SEDIMENT-SORTING PATTERNS IN
CONNECTICUT POOLS AND RIFFLES
Sediment-sorting characteristics in pools and riffles result from a complex interaction among hydraulics, channel geometry and sediment transport. The combined influence of high and low flows create a mixed population of sediment sizes in pools and riffles that have led to contradictory results in comparisons of these areas. To better understand sediment-sorting patterns in coarse-bedded New England channels, channel geometry and channel-bed sediment characterizations were performed at 39 locations on eight different channels in eastern Connecticut. Fourteen different geometric variables were determined from surveys at each site and used to predict sediment d50 values and Sorting Index values. The sediment d50 and sorting values are based on pebble-count characterizations of channel-bed sediments at each site. A Tukey-Kramer HSD comparison of the means indicate that pool sediments are significantly coarser than riffle sediments. Similarly, pool exit-slopes and riffles are significantly better sorted than pool centers. Regression analyses also suggest relations between the size of sediments in pools and riffles and a combination of geometric variables. The resulting relations are all significant at the 95% confidence level and have R-square values that range from 0.18 to 0.67. The degree of sorting in pool centers can also be predicted based on four geometric measures of pool dimensions with a resulting R-square value of 0.51. The findings suggest that the characteristics of the downstream section of pools provide an important control on sorting characteristics throughout the pool-riffle morphology. The correlation between channel geometry and sorting characteristics can provide a tentative model for prediction or design of channel-bed sediment characteristics in rivers for conservation or restoration purposes.
Julie Groce ('01) determines pool depth on Day Pond Brook, CT (1998).
Doug, Julie and Sierra measure particles sizes on the Salmon River, CT (1998).
Kim, Julie and Doug survey pool dimensions on the Salmon River, CT (1998).
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