Classification of rivers according to width
The Rosgen river classification contains - besides slope, entrenchment and sinuosity - the width. But it is mostly applicable to natural rivers, not so much artificial waterways ...

http://extension.umass.edu/riversmart/fgm-assessment-methods/rosgen-classification-natural-rivers-natural-channel-design

https://en.wikipedia.org/wiki/Rosgen_Stream_Classification

https://content.ces.ncsu.edu/application-of-the-rosgen-stream-classification-to-north-carolina

https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_024290.pdf