9371

• UCREFRP Catalog Number: 9371
• Author: Levee Removal Evaluation Group.
• Title: Green River levee Removal and Floodplain Connectivity Evaluation.
• USFW Year: 1998.
• USFW - Doc Type: CAP-6 LR,
• Copyright Material: NO

1
RESULTS
Development of a Base Vegetation Map
The seventeen vegetation types delineated from the TM data, and the total area of each,
are presented in Table 3.1. Note that there are no classes dominated by Salix sps. Although
Salix sps. are common along the Green River, they were not detectable at the resolution of the
TM imagery. In contrast, large patches of Tamarix ramosissima, Populus sps., and Lepidium
latifolium were identifiable. According to this map (Figure 3.2), the areal extent of giant
whitetop was 4,995 acres. The overall accuracy of the map was 83%.
Table 3.3 shows the area of each vegetation type within each restored floodplain, as
determined by classification of aerial photographs. Maps of each study area are displayed in
Figures 3.3-3.10. These classifications provide pre-restoration data on vegetation distributions,
and can be compared with post-restoration data to assess the effects of levee removal on
vegetation distributions.
E
11
Table 3.3: Area, in acres, of each vegetation type in each restored floodplain as of May 1996
Floodplain Water Emergent Native tree Exotic tree Native shrub Exotic shrub Native herb Exotic
Bonanza 15.9 5.6 4.8 3.2 7.9 8.8 3.8 5.5
Stirrup 16.1 0.0 6.0 1.6 3.5 8.7 14.5 7.0
Horseshoe 13.1 0.0 7.1 0.0 4.8 24.2 8.0 6.4
Baeser 25.2 0.0 26.8 0.0 15.8 14.0 2.3 8.5
Brennan 53.8 0.0 7.3 1.8 3.0 6.7 10.4 7.6
J4 13.3 4.3 2.3 0.8 0.9 13.6 8.1 5.2
V 76.3 83.4 36.8 0.0 0.0 51.2 32.1 20.7
Old Charley 333.0 0.0 51.4 0.0 29.3 130.6 32.5 38.9
Total 213.7 93.3 91.1 7.4 35.9 127.2 79.2 60.9
I Vegetation Monitoring in Recently Restored Floodplains

t
C
The 1998 transect data showed extensive colonization in excavated areas. The proportion
of each vegetation type is presented, by site, in Tables 3.4-3.6. Sites that were excavated in the
spring of 1997 showed recruitment of woody species and many herbs. Many cottonwood,
willow and saltcedar seedlings survived the first two growing seasons. Figure 3.11 illustrates the,\
change in vegetation composition throughout the 1998 growing season at the Bonanza site,
which was excavated in the spring of 1997. Sites that were excavated in 1998 were quickly
colonized by giant whitetop, which flowered and produced seeds at all sites. In genepl, whitetop
individuals will not flower or produce seeds during their first year of growth, so it is$kely that
26