INITIATION OF MOTION AND DIMENSIONLESS CRITICAL SHEAR STRESS IN A STEEP MOUNTAIN STREAM

摘要

Field measurements of travel length were performed in a small experimentalrncatchment of the Dolomites (Rio Cordon 5 km~2). A set of 420 sorted marked pebblesrn(0.032 < D < 0.512 m) was displaced across the stream and their movements werernchecked periodically.rnAfter introducing a criterion to define incipient motion condition based on the ratiornbetween pebble travel length and diameter, it is possible to establish the initiation ofrnmovements. The results are compared with the equimobility relationship gave byrnShields (1936) and modified by Parker (1995) and with selective entrainmentrnrelationship from other authors.