National Hydrography Dataset
U.S. Department of the Interior U.S. Geological Survey
Bill Smith
NHD Maintenance Training
Types of SubBasins
1. Headwater
2. Chain
3. Frontal
4. Isolated??
Headwater – a SubBasin where flow begins
Chain – One subbasin flows into another
Frontal – SubBasin that flows into an Ocean
Isolated – SubBasin where no flow exits
NHD Production Process for SubBasins
1:24,000-scale NHD was created based upon SubBasins.
Created from various ‘BEST AVAILABLE’ 1:24,000-scaledata, including:
USGS DLGsUSFS CFFsLocal data (if available)
Because various SubBasins were created by various personnel,production issues exist between adjoining SubBasins
NHD Stewardship
NHD Stewards
• The NHD is a living dataset• Revision updates needed• Quality updates needed• Organizations closest to the hydrography are most aware of ground truth• Such organizations should have the opportunity to serve as stewards• The USGS will assist
What is Stewardship?
Distributed Maintenance Typically on a State-by-State basis Suited to regional needs
Identifying a Primary Steward Agency recognized by entities within state as geospatial leader Acts as single POC to USGS Coordinates maintenance activities
What is Stewardship? (cont.)
Developing a Stewardship agreement
Roles defined in Memorandum of Understanding (MOU)
Draft “Boiler plate” MOU available, Example signed MOU’s available for review
Partner: Responsibilities and Procedures
The Partner agrees to: Act as the single entity
Represent the interests of the user community
Coordinate with others for the maintenance of sub-basins.
Accept input and adjudicate, and report the decision publicly.
Partner: Responsibilities and Procedures
Be responsive
Maintain an awareness of the activities of others
Provide contact information for management and technical issues.
Provide publicly available information on status of data stewardship activities.
Provide updates in the agreed upon format.
Partner: Responsibilities and Procedures
Provide metadata
Provide the USGS with updates that meet
agreed upon quality standards
Maintain quality assurance as follows:
a. Strive to ensure that the data is error free
b. Ensure that the core content is included
Utilize nationally consistent reach codes.
USGS: Responsibilities and Procedures
The USGS agrees to: Process transactions in timely manner Provide assistance to State Stewardship
program. Provide Maintenance tools, documentation, and
training Develop solutions to incorporate State
hydrographic data Communicate Transaction status
USGS: Responsibilities and Procedures
Provide reach code allocator Communicate NHD structure, format, or
content changes. Provide clear guidance for updates tracking. Provide documentation on update validation. Provide documentation on formats for update
transactions. Provide POC for management and technical
issues.
Data Ownership and Rights
All data produced, updated, and maintained in the NHD is public domain and thus is available to any interested party.
Financial Commitments
The Memorandum of Agreement (MOU) does not constitute a financial commitment on the part of either partner, but rather supports the two agencies to work cooperatively to exchange updates and continually make improvements to the NHD.
Period of Agreement
The agreement becomes effective on the last date of signature by both partners and continues until modified by mutual consent or unless terminated within 60 days written notice by either partner. The agreement will be reviewed periodically and amended or revised when required.
What are the advantages for participating in NHD stewardship?
Change management (Live Database) Statewide seamless dataset Allows for regional studies Share data Update notification Receive National updates Events Applications
Why do we need State Stewardship?
NHD Production Process for SubBasins
1:24,000-scale NHD was created based upon SubBasins.
Created from various ‘BEST AVAILABLE’ 1:24,000-scaledata, including:
USGS DLGsUSFS CFFsLocal data (if available)
Because various SubBasins were created by various personnel,production issues exist between adjoining SubBasins
Main Issues with existing NHD SubRegion data
Topology Issues
Measure (M-Value) Issues
Network Issues
Topology Issues in the NHD
A user may find NHDFlowline features that intersect.
Create Flowline Topology (1D) on the NHDFlowline feature classto check for:
Features that overlapFeatures that self overlapFeatures that self intersectFeatures that are multi-part features
a feature with one ComID, but is made upwith more than one part.
Topology Issues in the NHD
A user may find polygon features which overlap.
Create WaterArea (2D) topology on the NHDArea and NHDWaterbody feature classes to check for:
NHDAreas that overlapNHDWaterbodies that overlapNHDAreas that overlap NHDWaterbodies
Note: There are some legal exceptions:SwampMarsh over a LakePond
Measures (M-Value) - Used to Linear Reference ‘Events’ to the NHD.
Measures are created based on ReachCodes.Several features may exist with the same
ReachCode.Once a unique ReachCode is detected,
MEASURESare created, from Start to End
junctions.Start junction – 0%End junction – 100%
Errors include: Inconsistent or opposing flowDisconnected ReachCodes or GapsBranched ReachCodesMulti-part feature
Measures (M-Value) Issues in the NHD
Network - The Network allows a user to navigate the NHD.Can trace upstream or downstream.Are based on junction to junction connectivity.Tables are created (NHDFlow) defining START and
END.The NHDFlow table may be used to create analysis
softwareoutside of a GIS.
Allow modeling/navigation to resolve real world issues.
Connectivity is the main factor in a network.
Errors include: Inconsistent or opposing flowIsolated NetworksMissing NHDFlowline featuresGaps or breaks between NHDFlowline
features.‘Uninitialized’ versus ‘WithDigitized’
Network Issues in the NHD
Network
Network
How should this example Network?
Care to try this Network?
Questions ?