This page of our Assassin's Creed Valhalla River Raids guide explains what a river alert is and how it affects raids.
River Alert Level
River alert indicates how much you have enraged the residents of the surrounding settlements. The more settlements you attack, the more people will be informed about your actions. Each settlement that you attack can increase the chances of alerting the major headquarters that have the most interesting loot.
River alert vs. difficulty level
If the river alert level is at its highest, you may encounter many traps and dangers. Not only will the enemies spawn in larger groups, but they may also:
- Build barricades on rivers;
- Organize ambushes;
- Attack you by surprise;
- Attack you from the shore before you even get close to the settlement.