As the river enters the middle course the gradient of
the river becomes less steep. Lateral erosion becomes more important
and the river starts to meander.
A meander is a bend in a river as is
shown opposite. As the water flows round the bend the flow is fastest
on the outside of the bend where the river is deeper. Here the river
erodes the outside bank of the river and undercuts it to form a
River Cliff. On the inside of the bend the river is slow flowing
and shallow. This causes deposition to take place and a slip off
slope or point bar is formed. In fact the meander is caused
by hydrocoidal flow and the water travels around the meander like a
corkscrew - so if you have been on the ride at Alton Towers you now
know what a small pebble feels like as it travels through a meander!