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

Aerial photos covering 100 percent of the
floodplain were interpreted using an eight-power
lens and the naked eye. Delineations were made on
acetate overlays. Quality control and interpre-
tative consistency was achieved during this phase
by specialists each regularly examining the other's
work.
Mylar overlays for twenty-eight 1:24000
scale, US&5 topographic maps were produced by
standard zoom-transfer processes. Ground truthing
of these final interpretative products for the
1974 and 1982 eras was accomplished during a low--
eltitude flight over the entire length of the
study area= during a roadside survey along a 23-
miie length of secondary highwsy; and during visits
to preselected sites.
Mylar overlays for each era were digitized
using the WAMS (Wetland Analytical Mapping System)
digitizing system. Data analyses were performed
using a geographic 9nformation system, WTId)OW,
developed by tha U.S. F1ah and Wildlife Service.
~A Control Data Cyber 760 mainframe computer was
used for data processing.
RESULTS Af~D OBSERVATIONS
'How much riparian vegetatton existed in north-
east Montana along the Missouri Rtver during 1938,
1956, 1974 and- 1982 was investigated end is re-
ported. Broad changes in the composition of the
floodplain are documented, General patterns of
change ere described. Causes of change are dis-
cussed And their relative effects on floodplain
composition are put in perspective. Riparian
cover broadly included three cover types the
deciduous woodland for faresL), shrub-scrub, and
herbaceous cover types. A11 sreas of visible
agricultural disturbance and hard construction
were collectively referred to as developed cover
or land. Developed cover included the agriculture,
rights-of-way, and urban/ranchyard cover types.
Developed cover was most often void of riparian
vegetation.
The composition of the floodplain was not
stagnant, but was dynamic throughout the period
studied. Since 100 percent of the study area was
inventoried for all four eras, no statistical
analyses were performed. Differences were assumed
to be real. Compositlan was described 1n terms of
several measures. These were the area, density,
and percent of the floodplain represented by each
cover type. Broad changes were documented in
terms of the net gain or loss of a cover type
between eras.
General patterns are described based on these
changes. These patterns and the magnitude of the
changes were directly influenced by events caused
by both humans and nature. These events included,
but were not limited to, the conversion of riparian
vegetation to cultivated farmland; the erosion of
the shoreline by the Missouri River; the reduction
of forests and shrubs by mechanical and chemical
means as well as by burning; the abandonment of
developed land and subsequent regrowth of riparian
cover; the conversion of developed land to pasture-
land; natural succession; and growth. (Due to the
height categories of the shrub-scrub and woodland
types 1n the classification, plus inability to
ditferentlate between the photographic signature
of the herbaceous type and the seedling stage of
woody species, homogeneous areas dominated by
woody species could have-been classified as any
riparian type depending on whether the area was in
a seedling, sapling, or mature stage of growth.)
The effect of each event was not determined, but
the results of cumulative effects were summarized
in terms of broad categories of change.
Floodpiain Composition
Seversl measures are presented in Table 2 for
each cover type that together describe the ilood-
pialn composition in each era.
Table 2.--Floodplain cover types -Measures of composition by era.
Developed Land Riparian Habitat
Rights Urban/ Deciduous Shrub
Kinds of measurements Agriculture of~r,~y. Ranchvard Woodland Her~acgous Scrub
Percent of the floodplain
1938 24 0.2 0.6 10 52 14
2956 47 0.4 0.9 16 25 11
1974 51 0.5 1.0 20 21 7
1982 55 0.5 0.8 13 Z6 5
Density (a./sq.mi.)
-
1938 250 1 4 63 334 86
1956 301 2 6 101 158 71
1974 325 3 6 128 134 43
1982 349 3 5 81 168 34
Acres per cover type
1938 43,592 434 1,173 18,374 96,804 25,037
1956 84,809. 687 1,587 28,447 44,601 20,003
1974 94,263 992 1,792 37,082 38,849 12,548
1982 100 475 956 1 557 23 1Q~ 48 279 9 837