9700

• UCREFRP Catalog Number: 9700
• Author: Hayes, J.W., K.E. LaGory and G.L. Burton.
• Title: Consideration of site-specific floodplain inundation thresholds in implementing peak flow magnitude and duration recommendations in the middle Green River, Utah.
• USFW Year: 2005.
• USFW - Doc Type: Argonne National Labortory, Argonne, Illinois.
• Copyright Material: NO

Green River Floodplain Inundation

21

June 2005

6 UNCERTAINTIES

The proposed peak: flow management strategy was developed using the most recent
information available, but, as with the existing recommendations, uncertainties remain. Studies
should be conducted that evaluate the effectiveness of flow recommendations to provide for
floodplain connection and inundation and the subsequent benefits to native fishes. Topics that
should be addressed include, but are not limited to:

· Flow and stage at which floodplains with levee breaches at the elevation of 368 to
396 m3/s (13,000 to 14,000 cfs) flows become connected to the main channel and
sufficiently inundated to provide nursery habitat for razorback sucker larvae and
escapement of juveniles;

· Specific flows needed to adequately exchange retained water in depression
floodplains for the maintenance of suitable water quality;

· Area and depth of floodplain depression habitat that persists after peak: flows recede
and the relationship, if any, to the magnitude of the peak flow;

· Rate of sediment deposition and erosion in floodplain depressions as a function of
peak: flow and connecting flow magnitude and duration;

· Abundance of drifting razorback sucker larvae as a function of distance from the
razorback sucker spawning bar;

· Entrainment and retention of larvae in floodplain nursery habitats as a function of
specific flows;

· Entrainment of larvae into floodplain nursery habitats as a function of distance from
the razorback sucker spawning bar;

· Entrainment and retention of larvae into floodplain nursery habitats as a function of
the physical characteristics of the habitat including size, volume, local hydraulic
conditions, inlet(s), and outlet(s);

· Temporal relationships between drifting larvae and hydrology during the runoff
period with special attention to the timing and duration needed to entrain most
drifting larvae;

· The frequency of connection needed to successfully recruit razorback sucker larvae
into the adult population, including the frequency needed to sustain adequate water
quality and allow escapement of subadults and adults to the main channel; and

· The frequency oftotal drying (reset) needed to control nonnative fish populations.

Controlled experiments and associated studies should be performed that capitalize on
hydrologic conditions in a given year and that address as many topics as practicable in anyone
year. Valdez and Nelson (2004) also provided an overview of research needs to better understand
the relationship of river flow to proper functioning floodplains. Establishing a focused research
plan to address uncertainties associated with floodplain habitats is of critical importance to the