2) "Each glacier contains at least one main centerline as well as any number of tributary centerlines" ("at least" and "as well" as do not work together since at least one includes the others already). tried to clean up
3) "different framework and thus cannot be compared directly" Anyting can be compared but I think you mean what I reformulated to.
1) clearer from the start that main ist longest
2) "Each glacier contains at least one main centerline as well as any number of tributary centerlines" ("at least" and "as well" as do not work together since at least one includes the others already). tried to clean up
3) "different framework and thus cannot be compared directly" Anyting can be compared but I think you mean what I reformulated to.
4) also some reformulations to increase clarity.
5) check my note on Strahler number.