South Carolina StreamStats

StreamStats for South Carolina can be used to estimate the magnitude of peak flows for South Carolina under natural and urban streamflow conditions at the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2- percent annual exceedance probabilities. The reports below present the equations used to estimate the flow statistics, describe the uncertainty associated with the estimates, and describe the methods used to develop the equations and to measure the basin characteristics used in the equations. Users should familiarize themselves with the reports before using StreamStats to obtain estimates of streamflow statistics for ungaged sites.

• Feaster, T.D., Gotvald, A.J., Musser, J.W., Weaver, J.C., Kolb, K.R., Veilleux, A.G., and Wagner, D.M., 2023, Magnitude and frequency of floods for rural streams in Georgia, South Carolina, and North Carolina, 2017—Results: U.S. Geological Survey Scientific Investigations Report 2023–5006, 75 p., https://doi.org/10.3133/sir20235006.
• Feaster, T.D., Gotvald, A.J., and Weaver, J.C., 2014, Methods for estimating the magnitude and frequency of floods for urban and small, rural streams in Georgia, South Carolina, and North Carolina, 2011 (ver. 1.1, March 2014): U.S. Geological Survey Scientific Investigations Report 2014–5030, 104 p.
• Feaster, T.D., Clark, J.M., and Kolb, K.R., 2018, StreamStats for South Carolina—A multipurpose water-resources web application: U.S. Geological Survey Fact Sheet 2018–3070, 5 p., https://doi.org/10.3133/fs20183070.

Click below to view foundational layers and metadata for the South Carolina application, as well as specific sources and computation methods for basin characteristics:

• Musser, J.W., Kolb, K.R., Henley, J.C., and Doering, S.A., 2024, Foundational Geospatial Layers for South Carolina StreamStats 2024: U.S. Geological Survey data release, https://doi.org/10.5066/P132UCHM.
• Gurley, L.N., and Kolb, K.R., 2021, Land Cover Basin Characteristics Rasters for South Carolina StreamStats 2021: U.S. Geological Survey data release, https://doi.org/10.5066/P9LYEMJU.
• Kolb, K.R., Gross, T.A., Musser, J.W., and Rowley, T.H., 2021, Locations of Dams and Basins in South Carolina, derived from U.S. Army Corps Engineers National Inventory of Dams: U.S. Geological Survey data release, https://doi.org/10.5066/P9VGNFBO.
• Kolb, K.R., 2022, Impervious land cover raster derived from the National Land Cover Dataset (NLCD) 2019 for South Carolina StreamStats: U.S. Geological Survey data release, https://doi.org/10.5066/P9L4GTQX.
• Musser, J.W., and Kolb, K.R., 2022, Region layers for USGS South Carolina Bohman method hydrograph in StreamStats: U.S. Geological Survey data release, https://doi.org/10.5066/P93G318W.
• Swain, J.P., and Nardi, M.R., 2022, Gridded South Carolina StreamStats Runoff Curve Numbers by NLCD Landcover and SSURGO Soils Class: U.S. Geological Survey data release, https://doi.org/10.5066/P90O294J.
• Kolb, K.R., Heal, E.N., and Clark, J.M., 2018, Lidar-derived Data Layers for South Carolina StreamStats, 2007-2013: U.S. Geological Survey data release, https://doi.org/10.5066/P9Q8RSF5.
• Kolb, K.R, Clark, J.M., Gross, T.A, Gurley, L.N., Huffman, B.J, and Musser, J.W., 2019, Stream Lines Used to Produce the South Carolina StreamStats 2018 Release: U.S. Geological Survey data release, https://doi.org/10.5066/P9VDWVJO.

IMPORTANT INFORMATION CONCERNING ESTIMATED PEAK FLOWS

StreamStats outputs for ungaged sites provide estimates of both rural and urban peak flows. Use of the urban peak-flow estimates is most appropriate when impervious areas are 10 percent or more. In basins with impervious areas of less than 10 percent, the computed urban peak flow may be less than the computed rural peak flow. It is left to the discretion of each user, based on hydrologic judgment and knowledge of the area, to decide which computed peak flow to use.  The rural and urban equations are only applicable to basins not affected substantially by regulation from impoundments, tidal effects, channelization, levees, or other man-made structures.

Users are cautioned against using the equations outside of the ranges of values of the independent variables used to develop the equations, as potential errors are unknown in these cases. For the rural equations (Feaster and others, 2009), the range in drainage area is from 1 to 9,000 square miles. Impervious areas for streamgages used to develop the rural equations generally were less than 10 percent. For the urban and small, rural equations (Feaster and others, 2014), the range of applicable drainage area across all five hydrologic regions is from 0.10 to 459 square miles, and the range of impervious areas is from 0.0 to 47.9 percent. Table 11 in Feaster and others (2014), should be consulted for the ranges specific to each hydrologic region.

The South Carolina StreamStats application was developed from the best available elevation data for South Carolina. Light Detection and Ranging (LiDAR) derived digital elevation models (DEMs) at 30-foot post spacing were used as the basis for basin delineation and derivative topographic basin characteristics. The high-resolution elevation data provides an opportunity to provide the most accurate results from StreamStats for a variety of scientific applications.

The South Carolina LiDAR Consortium, sphere headed by the South Carolina Department of Natural Resources and consisting of numerous state, federal, and local government entities in South Carolina, began collecting LiDAR in 2007.  When work started on the South Carolina StreamStats project in 2014, both LiDAR-derived elevation and, with the exception of Georgetown County, hydrography data were available for the entire state at a 10-foot resolution.  The LiDAR-derived elevation data was resampled to 30-foot resolution, while hydrography data were kept at their original 10-foot resolution. Where LiDAR-derived products are not available, and for portions of the study area outside South Carolina, StreamStats is implemented by using LiDAR-based topographic data from the USGS 3D Elevation Program and the best-available hydrography, which at the time of development in 2018 was 1:24,000-scale National Hydrography Dataset (NHD). The local-resolution and 1:24,000-scale NHD were appended to make a continuous streams layer for the entire State and contributing watersheds of adjacent States.

The StreamStats application interfaces with the DEMs and the most current regional streamflow regression equations and datasets of landscape characteristics. Basin characteristics, such as rainfall data, topographic variables (such as slope and drainage area), and 2001, 2006, and 2011 National Land-Cover Datasets (NLCD) also are incorporated in the South Carolina StreamStats application.

Click on this link to obtain general information on the South Carolina application, as well as specific sources and computation methods for basin characteristics.