Last week we saw the source of the River Severn – a fairly flat piece of boggy land, near the top of a mountain in Mid-Wales.
The water begins trickling in a downhill direction and within a very short distance starts to collect in a channel.
Moving water will wash away any loose material that it is flowing over. The stronger the flow of water the more it can move, but even a trickle can carry tiny particles of dirt. Most of the time you can’t see it happening, but you can see the effects. The channel gets deeper.
Water flowing down the side slopes, to join the main stream, will also pick up and carry particles, resulting in a V shape with the main stream flowing at the bottom.
Less than ½ mile from the source of the Severn you can see this clear valley shape.