In Switzerland, anthropogenic activities have led to the channelization of numerous rivers, disrupting sediment transport, homogenizing river morphology, and significantly reducing the biodiversity of riparian ecosystems. Over the past 30 years, river widening has become a key measure to prevent riverbed incision and restore more natural dynamics in channelized rivers. These widenings alter river morphology, enabling in some cases a transition from straight channels to multi-thread morphologies. However, current approaches lack precise methods to characterize morphology and morphological changes within a widening. This project aims to characterize the effects of river widenings on the planform morphology of rivers, an essential parameter for sustainable river system management. For this purpose, two descriptive indices of morphology are used. First, the influence of various parameters on their calculation is analyzed. Then, a morphological classification based on these indices is proposed and compared to a visual assessment of morphology within the widening. Finally, the validity of two morphological predictors is evaluated. These objectives are investigated using a physical experimental model of local river widening conducted by Cristina Rachelly at the Laboratory of Hydraulics, Hydrology, and Glaciology of ETH Zurich and a physical experimental model of braided river conducted by Clemente Gotelli at the Environmental Hydraulics Laboratory of EPFL.