Why Do some Rivers Flow faster than Others

By Nidhi Nangia. Updated: January 16, 2017
Why Do some Rivers Flow faster than Others

The rate at which the water of a river flows through its channel determines the river’s velocity. There are hundreds of rivers across the globe. There may be more than one or two rivers in your own town itself, but you must have noted that one river flows faster than the other. In fact, the same river may flow slower and faster at certain places in its path. A river’s speed may range from 0m/s to as much as 3m/s, the fastest flowing river being the Atrato river in Colombia, which flows at a speed of 4900 cubic meters per second!

Have you ever wondered why this happens? This article is trying to find out why do some rivers flow faster than others.

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Shape of the river channel

The shape of the river channel plays an important role in affecting the speed of the river flow. As the river flows against its edges, it creates a kind of friction around the river’s perimeter, at its sides and also along its river bed. When the river water flows through a deep, wide river channel, it has to face less resistance, and thus flows faster. On the contrary, when the river flows through a shallow, narrow channel, the edges of the river will slow down the water molecules which are already in a smaller proportion. However, the center part of the river will keep flowing at the highest possible speed even under unfavorable channel conditions.

Volume of the river water

The water volume that flows through the river at a given period of time also affects the speed at which the river will flow. As the water volume increases in the river, its speed will automatically increase. For instance, if a stream flows into it at a certain point, it will increase the speed of the river as well. Increased volume of water can also have long-term effects on the river’s speed. More water in the river will cause more soil erosion along the banks of the river, thus resulting in a deeper, wider river channel through which the water can move more freely and quickly.

Roughness and smoothness of the river channels

If a river flows through a rough river channel, it will have so many boulders, pebbles and rocks to interfere with its flow. These can be either placed at the riverbed or on its sides. These will create a lot of friction, thus reducing the speed of the river flowing. If the channel of a river is smooth with fewer rocks and pebbles, its speed will be higher, as there will be less friction and it will have more energy to expend while it flows.

Why Do some Rivers Flow faster than Others - Roughness and smoothness of the river channels

Gradient of the riverbed

A river’s gradient refers to the steepness of its slope. The steeper its slope is, the higher its speed is bound to be. When river water flows down through a steep slope, the water is pulled down more strongly by the gravitational force, due to which it will fall down more quickly. If it flows down through a gentle slope, it will flow with a lesser speed and velocity.

Temperature of the river water

Rivers with hotter water temperatures are bound to travel faster than colder rivers, as their water has less viscosity and has fewer numbers of suspended particles as well. Due to this, it is allowed to move more freely and at greater speeds than colder rivers.

Why Do some Rivers Flow faster than Others - Temperature of the river water

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