Bradshaw Model

Discharge
INCREASES

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
INCREASES

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

Channel Depth
INCREASES

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

Velocity
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
INCREASES

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

Load Particle Size
DECREASES

As a river travels downstream, the eroded material becomes more rounded and smaller due to attrition.

Channel Bed Roughness
DECREASES

As a river travels downstream attrition smooths the bed since the bedload is much smoother.

Gradient (Slope Angle)
DECREASES

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.

NOT INCLUDED
Wetted Perimeter
INCREASES

Wetted Perimeter is the part of the bed and banks which is in direct contact with water. As CSA increases, wetted perimeter must rise

NOT INCLUDED
Hydraulic Radius
INCREASES

Proportionally, the increase in CSA > the increase in Wetted Perimeter. It is a measure of efficiency.

Categories: Geography