Global River Topology (GRIT)

The Global River Topology (GRIT) is a vector-based, global river network that not only represents the tributary components of the global drainage network but also the distributary ones, including multi-thread rivers, canals and delta distributaries. It is also the first global hydrography (excl. Antarctica and Greenland) produced at 30m raster resolution. It is created by merging Landsat-based river mask (GRWL) with elevation-generated streams to ensure a homogeneous drainage density outside of the river mask (rivers narrower than approx. 30m). Crucially, it uses a new 30m digital terrain model (FABDEM, based on TanDEM-X) that shows greater accuracy over the traditionally used SRTM derivatives. After vectorisation and pruning, directionality is assigned by a combination of elevation, flow angle, heuristic and continuity approaches (based on RivGraph). The network topology (lines and nodes, upstream/downstream IDs) is available as layers and attribute information in the GeoPackage files (readable by QGIS/ArcMap/GDAL). <strong>Regions</strong> Vector files are provided in 6 continental regions with the following codes: AF - Africa AS - Asia EU - Europe NA - North America SA - South America SP - South Pacific/Australia The domain polygons (GRITv04_domain_GLOBAL.gpkg.zip) provide 60 subcontinental catchment groups that are available as vector attributes. They allow for more fine-grained subsetting of data (e.g. with ogr2ogr --where). <strong>Network segments</strong> Lines between inlet, outlet, confluence and bifurcation nodes. Files have lines and nodes layers. <em><strong>Attribute description of lines layer</strong></em> Name Data type Description cat integer domain internal feature ID global_id integer global river segment ID, same as FID catchment_id integer global catchment ID upstream_node_id integer global segment node ID at upstream end of line downstream_node_id integer global segment node ID at downstream end of line upstream_line_ids text comma-separated list of global river segment IDs connecting at upstream end of line downstream_line_ids text comma-separated list of global river segment IDs connecting at downstream end of line direction_algorithm float code of RivGraph method used to set the direction of line width_adjusted float median river width in m without accounting for width of segments connecting upstream/downstream length_adjusted float segment length in m without accounting for width of segments connecting upstream/downstream in m is_mainstem integer 1 if widest segment of bifurcated flow or no bifurcation upstream, otherwise 0 cycle integer &gt;0 if segment is part of an unresolved cycle, 0 otherwise length float segment length in m azimuth float direction of line connecting upstream-downstream nodes in degrees from North sinuous float ratio of line length and Euclidean distance between upstream-downstream nodes, i.e. 1 meaning a perfectly straight line domain text catchment group ID, see domain index file <em><strong>Attribute description of nodes layer</strong></em> Name Data type Description cat integer domain internal feature ID global_id integer global river node ID, same as FID catchment_id integer global catchment ID upstream_line_ids text comma-separated list of global river segment IDs flowing into node downstream_line_ids text comma-separated list of global river segment IDs flowing out of node node_type text description of node, one of bifurcation, confluence, inlet, coastal_outlet, sink_outlet, grwl_change grwl_value integer GRWL code at node grwl_transition text GRWL codes of change at grwl_change nodes cycle integer &gt;0 if segment is part of an unresolved cycle, 0 otherwise continuity_violated integer 1 if flow continuity is violated, otherwise 0 domain text catchment group, see domain index file <strong>Network reaches</strong> Segment lines split to not exceed 1km in length, i.e. these lines will be shorter than 1km and longer than 500m unless the segment is shorter. A simplified version with no vertices between nodes is also provided. Files have lines and nodes layers. <em><strong>Attribute description of lines layer</strong></em> Name Data type Description cat integer domain internal feature ID segment_id integer global segment ID of reach global_id integer global river reach ID, same as FID catchment_id integer global catchment ID upstream_node_id integer global reach node ID at upstream end of line downstream_node_id integer global reach node ID at downstream end of line upstream_line_ids text comma-separated list of global river reach IDs connecting at upstream end of line downstream_line_ids text comma-separated list of global river reach IDs connecting at downstream end of line length float length of reach in m sinuousity float ratio of line length and Euclidian distance between upstream-downstream nodes, i.e. 1 meaning a perfectly straight line azimuth float direction of line connecting upstream-downstream nodes in degrees from North domain text catchment group, see domain index file <em><strong>Attribute description of nodes layer</strong></em> Name Data type Description cat integer domain internal feature ID segment_node_id integer global ID of segment node at segment intersections, otherwise blank n_segments integer number of segments attached to node global_id integer global river reach node ID, same as FID upstream_line_ids text comma-separated list of global river reach IDs flowing into node downstream_line_ids text comma-separated list of global river reach IDs flowing out of node domain text catchment group, see domain index file <strong>Catchments</strong> Catchment outlines for entire river basins (network components, including coastal drainage areas), segments (aka. subbasins) and reaches. <em><strong>Attribute description</strong></em> Name Data type Description cat integer domain internal feature ID global_id integer global catchment ID, same as global_id of segment/reach ID if is_coastal == 0 for respective catchments or the catchment_id for component_catchments, same as FID area float catchment area in km2 is_coastal integer 1 for coastal drainage areas, 0 otherwise domain text catchment group, see domain index file <strong>Raster </strong> Upstream drainage area, flow direction and other raster-based products are also available upon request.