Rivers

Flashcards about rivers

What is a river?

A natural stream of fresh water flowing on land to another body of water (ocean, sea, lake or other river)

Why are rivers important?

Rivers have sustained human and animal life for millennia, brought the first civilizations, and shape the earth through erosion and deposition.

What is erosion?

Wearing away of rock and soil

What is deposition?

Dropping sediment and soil somewhere

What landforms do erosion and deposition create?

Valleys, canyons, and other landforms

What is the upper course of a river?

The section at the beginning of the river nearest the source

What are common sources of a river?

A spring, a melting glacier, a lake

Where do rivers usually begin?

In an upland area, like the top of a mountain

What are features of the upper course of a river?

Source and V-shaped valley, sometimes waterfalls and rapids

What is a V-shaped valley?

A narrow, steep valley near the source of the river that cuts downward due to vertical erosion

What is the middle course of a river?

The part of the river that starts to widen and meander.

What are features of the middle course?

Tributaries, meanders, ox-bow lakes, and floodplains

What is a tributary?

Smaller rivers that join the main one

What is a confluence?

Point where two rivers meet

What is a meander?

A large bend in the river

What is an ox-bow lake?

A crescent shaped lake that forms when a meander is cut off from the main channel

What is a floodplain?

The flat land beside the water that may flood when the river overflows

What is the lower course of a river?

The final, end section of a river where the river flows into another body of water

What is the river mouth?

The area where a river ends and meets another body of water

What is an estuary?

A specific type of river mouth where a wide river mouth goes into the sea, mixing fresh water with salty sea water

What is a delta?

Triangular shaped landform where the river meets the sea caused by deposition of settlement

What is a watershed?

The dividing line between one river basin and the next; usually a ridge of higher land

What is a drainage basin?

Area of land that is drained by the river and its tributaries

What is the hydrologic cycle?

Describes the continuous movement of water on, above and below the surface of the Earth. This global circulation of water is a giant closed system.

Evaporation

water is warmed by the sun and turns to vapor

Transpiration

water movement from a plant into the atmosphere

Condensation

warm air rises and cools, turning into tiny water vapor. These form clouds.

Precipitation

water drops call has rain, hail, snow or sleet

Surface runoff

some rainwater just runs around the ground

Infiltration

the rest of the water soaks into the ground

Throughflow

as it soaks into the ground, some runs down the slope to the river

Groundwater

The rest soaks further down and fills the pores and cracks in the rock. This is now called groundwater

What are the three fluvial processes that rivers undertake?

Erosion, transportation, and deposition

Erosion

Wearing away of their channels and valleys by the water and materials it is carrying.

Transportation

movement downstream of water and load particles.

Deposition

settling of sediment of water and load particles.

Hydraulic action

In a fast-flowing river, water hits the river banks and causes the rock and sediment to break apart

Abrasion

rocks and stones scrape the river bed and wear them away like sandpaper

Attrition

Rocks and stones where each other away by banging together and knocking bits of each other

Solution/Corrosion

Water dissolves minerals from the bed and banks that helps to break them up

Suspension

fine material such as clay and sediment is carried by the river.

Solution

dissolved minerals are carried by the river.

Traction

large boulders and pebbles are rolled along the river bed.

Saltation

small stones, pebble and silt bounces along the river bed.

What does bankfull discharge refer to?

The top limit of water volume that the channel can contain. Any extra water in the channel will flood over the banks and flood the surrounding valley.

Name some examples of hard engineering

Dams and Reservoirs, Channel straightening, Embankments and Flood Relief Channel

Name some examples of soft engineering

Afforestation, Wetland restoration and River restoration

Dams and reservoirs

They can control water flow and be very effective during heavy rain. Dam: wall and Reservoir: water behind the wall

Channel straightening

River can be engineered to be straight to move away from flood-prone areas, speeds up the flow of the water but this can result to greater flooding downstream

Embankments

This is raising the river banks at the sides of the river, stops flooding and it is often used in towns and cities.

Flood relief channel

Manmade river/channel designed to divert excess water or bypass urban areas, reduces flooding threat

Afforestation

Planting trees to stop the waters flow and slow down movement of water to the river channel

River restoration

When a river has been artificially changed it may be of benefit to change it back to its original state and reduces the likelihood of a major flood downstream

Wetlands restoration

Wetland environments are drained and restored to be able to absorb and store excess water and This reduces the risk of flood downstream

Floodplain zoning

This restricts certain land use on the floodplains and Areas prone to flooding can be kept clear of houses and industry