River Landforms in Wales PDF

1.2.1a How do processes work together to create landform features at different scales in river landscapes in Wales? Waterfalls and gorges Meanders...

1.2.1a How do processes work together to create landform features at different scales in river landscapes in Wales? Waterfalls and gorges Meanders These form in the upper and middle course of a river where there are These are found in the lower course of a river. They are bends in the river different rock types. caused by lateral (sideward) erosion. Deposition Continued erosion Hard Rock on the inside and deposition bend of the river cause the as the river is meander to move flowing slower across the river’s Soft Rock forms a slip-off floodplain. slope. The river flows over the hard rock edge Over time the soft rock erodes backwards creating and down into the soft rock where it a hard rock overhang that eventually collapses into erodes it to form a plunge pool. the plunge pool, causing the waterfall to retreat backwards. It leaves behind a steep sided narrow Erosion on the outside bend as the bottomed valley called a gorge. flow is much faster. How and why do river landforms change over time? Fluvial erosion Fluvial transportation Fluvial deposition Abrasion is when rocks carried in the flow Solution is when dissolved minerals are When the flow of the water slows it has of the river smash into the banks/bed of carried in the flow of the water. less energy to carry sediment, so it is the river. Suspension is when fine particles are deposited. This can be on the inside bend Attrition is when rocks crash together as float in the river flow. of a meander or the banks and floodplain they move along in the river. Saltation is when rocks bounce along the of a river when it floods. Hydraulic Action is when air is forced into cracks in the banks/bed of the river, riverbed. forcing them to expand. Traction is when boulders roll over Solution is where chemicals in the river smaller rocks on the riverbed. dissolve minerals in the bank/bed of the river. V-shaped valleys Floodplains These are found in the upper course of a river where most of the erosion is vertical. In the lower course, a river, during a flood for example, breaks its banks and They have steep sides and a narrow valley floor creates a floodplain where deposition occurs on levees on either side of the river. Freeze-thaw weathering occurs along Biological weathering also occurs on the valley sides. This is when water the valley sides. Plant’s roots break up gets into cracks in the day and freezes the valley sides as they grow. overnight. As this continues, rocks break off and fall into the river.