Bradshaw Model

Bradshaw model

Bradshaw model

Is a geographical model that describes how a river changes along the course of a river

What does it tell us?

The model suggests that 8 river characteristics will change from the source to the mouth

What are the 8 river characteristics that will change?

Discharge, Occupied channel width, Water depth, Water velocity, Load quantity, Load particle size, Chanel bed roughness, Slope angle (gradient)

According to the model, what increases as the river moves downstream?

Discharge, Occupied channel width, Water depth, Water velocity, Load quantity

According to the model, what decreases as the river moves downstream?

Load particle size, Chanel bed roughness, Slope angle (gradient)

Discharge

increases

Occupied channel width

increases

Water depth

increases

Water velocity

increases

Load quantity

increases

Load particle size

decreases

Chanel bed roughness

decreases

Slope angle (gradient)

decreases

Discharge reason

Discharge is always increasing since tributaries feed more water into the stream. Throughflow, Groundwater Flow and Surface Runoff also increase contributing to discharge.

Channel Width Reason

Tributaries and flows directly increase 'volume' of water and river width increases due to lateral erosion.

Channel Depth Reason

Tributaries and flows directly increase 'volume' of water and river depth increases due to vertical erosion.

Velocity reason

Velocity increases since water accelerates downstream due to the forces of gravity. The river is also more efficient since proportionally less water is in contact with the bed and banks thus reducing energy lost to friction.

Load quantity reason

As river velocity rises, the river has more energy and is thus capable of carrying more load.

Load particle size reason

As river velocity rises, the river has more energy and is thus capable of carrying more load.

Channel bed roughness reason

As a river travels downstream abrasion smooths the bed.

Gradient (slope angle) reason

A river conducts vigorous vertical erosion in the upper course and lateral erosion in the lower course. Water can also only travel downhill due to forces of gravity.