The role of hydrologic processes and geomorphology on the morphology and evolution of sediment clusters in gravel-bed rivers

The use of fractals to quantify the morphology of cluster microforms

“…From the reach scale down to the grain scale, two main categories of bedforms have been identified, namely: (i) largescale bedforms, such as gravel bars and step-pool sequences (e.g., Whittaker and Jaeggi, 1982;Wohl, 1999;Chin, 2003); and (ii) small-scale bedforms, such as clusters (e.g., Papanicolaou et al, 2003;Wittenberg et al, 2007;Hendrick et al, 2010) and transverse ribs (e.g., Bluck, 1987).…”

“…Recent field studies (e.g., de Jong, 1995;Church et al, 1998;Kozlowski and Ergenzinger, 1999;Wittenberg, 2002;Strom and Papanicolaou, 2008;Hendrick et al, 2010) have identified different cluster morphologies, most of which have also been documented in laboratory investigations (e.g., Papanicolaou et al, 2003;Strom et al, 2004;Papanicolaou and Kramer, 2005). Based on Papanicolaou et al (2003), cluster morphologies can be discerned into two broader categories, namely, the 'elongated ' (or simply 'in-line'), and the 'nonlinear' (e.g., 'pseudo-triangle' and 'pseudo-rhomboid') ( Fig.…”

“…A cluster morphology classification scheme is provided in Fig. 1 (Papanicolaou et al, 2003;Strom and Papanicolaou, 2008;Hendrick et al, 2010). Analogous cluster morphology classification schemes to the one presented in Fig.…”

“…Because of the absence of definitions that adequately describe cluster morphology, earlier studies have examined cluster morphologic attributes in terms of their degree of similarity or dissimilarity with Euclidean shapes (e.g., line, triangle, rhomboid). This explains, for example, the use of loosely de-fined terms such as pseudo-rhomboid to indicate high resemblance of a cluster morphology with the rhomboid shape; or the use of terms such as 'dump deposit' when the cluster morphology significantly departs from a known Euclidean shape (e.g., Papanicolaou et al, 2003;Hendrick et al, 2010). In the broader sedimentologic and geomorphologic literature, well-documented studies describe the statistical properties of sediment bed profiles in clustered reaches using bed elevation variograms (e.g., Robert, 1988;Strom, 2006) and bed elevation structure functions (e.g., Nikora et al, 1998); however, these studies although useful for the description of bed profiles were not intended to describe morphology of clusters.…”

Influence of Gravel-Bed Porosity and Grain Orientation on Bulk Flow Resistance

“…), multiple roughness scales (e.g., small and meso-scale bedforms such as pebble clusters, steps, pools, etc. [11]) and therefore roughness properties may vary independently of grain size [12]. Some studies suggested that the standard deviation of bed-elevations may be used as characteristic vertical roughness scale (e.g., [3,[13][14][15]) and further studies focused on the determination of characteristic horizontal roughness scales through the analysis of longitudinal profiles or digital elevation models, respectively, using spectral analysis, correlation functions and structure functions (e.g., [12,13,16,17]).…”