Must define the concept
The article completely fails to define what makes a canal a summit-level canal. All it says is that it connects two rivers. But then the first example that satisfies that description is disqualified because it is too flat. The obvious conclusion is that the definition is, at the least, incomplete.
Furthermore, the article uses "summit level" as if it is such a common-place term that it needs no explanation. "The summit level was a flat cut" and "a 13-kilometer summit level". In fact, this term, if it exists at all, is so uncommon that it isn't even listed in the unabridged Webster's I have at hand. (Webster's does list "summit-level canal", also "summit canal", but that is not defined as "canal with a summit level".) I rather suspect that the term "summit level" as used here simply does not exist.