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River Tees - Coggle Diagram
River Tees
Human activity
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Cow Green reservoir
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Controls the river discharge and therefore velocity, and is therefore able to reduce flood risks downstream
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Reduces hydraulic action and abrasion, and therefore vertical and lateral erosion
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Tees Barrage
£54million barrier keeps the middle course of the river permanently at high tide - no salt water mixes in
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Urbanisation (at Yarm)
Pavements increase surface runoff and decrease infiltration as they are impermeable - this increases flood risks
Deforestation reduces water absorption, increasing flood risks
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Landforms
Upper course
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Waterfalls (High Force)
2 rocks of differing resistance, differential erosion occurs as they erode at different rates, creating a height differential. Hard igneous whinstone, soft sedimentary limestone
As the height grows, the strength of the water falling onto the lower rock erodes it even faster, undercutting the harder rock and forming a plunge pool
Eventually, the overhanging hard rock cannot hold its own weight and collapses
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V-shaped valleys
Steep gradient means river falls with more force, meaning more vertical hydraulic action and abrasion and therefore more vertical erosion
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Sides of valley get weathered away (solution, freeze-thaw/onion-skin weathering), and pieces fall down into the river, where they are transported away. As this process occurs, the valley becomes V-shaped
Middle and lower course
Meanders
Sides of the river with a higher velocity have higher rates of hydraulic action and abrasion, meaning higher rate of erosion. This cuts into the riverbank and forms a river cliff
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Sides of the river with a lower velocity have almost no erosion, and high amounts of deposition of alluvium, meaning this part of the river gets shallower. This eventually forms a slip off slope
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Oxbow lakes
When two meanders become very close to each other, occasionally a flood will mean that they connect. After this event occurs a number of times, the river naturally begins to take this more direct route
As the river velocity in the direct route grows, the river velocity in the old meanders diminishes, and over time more and more deposition occurs until eventually the meander is blocked off and the river no longer takes that route.
Floodplains/levees
During a flood, the river loses energy. When the water flows over the banks and deposits material on either side of the banks, the largest material (rocks) is deposited nearest to it, while the finer material such as silt is carried far into the floodplain
After each flood, a new layer of material is deposited
Eventually the material builds up so much that it is elevated well above the floodplain. It has formed a levee