The U.S. Geological Survey (USGS), in cooperation with the Fond du Lac Band of Lake Superior Chippewa (FDLB), Minnesota, analyzed the hydrologic and hydraulic conditions within the Stoney Brook watershed. The Stoney Brook watershed covers an area of 100.8 square miles in Carlton and St. Louis counties with most of the watershed within the Fond du Lac Reservation. Wild rice, which is harvested by the FDLB, naturally grows in the lakes on the Fond du Lac Reservation and is susceptible to damage from increased water-levels after substantial rainfall events. Channel modifications and frequency rainfall events were simulated to assess lake level conditions that could mitigate potential damages to the wild rice yields. The channel modifications were also used to evaluate options for improving conveyance and floodplain storage in the watershed. The study area consists of 77.9 square miles of the watershed with the downstream boundary located 2.4 miles downstream from the USGS streamgage Stoney Brook at Pine Drive near Brookston, Minn. (USGS station 04021520; U.S. Geological Survey, 2023). A hydrologic model was used to simulate precipitation runoff and outflow hydrographs from delineated subwatersheds in the Stoney Brook watershed. A two-dimensional hydraulic model was used to simulate streamflows, volume accumulation, lake water-levels, and inundation duration and depths. The hydrologic model was developed using Hydrologic Engineering Center–Hydrologic Modeling System (HEC–HMS) computer program (version 4.3; U.S. Army Corps of Engineers, 2022) for the simulation of single rainfall events. A total of 14 subwatersheds were used in the HEC–HMS model to represent the 77.9 square mile study area within the Stoney Brook watershed. The HEC–HMS model was calibrated using streamflow time series from the USGS streamgage Stoney Brook at Pine Drive near Brookston, Minn. (USGS station 04021520; U.S. Geological Survey, 2023) to two high-flow events: April 21–30, 2008, and June 19–July 1, 2012. The calibrated HEC–HMS model used 24-hour duration design rainfall events consisting of precipitation frequencies of 1-, 2-, 5-, and 10-year recurrence intervals (100-, 50-, 20-, and 10-percent annual exceedance probabilities) for the simulation of channel modification alternatives in the hydraulic model. The hydraulic model was developed using Hydrologic Engineering Center–River Analysis System (HEC–RAS) computer program (version 6.4.1; U.S. Army Corps of Engineers, 2023). The HEC–RAS model was calibrated using streamflow time series from the USGS streamgage Stoney Brook at Pine Drive near Brookston, Minn. (USGS station 04021520; U.S. Geological Survey, 2023) to two high-flow events: April 21–30, 2008, and June 19–July 1, 2012. Channel modification alternatives were developed in the HEC–RAS model as terrain modifications and were intended to improve flow conveyances and storage and wetland coverage within the floodplain. These terrain modifications include breaches in the bank spoils, reconnecting the original channel to Stoney Brook, and clearing the original channel of soil deposition and debris. The HEC–HMS with HEC–RAS scenarios were simulated using flows from 1-, 2-, 5-, and 10-year recurrence interval (100-, 50-, 20-, and 10-percent annual exceedance probabilities) precipitation events distributed over a 24-hour duration. The HEC–RAS model was used to determine differences in hydraulic characteristics such as: peak water-surface elevations in the lakes, peak flows, volume accumulation, and inundation durations and depths. This data release contains a zip file that includes the HEC–HMS and HEC–RAS model run files, model performance and calibration metrics, and model outputs used in this study.
References Cited: U.S. Army Corps of Engineers, 2018, Hydrologic Engineering Center Hydrologic Modeling System HEC–HMS 4.3. User’s Manual: U.S. Army Corps of Engineers software release, accessed October 10, 2022, at https://www.hec.usace.army.mil/software/hec-hms/downloads.aspx. U.S. Army Corps of Engineers, 2023, HEC–RAS—River analysis system version 6.4: U.S. Army Corps of Engineers software release, accessed October 2, 2023, at https://www.hec.usace.army.mil/software/hec-ras/download.aspx. U.S. Geological Survey, 2023, USGS surface-water data for the Nation, in USGS water data for the Nation: U.S. Geological Survey National Water Information System database, accessed October 2, 2023, at https://doi.org/10.5066/F7P55KJN. [Surface-water data directly accessible at https://waterdata.usgs.gov/nwis/sw.]