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

River. This strategy represented a cautious approach to floodplain enhancement (i.e. levee
removal) until it could be determined that it did not have a negative impact on other endangered
fishes.
The objectives presented in Lentsch et al. (1996) included reconnection of selected
floodplains to the river via levee removal, assessing the levee removal as a method of
reconnecting floodplains to the river, evaluating ecosystem responses to levee removal, use of
managed sites (i.e., Old Charley Wash) as a tool to assess importance of timing and duration of
inundation, and lastly, to design and implement adaptive management strategies. Associated
with the above objectives, four hypotheses were proposed:
H,: Floodplain habitats result in an increase in food resources and available habitat for
native fishes.
H2: Terraces (floodplains that drain as spring peak flows recede) and depressions (small
basins that retain water after spring peak flows recede) exhibit different dynamics
with respect to the native fish community due to differences in food supply and
timing and duration of inundation.
H3: Terraces and depressions produce different conditions for survival and growth of
endangered native fishes because of differences in predation rates by nonnative
and/or other native fishes.
Ha: The interaction between nonnative fish predator use and floodplain geomorphology
(depression vs. terrace) will result in changes in the composition of the [river] fish
community.
Lentsch et al. (1996) proposed a specific sampling design (discussed in greater detail in Chapter
4) to address the above objectives and hypotheses. The design included comparing nutrient
concentrations, invertebrate biomass, and fish abundance in natural and application (levees
removed) floodplain (terraces and depressions) sites in the middle Green River. An equal
number of terrace and depression sites were selected to represent either natural (no changes) or
application (levees breached to allow access to river flows at approximately 13,000 cfs)
treatments. In addition, an equal number of floodplain study sites were located in what were
designated as either high or low nonnative fish (i.e., centrarchids and ictalurids) density reaches
based upon previous electroshocking data (unpublished data, Todd Crowl, Utah State
University). The high nonnative density sites were in the lower reach of the study area below
Brennan Bottom, and low nonnative density sites were located above this site. A scope of work
was approved and funded by the RIP in fiscal year 1996 based upon the outline presented in
Lentsch et al. (1996).

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