The formation of Ox Bow Lakes due to meanders

The formation of Ox Bow Lakes due to meanders

1. The meander is asymetrical

   • Water is directed towards the outer bend, so that's where the water flows fastest. This is because the water is deeper so there is less friction between the water and river bed
     • The high velocity of the water causes high levels of hydraulic action and abrasion, so the river is undercut, and a river cliff is formed
       • On the inner bend the water flows more slowly. This is because the shallow water means more friction between the water and river bed
         • The reduced speed means that material carried in the river is deposited. This creates a 'slip off slope' (small beach) over time
           • Over time the meanders change shape and migrate across the flood plain
             • The main reason oxbow lakes form is that the deeper water on the outer bend continues to be eroded by hydraulic action
               • As a result, the outside bends move closer together and the 'meander neck' becomes narrower
                 • When there is high discharge (amounts of water in the channel) the river cuts straight through the neck of the meander as a shortcut
                   • Deposition through the new channel eventually seals off the old meander forming a straighter river channel
                     • The old meander is left isolated, forming an oxbow lake which is shaped like a horseshoe
                       • Over time, the lake dries up and fills with mud leaving a meander scar