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 ?