USGS, with assistance from Horizon Systems, is well into a project to produce High Resolution NHDPlus (HRNHDPlus). HRNHDPlus will be built from:
- The High Resolution National Hydrography Dataset (1:24,000-scale or better),
- The 1/3 arc-second National Elevation Dataset (approximately 10 meter ground spacing), and
- The Watershed Boundary Dataset.
For more information about these input datasets, visit: NHD at http://nhd.usgs.gov, NED at http://ned.usgs.gov and WBD at http://nhd.usgs.gov/wbd.html.
HRNHDPlus will differ from NHDPlusV2 in several ways:
- There is generally better spatial correspondence among the input datasets for HRNHDPlus.
- The native data format of HRNHDPlus will be file geodatabase and raster tif's rather than shapefiles and grids.
- The unit of processing and distribution will be HUC4s rather than HUC2s.
- The hydro-enforcement process has been significantly improved.
- In HRNHDPlus, EROM flow estimates will be mean annual, rather than mean annual and mean monthly as in NHDPlusV2.
The project has 5 phases:
- Phase 1: HRNHDPlus Build/Refresh Software Development
During this phase, the software to produce the NHDPlus vector components, raster components, and attributes is designed, programmed and validated.
- Phase 2: Data Validation
During this phase, the Build/Refresh software will be used in production to produce HRNHDPlus for hydrologic regions 06 and 01. This data will be subjected to extensive review to determine that the Build/Refresh software and workflow are producing expected results.
- Phase 3: Data Production and Release
This phase will produce HRNHDPlus data by 4-digit hydrologic units for the entire continental U.S. As data is produced it will be distributed on the NHD website http://nhd.usgs.gov. It is anticipated that the Build/Refresh software may need adjustments as production moves into different areas of the country.
Production of HRNHDPlus begins with the USGS National Geospatial Technical Operations Center (NGTOC) running the NHD data through the NHDPlus QAQC checks and fixing any data problems found. A 4-digit hydrologic unit (HUC4) dataset of NHD and WBD is delivered to the HRNHDPlus Build/Refresh process. The 19 step HRNHDPlus Build/Refresh process is performed which includes QA throughout. Finally, the data is delivered to the USGS Staged Products group for distribution.
- Phase 4: User Error Reporting
As the water resources community begins to use the data, it is expected that data errors in NHD and WBD will be discovered and corrected both by state stewards and by USGS. Also during this time, state stewards will continue to update and improve high resolution NHD and WBD. Both data corrections and enhancements will lead to phase 5.
- Phase 5: Data Refresh
As each 4-digit hydrologic unit of HRNHDPlus data moves into Data Refresh, it will be regenerated with updated NHD, WBD and NED. Change thresholds will be used for the NHD, WBD, and NED to determine when a HUC4 should be refreshed.
PROJECT STATUS: Phase 1 of the project is essentially completed with the possibility that the software may evolve in response to new data conditions. Phase 2 of the project has produced HRNHDPlus data for hydrologic region 06 which is undergoing review. HRNHDPlus data for hydrologic region 01 is in process after which it will undergo review. Phase 3 will begin with the public distribution of HRNHDPlus for regions 06 and 01. It is anticipated that Phases 4 and 5 will be concurrent with Phase 3.