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56 Earth

HOW DO RIVERS SHAPE THE LANDSCAPE?

A river’s load scours the river bed, deepening its

channel. The speed of the flowing water erodes the

river’s banks, making it wider. As the river winds

through the landscape, it gradually carves out

deep valleys in solid rock and deposits huge

amounts of debris to form a fertile plain.

In places where the river flows over soft

limestone, water seeps into the rock,

slowly dissolving it and forming

tunnels and caves.

HOW DO RIVERS BEGIN?

Rivers usually begin as a trickle of water high in hills

or mountains. Some come from rainwater or melting

snow. Most emerge from underground streams, formed

after rain or snow seeps into the ground then bubbles

back to the surface. As the water flows downhill, the

trickle swells into a stream and then, as side streams

called tributaries join it, into a wider river.

WHAT IS A RIVER’S LOAD?

As a river flows, it carries along material, or debris,

called its load. A river’s load includes rocks, stones,

and other large particles, which are washed along

the river bed. Finer particles float in the water.

RIVER FEATURES 3

In its upper level, a river is small

and rushes along its course.

Further downstream, as the land

becomes less steep, the river’s

flow is less turbulent. Tributaries

join it, increasing its volume of

water. Lower down, the river

flows more slowly over flatter

ground, carving wide valleys and

forming loops called meanders.

4 RAPIDS AND WATERFALLS

Rapids are formed on a river’s

upper course on steeply sloping

ground, where the river water

tumbles over hard rocks and

boulders, which are not easily

worn away. A waterfall is created

when a river wears away soft

rock on its bed but leaves a

shelf of hard rock above.

Rivers

Wide looping

meanders form

on gentle slopes

in broad valleys

River bank

is eroded on the

outer side of

each bend, making

the channel deeper

and wider

Sediment

is deposited where

the river slows and

drops its load

Islands may form if

higher ground is cut

off when a river

flows around it

River branches

into separate braids

or channels on

flatter ground

A river is a natural channel down which water flows

to the sea or a. LAKE. Throughout history, rivers have

provided water for drinking, farming, and industry, and

are a means of transport, food, and recreation. Some of

the world’s largest cities have grown up on river banks.