POOL DIMENSIONS IN COARSE-GRAINED,
NEW ENGLAND CHANNELS
Natural channels consist of diverse physical dimensions and characteristics, called the pool-riffle morphology. An understanding of this morphology is necessary for the successful design of a reconstructed or restored channel. To better understand pool geometry in coarse-bedded New England channels, pool geometry characterizations were performed on 150 different pools strongly influenced by natural channel constrictions. Data from 125 pools were used in least-squares, multiple regression analysis with eleven different independent variables to develop prediction equations for pool depth, length and exit-slope gradient. These equations were then tested using the 25 remaining pools. The regression analyses indicated that pool depth is significantly influenced by the average width of the channel, the pool expansion ratio, and the constriction gradient, with an R-square value of 0.39. Similarly, pool length is influenced by the average width of the channel and channel gradient, with an R-square value of 0.59. The exit-slope gradient is strongly influenced by the constriction gradient, as well as by the total drainage area, with an R-square value of 0.43. Using the resulting regression equations to predict dimensions for the 20 test pools yields average residuals near zero, although, as expected, large variations do exist. The results suggest that pool dimensions are related to both channel scale (average width and total drainage area) and local hydraulic conditions (channel gradient, constriction gradient, and pool expansion ratio).
Kim Hoffman ('00), Sushil Bhattarai ('00) and Sailesh Tiwari ('02) survey a pool in the green Mountains of Vermont (1999).
Kim and Sushil survey channel gradients on the Hancock Branch, NH (1999).
A large pool located on the Saco River, NH (1999).
Sushil and Sailesh survey channel-bed elevations on the West Branch Deerfield River, VT (1999).
Sushil and Kim survey a pool on the Zealand River, NH (1999).
Julie Groce ('01) and Kim Hoffman ('00) enjoy a break on the Salmon River, CT (1998).
Doug and Julie determine pool exit-slope length on the Salmon River, CT (1998).
This material is based upon work supported by
the National Science Foundation under Grant No. 9874751. Any opinions,
findings, and conclusions or recommendations expressed in this material are
those of the author(s) and do not necessarily reflect the views of the National
Science Foundation.
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