Rivers Flashcards
What are the names of a rivers courses?
lower course
middle course
upper course
What is a drainage basin?
an area of land where water from rain or snow melt drains downhill into a body of water such as a river
What is a watershed?
the area of high land forming the edge of a river basin.
What is a long profile of a river?
a way of displaying the channel slope (gradient) of a river along its entire length
3 types of cross profile of river?
.V shaped valley (steep sided - narrow shallow)
.floodplain (wider, flat - wide and deep)
.levees (very wide and flat - wide and deep)
Why does gradient of a river change along its long profile?
shows a steep upper course as this section is in upland areas made of hard rock
middle and lower course the land becomes flatter because rock around is softer.
What is cross profile of a river?
a section taken sideways across the channel or valley
What is channel depth?
downstream change, reason
how deep the channel is
↑ river deep due to erosion - more water added by tributaries
What is channel depth?
downstream change and reason
how wide channel is
↑ rock erodes away at lower course- rock is softer
What is gradient of a river?
downstream change, reaosn
how steep the channel is
↓ land further down is flatter because rock softer as go down
What is load quantity?
downstream change, reason
average amount of sediment
↑ faster water can erode more material and carry more material
What are fluvial processes?
term given to processes that shape our rivers
What is the velocity of a river?
downstream change, reason
speed of the water
↑ friction lower in lower course because river is wider, deeper and smoother
What is load size?
downstream change, reason
average size of sediment and point of river
↓ attrition means sediment is eroded into smaller sediment - goes downstream
What is channel bed roughness?
downstream change, reason
amount of friction between river bed and water
↓ abrasion means river bed will be eroded to smoother downstream where velocity is higher.
What is discharge of a river?
downstream change, reason
volume of water flowing through the river
↑ water added by tributaries, water is travelling faster, rivers are wider and deeper
What is Hydraulic action (river)?
power or water eroding river bed and banks
What is abrasion (river)?
rocks carried along river wear down bed and banks
What is attrition (river)?
rocks being caried by river smash together and break
What are interlocking spurs?
fingers of land that jut out into the river valley where streams and rivers are forced to flow around in the upper course.
How to form a waterfall?
river flows down along hard rock
when reaches it erodes soft rock creating a plunge pool formed by hydraulic action and abrasion
cliff becomes unstable falls by gravity
continues until waterfall shape is formed
What is solution (river)?
chemical erosion caused by dissolving rocks in river water
how does a meander develop?
.slower flow on inside, faster flow on outside.
.erosion on outside deposition on inside
.outside wears away and a meander is formed.
.more erosion and deposition creates a horse shoe shape, until river cuts straight across.
.eventually not going round bend anymore so it detaches and dry’s out forming an oxbow lake.
What is thalweg?
line of fasted flow in a river
why does thalweg go to outside of meanders?
because it cant go quickly round a turn and needs to keeps it momentum by going a slightly longer route.
where are floodplain and levees found?
middle and lower course
What is a floodplain?
An area of low-lying land next to a river which is prone to flooding
What are levees?
naturally raised river banks found on the sides of a river channel that is prone to flooding. They are formed after a flood deposits sediment on the flood plain close to the river
natural factors that lead to flooding?
.heavy rainfall
.very dry ground
.layers of impermeable rock
.steep sided valley
What is a hydrograph?
shows two graphs – a bar chart showing rainfall and a line graph showing discharge from before, during, and after the rain storm. A hydrograph shows you the ways in which a river is affected by a storm
manmade factors that lead to flooding?
.building urban areas
.climate change
.deforestation
.agriculutre
What is lag time?
The time taken between peak rainfall and peak discharge
what is discharge measured in?
cumecs
cubic metres per second
What is the rising limb?
Shown on a hydrograph,
period of time river discharge increases
what is the falling limb?
A period of time in which the river discharge decreases
What is baseflow?
A volume of water. it is water from the ground, flowing into the channel over a long time
hard engineering for rivers?
.dams + reservoirs
.channel straightening
.embankments
.flood relief channels
what are dams and reservoirs?
+, -
they regulate river flow and reduce the risk of flooding
+ flood prevention, water storage, generate hydro electric power
- expensive, large areas of land required
What are embankments?
+, -
raising the river bank
+hold more water, cheap
- unnatural, increase flood risk downstream
What is channel straightening?
+, -
You cut meanders to form a straight channel
+ speeds flow of water, protect vulnerable areas
- unattractive, damage wildlife habitats, increase flood risk further down stream
what are flood relief channels?
+, -
floodwater flows into the relief channel and is taken either to an area where it can be absorbed, or re-enters the river further down its course.
+remove excess water, create wetlands
- expensive 110 million (12km)
Soft engineering types for river?
.afforesting
.wetlands + storage areas
. floodplain zoning
.river restoration
.flood warning and prep
What is afforesting?
+, -
planting trees along river valley
+ absorb water, natural
- loss of grassland
What is wetlands and storage areas?
+, -
store water
+ efficient for storing water
- still releases water out
What is floodplain zoning?
+, -
not putting houses and buildings on land with high flood risk
+ less damage is caused
- not always knowing how big flood will be, cant move houses that are already on the land
What is river restoration?
+, -
reintroduces meanders to rivers and restores physical process
+ natural
- can return to its original way without a lot of maintenance
What is flood warning and preparation?
+, -
The environmental agency monitors rivers and gives out warnings through newspapers, TV, radio and internet when they are likely to flood so people can prepare.
+ time to protect properties
- cant access warning, flash floods can happen too quickly, land still floods
