Quasi-Universal Length Scale of River Anabranches

Looping patterns, where channels divide and reconnect further downstream, are widespread in natural rivers. Here, we build an extensive dataset of different gravel-bed and sand-bed rivers around the world encompassing a wide range of physiographic and sedimentological conditions. Field data show the existence of quasi-universal relations for the anabranches length when scaled with bankfull hydraulic geometry variables of the main upstream channel. The dimensionless length is found to be nearly slope-invariant, identifying a clear difference with respect to deltaic systems. This scaling relationship is explained by interpreting the dynamics of river loops as basically controlled by a two-way interaction between their constitutive elements, bifurcations and confluences. The identification of a quasi-universal length scale provides insight on the morphological evolution of multi-thread networks and constitutes a key information for the design of self-sustaining river restoration interventions.