National Wetlands Inventory Mapping In Vermont

Ralph Tiner, Regional Wetland CoordinatorU.S. Fish and Wildlife Service

Northeast RegionHadley, MA

Background

National Program 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

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

Limitations of Photointerpretation for Mapping Wetlands

Photo Scale Seasonality (environmental conditions at time

of photo capture) Photo Quality Wetlands that are difficult to photointerpret

Photo Scale vs. Area

Scale Area In One Square Inch

1:80K 1020 acres

1:58K 540 acres

1:40K ~250 acres

1:24K 92 acres

1:12K ~25 acres

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 = 0.25-0.50 acre 1:12,000 = 0.10 acre

1:80K vs. 1:58K

1:40K vs. 1:24K

1:24K vs. 1:12K

1:80K vs. 1:40K

1:80K vs. 1:12K

Photo Scale vs. # of Photos

Scale # of Photos/Quad #Photos/VT*1:80,000 1 1601:58,000 1.5 2401:40,000 4 6401:24,000 20 32001:12,000 42 6720

*Estimates based on 58 sq. mi/quad and Vermont land surface area.

May be approx. 220 quads (1:24K) covering the state

Pen Width vs. Ground Distance

Earlier maps were hand-drawn, so pen-width was a factor.

Scale 000 (0.25mm) 0000 (0.18mm)

1:80K ~67ft ~50ft

1:58K 48ft 34ft

1:40K 33ft 23ft

1:24K 20ft 14ft

1:12K 10ft 7ft

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

Wetland Type

Easy 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)

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

Photo Quality

Emulsion 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)

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)

NWI Results vs. Hydric Soils

NWI

220,000 acres

3.7% of the state

Soil Data

341,000 acres

5.5%

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)

Status of Updates in Vermont

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 FWS QC, automated verification

Enhanced NWI

Current NWI database Add other descriptors:

Landscape Position Landform Water Flow Path Waterbody Type

Use data to predict wetland functions

LLWW Descriptors

Landscape Position 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.

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

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