why does a river get wider as it goes downstream?

Answer 1

greater volume of water on lower slopes allowing slower velocity which also increases volume. also the land is generally flatter to allow larger channels

Answer 2

Upper-course river features include steep-sided V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges.

Middle-course river features include wider, shallower valleys, meanders, and oxbow lakes.

Lower-course river features include wide flat-bottomed valleys, flood plains and deltas.

Upper-course features

As the river moves through the upper course it cuts downwards. The gradient here is steep and the river channel is narrow. Vertical erosion in this highland part of the river helps to create steep sided V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges:

As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs which look a bit like the interlocking parts of a zip.

When a river runs over alternating layers of hard and soft rock, rapids and waterfalls may form.

Middle-course features

In the middle course the river has more energy and a high volume of water. The gradient here is gentle and lateral (sideways) erosion has widened the river channel. The river channel has also deepened. A larger river channel means there is less friction, so the water flows faster:

As the river erodes laterally, to the right side then the left side, it forms large bends, then horseshoe-like loops called meanders.

The formation of meanders is due to both deposition and erosion.

The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy.

On the inside of the bend, where the river flow is slower, material is deposited.

Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake.

Lower-course features

In the lower course, the river has a high volume and a large discharge. The river channel is now deep and wide and the landscape around it is flat. However, as a river reaches the end of its journey, energy levels are low and deposition takes place.

The river now has a wide floodplain. A floodplain is the area around a river that is covered in times of flood. A floodplain is a very fertile area due to the rich alluvium deposited by floodwaters. This makes floodplains a good place for agriculture. A build up of alluvium on the banks of a river can create levees which raise the river bank.

Deltas are found at the mouth of large rivers - for example, the Mississippi. A delta is formed when the river deposits its material faster than the sea can remove it. There are three main types of delta, named after the shape they create:

Arcuate - the land around the river mouth arches out into the sea, the river splits many times on the way to the sea, creating a fan effect.
Cuspate - the land around the mouth of the river juts out arrow-like into the sea.
Bird's foot - the river splits on the way to the sea, each part of the river juts out into the sea, rather like a bird's foot.

Answer 3

The terrain through which a river passes flattens out as it flows downstream, so when there is more water, it can broaden into a wider area than in a canyon. Think of the Mississippi, or the Amazon.

Answer 4

It has more water to carry. The water shed adds more and more as the river flows downstream.

Answer 5

Basically rivers are classified into two types - Effluent River and Influent river.

The rivers get widened due to increased discharge of water bcos of their tributaries - Effluent River.

However Influent rivers get dried up before they reach their destination. The reason is due to seepage into ground, evaporation, use by plants and animals and humanbeings.

Answer 6

Also important to ad the river has more "spare" energy toward to bottom of a river and will erode more sideways, hence meanders.

Answer 7

it carries more volume of water as it goes down stream hence it gets wider or deeper

Answer 8

it erodes the riverbank as it flows eventually meandering