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Riparian Area Inventory and Monitoring
Using Large Scale Color Infrared Photography 1
Paul Cuplin 2
Abstract.--Variables that can be photointerpreted from
large scale color infrared airphotos with ground data and
used to monitor change in stream/riparian areas are stream
width; floodplain width; stream channel stability; stream
bank stability; stream shade; ground cover of trees,
shrubs, and herbaceous vegetation; bare soil; riparian
area and width; and density and structure of large trees
and shrubs.
Photo interpretation of large-scale airphotos combined with ground truthing produces a
smaller list of riparian vegetation information
that can be determined. These variables are as
follows: vegetation type and subtype; width of
riparian vegetation zone; riparian area acreage; structure of trees and shrubs; percent
ground cover of trees, shrubs, and herbaceous
vegetation; percent bare soil; and density of
large shrubs and trees.
INTRODUCTION
Remote sensing is the collection and analysis of information about lands and resources,
using a device not in physical contact with the
lands or resources. Remote sensing includes
techniques such as analysis of satellite, Side
Looking Airborne Radar, thermal infrared scanning data; and the interpretation of aerial
photography.
Stream variables that can be measured from
the airphotos are stream width, stream channel
stability, streambank stability, floodplain
width, and stream shade.
The size and shape of riparian areas can
often be determined from satellite digital analysis or interpretation of small-scale airphotos. However, large-scale airphotos at
scales ranging from 1:1,000 to 1:4,800 are
needed to interpret detailed information on
streams and riparian vegetation. The 1:1,000
scale is preferred for ease of photo interpretation and good resolution. It is difficult to
obtain stereo coverage at 1:1,000 scale due to
9- x 9-inch film recycling speed and safe lowlevel aircraft altitude. The compromise scale
of 1:2,000 is acceptable and obtainable.
Subtle changes in riparian vegetation are
difficult to detect on airphotos. Conversely,
catastrophic changes due to flooding can be
easily monitored, and the amount of riparian
area lost can be readily calculated.
The method used to detect change in the
stream/riparian area is to visually compare the
baseline and monitoring airphotos. If changes
are apparent, a sample site that appears in
both airphotos is selected and key variables
measured to determine the amount of change that
has occurred.
Color infrared photographs are especially
valuable for vegetation analysis. Color tones,
along with shape, size, pattern, shadow, and
texture, are used to identify individual tree
and shrub species in riparian areas.
Types of riparian vegetation information
that can be collected on the ground are vegetation type and subtype; width of riparian
vegetation zone; species composition of shrubs,
trees, grasses, and forbs; bare soil; plant
density by species; condition class; plant reproduction; upward, downward, or stable trend;
tree and shrub structure; and potential natural
vegetation community.
APPLICATION OF LARGE-SCALE AIRPHOTOS FOR
INVENTORY AND MONITORING
Ground sampling or familiarity with the
riparian vegetation photographed is essential
for accurate photo interpretation. Vegetation
transects and tree, shrub circular characterization plots are transferable in general terms
to large-scale airphotos. Trees, and some
shrubs, can be readily identified by species;
grasses and forbs cannot be identified by
species unless a photo scale of 1:100 to 1:300
is used .. See table 1 for variables that can
be identified on a scale of 1:2,000.
lpaper presented at the Riparian
Ecosystems and Their Management Symposium,
[Tucson, Arizona, April 16-18, 1985].
2Paul Cuplin is a Fishery Biologist,
Bureau of Land Management, Denver, Colorado.
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The most easily detected changes in a
riparian area would be a reduction in foliar
cover and an increase in bare soil. These
changes may be obvious upon inspection of the
baseline (original) photo compared with the
monitoring photo taken five to ten years
later. The cause of the change may be answered
only by on-the-ground inspection; thus the
photos offer the opportunity to monitor change
but not the cause.
Table l.--Variables that may be photo interpreted from 1:2,000 scale color infrared
airphotos combined with on-the-ground data
collection.
Variable
Photo Interpretation
Vegetation Type
and Subtype
Riparian Area Width
and Acreage
Yes
Yes
GROUND DATA COLLECTION
Plant Species
Composition
Trees
Shrubs
Select ground data sites that are accessible and representative of the riparian
vegetation and stream conditions. One site per
1- to 3-mile stream segment may be sufficient
for airphoto interpretation. If there are
significant differences in a stream segment,
additional data collection sites should be
esta blished.
Yes
Yes, some shrubs
such as willow and
baccharis
No
No
Grasses
Forbs
Ground Cover
% Trees
% Shrubs
% Herbaceous
Vegetation
% Bare Soil
Yes
Yes
Density
Yes
Yes
Take color print 35-mm photographs of the
stream/riparian area (upstream, across
stream, and downstream) at the site where
the airphoto target is placed.
Yes, large trees
and some shru bs
such as cottonwood
and willow
Collect stream inventory of 1/10 mile of
stream segment.
Reproduction
Yes, young trees and
shrubs but not
seedlings
Condition Class
No
Trend
Yes, as related to
change in the
amount of ground
cover and bare soil
Potential
Structure
Stream bank Shade
Stream Width
Floodplain Width
Streambank Stability
Streambed Silt
Stream Channel Stability
ON-SITE DATA COLLECTION
Determine the dominant and subdominant
herbaceous vegetation, shrubs, and trees,
and the percent bare soil.
Take additional field notes that may
assist in photo interpretation.
ACQUISITION OF LARGE-SCALE LARGE-FORMAT
(9- x 9-INCH) AERIAL PHOTOGRAPHS
The 9- x 9-inch format is easy to work
with, and most photo interpretation can be
accomplished with a minimum of equipment. The
9- x 9-inch photos are identified by date,
fiducial marks, agency, photo scale, state
symbols, roll number, and exposure number.
Photos can be easily filed, and extra prints
can be ordered as needed for field use.
No
Yes, height of trees
and shrubs
Yes
Yes
Yes
Yes
Yes
Yes
A 9- x 9-inch format photo covers approximately 52 acres, or 2,250,000 square feet, at a
scale of 1:2,000. At this scale, riparian
zones on first, second, and third order streams
are easily photographed with a good margin of
the adjacent upland.
BASELINE
Original large-scale airphotos of a
riparian area provide an overview of existing
conditions in terms of the readily interpreted
variables. Subsequent airphotos over time provide the means of detecting change in these
variables. Subtle change due to the lack of or
above normal precipitation may not be evident
as compared to the catastrophic change caused
by a lOO-year flood.
Assistance on airphoto acquisition should
be sought from a remote sensing coordinator.
The publication "Aerial Photography
Specifications," June 1983, BLM, is available
from the Branch of Remote Sensing (D-442),
Denver Service Center, BLM. This publication
provides detailed specifications for acquiring
aerial photographs via contract.
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Sample Size
Provide the photographer with a USGS quad
map that shows the beginning and end of each
stream/riparian area to be photographed. Delineate flight lines on the maps to indicate to
the photographer the direction of airplane
travel and the midpoint and width of each flight
line according to the photo scale that has been
requested.
The sample size used to determine change
should be large enough to represent the area
and the changes that have occurred. Select a
representative site that can be identified on
both baseline and monitoring airphotos.
Accuracy
SUGGESTED STREAM/RIPARIAN INVENTORY AND
MONITORING PROCEDURES USING LARGE-SCALE COLOR
INFRARED AIRPHOTOS AND GROUND DATA
Determine the accuracy required to assess
a variable to assure that the correct variable
is being assessed and that changes are the
result of management and not the result of
natural variation caused by precipitation or
other influences.
Baseline Inventory
Identify the stream/riparian segment.
Results
Describe existing condtions for the
stream/riparian segment.
If results are uncertain, select other
comparative areas for analysis. From the
changes detected in photo interpretation,
determine if management objectives were
achieved.
Identify resource needs and concerns.
Area Management
Describe the management for the area.
CONCLUSIONS
Identify the objectives and management
goals for the area.
The use of large-scale color infrared
airphotos for inventory and monitoring riparian
areas is best applied at a scale of 1:2,000 in
9- x 9-inch format.
Identify improvement goals and the changes,
such as increasing the amount of ground
cover, narrowing stream width, or increasing the number of trees and shrubs, that
can be measured.
Ai rphotos that were taken from a small
bubble type helicopter while using a handheld
35-mm camera have application to small projects. However, if several miles of stream/
riparian area are to be photographed, it can
best be done by an airphoto contractor with a
9- x 9-inch mapping camera.
Variables
Variables that can be used to easily detect
changes are as follows:
Variables that can be photointerpreted
from large-scale color infrared airphotos with
ground truth and that can be used to detect
change in the stream/riparian area are stream
width; floodplain width; stream channel stability; stream bank stability; stream shade;
ground cover of trees, shrubs, and herbaceous
vegetation; bare soil; riparian area and width;
and density and structure of large trees and
shrubs.
Ground cover--An increase or decrease in
ground cover of trees, shrubs, and
herbaceous vegetation, and in bare soil
can be detected by visual observation of
large-Reale airphotos.
Stream width--Changes in stream width can
be easily measured on large-scale airphotos. These changes are an early indicator of improving or degrading stream
conditions. Stream width increases under
heavy livestock grazing and narrows during
the recovery period of no livestock grazing.
LITERATURE CITED
U.S. Department of Interior, Bureau of Land
Management. 1983. Aerial Photography
Specifications. BLM Denver Service
Center. Denver, CO. l5pp.
Channel and bank stability--Stream channel
and streambank stability can be readily
interpreted from large scale airphotos.
Size of riparian area--Riparian area width
and acreage can be readily measured on
large-scale airphotos.
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