Ox bow lake
1- Erosion of outer bank forms river cliff. Deposition inner bank forms slip off slope
2- Further hydraulic action and abrasion of outer banks, neck gets smaller
3- Erosion breaks through neck, so river takes the fastest route, redirecting flow
4- Evaporation and deposition cuts off main channel leaving an oxbow lake
Waterfall
1- River flows over alternative types of rocks
2- River erodes soft rock faster creating a step
3- Further hydraulic action and abrasion form a plunge pool beneath
4- Hard rock above is undercut leaving cap rock which collapses providing more material for erosion
5- Waterfall retreats leaving steep sided gorge
Floodplains and levees
When a river floods, fine silt/alluvium is deposited on the valley floor
- Closer to the river’s banks, the heavier materials build up to form natural levees
Advantages of floodplains
- Nutrient rich soil makes it ideal for farming
- Flat land for building houses
Meanders
- thalweg is the fastest flow of river on the outside bend
= more energy to erode outside bend - hydraulic action and abrasion erodes the river bed and bank
= causes a river cliff - inside bank has low energy
= not enough power to erode
= areas of deposition
= slip off slope formed by deposition
= sediment is dropped off and builds up due to low energy
Levees
- long, narrow ridges alongside river made of gravel, stones, alluvium
- steeper on channel side than land side
- occur in lower course of river when there’s increase in water volume flowing downstream and flooding occurs
- sediment that has been eroded further upstream is transported downstream
- when river floods sediment spread out across floodplain
- friction with land reduces velocity and causes deposition
- when flood occurs river looses energy and larger materials deposited first on side of river banks
- after many floods sediment builds up to increase river bank height
= levees become higher than surrounding floodplain
