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<br />NAU Sand Bar Studies
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<br />Final Report
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<br />Field Measurements of Bed and Suspended Sediment
<br />Bed and suspended sediment samples were collected during the 1996 Controlled Flood, in August-
<br />September 1997, and during the 1997 Test Flow by the USGS at streamflow gaging stations on both
<br />the Colorado and Paria Rivers, We discuss only the data pertaining to Marble Canyon and upper
<br />Grand Canyon in this report (Fig, I), Konieczki et al, (1997) and Topping et al, (1999) report the
<br />grain-size analyses of samples collected in 1996. The sites on the Colorado Ri ver are located at Lees
<br />Ferry (streamflow gaging station #09380000), 100 Ian downstream from Lees Ferry just above the
<br />confluence with the Little Colorado River (streamflow gaging station #09383100), and 42 Ion
<br />downstream from the Little Colorado River confluence (streamflow gaging station #09402500),
<br />Following the usage of Topping et al, (2000a, 2000b) we informally refer to these gages as the Lees
<br />Ferry gage, the lower Marble Canyon gage, and the upper Grand Canyon gage, respectively,
<br />Streamflow gaging on the Paria River is located just upstream from the confluence with the Colorado
<br />River at Lees Ferry (streamflow gaging station #09382000) and is herein referred to as the Paria gage,
<br />Cross-sectionally averaged suspended-sediment samples were collected from the USGS cableways
<br />once to several times daily using 0-77 bag samplers and the equal-discharge increment methodology
<br />described by Edwards and Glysson (1988). Bed sediment was sampled across the channel at one or
<br />more locations using a BM-54 sampler, Concentrations of suspended sediment were determined using
<br />standard USGS techniques (Guy, 1969), Use and estimates of error in sampling Colorado River
<br />sediment are described in Konieczki et al. (1997) and Topping et al, (2000a).
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<br />Field Studies in the 3.km Reaeh Downstream from the Paria River
<br />We examined the volume and distribution of sand initially deposited in the Colorado River in a
<br />3-1an long reach below the confluence with the Paria River (Fig, I), The study reach is 1.5 Ion
<br />downstream from Lees Ferry and 0,25 Ian downstream from the mouth of the Paria River. Bedrock at
<br />river level is the Permian Kaibab limestone, The 3-1an reach has a gradient of 0,000625 at a discharge
<br />of 227 mlls (8,000 fels) (H, Shiek, written comm" 1999), and extends from the downstream half of
<br />the Paria Riffle fan-eddy complex to the upstream part of the Cathedral Wash riffle fan-eddy complex,
<br />We divided this reach into four segments, each less than I-Ian long, and each bounded upstream and
<br />downstream by debris fans, rock falls, or river bends (Fig, 1), The segments are informally numbered
<br />in the downstream sequence in which they occur, The eddy along the right bank of Segment I is one
<br />of the largest in the Colorado River ecosystem, We refer to this eddy as Eddy I. We surveyed 37,600
<br />m2 of Eddy I that were inundated during the study period. Segment I also contains an eddy on river
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