Erosional and depositional river landscapes LS: Apply knowledge of Erosional processes to understand how erosion forms river landscapes. Describe the formation of Ox-Bow lakes and Flood plains Fully explain the formation of waterfalls.

Starter activity Read pages in KS3 Geography book and learn what a drainage basin is. Answer question 6 and 7 on page 41. Erosion processes in Rivers Rivers have 4 different processes of erosion which break down rocks in Drainage basins, you need to understand what a drainage basin is and what erosion is to be able to continue. Hydraulic action is when the River water waves smash against river channels and the force of river waves break rocks off these cliffs. Abrasion is when the rocks rub against the river bed or against the river cliff and as they rub against, they change shape and break up. Attrition is when two or more rocks grind and rub against eachover changing the shape and making the rocks into smaller intervals. Corrosion is when soluble rocks in water such as clay may fall into the river and dissolve to form a soluble solution in the water.

Erosional river landscapes Waterfalls and interlocking spurs are landscapes formed from erosion, lets begin with waterfalls, 1. The river flows over an area of hard rock followed by an area of softer rock. 2. The softer rock is more easily eroded, and as this softer rock is eroded, it forms a step up slope (like a step) 3. Eventually after continuous abrasion to the soft rock the rock will give in and form a large slope, this is the birth of a waterfall. 4. At the bottom of the waterfall, the softer rock is forced to wear away at the surface rock by the force of water being pushed on, this process creates a plunge pool, a deep area of water. 5. The hard rock is still capable of being eroded by river flow, so as the water continues to flow over this harder rock, it will eventually erode and make the river retreat, as the river retreats it forms a gorge.

Interlocking spurs Interlocking spurs, like waterfalls are formed in the Upper course of a river, there are higher hills, and as rivers flow at these hills, they are forced to wind round these hills because rivers can't erode laterally, instead eroding vertically, making twists and turns in the river. An example of interlocking spurs is in the upper course of the River Clyde.

Erosional and depositional river landscapes A Meander is formed from erosion and deposition, deposition is just the drop off of rock as a river may slow down in velocity. These landscapes are in the lower course of a river. Meanders have an inside bend and an outside bend, the inside bend is more shallow, so the velocity of the river is slower and therefore more deposition occurs here than erosion, this will then form slip-off slopes (like you see at beaches) the outside bend is more deeper and has a much faster velocity, there is more erosion here, the erosion here creates river cliffs. The continuation of erosion and deposition in Meanders can create Ox-Bow lakes, as the necks of the meanders get closer due to rapid erosion on the river cliffs, they will eventually break through forming a longer straight river where the current is fastest, because it takes the easiest flow, at the slip off slopes where the deposition occurs, the rapid deposition eventually cuts off the meander to the river leaving an ox-bow lake.

Flood plains, Levees and Deltas All of these landforms are also formed in the lower course of a river. A flood plain is basically a flat area of land, it is flat because as a meander floods, the water goes onto this plain and the material transported by the river is deposited on this land, this makes the land a flat low lying area. You need to understand what a flood plain is to understand Levees and deltas. A levee is a natural embankment, when a river floods, the first place the deposition occurs is just on the bank, so as deposition occurs the land will raise and form embankments by the river. A delta is a low-lying area close to the rivers mouth, as a river slows down on its course, more deposition occurs, eventually the deposition of material will cut off the rivers flow and the river will be forced to flow onto the flood-plain and create a new route to the sea, these new rivers are called distributaries. This continues to happen until you get loads of small distributaries.

Exam style questions 1) Study the figure below of a rivers lower course a) Name 3 features found in a rivers lower course I … ii Iii b) Describe the formation of an ox-bow lake, you may also draw a diagram to help. … c) Tick which box is correct: A floodplain is flat because of... Occurring erosion Occurring Deposition Occurring transportation It is a river *d) Fully explain how hard engineering is done in a river to prevent flooding of a river. Explain the: Advantages and disadvantages Effectiveness Sustainability Comparison to soft engineering strategies