MODELING POOL-RIFFLE MORPHOLOGIES IN NEW ENGLAND TO PREDICT PERCENT POOL, RIFFLE AND RUN LENGTH

Forced pools are common features in New England and result from obstructions created by boulders, bedrock and large woody debris (LWD). A revised Monte Carlo simulation approach and developmental computer model was created to predict pool formation, spacing and the percent length covered by pools, riffles, scour holes and runs based on input data that include channel slope, width, the number of small and large boulders, and the number of 10-30 cm, 30-60 cm and >60 cm pieces of LWD. A minimum distance develops between successive pools because of the backwater and turbulent conditions needed for pool formation. The statistical-empirical model predicts obstruction location and pools are assigned different probabilities of development depending on the obstruction type. The total number and spacing of pools, riffles and scour holes thus reflects the number and locations of obstructions and characteristics of the pool-riffle couplet. The model was tested on New England channels to verify the model. The model accurately mimics some statistical attributes of channel morphology.