8251

• UCREFRP Catalog Number: 8251
• Author: Rakowski, C. L. and J. C. Schmidt.
• Title: The Geomorphic Basis of Colorado Squawfish Nursery Habitat in the Green River Near Ouray, Utah.
• USFW Year: 1996.
• USFW - Doc Type: #93-1070,
• Copyright Material: NO

Draft Fmal Completion Report to UDWR for Contract #93-lOiO. Amendment 3

v

redistribution of sediment and the large-scale response of the channel features to flood passage.

Three geomorphic settings create the majority of nursery habitat lli the 10-km study reach. These settings are

(1) the downstream end of secondary channels. (2) the upstream end of secondary channels. and (3) inactive chute

channels. The first and third of these settings are also the most common location of deep nursery habitats. Overall. a

small number of sites provide the majority of the total area of deep habitats in any year.

The number and size of these habitats changed from year to year in this study. The hig!1 magnitude flood of

1993 did not significantly increase the number or total area of deep nursery habitats. but the total number and area of all

habitats greatly decreased. In contrast, the number and area of deep habitats and total habitats decreased after passage of

the relatively small flood of 1994. The 1994 flood created more habitats than did the 1992 flood.

Analysis of the geomorphic settings of nursery habitats at the detailed study site show that different settings

create available habitat at different discharges (Fig. ES 1). Thus, the shape of discharge-dependent habitat availability

curves (HAC's) in any year is determined by the topographic relief and relative size of the geomorphic features that

WATER SURFACE ElEV AllON. IN METERS
93.5 94.0 94.5 95.0 9 .5
14000
en
;12~ X
SECONDARY
CHANNEL ~~\
~1(XX)Q
:J ISOLAlED
0
en 8000 POOL
~
~ V BAR rop
-< 6000
~
~ 4000
>- I~\ ~-..
Ii]
en 2000 I II ,..~,
~ I I I />1'
z
0
0 50 100 ISO 200 250 300 3SO
DISCHARGE. IN CUBIC METERS PER SECOND

FIGURE ES 1. Decomposition of the localized habitat availability curve by geomorphic classification. Area of
available habitat is separated into geomorphic components (for example, the habitats associated with the secondary
channel, superimposed bars. and isolated pools). Dashed and solid lines indicate 1993 and 1994 habitats, respectively.
. The total available habitat in 1993 and 1994 are indicated by X's and +'s, respectively. The lines do not always
coincide with the markers but the addition of the curves for available habitat in each geomorphic setting for each year
results in habitat availability curve shown in Figure 31.