(Paper 1) River Channel Processes and Landofrms Flashcards
Abrasion
Is the wearing away of a riverbed and bank by the load which is being carried by the river
Attrition
Is the wearing away of rocks and pebbles being carried by the river as they rub against one another making them smaller and rounder.
Capacity
Refers to the total load that a stream can carry
Competence
Refers to the size of the largest particle in the steam
Discharge
Refers to the amount of water passing through a certain point and is referred to in cubic meters per second (CUMECS)
Helicoidal flow
Is the flow of water in a corkscreweing motion, and is responsible for the formation of meanders.
Hydraulic action
The process where water is forced into cracks in the river banks and this causes the sides to weaken an peices can break off.
Laminar flow
Is when water flows parallel to the river bed
Load
Is the particles of sediment and dissolved matter which is carried along by the river flow.
Solution
Is the removal of chemical components from different rocks such as chalk these minerals are dissolved and carried in the river flow.
turbulent flow
Is the aggressive flow that involves eddying and vertical movement
Pools
Are the deep hollows scoured in the bed of a river usually found on the outer edge of meanders.
Riffles
Small scale ridges formed of small pebbles and cobbles and is found between meanders in the straight section of a river.
Upper Course
-steep gradient
-lower average velocity due to boulder obstruction and friction causing a turbulent flow
-narrow and shallow channel
-V shaped valley due to vertical erosion
-High levels of erosion/weathering of slopes freeze thaw occurrring at higher altitudes.
Middle Course
-Gentle gradient
-Higher velocity
-Meanders, Gorges, Oxbow lake, Floodplains
-Smaller rocks, wider and deeper
-Flatter valley floor with bluffs.
-natural erosion, abrasion,attrition, deposition transportation.
Lower course
-Very gentle gradient
-highest velocity until river reaches th mouth.
-mudflats, meanders, ox bow lakes, flood plains,leeves, river deltas.
-Very wide channel and deep with levees
-flat an wide with slopping bluffs
-deposition is a key process at the mouth forming river deltas etc
Vertical erosion
occurs mainly in steep rocky upland areas. The geology of the river bed will affect the rate at which it erodes at.
Lateral erosion
occurs where the river gradient is a lot less. The geology and strength of the bed and banks will affect the rate at which it erodes.
Factors effecting erosion
-Load
-velocity
-gradient
-geology
-PH
-human impacts
Suspension
form of river transportation small particles are carried suspended in the water.
Traction
Transportation for large rocks and boulders which are rolled along the river bed being pulled by the river flow.
Saltation
rocks which are to large to be transported in suspension are bounced along the rover bed.
V shaped Valleys (upper course)
step 1
-Vertical erosion occurs as rocks and boulders are bounced an scraped along the river bed.
Step 2
-Weathering, as the river cuts downwards the sides are attacked by weathering. Overtime causes bits of soil and rock to loosen and break off.
Step 3
-Mass Movement, material slowly creeps down the slope and falls into the river and is carried away by the river flow.
-Step 4
- This ends in the creation of a V shaped valley.
Pot Holes (upper course)
-Pebbles get caught in a hollow in the riverbed.
-Hollow would have formed from abrasion and or hydraulic action.
-The turbulent current and flow in the upper course swirled pebbles around.
-the pebbles are forced into hollows and the swirling moving from the turbulent flow causes a drilling motion making it wider and deeper.
