1. NHD Watershed: Tools and Applications
By Pete Steeves, USGS Water Resources Discipline
Northboro, Massachusetts

2. Acknowledgements Jennifer Hill, Horizons Systems Corporation
Aleda Freeman, MassGIS
Craig Johnston, USGS

3. This Talk Focuses on: 2 NHD ArcView Toolkit extensions
NHD Watershed
NHD Watershed Characteristics
3 Applications of these extensions
VT Flood Frequency project
New Hampshire Low Flow project
Massachusetts Perennial / Intermittent streams project

4. Background
Massachusetts Watershed Analyst (MassGIS and USGS collaboration)
Tools and datasets not immediately transferable nationally
An application, Massachusetts ‘Streamstats’ showcases the applicability of these tools

5. NHD Watershed: Objectives
To develop a tool in the NHD ArcView Toolkit which delineates a watershed from any point location on NHD reaches quickly, reliably, and accurately
To relate the resulting watershed to the reach and measure of the selected point (in essence, create a “polygon event”)
To horizontally integrate 3 earth-surface-based physiographic datasets (hydrography, basin boundaries, and elevation data) through a series of pre-processing steps
To document the pre-processing steps for others

6. National Datalayers Hi-resolution NHD (1:24,000 scale)
12-digit hydrologic unit (HUC) boundaries (future WBD) (1:24,000 source scale)
National Elevation Dataset (NED)

7. Pilot HUC: White River Basin, VT (01080105)

8. Pre-processing steps - NHD
Convert the NHD route.rch table to an arc coverage and direct all flow downstream
Remove all routes that are not connected to major networks
Optionally remove sections of braids (resulting in a dendrite network)
Extend the exit centerline ~ 50 meters beyond the HUC boundary

9. Example: Removing a Braid

10. Pre-processing steps - WBD
Optionally add sub-basin boundaries to the 12-digit HUC datalayer.
Buffer the 8-digit HUC boundary 4000 meters for the subsequent TOPOGRID command analysis area
Buffer the 8-digit HUC boundary 50 meters to ensure the vector boundary will be used in all raster analysis steps

11. Example: Adding Sub-basins

12. Pre-processing steps - NED
Run TOPOGRID to drainage enforce the NED to NHD. Input includes:
The edited dendrite network from NHD
A NED-derived point coverage of elevation values
Use a series of GRID steps to exaggerate the watershed boundary ridges where TOPOGRID output coincides with the WBD
Run ‘agree.aml’ to ‘canyonize’ the dendrite using output from the TOPOGRID/ridge steps, further enforcing the NED to NHD

13. Example: Enforcing NED to NHD

15. Final Pre-processing Steps
Use the drainage enforced elevation grid to produce the flow direction and flow accumulation grids (then discard the drainage enforced elevation grid)
Use the ‘WATERSHED’ command to delineate a catchment for every NHD reach in the dendrite coverage
Load the appropriate datasets into a standardized ‘NHD Watershed’ directory

16. Reaches Catchments

17. NHD Watershed Directory Structure

18. How NHD Watershed Works
The user selects a point on a reach
NHD Navigate determines all upstream reaches from that point (including the partial reach segment of the selected reach)
A relate is performed between reaches and catchments to select all upstream catchments
A partial catchment is determined within the selected reach catchment
The partial catchment is combined with selected upstream catchments and internal boundaries are dissolved
Attribution of the newly delineated watershed includes the reach code and measure of the user selected point

20. NHD Watershed Fun Facts
Is an ArcView 3x extension
Is designed to work with NHD and the NHD ArcView Toolkit
For full functionality the user needs Spatial Analyst (a ‘watershed for confluences only’ option can be used without Spatial Analyst)
The extension, pre-processing instructions, list of available HUCs, and other related info is available on the NHD website: under ‘Applications’

21. NHD Watershed Characteristics: Objectives
A generic extension which helps guide users to summarize basin characteristics of choice for newly delineated watersheds
Built on top of NHD Watershed
An open, well documented script environment for users to modify as needed

22. NHD Watershed Characteristics (cont.)
Designed as a transition tool from the general NHD Watershed environment to the specific user application environment
Not yet available on the NHD website

23. Applications Vermont Flood Frequency project
New Hampshire Low Flow project
Massachusetts Perennial / Intermittent Streams project

24. Vermont Flood Frequency
USGS NH District cooperative effort with VT Department of Transportation
Regression equation estimates of peak flow for any point on any stream in Vermont
The entire state has been processed for use in the NHD ArcView Toolkit

31. New Hampshire Low Flow
USGS NH District cooperative effort with the State’s Geological Survey
Seasonal and annual statistics for:
Ground water recharge
Low flow
Hydro-climatic data (PRISM) used extensively as a source for significant seasonal predictors including: temperature, snow fall, and precipitation

32. Massachusetts Perennial / Intermittent Project
Needed by Mass. DEP for regulatory purposes in enforcing the State’s River Protection Act of 1996
A logistic regression equation has been developed to determine these points
The NHD Watershed and NHD Watershed Characteristics tools are being used in batch mode to find these points and map them

33. Watershed Characteristics
Basin area
Percent area of stratified-drift (sand and gravel) deposits
Drainage density (length of streams / drainage area)
Mean basin elevation
Percent area of forested land

36. In the works….
Considering the transition of the NHD Watershed and NHD Watershed Characteristics extensions to the NHDinGeo environment along with other NHD Toolkit functions
Working with NHD Watershed preprocessed datasets in the ArcHydro global tools environment