rivers - levees

rivers - levees

1. CHARACHTERISTICS

   • Naturally raised river banks found on either or both sides of a river channel that is prone to flooding
   • Raised river banks
     • 2-8 metres high in the uk
   • Made of: gravel,stones and alluvium.
   • Grading of sediments
     • Coarsest and largest closest to the channel
   • Steep sided
     • Steeper on the channel side than the landward side
   • Fairly flat on the top
     • Covered by grass and often used as a footpath

2. FORMATION

   • 1) river bursts it's banks
   • 2) land causes more friction than the channel
   • 3) river velocity reduces causing deposition
   • 4) different sizes of sediment
   • 5) heaviest sediment is deposited first- closest to the river
   • 6) size of sediment deposited gets progressively smaller and lighter the further from the river you go
   • 7) heaviest sediment forms the base of the levee
   • 8) each successive flood builds up the banks higher
   • 9) however each flood also builds up the river bed