rivers Flashcards
what is a drainage basin
the area of land drained by a river and its tributaries
what is watershed
the edge of a drainage basin
what is a conlfluence
where 2 rivers meet
what are tributaries
small rivers conecting to the main river
what is the source
the start of a river
what is the mouth
the end of a river
what is a meander
a bend in a river
what is scree slope
loose debris or material that is left over from erosion
what is a convex slope
carved and round slopes. goes from less to more steep
what is a fluvial
the physical interaction of flowing water and the natural channels of rivers and streams (flow)
what is discharge
the volume of water in a river
what is velocity
the speed of something
what is the main thing that happens in the upper course
predominatly erosion
what is the main tning that happens in the middle course
transportaition
what is the mian thinfg that happesn in the lower course
lots of depositions
what does verticle erosion do and where does it occur
upper course
steep graidient
narrow river
what does lateral erosion do and where does it occur
occurs in the middle course
gentle gradient
normal river
what does attriition do and where does it occur
lower course
very gentle gradient
wide river
what does the bradshaw modle describe
how a river’s characteristics vary between the upper course and lower course of a river.
what are the six different types of erosion
hydralic action
abrasion
attrition solution
vertical erosion
lateral erosion
what are the four different types of transportaition
traction
slatation
suspension
solition
where are v shaped valleys formed
they are formed in the upper course or a river due to the verticle erosion causing it to carve into the rock
what are interlocking spurs
The river cuts down into the valley. If there are areas of hard rock which are harder to erode, the river will bend around it. This creates interlocking spurs. When viewed from downstream, these spurs appear to be locked together.
how are water falls created
water falls form in an area where a river flows over harder rock with overlays of sofetr rock
the less resistant rock is the eroded and over time a plunge pool is created hydraulic action causes the plunge pool to undercut the more resistant rock above
the overhang of the resisnat rock can no longer support its own weight due to gravity and weathering so it collapses
the debris from the collapsed averhang speeds up erosion through abrasionthe water fall retreates
what is a gorge
A deep, narrow passage that usually has a river running through it..
how are gorges formed
they are formed when waterfalls retreate over time
how are meanders formed
as a river goes around a bend most of the water is pushed towards the outside. This causes an increased speed and therefor erosion through hydraulic action and abraison.
the lateral erosion on the outside bend casuses undercutting the bank from the river cliff
water on the inner bend is slowercausing the water to slow down and deposite material
the build up of the deposited sediment is known as the slip off slope
what is the thalweg
the fastest part of the river
what are the charcteristics of the outside bend of a meander
what are floodplains made out of
they are made out of alluvian a sediment which is deposited by a river when it floods making it very fertile
where are levees found
in the lower river section
how are levees formed
first there has to be a flood when it floods the river leaves the channle the watre therefor looses energy as a result of deposition occurs heavier sediments are deposited first nearer the river bank causing a hole to ba made which is known a s a levees these build up over mnay floods
how are estuarys formed
as the river approcahes the sea thevelocity and enrgy deacreases as the risibg tide block the river water this causes the increased deposition of sediment creating mudflat and saltmarch enviroment
what features are created by erosion
wtaerfalls
gorges
v shaped valleys
interlocking spurs
what features are created by deposition
levees
flood plains
estuarys
what features are created by both deposition and erosion
menaders and ox bow lakes
how does the drainage basin system work
precipitation trees ca intercept the wter ehich is where transpiraition and evapouration occurs
otherwise it is stored in the surface it then in infilltrates into the soil which is where it can go to the river or the gets prelocated to ground wter sources which then flos to the river undergorund
what are some factors that affect flooding
no vegitaition
bad drainage
heavy rainfall
saturated ground
what is precipitaition and how can it affcet flooding
it is a physical factor
this can cause rivers to overflow and flood
torential rain can lead to sudden flash floods
what are steep slopes and how does it affect flooding
it is a physical factor
in moutain enviroments steep slopes encourage a rapid transfer in water towards river channles
what is urbanisaition and how does it affct flooding
this is a h8uman factor
this is where citys buildup in infastructure this cause a large amount of impermeable rock being used this causes the water to stay on the surfcae as the gorund cant soak it up
what is deforrestaition and how does it affect flooding
this is a human factor
a large percentage of water that flows is soaked up by trees or various vegitation if you remove this there will be floods
what is agricuklture and how does it affcet flooding
this is a huamn factor in arable farming soil is often exposed to the elements for long periods of time this can lead to poor surface run off
what is geology and how does it affcet flooding
this is a physical factor
impermeable rock such as shale and clay encourage water flow overland and in its channles.This speeds up water flow and makes flooding more likly
what is a floodhydrograph
this shows how a rivers discharge changes in repsoe to a precipitaition event
what is the lag time on a flood hydrograph
the time between peak rainfall and peak discharge
what is the rising limb in a flood hydrograph
represents the rise of water after a period of rain
what is the falling limb in a flood hydrograph
represnts the reduction in the amount of rainfall reaching the river channle
what are the two types of flood hydrograph
flashy and subdued
what are the charcteristics of a flashy flood hydrograph
small basin
high drainage density
impermeable rock
urbanisaition is the land use
they have steep relife
saturated soil
heavy rain fall intensity
what are the charcteristics of a subdued flood hydrograph
large drainage basin
low drainage denisty
permebale rock
forrest are the land use
gentle relife
dry soil
low ranfall intenisty
what is the main differneces in hard and soft engineering methods
hard engineering is
exspensive
often unattractive
often need maintainance
can disrupt people lives
where as soft engineering
cheaper
sustainable
less disruptive
works with nature
what are some examples of hard engineering that is used to prevent flooding
dams and resivours
channles straightening
embankments
flood relife channles
what are the bennefits of channle straightening
its speeds up water flow
and prevents flooding of vulnerable areas
what are the negatives of channle straightening
un attractive and unattural
what are the positives of embankments
cheaper
more sustainable
looks more natural
what are the negatives of embankments
exspenive and unatural
what are some examples of of soft engineering in rivers
river restoraition
planting trees
flood plain zooning
what is river restoraition
whre the course of a river has been change artificially
this is a natural
what is flood plain zoning
this restricts differnr land uses and certain locaition
what happened at banbury flood manegment scheme
located in the cotsworlds north of oxford banbury experienced a history of devastaiting floods this led to the closure of the town railway staition. More than 150 homes and buissness where affected so in 2012 they spent 18.5 million on a 2.9 km earth embankment and they raised the a361 to prevent the road from dlooding
