A river is divided up into three sections called courses. There is the upper, middle and a lower course. A river starts in the upper course, usually an elevated section of land such as a mountain ...

It’s a slow process, but it can significantly alter the Earth’s surface over geological time scales. “An interesting river system ... them up faster than erosion is wearing them down.

The city extended the area where erosion reviews for new development along the sensitive riverbank must take place.