Explain river channel morphology and ir engineering significances.

River channel morphology refers to the channel pattern and channel geometry at several points along a river channel. River is a mass of water that flows along a path -high to low gradient carrying different materials and responsible for different geological actions, such as erosions, transportation, and deposition of sediments. Rivers channels are of following types:

• Straight river
• Meandering river
• Braided river

This type of river follow straight path. The topography of the area is characterized by steep relief. The gradient of the river path is also high. Since the energy of such river is high, the erosional rate is intensively higher than the deposition of sediments. Deep scouring along the river is higher than the side cutting. Straight rivers are dominantly occurred in Higher Himalaya region.

River channel morphology refers to the channel pattern and channel geometry at several points along a river channel. River is a mass of water that flows along a path -high to low gradient carrying different materials and responsible for different geological actions, such as erosions, transportation, and deposition of sediments. Rivers channels are of following types:

• Straight river
• Meandering river
• Braided river

 Straight Rivers:

This type of river follow straight path. The topography of the area is characterized by steep relief. The gradient of the river path is also high. Since the energy of such river is high, the erosional rate is intensively higher than the deposition of sediments. Deep scouring along the river is higher than the side cutting. Straight rivers are dominantly occurred in Higher Himalaya region.

Meandering Rivers:

This type of rivers follows a zigzag path. The topography of the area is characterized by moderate relief. The gradient of the river path is so moderate that the river strikes in one end and returns to the other direction making the path zigzag. The river is widened and flow with lower velocity than that of straight rivers. Since the energy level of such river is medium, the erosional rate and depositional rate of such river is comparatively equal. The side cutting by the river is higher than deep scouring along the rivers. In the striking bank, the side cutting is higher with higher erosional rate and opposite to the strike bank is a depositional bank where depositions of sediments takes place. Due to this phenomenon, the channel shifting is prominent in such types of river system. Meandering rivers are dominantly occurred in the midlands and Lesser Himalayan region.

 Braided Rivers:

In this type of rivers,a single river is diverted into several paths and may converge to single later. The topography of the area is characterized by low relief. The gradient of the river path is so low and the river area is widened and flow with lower velocity. Since the energy level of such river is low, the depositional rate of sediments is intensly larger than the erosional rate. Many channel bar occur along the river path. Due to this phenomenon the channel shifting is prominent in such types of river system. Braided rivers are dominantly occurred in Terai region.

Engineering Significance Of Different Types Of River System:

A civil engineer has to face different types of river channels for the construction of different types of civil engineering structures as well as for the survey of availability of the construction materials. Some of the  Engineering Significance Of Different Types Of River System can be shown by the following points:

• If a bridge is to be constructed on a straight river, it is not applicable to make a foundation in the river channel as scouring is intense along the path. As side cutting is lower in such case, an arc bridge may be a good option.
• In the meandering river, if the bridge is constructed in curved portion , then the foundation on the striking bank may not be affected. Instead in such conditions, the site of the bridge may be proposed in the straight portion of the meandering river.
• In the braided river condition, a span of bridge must be high with many pillars on the river path.
• For hydropower site, in straight river condition, run off type hydropower is applicable. In meandering type, run off as well as reservoir may be proposed according to the site condition. In the low land braided condition, the hydropower project may be unfeasible due to low gradient and high sedimentation problems.