Michal J. Niemoczynski Thomas P. Suro Kevin B. Mulligan Kevin M. Molongoski 20260424 Model application Denver, CO U.S. Geological Survey Niemoczynski, M.J., Suro, T.P., Mulligan, K.B., and Molongoski, K.M., 2026, HEC-RAS two-dimensional hydraulic model of alternative weir designs for the Millstone River at Blackwells Mills, New Jersey: U.S. Geological Survey data release, https://doi.org/10.5066/P14T93HI. https://doi.org/10.5066/P14T93HI Thomas P. Suro Michal J. Niemoczynski Kevin B. Mulligan 2026 publication Scientific Investigations Report 2026-5002 Reston, VA U.S. Geological Survey Suro, T.P., Niemoczynski, M.J., Mulligan, K.B., 2026, Analysis of alternative weir designs for improved passage of select fish at the U.S. Geological Survey streamgaging weir at Blackwells Mills, New Jersey: U.S. Geological Survey Scientific Investigations Report 2026-5002, https://doi.org/10.3133/sir20265002. https://doi.org/10.3133/sir20265002 Streamgaging weirs, like the ones used by the U.S. Geological Survey (USGS), play a critical role in providing accurate and stable streamflow data, but their presence can affect the passage of diadromous fish species such as river herring and American shad. In some situations, weirs existing in rivers and streams are no longer used because they were part of a farm irrigation system or some type of industrial operation. Removal of those structures can restore the river to a more natural state in those reaches. The weir at the USGS streamgage 01402000 Millstone River at Blackwells Mills, New Jersey is not an obsolete relic from an old agricultural or industrial operation rather it was purposefully built as a hydraulic control structure that provides precise and stable control for the measurement of stage and computation of continuous streamflow. To satisfy the dual need of maintaining accurate streamflow data and improved fish passage for select species of fish during migration season, the USGS proposed development and evaluation of two alternative weir designs that would meet the criteria established for successful passage of the American shad, alewife, and blueback herring during their migration season from April 14 through May 28 of each year. The designs also are needed to maintain adequate control of the upstream pool elevation necessary for precise computation of streamflow that is used by state agencies for municipal water-supply purposes for surrounding communities. Alternative weir designs incorporating two different weir modifications within the center section of the Blackwells Mills weir were modeled using two-dimensional hydraulic modeling software (HEC-RAS) and three-dimensional computational fluid dynamics software (FLOW 3D HYDRO) to simultaneously evaluate conditions for passage of the target fish species and impacts to streamflow computation at the Blackwells Mills streamgage. The models were calibrated to existing conditions around the weir location using surveyed elevation data and recorded stage, streamflow, and velocity in the Millstone River. This data release contains the input and output data for the two models used to complete the analysis of the alternative weir designs. The contents of this data release support the following publication: Suro, T.P., Niemoczynski, M.J., Mulligan, K.B., 2026, Analysis of alternative weir designs for improved passage of select fish at the U.S. Geological Survey streamgaging weir at Blackwells Mills, New Jersey: U.S. Geological Survey Scientific Investigations Report 2026-5002, https://doi.org/10.3133/sir20265002. The HEC-RAS two-dimensional hydraulic model is intended to provide state and local government officials, planners, and agencies with tools to evaluate alternatives to the present weir structure at the Millstone River at Blackwells Mills streamflow gage that balance the interests of improved diadromous fish passage and those of water resources for the State of New Jersey. To maintain the native structure of the HEC-RAS model and to accommodate the large number of output files included within this data release, the zip file is large (3.18 GB). Please make sure you have ample space on your computer to accommodate the download and unzipped files. The unzipped HEC-RAS model application is 4.23 GB. 2026 publication date Complete None planned -74.580211 -74.571274 40.481400 40.470256 ISO 19115 Topic Category inlandWaters biota environment USGS Thesaurus migratory species hydraulic engineering fish water resources mathematical modeling streamflow surface water (non-marine) river systems stream discharge aquatic ecosystems ecology migration (organisms) None 2D hydraulic model HEC-RAS streamgage weir dam USGS Metadata Identifier USGS:68307326d4be0269904c2372 Common geographic areas New Jersey Millstone River Somerset County Blackwells Mills None. This dataset is provided by USGS as a public service. Please see 'Distribution Info' for details. Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from this data release. The input and output files for the HEC-RAS hydraulic model are provided to support the analyses documented in the associated report (https://doi.org/10.3133/sir20265002). Although the information contained in the model files may be useful for other purposes, it is incumbent on the user to understand the purpose, construction, and limitations of this model. Data have been checked to ensure consistency with the accompanying report. If any errors are detected, please notify the originating office. Michal J. Niemoczynski U.S. Geological Survey, Northeast Region Hydrologist mailing address

3450 Princeton Pike Suite 110

Lawrenceville NJ 08648 US 609-771-3989 609-771-3915 mniemocz@usgs.gov Funding: New Jersey Department of Environmental Protection None Unclassified None The HEC-RAS two-dimensional model simulations was run with version 6.5 of United States Army Corps of Engineers (USACE) Hydrologic Engineering Center (HEC) River Analysis System (RAS). The model was run on a PC using an Intel(R) Core(TM) i9-10940X CPU @3.3Ghz with 64.0GB of RAM and employing Microsoft Windows 11 Enterprise Edition (64-bit) Operating System. U.S. Army Corps of Engineers 2005 Publication Washington, D.C. U.S. Army Corps of Engineers, Hydrologic Engineering Center Detailed description of the model input and output files included in this data release can be found in this model code documentation report at https://www.hec.usace.army.mil/software/hec-ras/documentation.aspx. Additional information can be found online at: https://www.hec.usace.army.mil/software/hec-ras/. https://www.hec.usace.army.mil/software/hec-ras/documentation.aspx U.S. Army Corps of Engineers 2025 publication Washington, D.C. U.S. Army Corps of Engineers, Hydrologic Engineering Center https://www.hec.usace.army.mil/confluence/rasdocs/r2dum/latest Prior to simulating flows using the alternative weir designs, the model was calibrated against observed conditions at the existing streamgaging weir at the Millstone River at Blackwells Mills, New Jersey streamgage. The HEC–RAS 2D hydraulic model simulated conditions very well at the calibration locations upstream and downstream of the weir with simulated flows at the three calibration targets of 98 cubic feet per second (ft3/s), 251 ft3/s, and 487 ft3/s matching observed surface-water elevations within 0.00 feet (ft) compared to the observed upstream water surface. At the lowest calibration flows of 10 and 50 ft3/s, the simulations matched observed values at -0.03 ft and -0.01 ft, respectively. No formal logical accuracy tests were conducted. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record and the associated model documentation report (https://doi.org/10.3133/sir20265002) for additional details. No formal positional accuracy tests were conducted. No formal positional accuracy tests were conducted. Jeffrey J. Danielson Dean J. Tyler 2015 raster digital data To access the Topobathymetric digital elevation model (TBDEM) with a 1-meter cell size, scroll to the bottom of the webpage to 'Access Data'. Select 'CoNED Project Reviewer'. Select the "New Jersey and Delaware' data for download. https://doi.org/10.5066/F7Z60MHJ Digital and/or Hardcopy 18800101 20140701 ground condition TBDEM for NJ and DE Topobathymetric digital elevation model (TBDEM) for the HEC-RAS two-dimensional model reach U.S. Geological Survey 2025 tabular digital data https://doi.org/10.5066/F7P55KJN Digital and/or Hardcopy 20140801 20141031 observed NWIS Observed flow and stage hydrographs for the Millstone River at Blackwells Mills within the model study reach. New Jersey Department of Environmental Protection, Bureau of GIS 2024 vector digital data https://gisdata-njdep.opendata.arcgis.com/datasets/njdep::land-use-land-cover-of-new-jersey-2020-1/about Digital and/or Hardcopy 2020 observed Land use/Land Cover of New Jersey 2020 Land use and land cover data used to establish roughness coefficient values for the 2D hydraulic model. HEC-RAS model geometry was created following general guidelines within the HEC-RAS user's manual (https://www.hec.usace.army.mil/software/hec-ras/documentation.aspx). This included import of the topobathymetric digital elevation model (TBDEM) (Danielson and Tyler, 2015) for terrain generation and construction of the two-dimensional (2D) model perimeter and mesh. This also included import of the land-cover feature class (NJDEP, 2024) used to define channel and assign overland roughness coefficients for the 2D model. TBDEM for NJ and DE Land use/Land Cover of New Jersey 2020 20241202 Modification of the 2D model geometry. This involved adjusting the channel elevations within the terrain using field-surveyed cross-sections and input of the streamgaging weir structure using the 2D connection editor. Model breaklines, reference points, and other geometry features were also added during this step. 20250124 Input of model boundary conditions including flow hydrographs (U.S. Geological Survey, 2025) and normal depth downstream. This step involved using the unsteady flow editor to generate boundary conditions for the 2D hydraulic model. NWIS 20250124 Adjustment of geometry parameters to allow calibration of the model to observed conditions included adjustment of roughness coefficients, weir coefficients, and downstream boundary conditions. 20250124 The existing calibrated model geometry was copied to facilitate modification of the existing weir geometry with the alternative trapezoidal designs. These designs were run in separate model simulations to obtain results. 20250312 Transverse Mercator 0.9999 -74.5 38.83333333333334 492125.0 0.0 coordinate pair 0.00000000728570537233964 0.00000000728570537233964 survey feet North American Datum of 1983 (NAD 83) Geodetic Reference System 1980 6378137.000000 298.257222 North American Vertical Datum of 1988 0.01 feet Implicit coordinate This model application data release contains all the model input and output files needed to replicate the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20265002). Suro, T.P., Niemoczynski, M.J., Mulligan, K.B., 2026, Analysis of alternative weir designs for improved passage of select fish at the U.S. Geological Survey streamgaging weir at Blackwells Mills, New Jersey: U.S. Geological Survey Scientific Investigations Report 2026-5002, https://doi.org/10.3133/sir20265002. Detailed description of the HEC-RAS model input and output files included in this data release can be found in this model code documentation report at https://www.hec.usace.army.mil/software/hec-ras/documentation.aspx. Additional information can be found online at: https://www.hec.usace.army.mil/software/hec-ras/. U.S. Army Corps of Engineers, 2025, HEC-RAS river analysis system: HEC-RAS User’s Manual, version 6.6, accessed December 31, 2025, at [Also available at https://www.hec.usace.army.mil/software/hec-ras/documentation.aspx] U.S. Geological Survey GS ScienceBase mailing address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although the data, software, and related material have been processed successfully on a computer system at the U.S. Geological Survey (USGS), reviewed for accuracy and completeness, and approved for release by the USGS, no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Although the data have been subjected to rigorous review and are substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, the data are released on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from authorized or unauthorized use. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Digital Data 1.0 3180 https://doi.org/10.5066/P14T93HI None 20260424 GS-W-NJ Data Release New Jersey Water Science Center Data Release Manager mailing address

3450 Princeton Pike, Suite 110

Lawrenceville NJ 08648 US 609-771-3900 609-771-3915 gs-w-nj_datarelease@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998