway2 Medium to dense brush (between normal and maximum) 0.1 <strong>Floodplain</strong> <strong>(Floodplains)</strong>   Dense Woody Dense willows, summer straight (minimum) or heavy stand of timber, down trees, little undergrowth (normal) 0.1 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 Summary of Assumptions: Accuracy of discharge measurements of river gages (expect up to 10% error in discharge measurement). Data used for 2018 from the Menard, TX gage at San Saba River has been approved by USGS 3DEP terrains have a 1-m resolution. Field-measured cross-section location (quality assurance/uncertainty related to the field-measured wetted width). The data provided in 1D cross-section dimensions are minimal laterally, but rather high resolution longitudinally down the channel. River area between 1D cross-sections is interpolated. Bank to measured depth contours and measured depth to measured depth contours are uncertain. Unmeasured pools and widening locations have assumed depths that conform to channel energy grade. Actual bathymetries are most uncertain in these locations relative to other channel areas, as channel slopes cannot be assumed to be constant in backwater areas. The structure, number of culverts, and dimensions of low-water crossings were not collected nor input into the model. Groundwater contributions and losses were not incorporated into the model. Related Works: Cushway KC. (2023). Go with the flow: impacts of high and low flow conditions on freshwater mussel assemblages and distribution. Master’s Thesis, Texas State University. 114 pp. Cushway KC, Harris AE, Piercy CD, Mitchell ZA, Schwalb AN. (2024) Go with the flow: Impacts of high and low flow conditions on freshwater mussel assemblages and distribution. PLoS ONE 19(2): e0296861. https://doi.org/10.1371/journal.pone.0296861 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. (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 ZA, Cottenie K, Scwhalb AN. (2023). Trait-based and multi-scale approach provides insight on responses of freshwater mussels to environmental heterogeneity. [Dataset]. Dryad Data Repository. https://doi.org/10.5061/dryad.msbcc2g3d
description: HEC-RAS 6.2 is a free hydraulic analysis software available from
 US Army Corps of Engineers.
description: # Hydraulic model (HEC-RAS) of the Upper San Saba River between Fort
 McKavett and Menard, TX ## Description of the data and file structure Many
 of the files are specific to HEC-RAS and may be opened with HEC-RAS 6.2 or
 later version. HDF (Hierarchical data format) are datasets that can be
 opened with an alternative software such as that provided by
 [https://support.hdfgroup.org/products/java/hdfview/](https://support.hdfgroup.org/products/java/hdfview/) (Enclosed files listed alphabetically) * Backup.p01: HEC-RAS-generated backup of the Plan file. This associates inputs with simulation options in HEC-RAS. * Backup.u01/Backup.u01.hdf: HEC-RAS-generated backup of the Unsteady Flow data and associated HDF file. * UpperSanSaba.b01-b23: Boundary conditions (inflow outflow) for the simulation, viewable from HEC-RAS interface. * UpperSanSaba.bco01-bco29: Unsteady flow log output files, viewable from the HEC-RAS interface. * UpperSanSaba.c06: 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. * UpperSanSaba.dss: Unsteady flow output as time series data for the unsteady simulation from HEC-RAS, viewable from any program that can read dss files. * UpperSanSaba.f01-f03: Steady flow simulations used to develop the "hot-start" or starting water surface elevations for low-flow conditions, speeding up the low-flow simulation. * UpperSanSaba.g06: Geometry file for the simulation, associates terrain, landcover, and 2D model areas with one another. * UpperSanSaba.g06.hdf: Geometry file for the simulation as an HDF file. * UpperSanSaba.IC.O01-O29: Initial conditions (t=0) for the respective Unsteady flow simulations. * UpperSanSaba.O06: Computed results for unsteady flow simulations, can only be read by HEC-RAS user interface (Simulations can be rerun by user). * UpperSanSaba.p01-p27: Unsteady flow plans with associated input files and simulation options. HDF versions may be opened with the HDF software. * UpperSanSaba.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. * UpperSanSaba.rasmap and rasmap.backup: RASMAP is the spatial GUI in HEC-RAS, and these files contain symbology and settings for this interface. * UpperSanSaba.u01-u14: 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. * UpperSanSaba.x01: Run file for unsteady flow, created by HEC-RAS so that unsteady flow may be simulated/computed. * UpperSanSabaFinal.p05: Unsteady flow plan and associated HDF. \== 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/) 1D folder: * UpperSanSaba.f03: Steady Flow data for 1D hotstart used to fill channel in HEC-RAS. * UpperSanSaba.O05: Output file for 1D hotstart. * UpperSanSaba.p05/UpperSanSaba.p05.hdf: Plan file and associated HDF for 1D hotstart. * UpperSanSaba.r05: Run file for steady flow 1D hotstart. 15cfs_2D-115cfs_2D folders: * HEC-RAS-generated post-processing HDF files for calibration flow (15cfs) and validation flows (45cfs and 115cfs). See attached report for details about calibration and validation of the HEC-RAS model. D15cfs-D12780cfs folders: * HEC-RAS generated post-processing HDF files for example discharges occurring in the upper San Saba River. Geometry folder: * 102739_TXCentral_SP_Feet.prj: HEC-RAS project file used to define the projected coordinate system of the HEC-RAS interface. Set to Texas Central State Planes (feet). * IDW_Apr15.hdf: Contains the terrain used for the simulation, bathymetry was "burned" in and computed via Inverse Distance Weighted method described in the attached report. * IDW_Apr15.Merge_Apr15.tiff: Terrain for the simulation in a raster format. * IDW_Apr15.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). hotstart folder: * HEC-RAS-generated post-processing HDF file for 2D unsteady 15cfs hotstart Land Classification folder: * Landcover.backup.hdf: HEC-RAS-generated backup of the Land Cover file. * Landcover.hdf: Contains the landcover used for the simulation. * Landcover.tiff: Landcover for the simulation in a raster format. ## Version Information: The updated version of the HEC-RAS model includes the following changes from the original submission: * Updated unsteady flow files that reference only 2D model geometry * Increased documentation of references and resources in unsteady flow files, plans, and model description * Corrected file path for land cover file * Removal of unnecessary land cover and geometry files ## Sharing/Access information Data was derived from the following sources: * 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. * USGS 3DEP data * NAIP aerial imagery