hard engineering rivers
Embankments - raised banks along the sides of a river
ADVANTS -can be used pedestrian paths beside river- provide habitats plants & animals - if cncrete stop bank errosion
DISASVANTS - OFTEN NOT BUILT HIGH ENOUDGH - CAN BE UGLY SPOIL VIEW
CHANNELISATION- A RIVER CHANNELmay be deepened- allowing it to carry more water - or straighned to increase alters travel speed
ADVANTS- EFFECTIVE has it protects immediate area as water moving away faster - long lasting
DISADVANTS- GREATER RISK OF FLOOD DOWN STREAM - UNATURAL -INTRUSIVE
DAMS CONTROL WATER FLOW - ADVANT STORED WATER CAN GENERATE HYDROELECTRIC POWER
DISADVANTS - SEDIMENT TRAPPED BEHIND WALL - LEADS TO ERROSION DOWNSTREAM . settlements may be lost when river valley flooded to form reserviuor
Soft Engineering Rivers
Flood plain zoning - local auth &government intro policies to control urban devel close /on flood plains ADVANTS -Sustainable reduces flood & buil demage . No builing means less surface run off Disadvants - REsistance to resticting developments when there is a shortage of housing - Planning controls relaxed in LIC s
WASHLANDS=River alloed to flood naturally in wasteland areas to [prevent floods elsewhere .ADVANTS - Natural wetlands for birds & plants - deposited silt may enrich soil - turning it into argricultural land .- large area of land are taken cant be built on - prod land may become marshland
WARNING SYSTEMS - NETWORK OF SIRENS T WARN PEOPLE OF POSS FLOOD -advants- cheap electrical commun very effective way t inform people Disdavants Sirens - vandalised not enough time 4 residents to prepare
AFFORESTATION - Trees planted to intercept rainfall in catchment area of river-- slows down flow of water to river . ADVANTS - CHEAP SOIL ERROSION IS AVOIDED DISADVANTS SOIL CAN BE ACIDIC -Increase fire risks due to Leisure activities in forest
EXAMPLE - River NENE -NORTHAMPTON
2002 - level of land at WEEDON was raised by 10 m by building an embankment across the river - water stored behind the embankment in flood times .
2003- flood warning system improved Residents in FAR COTTON cotton area wud be given 2 hrs notice of flood occurring .
2007- a washland was createdin the UPTON AREA - WHERE 1.2 MILL cubic metres of water cud be stored during x of major flood. major roads A45 ARE ON EMBANKMENTS 6 M HIGH . Railway station has been protected by building 4 m flood walls at Foot Meadow .
plate tectonics - theory of explanation for location of earth quakes & volcanoes . earths crust dividec into plates . the plates move a few cm s evry year as they float on the mantle . movement is caused by convection currents in the mantle. the movements cause the plates t collide or move apart .PRESSURE created at the boundaries causes earth quakes & volcanoes
CONVECTION CURRENT -a movement of heated material up through the mantle from earths core to crust .
HOTSPOTS=another place volcanoes occur - fixed points in mantle generating heat - intense heat build pressure - & MAGNA ERRUPTS - MAGNA RISING ABOVE OCEAN SURFACE IS A VOLCANO eXAMPLE galaogos Island & Hawaii
HOTSPOT - HAWAII ***
3 TYPES OF convergent plate boundary
- 1) where continental plate & an oceanic plate meet
- oceanic plate goes beneath the continentl plate ( its denser )
- the subduction causes deep trnch
- earth quake appear here
- occeani plate melts t form magna
- magna forces up wards to form volcano
- land buckles to form mountains
- 2 )Whe 2 occeanic plates meet
- Earthquake occurs
- occeanic plate melts t foirm magna
- magna forces its way up through cocean to form vocanoe
- 3 )where 2 continental plates meet
- crust rises to form fold mountains
- earthquakes occur here
- no volcanoes as crust not melted & subduedl
DIVERGENT & CONSERVATION PLATES
Divergent plate boundry - usually form under the occean - volcanoes created by occean ridges .
- as plate moves apart a gap is left
- magna forms new crust in gap between plates
- if magna reaches the oceab surface a volcano will emerge
COnservation plate boundry- when plates move alongside each other in the same direction at different speeds or in different directiions
- Earthquakes occur as they rub together as they become stuck at a pressure point
- eventually the crust will snasp & pates will move
***diagrams labeelled ***
measuring EARTHQUAKE MAGNITIUDE
- 2 diff between MERCALLI & RICHTER SCALES
Mercalli is subjective -wheras richerter scale is objective .
Richter scale is measure by a seismograph whereas the MERCALI SCALE IS MEASURED BY EYE.
measured ment of intensity of earhquake completed from eye witness accounts
measure on scale 1-12
person measuring it has t be at earthquake site.
measurement of magnitude of earthquake byseisomograph
measurement scale is 1-9 (each no split into 10 pts)
measurement can be at different location .
Epicentre on earthd surface - where worst effects of earth quake felt - inhabited where worst destruction infrastructure felt
FOCUS - point below earth surface - it is the point pressurebuil-up is released-shockwaves move out of this point
reasons why people live in areas of volcano
Economic - - soils very fertile - cheap geothermal energy is produced in these areas EGS Coffee grown on slopes of volcanoes in Colombia - Iceland Reyjavik cheap electricity
Social - People think little risk of happening or Government will help -all family & friends their 4 yrs - poverty cant afford tio move LIC eg Etna Italy familys on slopes
usa MT ST H elens erupted people refuse t move Environmental - scenic area & mant tourist visit - Mt Etna in SItourist shops - jobs trade peoples
Economic -scenic Areas - tourist industry jobs & mining industry in areas cOPPER MINED IN ChilE 2007 x2 people died people will take risk 4 jobs - Iceland tourist shown areas Social - wont happen to me or gov precauctions taken - Japan earthquake buildings safer Enviromental- Fantastic scenic venues foe wealthy -wont move - Malibu coastal resort usa
VOLCANIC ERRUPTION -Montserrat 1997
- CAUSES - Volcanic Island on a Destructive Plate boundary
- THe plates that meet are North American plate & Caribbean
- 1997 Chances Peak Volcano errupted
- Hugh ash cloud covering southern part pf island
- Polyroclasticflows of hot rock & ash thrown from volcano
Effects on people
19 KILLED FROM POLYCLASTIC FLOWS
- Villags destroyed farm & trant
- 150houses destroyed
- transport routes destroyed- Bramble air port - closed aid disrupted- roads blocked rocks ash
- people left never returned lost everything PSYCHOLOGICAL
Effects on Environment - 4 sqkm covered in ash/rocks
- Flows Pyroclastic caused river BELHAM TO FLOOD
- pyroclastic flows removed vegetation in south of island incl ridges surrounding Farrell s yard
exam practice - volcanoes
Using Egs - Give reasons why people continue to live in areas of volcanic activity .
Environmental reasons - beautiful scenery - attracts wealthy people want to live there Mtn Etna
- Economic reasons - tourist come / money & jobs for local people mtn Etnain SICILY. Coffee is grown on slopes in Colombia . electric power Reykjakic iceland
- Social Reasons - people think there is liitle risk & want t live near family & friends . Poverty in LIC countries cant afford to move .
Prediction of Earthquakes & volcanoes
- Prediction - Earthquakes - SEisometer - measure movement - can predict when earthquake is likely tro happen
- building design /defence -- earthquake proofie automatic shutters-come down over windows-eg san francisco airport has colomns on ball bearings - it moves with the quake
- education & planning Japan schools 76 business practice quake drills ie ducking under tables - . USA governments have info packs on how to pre-opare foe quakes