ABSTRACT
Step-pools are common in mountain river systems and act to dissipate energy (Heede, 1981; Chin, 1989). Consequently it is important to understand their hydraulic function and there is a burgeoning literature that considers the scaling of step-pool systems in steep gravel-bedded alluvial channels. Predominately the literature determines that the geometry of the steppool system can be described as a function of the step spacings and step heights, with the latter determined by the size of the largest clasts forming the steps (see Curran and Wilcock, 2005). The free variable is the step spacing, which is measured as the distance between the crests of the successive clast accumulations that constitute the steps. High flow events may destroy some or all of the clast accumulations, which are re-established in part during the recession limb of the flood or during subsequent competent flows (e.g. Chin, 1998). Thus step spacings might adjusted through time. In some systems, step spacing is relatively uniform (Chin, 2002), whilst in other systems the
spacing is more irregular (Zimmermann and Church, 2001; Curran and Wilcock, 2005).
