river landscaps Flashcards
name the 6 key features of a river basin
source = start of the river e.g. lake or spring
drainage basin = the area drained by s river and its tributaries
watershed = area between one drainage basin ad another
tributary = small stream or river that joins a bigger one
confluence = where two rivers meet
mouth or estuary = where the river meets the sea
characteristics of river from source to mouth
- steeper gradient & more friction = low flow
- narrow and shallow
- large angular sediment
- gradient is less steep = less friction
- more velocity
- wider and deeper
- rocks become rounder & load increases
- less friction is fast flow
- channel is deep and wide
- big load
- small sediment and sand
upper course features
waterfalls
interlocking spurs
rapids
gorges
middle course
meanders
river cliffs
slip off slope
ox bow lake
lower course
flood plains
levees
waterfalls
- river crosses a band of less resistant rock
- sudden drop = water fall
- softer is cut back quicker leaving an overhang over hang of harder rock
- overhang falls due to the weight of gravity and hydraulic action
- plunge pool is created
- waterfall retreats up the valley often forming gorge
interlocking spurs
- created when v shaped valleys are made
- little energy for lateral erosion
- river winds and bend to avoid hard areas
rapids
- ridges of hard rock = uneven slope
- e.g. in pludge pool
meanders
-river channel bends
-most of water is directed to outside
- outside = greatest erosion and deepest
(can form a river cliff)
-water is faster at outside due to less friction
slip off slope
formed at inside of the meander due to deposition
oxbow lake
- erosion continues on the outside banks of a meander
- deposition in the inside
- ends of the meander bend come closer
- in flooding the river joins ends together
- a new straight channel is made
- old bend is cut off
- oxbow lake is made
flood plains
-low flat that is flooded
levees
- river drops heavy material on flood plains
- builds up close to channel
- levees are formed after floods
human causes of flooding
deforestation
roots suck up water
leaves intercept with rain hitting ground
urbanisation
more surface run off because water cannot be absorbed by the ground
global climate change
increase global temperatures meaning ice melts & more storms & more rain
natural causes to flooding
intense rainfall
ground is water logged = surface run off from saturation
snow melting
sea levels rise and more water in summer
impermeable rocks
granite doesn’t let water through it so water runs off into rivers and lakes so levels rise and land floods
effects on people
- loss of animal and crop
- injury and death
- disease in water e.g. sewage
- loss of homes
- communication problems
effects on environment
- saturation means plants cannot grow
- animals get sickness
- contamination of soil
- land slides and rotational slumping
examples of flooding in people
Mozambique Africa:
- feb 2007
- homes and lives lost
- 121,000 homeless
- 12,000 livestock dead
- 16,000 chickens dead
- diaherra killed dozens from unclean water
northern uk - Lincolnshire and northwales
- 2007
- £2 billion worth of damage
- Lincolnshire = 40% of pea ruined
- wales = 40 tonnes of derbis crop and earth blocked only way out of barland 23 july
predicting and preventing flooding
forecasting
- warning and evaluation maps
- computers
- rainfall reports
- monitored by environmental agency
- computer simulation e.g. texas rice uni
- texas medical centre was evacuated before large flood 2001
buildings can be redesigned
LIC buildings are on stilts
planning
- land use zoning
- selecting where to build
- nome in Alaska uses this (1flood/100years)
define hard and soft engineering
hard
- controlled distribution of natural processes
- man made structures
soft
- ecological practises
- reduces erosion
- to achieve stabilisation
- to enhance habitats
- to save money
soft engineering examples llanrwist
land use zoning:
- un needed land is flooded
- water drains after a few days
- temp flood barriers protect homes
hard engineering lllanwrist
underground flood relief channel:
- £7million
- protects 96 homes and businesses
- divert water at times of maximum flow
- water is stored until peak flow has passed
impacts of flooding llanwrist
- 31st June 2004
- heavy rain = 126 flood warnings uk
- 6days = 417.8mm of rain in capel curig
- 86 valley properties flooded
demographic
-migration away from the area
social
- communication
- travel e.g. railway closed
- loss of belonging
- no outdoor sports
environmental
- crops and animals dead
- waterlog & saturation
- debris spread along landscape
economic
£7million to help with damage
£6 million to repair railway
decreased housing value
human causes to flooding in llanwrist
deforestation
- only 10% of drainage basin is covered by trees
- no roots or interception
- leads to saturation and surface run off
bridges
- reduces the amount of water flow
- leads to more water building up and flooding
channelization upstream
- more velocity
- higher risk of flooding
