Author(s): S. Parkinson; D. Caamano; P. Goodwin; R. Benjankar
Keywords: River; Restoration; Pool; Riffle; Velocity reversal
Abstract: Velocity reversal in pool-riffle sequences has been postulated as the primary mechanism for sustaining pools in gravel-bed rivers. Recent criteria have been developed to predict the occurrence of velocity reversal for a wide range of data published in the literature, but it is unclear whether velocity reversal will sustain pools under all field conditions and what the exceptions might be. The results of a 12-year geomorphic monitoring program in the South Fork Clearwater River in Idaho, USA are presented. This monitoring program incorporates river restoration projects that span five different restoration design approaches. The restored, degraded and protected reaches have each responded differently during the past decade providing a rigorous test of the pool sustainability criterion. The monitoring program showed that if the criterion is applied using post-restoration channel conditions, then a good correlation was achieved between the occurrence of velocity reversal and pool persistence, formation or disappearance. Exceptions were noted for forced pools created by constructed features such as grade control structures, as a result of local conditions caused by woody debris or constrained channel geometry.