Rivers Flashcards
What is a tributary?
A stream or river that flows into another river
What is a confluence?
The junction of two Rivers
What is the mouth?
Where a river ends
What is a river channel?
What a river flows in
How do tributaries affect a river’s discharge?
A rivers discharge will increase as tributaries join it
What is the River basin?
The area of land drained by a river
What is the watershed?
The edge of River basin
What is the source?
Where a river starts
What is interception?
Precipitation may not reach the ground surface if it is caught on leaves
It may then be directly evaporated
How does deforestation affect a river’s discharge?
If the area is deforested then the amount of surface runoff increases
More discharge
What does rainfall do to discharge?
Heavy continuous rainfall will increase a rivers discharge
What is the water table?
Upper limit of saturated rock or soil
It moves up or down according to rainfall conditions
Drought is down
What is a waterfall?
A steep drop in the course of a river
Why do waterfalls form?
Form when a band of hard rock lies over soft rock
Where along the river do waterfalls form?
In the upper course of a river
Water is fast-moving
How are meanders formed?
As river erode laterally, to right and then left side, it forms large bends called meanders
Water or roads and undercuts bank on outside of band– most energy here due to decreased friction
Material is deposited on inside of Bend – less energy here due to increased friction
When do oxbow lakes normally form?
During a flood when the river is particularly powerful
As floodwaters fall, alluvium is deposited sealing the river
What happens to the Oxbow lake?
Gradually the oxbow lake dries up forming a meander scar
What do flood hydrographs show?
The discharge of a river (m/s3) - line The rainfall (mm) - bar graph
What is lag time?
Time between the peak rainfall and peak discharge
What is a flood?
A flood occurs when a river burst its banks and water spills onto the floodplain
Why does flooding occur?
Tends to be caused by heavy rain
Steep sided channel – cause fast surface runoff
Lack of vegetation or Woodland – no transpiration means high surface runoff
In permeable drainage basin – water cannot percolate through rock, faster surface runoff
Urban area – concrete means impermeable, it drains take water to river channel, sloped roofs
How do you prevent a flood?
River engineering
Afforestation
Restriction of urban development on floodplains
What happens on the first stage of river?
Useful, upper, torrent
V-shaped valley
Steep Valley sides
Mainly a vertical erosion where river cuts downwards
Waterfalls, rapids, fast flowing water, whirlpools
Water rafting, Hydro electric, reservoir, hotels
