Do Cutoffs on Pristine Meandering Rivers Tend to Be More Upstream-Skewed than the Main Channel?

Meander bends are rarely symmetric in the streamwise direction. Instead, they tend to show a preferred skewing, with the apex either pointing upstream (upstream-skewed) or downstream (downstream-skewed). There are theoretical reasons for both planform morphologies, and both can be seen in the field. Here we focus on skewing in cutoffs versus skewing in the main channel bends, and consider reaches that generally display neck cutoffs rather than chute cutoffs. In order to avoid the effects of human interference, we have selected five natural reaches, from various places around the world, which are in remote locations with negligible engineering works. We use Landsat images and Google Earth Pro to extract planform data for our study reaches. In total, 936 channel bends and 144 cutoffs have been evaluated. The percentage upstream skewed (PUS) among bends and cutoffs is estimated as 50.8% and 84.4%, respectively. The results indicate that while upstream- and downstream-skewed bends are found with nearly equal frequency in freely meandering channels, single-bend cutoff loops are strongly biased toward upstream-skewing.