Olavorw
The example sentence is confusing because there are simpler ways to express the same idea. Keeping sentences simple usually improves clarity.
In an emergency, a native speaker would likely skip “それ 以上” and just use the negative form of the verb, like “近づかないで.” They might also reorder the words, placing “それ 以上” after “川に.” Books like Japanese Intermediate Grammar can be really helpful for reinforcing simple, clear sentence structures. You should check them out!