Laserfiche WebLink
Geomorphology Research Priorities September 2003 <br />planforms describe various levels of confinement of the river channel within the surrounding <br />geology, which in turn affects habitat characteristics relevant to endangered fishes. Restricted <br />meanders occur in broad alluvial terraces that are bounded by relatively more resistant geology. <br />Fixed meanders are confined by resistant geology on both outside and inside bends of the main <br />channel. Canyons consist of relatively straight sections of river with resistant geology on both <br />sides of the river. Habitat types considered included pools, runs, riffles/rapids, connected <br />backwaters, side channels, eddies, flooded tributary mouths, and flooded bottomlands. <br />Consideration also was given to potential use of reaches, assuming improvements in <br />conditions in response to implementation of flow recommendations, planned removal of existing <br />barriers to passage, and successful establishment of populations through augmentation. <br />Consideration of potential reach use was considered especially important for the razorback <br />sucker in the upper Colorado River subbasin, because existing levels of use are so low and so <br />few larvae and juveniles exist in the system. <br />Once we computed reach-habitat scores and scored the dependence of habitat <br />characteristics on hydrology and geomorphology, we searched the available literature for studies <br />that addressed important parameters in the highest scoring reaches and habitats. Remaining <br />information needs were those important relationships in priority reaches and habitats that had not <br />been addressed by previous studies. <br />In the Green River subbasin, the highest overall reach-habitat scores for species and life <br />stages combined are in the Split Mountain Canyon to Desolation Canyon reach. Habitats with <br />high scores in this restricted-meander reach include connected backwaters, side channels, <br />flooded tributary mouths, and flooded bottomlands. All are low-velocity habitats that serve as <br />critical nursery areas for Colorado pikeminnow and razorback suckers. <br />The extremely dynamic nature of backwater and side-channel habitats demands a greater <br />understanding of the geomorphic processes that form and maintain those habitats. Additional <br />research is needed to verify the existing conceptual model of backwater formation and more fully <br />understand underlying geomorphic processes, including the effects of antecedent conditions. <br />Studies are also needed to address the effects of base-flow variability (inter-annual, intra-annual, <br />and within day) on backwater and side-channel habitat availability and conditions. <br />Scores were high for spawning bar complexes in the Desolation and Gray Canyons reach <br />and in the Yampa Canyon reach because several species spawn in each. Studies are needed of <br />spawning bars in the Split Mountain Canyon to Desolation Canyon reach and in Desolation and <br />Gray Canyons to determine the effects of peak flow, base flow, and sediment characteristics on <br />the formation and maintenance of suitable spawning habitats. Although several studies have <br />examined geomorphic properties of the razorback spawning bar in the Split Mountain Canyon to <br />Desolation Canyon reach, additional study is needed to verify the existing conceptual model for <br />this bar and better understand the effects of peak-flow magnitude, peak-flow duration, peak-flow <br />frequency, peak-flow timing, and sediment on habitat conditions during the spawning period. <br />Several studies have examined the underlying geomorphic processes that affect the <br />formation and characteristics of backwaters and side channels in the upper Colorado River <br />x