1. National Wetlands Inventory Mapping In Vermont
Ralph Tiner, Regional Wetland Coordinator
U.S. Fish and Wildlife Service
Northeast Region
Hadley, MA

2. Background National Program Regional Status
90% of coterminous US mapped
50% digitized
Regional Status
12 of 13 states mapped
Updating in progress on a FWS priority basis and where outside funding is received

3. Purpose of Mapping
To inventory wetlands across the nation for natural resource conservation purposes
To identify and classify larger wetlands based on photointerpretation (recognizing limitations inherent in this approach)
To report on the status and trends of US wetlands and for states as mapping is completed
The NWI is not designed to map all the wetlands in any locality – that would require on-the-ground surveys applying wetland delineation techniques

4. Limitations of Photointerpretation for Mapping Wetlands
Photo Scale
Seasonality (environmental conditions at time of photo capture)
Photo Quality
Wetlands that are difficult to photointerpret

5. Photo Scale vs. Area Scale Area In One Square Inch 1:80K 1020 acres

6. Photo Scale vs. Mapping Unit
Photo Scale vs. Target Mapping Unit
1:80,000 = 3-5 acres
1:58,000 = 1-3 acres
1:40,000 = 1 acre
1:24,000 = acre
1:12,000 = 0.10 acre

7. 1:80K vs. 1:58K

8. 1:40K vs. 1:24K

9. 1:24K vs. 1:12K

10. 1:80K vs. 1:40K

11. 1:80K vs. 1:12K

12. Photo Scale vs. # of Photos
Scale # of Photos/Quad #Photos/VT*
1:80,
1:58,
1:40,
1:24,
1:12,
*Estimates based on 58 sq. mi/quad and Vermont land surface area.
May be approx. 220 quads (1:24K) covering the state

13. Pen Width vs. Ground Distance
Earlier maps were hand-drawn, so pen-width was a factor.
Scale 000 (0.25mm) (0.18mm)
1:80K ~67ft ~50ft
1:58K 48ft 34ft
1:40K 33ft 23ft
1:24K 20ft 14ft
1:12K 10ft 7ft

14. Scale Limits on Wetlands
Not simply acreage dependent
Relates to shape
one-acre block vs. one-acre linear
Relates to easy or difficulty of photointerpretation of type

15. Wetland Type Easy to identify types Harder to identify types
Marshes, bogs, seasonally flooded swamps, ponds
Harder to identify types
Drier-end wetlands
Evergreen forested wetlands
Temporarily flooded wetlands
Wetlands on slopes (seepage)

16. Seasonality Environmental Conditions Leaf on vs. Leaf off
Spring vs. Fall (leaf off)
Ambient weather
Water tables and flooding
Extreme flooding vs. droughts
Snow and ice

17. Photo Quality Emulsion Resolution Processing (over vs. under exposed)
Black and White (panchromatic)
True Color
Color Infrared
Resolution
Processing (over vs. under exposed)
Date (best available at 1:40K or smaller; now use DOQ/DOQQ)

18. Original NWI Maps for Vermont
1:80,000 CIR
October 1977
Target Mapping Unit = 3-5 acres
Inventory done in late 1970s/1980.
Mapping Procedures
Photointerpretation
Limited Field Work
Consultation with Soil Surveys? (No hydric soils lists/indicators)
Regional QC (spot checking)
National QC (spot checking)

19. NWI Results vs. Hydric Soils
220,000 acres
3.7% of the state
Soil Data
341,000 acres
5.5%

20. Updated NWI Mapping 1:40,000 CIR 1992-1994
Target Mapping Unit = 1 acre
Mapping Procedures
Edit original NWI data
Photointerpretation
Limited field checking
Consult with soil surveys (interpretation)
Regional QC (entire photo)
National QC (automated verification)

24. Status of Updates in Vermont

25. New Mapping Procedures (2006)
Edit existing NWI data
Photointerpretation on-screen
DOQ or DOQQ base
Limited field checking
FWS QC, automated verification
Add undeveloped hydric soil map units

27. Enhanced NWI Current NWI database Add other descriptors:
Landscape Position
Landform
Water Flow Path
Waterbody Type
Use data to predict wetland functions

28. LLWW Descriptors Landscape Position Landform Water Flow Path
Lotic, Lentic, Terrene
Landform
Floodplain, Basin, Flat, Fringe, Slope
Water Flow Path
Inflow, Outflow, Throughflow, Bidirectional Flow, Isolated
Waterbody Type
Pond and lake types, impounded rivers, etc.

29. Functional Assessment
9 Functions for Inland Wetlands
Surface Water Detention
Streamflow Maintenance
Nutrient Transformation
Sediment Retention
Shoreline Stabilization
Fish and Shellfish Habitat
Waterfowl/Waterbird Habitat
Other Wildlife Habitat
Conservation of Biodiversity

30. Updated NWI - Highlights
Smaller wetlands
Refined boundaries
Incorporates more hydric soil map units
Can be enhanced to be more descriptive
After enhancement, can use for preliminary functional assessments
Still will not map all wetlands – need ground surveys applying delineation procedures to do this; potential vernal pool mapping through remote sensing