Meanders and Ox bow lakes Distinctive landforms result from different processes as rivers flow downstream .
Lesson Objectives: <ul><li>Landforms resulting from erosion and deposition – meanders and ox-bow lakes </li></ul><ul><li>To describe and explain the asymmetrical cross section shape of a meander </li></ul><ul><li>To explain the formation of an ox bow lake </li></ul>
Meander bend on the River Conwy A B A cross section through a meander River Cliff FEATURE Slip off slope Erosion PROCESS Deposition Deep DEPTH Shallow Fast SPEED OF FLOW Slow CONCAVE CONVEX
What is a meander? (1 mark) Draw and label a cross-section from A–B through the meander (3marks) Explain how the features of a meander are formed (4 marks) A B River cliff Slip off slope
2007 Q2 (b) Explain why the meander cross-section has this shape <ul><li>The meander cross section is asymmetrical . The river cliff is formed on the outer bend of the meander. This is where the water is deeper and moves more quickly . Hydraulic action and abrasion wear away at the side of the channel, undercutting the river bank to form a river cliff. </li></ul><ul><li>The slip-off slope is formed on the inside bend by deposition of alluvium. Because the water is shallow and moving more slowly at this point the river load gets deposited to form a gentle slope. </li></ul>
River features: Ox – bow lakes <ul><li>With the aid of diagrams, explain the formation of an oxbow lake (6 marks) (AQAA04) </li></ul>Form from a meander, erosion on outside bend especially by hydraulic power , deposition on inside bends where water is shallower and lower velocity, neck narrows, breaks through in time of flood deposition seals ox bow lake. eventual loss of lake to form meander scar.