Middle Course of River Powerpoint

The 3 courses of a river !!!

Nicole Gubby

Objectives: To revise the three courses of a river.Revise the features in the courses of a river.

This PowerPoint will include information on the 3 courses of a river and the features in the 3 courses of a river

The upper course of a riverThe upper course is found in the mountains and hills where the river rises from its source in the mountains were the rivers starts off in streams the ground is like a sponge . Often waterfalls and rapids are also found in this course. The river is usually fast flowing in the upper course. There are lots of stones and boulders for the water to flow over. The river starts as a stream in the upper course and flows through V-Shaped valleys.

Water flows over hard rock. When it reaches the soft rock, the water starts to erode or wear away the soft rock. Over thousands of years, the soft rock is eroded and the river begins to cut down vertically into the rock. This makes a cliff over which the water can topple. Over time, the cliff becomes steeper and deeper and a waterfall is formed. At the bottom of the waterfall a plunge pool is created. Some of the water splashes onto the cliff and makes a large, hollow plunge pool by a process called undercutting.

The middle course of a riverThe middle course is where the river starts to become wider and deeper because loads of small streams which are formed in the upper course of the river form into one. The land which the river flows over becomes flatter. The river starts to meander or bend in the middle course which can also form some oxbow lakes.

Oxbow lakes

Oxbow lakes are formed when a bend in a river is cut off from the main channel by the forces of erosion. An oxbow lake will slowly be created as soil erodes and re-deposits, changing the river's original course.

Meanders

Meanders are formed by erosion and occur where a river has worn away its banks. Most erosion normally occurs on the outside bend of a meander. This is because the velocity (speed) of the river is faster. As well as the water hitting the banks, pieces of sediment may also be thrown against the river banks wearing them away. On the inside bend of a meander, the water flows more slowly. There is normally deposition on the inside bend. This is because the sediment is too heavy for the river to carry.

The lower course of a riverIn the lower course, the river has a high volume and a large discharge. The river channel is now deep and wide and the landscape around it is flat. However, as a river reaches the end of its journey, energy levels are low and deposition takes place.The river now has a wide floodplain. A floodplain is the area around a river that is covered in times of flood. A floodplain is a very fertile area due to the rich alluvium deposited by floodwaters. This makes floodplains a good place for agriculture. A build up of alluvium on the banks of a river can create levees which raise the river bank.Deltas are found at the mouth of large rivers - for example, the Mississippi. A delta is formed when the river deposits its material faster than the sea can remove it.

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