Shallow, narrow waterways constrain river monitors

How well would river monitors operate on the Trent-Severn Waterway?

Only up to a point: shallow and narrow sections would constrain them, though the estimate is explicitly from memory.

River monitors could operate along part of the waterway, with depth and width limiting how far they could proceed. The estimate is that restrictions become more troublesome beyond roughly the first third. This is explicitly Alex Clarke's recollection, with his kayaking experience offered as the basis for visualising the route. It does not establish navigable dimensions for a particular monitor.