National Hydrologic Geospatial Fabric Reference and Derived Hydrofabrics

The data release includes four parts:

• Reference Hydrofabric: Shown in the top tier of the figure above. Includes identifiers for mainstems and hydrographic features with a carefully constructed set of topological, physical, and geometric feature attributes. Carefully prepared geospatial representations of flowlines, catchments, and points of interest are included as well.
• Refactored Hydrofabric: A processed version of the reference hydrofabric where very small (less than about 500m flowline length) catchments have been consolidated into larger ones and very large catchments (greater than about 2km flowline length) are split apart to limit size or to better represent important network outlets. When refactoring, network density is preserved and all hydrologic locations from the reference hydrofabric are preserved.
• Target Size Hydrofabric: A version of the refactored hydrofabric that has been aggregated to achieve a specific target size of resulting catchment with prescribed upper and lower size limits. Important hydrologic locations from the refactored hydrofabric can be preserved (e.g. gage locations) but most catchment outlets are implied by the need to achieve a specified target catchment size.
• “Point of Interest” hydrologic location Aggregated Hydrofabric: A version of the refactored hydrofabric that has been aggregated as much as possible while maintaining a connected network for a provided set of on-network hydrologic locations. Some catchments can be very large where few points of interest are needed and other catchments may be very small where points of interest are close together.