7944

• UCREFRP Catalog Number: 7944
• Author: Hoar, A. R. and M. J. Erwin.
• Title: Relationships Between The Expansion Of Agriculture And The Reduction Of Natural Riparian Habitat In The Missouri River Floodplain Of Northeast Montana, From 1938 To 1982, ‎(paper-North American Symposium on Riparian Ecosystems and Their Management)‎.
• USFW Year: 1985.
• USFW - Doc Type: April 16-18, 1985.
• Copyright Material: NO

;y,

l
,,
Broad changes in the floodplain composition are
documented. Some general patterns and causes of
change sre identified and put in perspective.
STUDY AREA
The study area included the forests and other
riparian vegetation slang a 18b-mile reach of the
Missouri River in northeast Montana. In addition
to the riparian vegetation, the study-area encom-
passed the remainder of the "historic" floodplain
and the Missouri River. The terrestrial acreage
of the floodplain varied between 180,134 and
185,526 acres, depending upon the water level of
the river at the time the aerial photographs were
taken.
The western boundary of the study area was
Fort Peck Dam. The eastern boundary was near the
confluence of the Yellowstone River 1n North
Dakota. Specifically, ft was the north-south
section line located in T152N, R104W that falls
between Sections 8 and 9; 16 and 17; 20 and 21;
and 28 and 29. Because the north and south bound-
arlea were the extreme outer limits of the Missouri
River "historic" floodplain, all of the potential
riparian zone was eontsined therein.
There were five titles either within or near
the study area, none of which exceeded a popula-
tion of 1D,000. Most had less than 2500 residents.
Farming and grazing were the main land-uses within
the eras during the period studied.
METHODS AND MATERIALS
Included below are general descriptions of
the interpretative classification system, the
aerial photography and its interpretation, field
verification, map production, and the digitizing
and data processing systems used during this
project.
Lend-Cover Classification System
A land-cover Classification was used that
included general surface features that could be
reliably identified on new black end white aerial
photographs produced Trom old negative film. The
system was designed to be compatible with classl-
ficatiorts alresdy in existence for wetlands
(Cowardin et a1. 1979) end riparian vegetation
:(Bachelor et s7. 1982), but also to include fea-
~tures developed by humans such as agriculture,
roads, residential areas, and so on.
Understory vegetation was not part of the
classification because it could not be identified
on older photographs. Surface cover was classified
in terms of the tallest visible layer of homoge-
neous areas. The interpretation process was stand-
ardized so that each surface facture was inter-
preted in a particular order on each photo and
minimum recognized sizes were established for each
type. These standards are presented fn Table 1.
Table 1.--Standards for interpretation of surface
features on the Missouri River floodplain.
Order of Minimum
Photo Inter- Polygon
Surface Feature oretation Size (acres)
Floodplain 1 N.A.
UrbanJRanchyard 2 0.25
Deciduous Woodland 3 0.25
Shrub-Scrub 4 0.25
Herbaceous 5 0.25
Agriculture 6 10.00
Rlahts-of-way 7 N.A.
Floodplain
The first order feature was the floodplain.
It was defined as a reiatlveiy flat expanse of
land bordering the Missouri River (but not
including the river) and extending north and south
to the extreme limits of the "historic" f~ood-
plain. Contained. within the floodplain were all
oxbows, historic meander lines, and other telltale
signs of rlverine activity. So that all of the
land would be classified, islands were considered
to be part of the floodplain. The floodplain
boundary was largely based on natural rather than
such men-made features as canals, railways, or
highways.
Portions of the boundary between the upland
end the floodplain, and many of the original
terrace contours, ware 1ndlacernlble on the 1987
film (due to recent agricultural grading of upper
terraces). These boundaries were clearest on the
1938 black and white photography. Thus, the flood-
plain boundary delineated on the 1938 photography
served as the boundary within which the photography
of all subsequent eras was interpreted. The bound-
ary was arbitrarily drawn across tributary rivers
or streams as they entered the Missouri River
floodplain. This boundary defined the limits of
the study area.
Urban/Ranchyard
The Urban/Ranchyard category included rural,
urban, residential, commercial, and multiple-use
development. Some mature -trees and "'L"-shaped
windbreaks associated with farm and ranch sites
were sometimes included in Lhis category. In such
cases, the delineation of the "yard" was somewhat
sub~ectlve, depending upon the various clues
visible to the interpreter.
Deciduous Woodland
Riparian deciduous woodlands were categorized
by percent-canopy closure. Stands with less than
ten percent closure were incorporated into oth
categories; e.g., herbaceous or shrub-scrub.
stands with a canopy closure equal to or great
than ten percent were included in the woodland
type. This type encompassed extensive woodlan
tracts, farm woodlots, stands in and between a
eulturat fields, and linear windbreaks not ~