Rivers Flashcards
what is a long profile
it shows the gradient of the river on its journey from source to mouth
what is the source
where river starts
what is the mouth
where river meets the sea
what does a river try to achieve
a smooth curve
how does a river profile change
by erosion transport and deposition
what is the profile of the upper course (4)
verticle erosion by hydrolication
steep gradient
travels through mountains
low velocity
what is the profile of the middle course (5)
travels through hills
high velosity
gradient less steep
lateral erosion
wider channels
what is the profile of the lower course (6)
travels through low lying land
gentle gradient
very wide valley
deposition
wide deep channel
high velocity
why does discharge and velocity increase down stream
the volume of water increases
what is cross profile
a section taken sideways across a river
what is channel cross profile
just the river
what is a valley cross profile
channel valley floor and slopes
how does cross profile change and why
in narrow shallow channel upper couse of the river erodes by hydraulic and abraison
as it travels more water joins and increases volume and velocity so deeper channels are cut
at middle course the channel is wide and less verticle erosion but more lateral making the banks wider
at lower course the river is wider and deeper
what causes interlocking spurs and rapids
erosion
what is an interlocking spur
high landforms found at the upper coarse of the river either side - zip like
what are the characteristics of interlocking spurs (3)
steep gradiet
projections each side separated by the river
high slopes
what are rapids
fast flowing sections of river where there is a steep gradient and different rock
what are the characterisitics of rapids (3)
turbulent water flow
steep gradient
uneven bed
what is a waterfall
where water falls down a verticle drop
how is a waterfall formed
where hard rock is above soft rock the soft rock is eroded by falling water forming a step and undercutting so an overhang collapses into a plunge pool
how is a gorge formed
from a waterfall it leaves a gorge
name 4 ways a river erodes
hydraulic action
abrasion
solution
attrition
what is hydraulic action
when water is forced into cracks in the bank
what type of erosion is hydraulic action
in upper course it is verticle
in lower course it is lateral
what is abrasion
boulders/stones scape and wear the river bed
wat type of erosion is abrasion
vertical and lateral
what is solution
disolving of rocks
what is attrition
rocks banging into each other as they are transported
what type of erosion is attrition
vertical and lateral
what is transported by rivers
material that has weathered or eroded
name 4 types of transportation
solution
suspension
traction
saltation
what is solution
materials are disolved in the water
what is suspension
light materials are carried along
what is saltaion
pebbles bounce along the bed
what is traction
large boulders roll along the bed
what is deposition
rivers drop sediment
when do rivers deposit its load
when velocity falls
what is the result of deposition
when velocity falls boulders are deposited first and finer particles deposited last
what is flood risk dependent on
how quickly precipitation gets into a river
how is flood risk increase
heavy rain
sudden snow melting
saturated soil
farming
urbanisation
how do rocks increase flood risk
they can be impermeable
what are human causes of flooding
infastructure - roads and buildings
disappearing gardens
felling trees which reduces interception
changes in farming
what is a hydrograph
they show how a river responds in response to rain
what do the axis on a hydograph measure
verticle = amount of rain
horizontal= time
name 2 types of hydrograph
flashy - storms
soil is impermeable
a small river basin
urban area
slow - low flood risk
what are river management strategies
river engineering to stop floods
2 categories of river management strategies
hard and soft
name 4 examples of hard engineering
dams
channel straightening
embankments
flood relief channels
describe a dam and outline the 3 positives and 4 negatives
a concrete structure to control flow by creating an artificial lake
+ provide hydro electric power, prevent floods and increases tourism and recreation
- expensive, loss of farm land, habitats damaged and people displaced
describe channel straightening and out line 3 positives and
4 negatives
cut meanders
+ reduce flood risk, decrease insurance premiums, improve navigation
- increases flood further down river, expensive, habitats effected, unatractive
describe embankments and outline 3 positives and 3 negatives
raise banks so river can hold more water
+ reduce floods, creates walkways, provides new habitats
- expensive, artificial and unattractive, if they fail cause serious floods
what landforms result from erosion and deposition
meanders and oxbow lakes
where do meanders form
middle and lower course
describe how meanders form
fast velocity swings around outside bend of meander eroding banks to form river cliff where water is deep
inside bend where velocity is low deposition occurs forming slip off slope
overtime lateral erosion on outside bend widens river valley
where are oxbow lakes commonly found
middle or lower course
what are oxbow lakes
old meander
the bend is cut off by faster flowing water during floods
which environmental conditions are common for meandering rivers
gentle gradient
fine sediment
steady rain throughout year
what are riffles
shallow area of meander - straighter sections- rocky bends
what are pools
deeper areas of meander
fine sediment slow flow
what landforms result from deposition
leeves
flood plains
esturies
what is a leeves
raised river bank found in lower course of river
when are leeves formed
during flooding when water overflows onto flood plain
how are leeves formed
as water overflows there is a reduction in velocity
this causes sediment in suspension to be deposited on bank
each flood casuses sediment to raise
name 4 types of soft engineering
flood plain zone
flood warning
plant trees
river restoration
describe flood warning and outline 3 positives and 2 negatives
monitors rivers so floods can be predicted warn and evacuate
+ helps to prepare, it is sustainable , it is low cost
- need equipment and people dont always respond
describe flood plains and outline 3 positives and 1 negative
local planning restricts land use
+low cost, it reduces impermeable rock and reduces insurance
- restricts ecconomic development
describe planting trees and outline 4 positives and 2 negatives
increases the interception of rain
+ benefits wild life, natural, inexpensive, helps tore carbon
- reduces habitats, loss of farmland
describe river restoration and outline 2 positives and 3 negatives
restores straightened channels to meanders and slows down water flow
+ recreates the natural environment, reduce floods
- inexpensive, changes land, some flooding
facts about Jubilee River flood relief channel (3)
created in thames in 2002 cost £110 million
what 3 catergories of issues because of Jubilee flood relief channel
social issues
protects rich areas at expense of poor and paddle boaters disrupted because of wier
ecconomic issues
most expensive scheme in uk, maintainemce costs are high and additional measures are needed down strean where the problem has been shifted
environmental issues
it flooded badly in 2014 it damaged habitats and it is unattractive
facts about banbury resevoir
completed in 20212 at cost of £18.5 million
what are 3 categories of issues because of banbury resevoir
social
transport disruptionis improved, new footpaths installed, local less worried about flooding
ecconomic issues
benefits of protection = £100 million and lower insurance
environmental
habitats destroyed
what is discharge of water
excess water.
