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

INTRODUCTION
Riparian vegetation plays an important role in riverine ecosystems. Riparian vegetation
offers structural cover for various animals, especially juvenile fish, macroinvertebrates and birds
(Naiman and Decamps 1997), and contributes detritus to the adjacent river channel (Neckles and
Neill 1994). This detritus provides nutrients for periphyton, bacteria, and detrivores in the
immediate area and at downstream sinks (Vannote et al. 1980). Characteristics of detritus, such
as its rate of decomposition, can affect the productivity of the entire ecosystem (Lindeman 1942,
Ovington 1962). If riparian species exhibit different morphologies or rates of decomposition,
their distributions could influence the spatial patterns of habitat quality and productivity (Lewis
1998). Riparian vegetation also moderates hydrologic events (Hickin 1984). Above-ground
plant tissue provides roughness that reduces water velocity, causing sediment deposition on
floodplains (Everitt 1968). Root masses retain bank and floodplain soils, thus providing a
medium for infiltration of floodwaters. Riparian vegetation often dampens hydrologic regimes
through uptake and release, enabling floodplains to act as natural filters and to remove pollutants
from rivers (Mitsch and Gosselink 1986).
Flood regime and floodplain topography have a large influence on the distributions of
riparian plant species. Thus, floodplain restoration may affect vegetation distributions. A major
concern of the Green River Restoration Group is the effect of floodplain restoration on
vegetation, particularly the exotic perennial herb Lepidium latifolium (giant whitetop). This
noxious weed has become abundant in riparian ecosystems in the American Southwest during the
last few decades. Giant whitetop possesses the typical life history characteristics of an invasive
exotic plant: it grows rapidly, it colonizes disturbed areas, and throughout the growing season it
produces abundant seeds that are easily dispersed by wind and water (USDA 1974). Therefore, it
poses a potential problem in agricultural areas where the soil is periodically disturbed.
The purpose of this study was to monitor the short-term effects of floodplain restoration
on vegetation. We had three major objectives. Our first objective was to develop pre-restoration
vegetation maps of restored floodplain sites from two data sources, and to compare the accuracy
and efficiency of these two approaches. The second objective was to monitor colonization at
restored sites. The third objective was to identify environmental factors that influence whether
sites will be colonized by giant whitetop.
METHODS
Development of a Base Vegetation Map
The existence of remotely-sensed data of the Green River in the Uintah Basin provides a
tool for examining spatiotemporal vegetation patterns. Different vegetation types have distinct
canopy characteristics, such as pigmentation, surface texture, orientation of leaves and branches, _
total biomass, and moisture content (Colwell 1974, Gates et al. 1965, Gates 1970). These
characteristics allow us to distinguish among different vegetation types using remotely-senstA
data. Classification of aerial photographs has been used to detect vegetation changes in pany
riparian systems (Graf 1978, Johnson 1994, Miller et al. 1995; see also Ellis and Woitt?pw ch
1989). .
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