Slope Units produced from Slope Unit Maker (SUMak) over the contiguous United States, Hawaii, and Puerto Rico

Slope units divide terrain by drainage and divide lines to create mapping units that capture individual hillslopes. Using the software slope unit maker (SUMak) (Woodard, 2023), we delineated slope units across the contiguous United States, Hawaii, and Puerto Rico that are scaled to the fluvial-hillslope threshold (Woodard et al., 2024). Data are organized according to their respective watershed hydrologic unit codes (HUC). The HUC watersheds are designed so that lower-order watersheds (e.g., HUC 4) nest within higher-order watersheds (e.g., HUC 2). The parent directories in this repository are named after the HUC 2 watersheds, and their subfolders are named after the HUC 4 watersheds. Each HUC 4 subfolder contains shapefiles of the delineated stream network, intermediate basins, and slope units. We aggregated all the results of the HUC 8 processed data into one file for each feature within the HUC 4. Shapefiles that show the extent of the HUC watersheds are available at U.S. Geological Survey (2025). Files are named by the HUC 4 code, followed by ‘streams’, ‘intBasins’, and ‘slopeUnits’, for the streams, intermediate basins, and slope units, respectively (e.g., ‘0202intBasins.shp’).

References cited:

U.S. Geological Survey, 2025, USGS Watershed Boundary Dataset (WBD), accessed January 10, 2025, at https://prd-tnm.s3.amazonaws.com/index.html?prefix=StagedProducts/Hydro….

Woodard, J.B., 2023, Slope Unit Maker Software: US Geological Survey Software Release, https://doi.org/10.5066/P98NXFTN.

Woodard, J.B., Mirus, B.B., Wood, N.J., Allstadt, K.E., Leshchinsky, B.A., Crawford, M.M., 2024, Slope Unit Maker (SUMak): an efficient and parameter-free algorithm for delineating slope units to improve landslide modeling, p. 1–12, https://doi.org/10.5194/nhess-24-1-2024.