This drainage direction map for North America defines the direction of flow from each cell in the conditioned digital elevation model to its steepest downslope neighbor. Values of flow direction vary from 1 to 128. There are eight valid output directions relating to the eight adjacent cells into which flow could travel. This approach is commonly referred to as an eight-direction (D8) flow model and follows an approach presented in Jenson and Domingue (1988). All final outlet cells to the ocean are flagged with a value of 0. All cells that mark the lowest point of an endorheic basin (inland sink) are flagged with a value of -1. This data is derived from elevation data of the Shuttle Radar Topography Mission (SRTM) at 15 arc-second resolution approx. 500m at the equator. The goal of developing HydroSHEDS was to generate key data layers to support regional and global watershed analyses, hydrological modeling, and freshwater conservation planning at a quality, resolution and extent that had previously been unachievable. This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.
Users may apply HydroSHEDS for non-commercial purposes. Any modification of the original data by users must be noted. The authors of HydroSHEDS may request reprints of publications and copies of derived materials. The user shall not reproduce, convert, (re)publish, (re)distribute, (re)broadcast, (re)transmit, sell, rent, lease, sublicense, lend, assign, time-share, or transfer, in whole or in part, or provide unlicensed third parties access to the data and related materials without explicit written permission from the authors. We kindly ask users to cite HydroSHEDS in any published material produced using this data. If possible, please provide online links to http://www.worldwildlife.org/hydrosheds for general information, and/or http://hydrosheds.cr.usgs.gov for data download and technical information.
Rights Holder:
HydroSHEDS has been generated through the extensive use and incorporation of data products provided by various other authors. The data and related materials may thus contain proprietary and confidential property of these authors and/or their licensor(s). HydroSHEDS data and related materials are protected by United States copyright or sui generis laws and applicable international copyright treaties and/or conventions.