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, FLOW 3D HYDRO computational fluid dynamics 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 FLOW 3D HYDRO three-dimensional computational fluid dynamics 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. The FLOW 3D HYDRO three-dimensional computational fluid dynamics model output files are large, with the compressed (zip) file being 114 GB. Please make sure you have ample space on your computer to accommodate the download and unzipped files. The unzipped FLOW 3D HYDRO model files are 329 GB. The executable for the FLOW-3D HYDRO model is proprietary and requires a valid software license to run simulations or perform post-processing, and cannot be included within this model application data release. Detailed description of the FLOW-3D HYDRO model input and output files included in this data release can be found in the model capabilities webpage located at https://www.flow3d.com/modeling-capabilities/water-environmental-models/. The output files can be viewed by using the ParaView software executable included in this data release. More specific information can be found in the README file included with the FLOW 3D HYDRO model application child item. 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 FLOW 3D hydro hydraulic model streamgage 3D weir dam USGS Metadata Identifier USGS:68307388d4be0269904c237a 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 FLOW 3D HYDRO computational fluid dynamics 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 FLOW 3D HYDRO computational fluid dynamics model simulations were run with version 2024R1 and 2025R1. The model was run on a PC using an Intel(R) Xeon(R) w7-249SX processor @2.5Ghz with 128.0GB of RAM and employing Microsoft Windows 11 Enterprise Edition (64-bit) Operating System. Weir structures for the existing, trapezoidal-notched, and V-notched configurations were modeled in OnShape computer-aided design (CAD) software version 1.196. 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. A calibration simulation was performed using the existing weir geometry to confirm that the FLOW 3D HYDRO model produced streamflow estimates consistent with measured data. This test run was configured with fixed headwater and tailwater elevations, based on the 2D HEC-RAS model output at the upstream and downstream boundary locations. The model-calculated streamflow rate was 252.4 cubic feet per second (ft3/s), compared to a rated streamgage value of 251 ft3/s at the site (U.S. Geological Survey, 2025). The simulated discharge was within 1-percent of the observed value, which was considered an acceptable level of agreement. 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. U.S. Geological Survey 2022 raster digital data https://www.sciencebase.gov/catalog/item/635cbfc5d34ebe442504cc82 Digital and/or Hardcopy 2022 publication date USGS 3DEP LiDAR Lidar elevation data set used for the FLOW 3D HYDRO computational fluid dynamics 3 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. Creation of bathymetric raster surface input for Flow3D HYDRO model geometry began with bathymetric survey data collected by the U.S. Geological Survey, New Jersey Water Science Center (NJWSC) in October 2023 which included cross-sections upstream, downstream, and across the weir. To supplement gaps in the embankments, USGS 3DEP LiDAR data ( U.S. Geological Survey, 2022) was incorporated, which met Quality Level 2 standards. Both datasets were imported into CloudCompare (v2), an open-source software designed for processing and analyzing 3D point clouds and triangular meshes, where datums were aligned and, point clouds were merged, and interpolated to generate a 5 feet (ft) × 5 ft raster surface. USGS 3DEP LiDAR 20241202 OnShape (version 1.196), a cloud-based computer-aided design (CAD) and product development platform that enables 3D modeling, was used to model the existing weir structure and shape using the New Jersey Water Science Center (NJWSC) October 2023 survey data. OnShape was then used to make weir design modifications for the trapezoidal and V-shaped alternatives. 20250124 A stereolithographic (STL) file for the existing weir geometry developed using Onshape was imported for use within FLOW 3D HYDRO software. 20250124 Adjustment of geometry parameters to allow calibration of the model to observed conditions included adjustment of roughness coefficients, flow boundaries, weir coefficients, and tailwater elevations. NWIS 20250124 Existing weir geometry was modified in Onshape to allow for implementation of alternative weir designs. These designs were run in separate model simulations to obtain results including changes in water-surface elevations and channel velocities. 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 FLOW-3D HYDRO model input and output files included in this data release can be found in the model capabilities webpage located at at https://www.flow3d.com/modeling-capabilities/water-environmental-models/ Flow Science, Inc., 2026, FLOW-3D, Modeling Capabilities, accessed January 5, 2026, at https://www.flow3d.com/modeling-capabilities/ 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 114000 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