Archive of the Hydrologic and Hydraulic Models used in the Analyses of the Silver Creek Basin and Selected Tributaries Associated with Scott Air Force Base, Illinois, 1992–2050

The U.S. Geological Survey (USGS), in cooperation with Scott Air Force Base (SAFB), Illinois, assessed the effects of temporal land-use development in the Silver Creek Basin, the potential effects of projected changes in future precipitation, and the effects of added detention storage in selected tributaries near SAFB. A hydrologic model was used to simulate precipitation runoff and streamflows for subbasins included in the Silver Creek Basin spanning 464 square miles upstream from the USGS streamgage at Freeburg, Ill. (USGS station 05594800; U.S. Geological Survey, 2023). A two-dimensional hydraulic model was used to simulate water-surface profiles and flood inundation extent of a localized area within the basin that includes SAFB and the vicinity.

The hydrologic model was developed using Hydrologic Engineering Center–Hydrologic Modeling System (HEC–HMS) computer program (version 4.9; U.S. Army Corps of Engineers, 2022) for the simulation of single rainfall events. The HEC–HMS model was developed to provide information at two scales—a basin scale and SAFB focus-area scale—to meet the study objectives, and subbasins within the model varied to meet the objectives of the two scales. The basin-scale model was developed using subbasins at the hydrologic unit code 12 level (U.S. Department of Agriculture, 2021) corresponding to areas of 5.7 to 57.6 square miles. The SAFB focus area, located within the basin scale model, included small (0.14 to 2.4 square mile) subbasins used to simulate streamflow within selected tributaries on and adjacent to SAFB. A total of 41 subbasins were used in the HEC–HMS model to represent the 464 square mile basin. The basin-scale HEC–HMS model was calibrated and validated using streamflow time series from the USGS streamgage at Freeburg, Ill. and the USGS streamgage near Troy, Ill. (USGS station 05594450; U.S. Geological Survey, 2023) to six high-flow events: June 21, 2015, September 8–10, 2018, January 12–13 2020, August 12–13, 2020, July 26–27 2022, and March 23–26, 2023. The calibrated HEC–HMS model used 24-hour duration design rainfall events consisting of precipitation frequencies of 2-, 10-, 25, 50-, 100-, and 500-year recurrence intervals (50-, 10-, 4-, 2-, 1- and 0.2-percent annual exceedance probabilities) for 24 HEC-HMS-only scenarios used in determining hydrologic effects of land cover and projected precipitation on a basin scale. The HEC–HMS basin scale conditions consisted of historical (1992) land cover, current (2019) land cover, planned land cover, and planned land cover with projected (2050) precipitation. The HEC–HMS model was used to assess hydrologic changes in magnitude of peak streamflow, timing of the peak, cumulative volume of runoff for the subbasins.

The hydraulic model was developed using Hydrologic Engineering Center–River Analysis System (HEC–RAS) computer program (version 6.5; U.S. Army Corps of Engineers, 2023). Detention storage scenarios were developed in the HEC–RAS model to assess the potential effects of a representation of amended storage on the hydrology at a reference location rather than to serve as a prescriptive design for mitigation of peak streamflows. The HEC–RAS model was calibrated using high-water marks and continuous pressure transducer water-level data for three events: August 12–13, 2020, July 26–27 2022, and March 23–26, 2023. An additional 28 scenarios using HEC–HMS and HEC–RAS were used to determine hydraulic changes within the SAFB focus area resulting from detention and projected precipitation options. The HEC–HMS with HEC–RAS scenarios were conducted using simulated flows from 2-, 5-, 10-, 25, 50-, 100-, and 500-year recurrence interval (50-, 20-, 10-, 4-, 2-, 1- and 0.2-percent annual exceedance probabilities) precipitation events distributed over a 24-hour duration. The HEC–RAS model was used to determine differences in hydraulic characteristics (water-surface profiles and inundation extents) of streams within and adjacent to SAFB resulting from added detention and the projected (2050) precipitation condition. 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, 2022, Hydrologic Engineering Center—Hydrologic Modeling System (HEC–HMS 4.9): U.S. Army Corps of Engineers software release, accessed February 22, 2022, at https://www.hec.usace.army.mil/software/hec-hms/downloads.aspx.

U.S. Army Corps of Engineers, 2023, Hydrologic Engineering Center—River analysis system (HEC–RAS 6.4): U.S. Army Corps of Engineers software release, accessed October 15, 2022, at https://www.hec.usace.army.mil/software/hec-ras/download.aspx.

U.S. Department of Agriculture, 2021, GeoSpatial data gateway: U.S. Department of Agriculture, Natural Resources Conservation Service, accessed November 3, 2021, at https://datagateway.nrcs.usda.gov/GDGOrder.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 May 4, 2023, at https://doi.org/10.5066/F7P55KJN. [Surface-water data directly accessible at https://waterdata.usgs.gov/nwis/sw.]