Chapter 9: Rivers Flashcards
Source
The beginning or start of a river
Cource
The route a river takes to the sea
Confluence
The point at which two rivers or streams join together
Tributary
A stream or smaller river that flows into a large stream or river
Mouth
The point where a river comes to an end, usually when entering the sea
Drainage basin
The area of land drained by a river
Watersbed
The area of high ground which seperates two drainage basins
Estuary
The part of a river mouth that is tidal
Stages of a river
Youthful stage (upper) Mature stage (middle) Old stage (lower)
Procss of river erosion
Hydraulic action
Abrasion
Attrition
Solution
Hydraulic action
The physical force of the moving water wears away and breaks off the rock and soil from the banks and bed of the river.
Abrasion
Small stones carried by the river wear away the banks and bed of the river
Abrasion
Small stones carried by the river wear away the banks and bed of the river
Attrition
The small stones in the river are worn down and broken up as they hit off each other
Solution
Rocks, such as limestone, and soil are dissolved by acids in the water
The process of a river
- The motion of water hitting against the surface
- Scraping or wearing away
- The impact of the rock grains hitting off one another
- Minerals are dissolved in the water and carried along
Processes of River transportation
Rolling
Bouncing
Suspension
Solution
Rolling
The larger stones are rolled along the bed of the river. This process is known as traction
Bouncing
The smaller pebbles are bounced along the bed of the river. This process is known as saltation
Suspension
Light materials float along in water
Solution
Materials dissolve and are carried along
Youthful stage (upper)
Steep
Fast flowing
Low volume of water
Erosion
V shaped valledy, narrow, shallow channel
Interlocking spurs, waterfalls
Mature stage (middle)
Gentle sloping
River stars to slow down
Higher volume of water
Erosion and deposition
Open, gently sloping, wider, deeper channel.
Meanders, oxbow lakes
Old stage (lower)
Levelling off
Slow moving
Largest volume of water
Deposition
Flat and wide flood plain.
Flood plains, levees
Process of river deposition
Reduction in the rivers speed
Increase in load size
Reduction in the rivers volume
When the gradient levels off
Formation of a V shaped valley
The force of moving water in the river cuts downwards into the river bed, making it deeper. This process is called hydraulic action. It creates a deep, narrow valley.
Mechanical weathering and massmovement also weather the sides of the valley, breaking down rock and soil.
The material that falls into the river is carried downstream as part of the river’s load
Example: the upper course of the river Liffey, Lee and Moy
Meanders
Curves or bends in the river in its mature stage. Meanders are formed by both deposition and erosion
Owbow lakes
An oxbow lake is a horseshoe-shaped lake that is formed when a meander is cut off from the river
Flood plains
A flood plain is a wide, flat area of land on either side of the river in its old stage. The river is now nearing the sea, and deposition had become the main process.
Levees
A levee is a build up of alluvium on the banks of a river. Levees are caused by floods
Deltas
Deltas are landforms of deposition found in the old stage of a river. A delta is a triangular or fan shaped area of land at the mouth of the river where it enters a lake or the sea.
Interlocking spurs
Interlocking spurs are areas of high ground that jut out at both sides of the V-shaped valley.
Waterfalls
A waterfall is a vertical drop in the cours of the river in its youthful stage.
Patterns of drainage
Dendritic
Trellis
Radial
Deranged
Dendritic
In a dendritic system, many triburary streams combine before joining the main river.
Trellis
As a river flows along, smaller tributaries feed into it from the steep slopes on the sides of mountains. These tributaries enter the main river at an angle close to 90 degress, creating a drainage system that lookw like a trellis
Radial
The stream radiates outwards from a central high point. This resembles the spokes on a bicycle wheel
Deranged
There is no clear pattern to the rivers.
