Types of channel

•Straight Channel•Braided Channel•Meandering Channel

Straight channels• Mainly in the upper zone

• Channel located upon rock

• Single channel with pools and riffles

• Thalweg moves from side to side

• Vertical erosion (incision) predominant

• Saltation and traction main method of transport

• Main landforms: V-shaped valley, waterfalls, gorges

Braided Channel

• Mainly in the middle zone

• Flows upon coarse alluvial material

• Several roughly parallel channels intersecting at points

• Whole channel system is straight but channels wander from side to side within the flood plain

• Major deposition occurs after discharge decreases

• Lateral erosion occurs between floods

• Main landforms are multiple channels separate

Meandering• Found mainly in the lower zone

• Channel flows upon fine alluvial material

• Channel wander in a regular pattern from side within the flood

• Lateral erosion and deposition moves channels across the flood plain as meanders

• River meanders themselves move downstream

• Suspensions are main method of transport

• Main landforms: levees, ox-bow lakes, point bars, slip-off slope, bluffs

The long profile

Long Profile of a river• Graph drawn along the course of a river from the source to the mouth

• Shows that they have a concave shape with a steeper upper reach and a gentler lower reach

• Ideal profile is called the ‘graded long profile’

• In this ideal situation, the river is in a state of dynamic equilibrium where there is a balance between the rate of erosion and the rate of deposition

• This balance is always transitory as the slope (profile) has to adjust constantly to changes in the river

• These can cause short-term increases in either the rate of erosion or deposition until the state of equlibrium has again been reached