Recently started playing this map. I believe it came with the Natural Disasters DLC. I love the layout but I'm confused as to why this keeps happening. I have not done any terraforming. I have built quays along the river and a few bridges over it, but this was happening before I built anything. It doesn't affect the gameplay much, other than my fishing industry along the river when the boats get stuck because of the "tsunamis" in the river. I do have disasters disabled, but this still happens every few minutes. It's mostly the visual that bugs me, but not knowing what's causing it also eats at me. It doesn't flood anything the "tsunamis" only happen in the river. It starts about 1/4 of the way in from the opposite bay then follows the length of the river and then out to sea off the edge of the map. It's just weird. I play on Xbox Series X, no mods.