DOI: 10.5061/dryad.k3j9kd5gr
title: Hydraulic model (HEC-RAS) of downstream of Tuttle Creek Reservoir at the confluence of the Big Blue River and the Kansas River near Manhattan, KS

description: A 2D Hydraulic model (HEC-RAS) for below Tuttle Creek Reservoir at the
 confluence of the Kansas River and the Big Blue River near Manhattan, KS
 is presented. Model geometry is based on United States Geological Survey
 (USGS) 3DEP data (2015), with underwater bathymetry “burned” in using
 cross-sections sampled in the field in April of 2023. The model was
 calibrated based on water surface measured during data collection. The
 hydraulic simulations correspond to streamflows during which fish
 monitoring data were collected by researchers at Kansas State University
 (L. Rowley and K. Gido, to be published). Results from the hydraulic
 model, coupled with a sediment transport model, will be used to study fish
 and macroinvertabrate ecological response to streamflow.
description: The following is a summary of data utilized for developing a
 bathymetric terrain for 2D hydraulic modeling using HEC-RAS. Data used for
 model calibration and validation is also discussed.
   Available Data
 Cross-section elevation data were collected by the United
 States Army Corps of Engineers (USACE) Kansas City District at
 approximately 200-foot to 1000-foot increments at the confluence of the
 Big Blue River and the Kansas River near Manhattan, Kansas. The following
 equipment was used by two complete surveying teams:
 • Ohmex SonarMite single beam echo sounder SFX @
 200khz,  • Ohmex SonarMite single beam echo sounder
 DFX @ 28kHz & 200kHZ,  • Trimble R12i 0096
 & 0098,  • Trimble R8 1984 &
 6282   The cross-section
 elevation data were collected by boat and supplemented by hand-carried,
 pole-mounted Trimbles on April 10 to 14, 2023. The USGS gage on the Big
 Blue River near Manhattan, KS (06887000) had an average discharge of 425
 cfs during the field collection time period (Figure 1). A USGS gage
 downstream of the confluence, Kansas River at Wamego, KS (06887500) shows
 an average discharge of 780 cfs at the same time period (Figure
 2).         Figure 1 (Refer
 to supplemental information file). USGS gage Big Blue R NR Manhattan, KS –
 06887000 discharge data for the week of April 11, 2023 – April 15, 2023.
 The average flow was taken as 425 cfs.      
   Figure 2 (Refer to supplemental information
 file). USGS gage Kansas River at Wamego, KS (06887500) discharge data for
 the week of April 11, 2023 – April 15, 2023. The average flow was taken as
 780 cfs. Wamego, KS is downstream of the Big Blue River and Kansas River
 confluence and represents combined flow for both tributaries.
   Figure 3 (Refer to supplemental
 information file). Map of bathymetric cross-sections collected in April
 2023 near Manhattan, KS. Arrows show flow direction. Inset is the data
 collection location relative to the state of Kansas.
  
 <strong>Terrain</strong> The
 field data collection featured 56 cross-sections. HEC-RAS 6.3.1 was
 utilized to create a bathymetric surface by interpolating 1-D
 cross-sections, while a 1-m resolution USGS 3DEP terrain (2015) was used
 for the floodplain and surrounding areas. A more recent USGS 3DEP (2018)
 data was available but featured higher stream flow than the 2015 data
 collection and therefore, more of the channel was submerged. Overall, the
 difference between 2015 and 2018 had a mean deviation of ~0.04 feet, with
 a majority of the differences in the channel ranging between +/-0.5 feet.
 Islands in this reach are unvegetated and prone to movement, and therefore
 the exact channel form is uncertain. However, it is assumed that relative
 island areas are consistent throughout the reach, and 2015 LiDAR was used
 to delineate the most island area as possible. 
   To build the bathymetric terrain, a
 similar process as what was discussed in Harris et al. (2023), field
 collected data were imported into ArcGIS Pro 3.0 as a point shapefile. To
 preserve georeferencing, the point shapefile was segmented into groups of
 3-4 cross-sections and these cross-sections were interpolated into
 mini-surfaces using the Inverse Distance Weighted (IDW) spatial analysis
 tool. These mini-surfaces were brought into HEC-RAS and cross-sections
 were drawn to intersect with these field surveyed locations. The 1-D
 cross-sections were then used to create a TIFF for the entire channel
 area. The 1D interpolation captures the channel centerline between
 measured cross-sections but meanders and channel widening may not be
 covered by the interpolated channel. The channel raster was broken into
 its component objects or “exploded”, in ArcGIS Pro using the Raster to
 Point tool. The points were then interpolated using the
 Inverse-Distance-Weighted interpolation tool (IDW). This creates a terrain
 that covers meanders and channel expansion while maintaining fidelity to
 the original channel raster.  
 Areas where the terrain was inundated at the time of LiDAR data
 collection are “flat” and referred to as a hydro-flattened surface. The
 Slope tool in ArcMap was used to delineate these hydro-flattened areas and
 a shapefile tracing unsubmerged islands was used. The IDW surface was
 clipped to the hydro-flattened extents and then mosaicked with the
 original 3DEP terrain to create a seamless bathymetric and topographic
 surface.    The field data
 collected in April 2023 (Figure 3) required supplemental information to
 cover a fish monitoring instance upstream of the bridge at Pillsbury
 Drive/177. In September 2021, the USACE Kansas City District collected
 sediment samples with XY-georeference and depth measurements. The LiDAR
 hydro-flattened surface was used to estimate the energy grade slope from
 the new cross-section to the recent field monitoring extents. The model
 scenario or “plan” on the April 2023 extents was run at a similar flow as
 was occurring in September 2021. The combination of water surface
 elevation at that flow (780 cfs), the energy grade slope in the 3DEP data
 and field measured depth in 2021 were used to estimate the elevation at
 the channel bed.   
 <strong>Land Cover</strong>
 Land cover was delineated using the Multi-Resolution Land
 Characteristic (MRLC) Consortium’s 2019 National Land Cover Data (NLCD)
 (MRLC 2016). Fifteen types of landcover were identified for this study
 area by the NLCD: Hay-Pasture, Shrub-Scrub, Developed Low Intensity,
 Developed Medium Intensity, Cultivated Crops, Deciduous Forest,
 Herbaceous, Develop Open Space, Developed High Intensity, Woody Wetlands,
 Emergent Herbaceous Wetland, Open Water, Mixed Forest, Barren Land, and
 Evergreen Forest. Manning’s n values were selected based on a range of n
 values along with a “Suggested Initial n” provided by Krest Engineers
 (2021) (Table 1).   Table 1.  A table representing
 a range of Manning’s n values, a suggested Manning’s n value, and percent
 imperviousness for each NLCD land cover type. (Krest Engineers,
 2021)   <strong>Model
 Settings</strong> The 2D HEC-RAS mesh was set
 to 40-feet square, with breaklines to orient cell edges along areas of
 steep elevation change or to support model convergence. Boundary
 conditions were placed at three locations in the 2D flow area: the inflow
 of the Big Blue River (boundary condition type: flow hydrograph), the
 upstream end of the Kanas River (flow hydrograph), and the downstream end
 of the Kanas River (normal depth). An energy grade slope was given as
 0.0005 ft/ft for the Big Blue River and 0.0003 ft/ft for the Kansas River.
 Advanced time step control adjustments were implemented using Courant’s
 Criterion, with a minimum Courant of 0.75 and a maximum of 3. 
  
 <strong>Calibration</strong>
 The suggested value from Krest Engineers (2021) was the initial
 Manning’s n used for each land cover type (Table 1). The hydraulic model
 was then run, and the Manning’s n was changed to better conform to water
 surface elevations observed during field data collection.  Flows
 corresponding to the field collection dates were 415 cfs for the Big Blue
 River and 360 cfs for the Kansas River. These streamflows were determined
 by cross-referencing the field collection dates (April 10 to 14, 2023) to
 continuous monitoring data available from USGS at gages Big Blue R NR
 Manhattan, KS (06887000) and Kansas R at Fort Riley, KS
 (06879100). The 2D model simulation results were
 compared to the field-measured water surface elevations at each channel
 cross-section with the ArcGIS Zonal Statistics as Table tool. Model
 improvement was determined by calculating the Root Mean Square Error
 (RMSE) of the simulated water surface elevation to the field observed
 water surface elevation, and the Manning’s n values resulting in the
 lowest error were selected. Following calibration, the model has overall
 RMSE of 0.29 ft for depth. The final Manning’s n values used for all the
 following simulations are included in Table 2. 
   <strong>Land Cover </strong> <strong>Mannings n</strong> Open Water 0.025 Emergent Herbaceous Wetlands 0.05 Woody Wetlands 0.045 Herbaceous 0.025 Mixed Forest 0.08 Evergreen Forest 0.08 Deciduous Forest 0.1 Scrub-Shrub 0.07 Hay-Pasture 0.025 Cultivated Crops 0.02 Baren Land 0.023 Developed, Open Space 0.03 Developed, Low Intensity 0.06 Developed, Medium Intensity 0.08 Developed, High Intensity 0.12 Table 2. The selected Manning’s n per Landcover classification after calibration   <strong>Simulations</strong> Apart from the calibration simulations, further simulations were conducted to match additional fish data collection from July 17 – 21, 2023 and October 2- 6, 2023. USGS gages, Big Blue R NR Manhattan, KS (06887000) and Kansas R at Fort Riley, KS (06879100), were used to find the discharge rates (in cfs) during those fish sampling periods. While discharge was consistent throughout the weeks for some gages (Figures 4 and 7), others showed differences greater than 10% or 100 cfs (Figures 5 and 6). The gages that showed significant differences were divided into two sub-simulations for the lower and higher flows during that week.    <strong>USGS Streamflow Data for July 17 - 21, 2023</strong>       <strong>HEC RAS Scenario</strong> <strong>Description</strong> <strong>River</strong> <strong>Simulation Flow (cfs)</strong> July_KS_LF July lower flow Big Blue 500     Kansas 330 July_KS_HF July higher flow Big Blue 500     Kansas 490 Table 3. A table representing each scenario ran for the week of July 17, 2023 – July 21, 2023 with HEC RAS descriptions and USGS streamflow data.    <strong>USGS Streamflow Data for October 2 - 6, 2023</strong>       <strong>HEC RAS Scenario</strong> <strong>Description</strong> <strong>River</strong> <strong>Simulation Flow (cfs)</strong> October_BB_LF October lower flow Big Blue 570     Kansas 200 October_BB_HF October higher flow Big Blue 660     Kansas 200 Table 4. A table representing each scenario ran for the week of October 2, 2023 – October 6, 2023 with associated HEC RAS descriptions and USGS streamflow data.   Figure 4 (Refer to supplemental information file). USGS gage Big Blue R NR Manhattan, KS – 06887000 discharge data for the week of July 17, 2023 – July 21, 2023. The average flow was taken as 500 cfs.    Figure 5 (Refer to supplemental information file). USGS gage Kansas R at Fort Riley, KS - 06879100 discharge data for the week of July 17, 2023 – July 21, 2023. Because the differences in high and low flows were significant (&gt; 100 cfs) the lowest flows and highest flows were averaged for two sub-simulations of 330 cfs and 490 cfs.    Figure 6 (Refer to supplemental information file). Big Blue R NR Manhattan, KS – 06887000 discharge data for the week of October 2, 2023 – October 6, 2023. The differences in high and low flows were considered not significant (&lt;100 cfs), the substantial increase in discharge on October 4th resulted in the lowest flow and peak flow being averaged for two sub-simulations of 570 cfs and 660 cfs.   Figure 7 (Refer to supplemental information file). USGS gage Kansas R at Fort Riley, KS - 06879100 discharge data for the week of October 2, 2023 – October 6, 2023. The average flow was taken as 200 cfs.    <strong>Summary of Assumptions</strong>: 1. The accuracy of discharge measurements from river gages has a margin of error up to 10%. The data used for 2023 near the Manhattan, KS gages at Big Blue River and Kansas River has been approved by USGS. 2. The accuracy and reliability of field-measurements are subject the accuracy of tools used for field measurement. 3. The data provided in 1D cross-section dimensions are minimal laterally, but there was a rather high data resolution longitudinally in the channel. River area between 1D cross-sections is interpolated. Bank to measured depth contours and measured depth to measured depth contours are uncertain.  4. 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. 5. Bridge structures were not included into the model. 6. Groundwater contributions and losses were not incorporated into the model. 7. The model does not incorporate sediment transport, so changes in islands configurations or scour/deposition is not simulated.   Usage Notes: HEC-RAS 6.3.1 is a free hydraulic analysis software available from US Army Corps of Engineers.    <strong>Reference</strong>:  Krest Engineers, LLC. 2021. Manning’s n (Roughness Coefficient) for HEC-RAS 2D Modeling. Written January 10 2021 on RASHMS.com. https://rashms.com/blog/mannings-n-roughness-coefficient-for-hec-ras-2d-modeling/.   Harris, Aubrey, Samantha R. Wiest, Kiara Cushway, Zachary Mitchell, Astrid Schwalb. 2023. Hydraulic model (HEC-RAS) of the Upper San Saba River between Fort McKavett and Menard, TX [Dataset]. Dryad. https://doi.org/10.5061/dryad.pc866t1tt   Multi-Resolution Land Characteristic (MRLC) Consortium: National Land Cover Database. 2016. 2019 National Land Cover Data. https://www.mrlc.gov/data  US Geological Survey, 2020-03-30, USGS one meter KS South Central AOI 2 Manhattan 2015: USGS.
description: # Hydraulic model (HEC-RAS) of downstream of Tuttle Creek Reservoir at the
 confluence of the Big Blue River and the Kansas River near Manhattan, KS
 [https://doi.org/10.5061/dryad.k3j9kd5gr](https://doi.org/10.5061/dryad.k3j9kd5gr) ## Description of the data and file structure Many of the files are specific to HEC-RAS and may be opened with HEC-RAS 6.3.1 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 * LandcoverB_122223.hdf: Contains the landcover used for the simulation. * LandcoverB_122223.tiff: Landcover for the simulation in a raster format. * Terrain_121123.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_121123.Terrain_121123.newterr_1211.tiff: Terrain for the simulation in a raster format. * Terrain_121123.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). * TuttleCreek.b11-b16: Boundary conditions (inflow outflow) for the simulation, viewable from HEC-RAS interface. * TuttleCreek.bco11-bco16: Unsteady flow log output files, viewable from the HEC-RAS interface. * TuttleCreek.c04: 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. * TuttleCreek.dss: Unsteady flow output as time series data for the unsteady simulation from HEC-RAS, viewable from any program that can read dss files. * TuttleCreek.g04: Geometry file for the simulation, associates terrain, landcover, and 2D model areas with one another. * TuttleCreek.g04.hdf: Geometry file for the simulation as an HDF file. * TuttleCreek.IC.O11-O16: Initial conditions (t=0) for the respective Unsteady flow simulations. * TuttleCreek.p01,p11-p16: Unsteady flow plans with associated input files and simulation options. * TuttleCreek.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. * TuttleCreek.rasmap and rasmap.backup: RASMAP is the spatial GUI in HEC-RAS, and these files contain symbology and settings for this interface. * TuttleCreek.u04-u07, u10: 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. * TuttleCreek.x04: Run file for unsteady flow, created by HEC-RAS so that unsteady flow ay be simulated/computed. 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/) ## Sharing/Access Information Data was derived from the following sources: * United States Army Corps of Engineers (USACE) Kansas City District * USGS 3DEP data * NAIP aerial imagery