It sounds like you might be thinking about how erosion works on a river bend, specifically on the outside of the bend. If that's the case, here's why:

* Water Flow: The water in a river doesn't flow in a straight line. Instead, it flows faster on the outside of a bend due to the shape of the channel. This faster water has more energy.

* Increased Energy: The increased energy of the water on the outside of the bend allows it to carry more sediment and erode the riverbank more effectively.

* Centrifugal Force: There's also a centrifugal force acting on the water as it flows around the bend. This force pushes the water towards the outside of the bend, further increasing the flow velocity and erosive power.

The result is that the outside of the bend erodes, creating a steeper bank and widening the river channel.

Let me know if you had something else in mind when asking about erosion on the outside. I'd be happy to explain further!