River Valley: Definition, Formation, Characteristics, Types and Ecological Value

River valleys are the landforms created by the erosive and deposition action of flowing water over time. These low-lying, fertile lands carved out by flowing water have always been centres of farming, settlement, trade and culture for many centuries. From Indus valley civilization to the Egyptian Nile valley civilization, river valleys are the beginning of many ancient civilizations. This article explains what river valleys are, how they form, their different types and why they remain so important today.

Table of Contents 

• What is a River Valley
• How are River Valleys Formed
• Types of River Valleys
• Importance of River Valleys

What is a River Valley

The word ‘valley’ is derived from the Latin word vallis which means a long depression between hills or mountains. A river valley is a long, low area of land through which a river water flows. This area is formed over thousands or millions of years as the river washes away rock and soil along its path. A river valley is typically V-shaped during its younger stages and turns into U-shape as it ages and widens over time. 

How are River Valleys Formed

A river valley formation is an incredibly slow process that happens through the steady wearing away of rock and soil by moving water, wind, rain or ice. The flowing water of rivers cuts the rocks and soil vertically as well as laterally and drops sediments such as mud, sand or pebbles into the other flat area. The two main processes shape a river valley are:

Erosion: The river flowing downhill cuts the land, carrying away rock and soil. There are two ways in which this erosion happens: vertical erosion and lateral erosion. Vertical erosion is downward cutting of soil by a river, which creates a deep valley floor, while lateral erosion is sideways erosion that widens the valley.

Deposition: The river water in its middle or lower course cannot carry all its sediments and deposits them into some area that creates a flat fertile valley floor. This process forms the physical structure and landscape of river valleys, especially during the middle and lower course of the river.

Types of River Valleys

V-shaped Valley: It is a narrow, steep-sided valley mainly formed by vertical erosion down the valley slopes. They usually form near the source of a river, where the landscape is steep and the river is in its upper course with highly fast flowing water. During this stage a very distinctive v-shaped valley begins to form.

U-shaped Valley: As the lateral erosion starts widening the initially created v-shaped valley it starts to take U-shape. It is not only formed by rivers. The glaciers carving through a V-shaped valley, widens and deepens it into a broad U-shape valley. For example, valleys in the Himalayas.

Gorges and Canyons: Usually found in dry regions with limited vegetation these steep and narrow valleys are steep V-shaped valleys with rocky walls. The example of one such valley is Indus gorge near Ladakh. Canyons are often larger and wider than gorges.

Flat-floor Valley: This type of valley is formed during the middle or lower course of the river. It is where the river deposits large amounts of sediments to create extremely fertile wide and flat land. One famous example is the Indo-gangetic plain.

Importance of River Valleys

• Biodiversity: These valleys are home to extraordinary biodiversity and their calm waters have always been a source of life for many plants and animals species. 
• Agriculture: River valleys have been home to agricultural settlements since ages. In the past they served as both farmland and transportation routes.
• Hydropower Plants: Many river valleys are the power houses for natural and renewable energy. They are ideal to build dams and generate electricity.
• Fresh Water Supply: The water stored in dams in the river valleys serves millions of people in different ways. It is used for municipal, industrial and agricultural use.
• Transportation: The river flowing through various valleys has always been an important way of transport, trade and commerce.