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NHD Project Status

Network Improvement

The Network Improvement project was chartered in June, 2011 with the goal to identify and correct network problems existing in the high resolution NHD. The scope of this project covers the complete high resolution NHD, including sub-basins extending into Canada and Mexico, for the conterminous U.S., Alaska, Hawaii, and the U.S. territories. Horizon Systems was tasked to analyze the network by NHD Region and determine the location of network issues. The NGTOC is then taking action to rectify breaks in the network, with input from NHD POCs and data stewards.

The following QC checks are being run and appropriate edits will be made to the NHD to correct network issues identified.

    • Flow Table Entry Never Navigated
    • Improper Network End
    • Invalid Flow Table Entry
    • Improper Network Start
    • Duplicate Flow Table Entry
    • Incomplete Divergence
    • Flow Table and Flowline Ftype Disagree
    • Flow Table and Flowline Flowdir Disagree
    • Isolated Network
    • Coordinate Order and Flow Table Disagree
    • Flowlines Touch But Do Not Relate in Flow Table (not Canal/Ditch)
    • Flowline Not in Linear Reach
    • Nonlinear Reach
    • Circular Flowline
    • Flowline with LengthKM = 0
    • Nonlinear Flowline
    • Nonlinear Named Path
    • Flowline with both Flowing and Non-flowing Flowtable Entries
    • Waterbody Reach Has Multiple Waterbodies That Do Not Touch
    • Microgaps
    • Duplicate NHDFlowline Features
    • Coastline Dangles

Hydro/Image Integration

The goal of Hydro/Image Integration is to ensure hydrography data is sufficient to support accuracy requirements for USTopo production. This is done by:

Reviewing current NAIP imagery and updating the NHD to add lake/ponds 500,000 meters or larger and modifying the position of lake/ponds that are: greater than 1.0 sq km, that do not have an elevation value, if the shorelines are off by more than 500 ft, and to realign stream/rivers polygon features that are greater than 100 ft wide, when the position of the banks have moved more than 1000 ft.

National Water Information System Point-Event Indexing

The goal of National Water Information System (NWIS) Indexing Project is to create high-resolution NHD stream gage and water quality event features from NWIS data by indexing (snapping) the station to the appropriate position on the NHDFlowline. Links to external scientific data are known in the NHD as events. Because the NHD is designed as a connected flow network, events make many kinds of scientific analysis possible; such as how a source of poor water quality upstream might affect a fish population downstream, or how dams affect water temperatures downstream. The USGS is currently adding point events to the NHD including steam gages, water quality stations, dams, and diversions. The map shows progress of NWIS gage and water quality station indexing by Subregion.

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Last modified: Friday, 16-Dec-2016 09:36:37 EST