April 22, 2025 USGS Hydrography Community Call: 3D Hydrography Program Announcements and "Updating historical flow permanence classifications with probabilistic continuous-value estimates” Presentation

Steve Aichele, the National Geospatial Program Hydrography Management and Planning Lead, announced release of the Elevation Derived Hydrography Specification 2024 Revision A3 and updates on the following:   

• 3DHP flowline feature type change: “River” changed to “Channel line”
• Upcoming HydroAdd3D Beta testing opportunity
• Retirement of the nhd@usgs.gov email  
• USGS Hydrography staff changes 

Stacey Archfield, Research Hydrologist with the USGS, and Dave Blodgett, Research Engineer with the USGS, presented results of research and development efforts to support the 3D Hydrography Program’s objective to represent 3DHP hydrographic feature flow using a continuous value probability and uncertainty estimates for features in 3DHP data. Hydrographic features on topographic maps and the National Hydrography Dataset classified a feature’s flow characteristics into three categories – perennial, intermittent, or ephemeral. These determinations were usually made by crews conducting field surveys for the original paper topographic maps (1947-1992). These classifications were subject to differences in field interpretation, changes in definitions through time, and even bias based on whether the field survey was conducted in a wet or dry year. The 3D Hydrography Program will replace these categorical classifications with a continuous value probability and uncertainty estimates.  The presentation described the process to develop the first iteration of these values using survival regression techniques, illustrated some of the results, and discussed some of the limitations based on both the available data and the approach.