bradshaw model. upstream downstream discharge occupied channel width channel depth average velocity...
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Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Discharge
• The volume of water that passes through a cross-section per unit of time.
• Cubic metres per second.
• Increases due to the input from a greater amount of the river basin above that point.
Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Occupied Channel Width
• Distance across the actual channel, measured at the water surface.
• Increases due to increase in discharge, input from tributaries etc.
Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Channel Depth
• The height from the water surface to the stream bed.
• Increase downstream as does the size of the river.
• Line connecting places of greatest depth is called the thalweg.
Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Average Velocity
• Is the speed of water flow (distance travelled per unit of time).
• Steady increase downstream.
• How can it be so if the gradient is deceasing? (imagine 2 slides – one steep, one less so).
• Downstream the river becomes more efficient with proportionally less contact with its bed and banks.
• Shown by higher Hydraulic Radius and lower Channel Bed Roughness.
Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Load Quantity
• Capacity of the river.
• Total load of all sizes.
• Increases with discharge and velocity.
Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Load Particle Size
• Decreases considerably downstream.
• Angular pebbles become more rounded.
• Attrition.
Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Channel Bed Roughness
• Decreases because of fewer stones etc, small load particle size etc.
Upstream Downstream
Discharge
Occupied channel width
Channel depth
Average velocity
Load quantity
Load particle size
Channel bed roughness
Slope angle (gradient)
Slope Angle
• Decreases.
