HYDROSPHERE Rivers processes, profiles and landforms

HYDROSPHERE What do you remember/know about rivers??? In your groups, spend 5 minutes noting down anything you can think of.

HYDROSPHERE In this section we will cover... River Processes –Erosion, Transport, Deposition Profiles –How a river changes as it progresses towards its mouth. Landforms/features –Key features and how they are formed.

HYDROSPHERE Rivers processes Rivers like glaciers and the sea, are important forces in shaping the landscape. All three not only erode the land but also transport and deposit eroded material.

Erosion Processes Hydraulic action - When the sheer force of the water in the river dislodges particles for the rivers bed and banks Corrasion - When smaller material carried in suspension rubs (like sandpaper) against the banks of the river. Can produce potholes. Corrosion - When acid in the water dissolves the rocks (such as limestone). Attrition - Boulders and other material are transported along the bed of the river, these collide and break in to smaller pieces. These erosion processes obviously take a long time to shape the land and they are difficult to observe. But the land will wear down more quickly if the rocks around the river channel are softer and have more cracks.

Transportation Traction: The largest rocks in the river are rolled along the bottom of the river by the force of the water. This primarily occurs in the upper reaches of the river. Saltation: Smaller rocks are bounced along the riverbed in a leap frog motion. This occurs most in the upper and middle sections of the river. Suspension: The water carries smaller particles of material. This process occurs throughout the course of the river, but increases the closer you are to the mouth of the river. Solution: Material is dissolved within the water and carried along by it. Primarily this occurs in the middle and lower reaches of the river. When a river carries material this is called the load. The river transports its load by a possible 4 processes

Deposition As rivers reach a base level by entering the sea or loch. When rivers overflow their banks. On the inside bend of a meander. With a sudden decrease in gradient. Processes and Energy The critical erosion velocity curve. The settling velocity curve. Deposition by rivers takes place when they can no longer transport their loads. Any velocity decrease may occur:

HYDROSPHERE Hjulstrom curce Velocity in relationship to particle size