Meandering Streams

Some streams run pretty straight, while others tend to meander - that is, they twist and wind their way along. Why is that? Sometimes a stream needs all of its energy for down-cutting. Maybe it´s cutting through rock that´s hard to erode. Or maybe it´s quite high, and has a long way to cut down to get to the right elevation to join the next stream. Then it uses all of its energy to cut straight down. On the other hand, if the rock isn´t very hard to erode, or if the stream is almost at the right elevation to join the next stream, it uses its energy for some downcutting but also for some side-cutting. That means the stream will develop twists and curves along the way, using its energy to erode back and forth and build a floodplain.