Rivers (Fluvial Hydrology)

Rivers (Fluvial Hydrology)

Erosion and Transportation

The Hydrological Cycle

Transportation

Saltation: The process of load bouncing a long a river bed.

Traction:

The process of large pieces of load rolling along a river bed.

(where is this likely to happen?)

Check your terminology here:

http://quizlet.com/class/1483199/

All that load must go somewhere....

Suspension: The process of smaller pieces of load being carried in a rivers flow.

Solution: The processed of dissolved pieces of material being transported in a solution.

The river can transport material when it has excess energy. The river transports in four main ways;

traction,

saltation,

solution and

suspension.

Material carried

by a river is know as load.

Drainage Basin

Candidates should be able to:

Demonstrate an understanding of the work of a river in:

ERODING, TRANSPORTING, DEPOSITING

EROSION

Reference should be made to the erosional processes of:

Hydraulic action,

Corrasion,

Corrosion (solution) and

Attrition.

The drainage basin acts as an

open system,

with a number of:

inputs,

outputs,

stores and

transfers.

EROSION

River transport should include the processes of:

Traction,

Saltation,

Suspension and

Solution.

DEPOSITION

Reasons WHY and WHERE in a river’s course deposition takes place should be studied.

It should be realised that the effectiveness of the river processes concerned will vary according to the:

volume and

velocity of the running water and the

nature of the load (boulders, pebbles, sand and silt) which, in turn, will be affected by the bedrock along the course of the river

• Describe and explain the landforms associated with these processes.

A study should be made of the following:

Forms of river valleys –

long profile and shape in cross section,

rapids,

waterfalls,

potholes,

meanders,

oxbow lakes,

deltas,

levées and

flood plains.

Erosion - remember

In the upper course near the source there is more vertical (up/down) erosion and

In the lower course near the mouth, there is more horizontal (side/sidel) erosion.

This is because near the source a rivers' load is bigger and more angular and therefore less likely to be suspended in a rivers flow.

Instead it will bounce and crash into the bed, causing vertical erosion.

However, nearer the mouth load is smaller and smoother and therefore more likely to be suspended and therefore more likely to crash in the banks, causing horizontal erosion.

Because of erosion a rivers' load tends to get smaller and smoother as you move from the source to the mouth.

Erosion

The process of wearing away of rocks and soil.

The river erodes in four main ways;

Attrition,

Corrosion,

Corrasion and

Hydraulic action

Attrition:

Load crashing into each other in a river. This normally happens with suspended load

Simply: The rocks smash into the other rocks.

This is why in the lower courses, the rocks are rounder and smoother

Corrosion (solution): The process of water dissolving a rivers' load as well as its bed and banks. (remember chemical weathering?)

Will depend on temperature, and chemicals in the water (think Carbonic acid, etc)

Corrasion (Abrasion):

The process of a rivers' load crashing and rubbing into a rivers' banks and bed causing pieces to break off.

potholes may form when a pebble is trapped in a small hole, and the water forces it round and around in a circle, wearing away at the rock.

Hydraulic Action

Water and air getting into cracks in a rivers banks and bed causing erosion through increased pressure.

RECAP