Question

what are side valleys?​

Answer 1

The term "side valley" is used for higher order valleys near mountains (example above: the Pennines), as opposed to lower valleys that do not have a strong relief. This is because the "main stem river" (into which the secondary river flows) passes much more water than its tributaries and therefore. has a lower current.

Answer 2

☆The term "side valley" is used for higher order valleys near mountains, as opposed to lower valleys that do not have a strong relief☆