Example - How the coast is Managed in Walton -on -
1977 - Groynes built to stop longshore drift from south to north
Cliff regraded & drainage channels installd to produce gentle more stable
Slope planted with gorse & nettlesto stop people climbing on cliff
Sea wall built to protect the soft London clayat the bottom of the cliff
1998 -300 tonnesof Leicester granite placed aaround TOWER BREAKWATER
1999 BEACH REPLENISHED with sand & gravel from Harwich Harbour
Terms - Watershed = the boundry of the river basin Confluence = the point 2 rivers meet .Tributary - a stream the joins a larger river .Source - start of a river MOUTH where a river meets thge sea
Describe 3 process used by rivers to erode their beds
1Hydrauli action - the pressure of water againsts the banks & beds of river , including compressed air in ceacks - as water gets into cracks it compressess air in the cracks - putting pressure on the rocks & pieces break off
2 Corrasion - Particles being carried by the river thrown againsts its banks
3 Corrosion - Chemical Reaction between rocks types in river water .
Process of biological weathering
Seed is dropped in a crack soil is trapped around it - seed germinates - puts out roots wich crack/break the rock apart
Rivers- Mass movement
Slowest downhll movement - gravity pulls water in the soil - soil particles move with water heavy rainfall causes faster downhill move - slope has ripples called Terracettes
Happens when a bank slips into a river , common where river passess through clay . Dry weather makes the clay contract & crack- when rain falls -water gets into cracks absorbed making it heavy- suil becomes saturated - rock is weakened & slips into river pulled by gravity . rock has slipped on the slip plane of rock .
key terms page 49
Land forms found in River Valleys
Draw Plunge pool formed by force of water . Deepened by Corrasion as sediment being carried by water scraped against the bottom & sides . 2
2 Soft Rock erroded by slash back caused by Hydraulic action 3 overhang has fallen due to lack of support & pull of gravity . waterfall retreats up stream to leave a gorge .
are barriers of hard ressistant rock which the river cannot easily erode . the river weaves its way around them .
landforms in river valleys
meander & ox- bow lakes diagrams pg 51
area flat land on either side of a river
when 2 muck water in the river this area will flood as water moves out of the river onto the land .. the water on the land is shallower - therefore more friction & sediment is dropped.
the water drops the heaviest material on the banks - lighter material ie silt further away . deposited material forms floodplain
Levee - a high bank at the side of a river which is built up at times of flood .
River Flooding & flood prevention
Physical causes of river flooding=Valley has steep slopes -water will move into rivers quickly causing freq flooding . Areas formed from impermeable rocks - floods often . Rain over a no of days ground becomes saturated-excess water flows stright in rivers causing floods .Heavy snowfall & sudden rise in temps rapid thaw - rivers unable to cope with amount of water.
Human causes = vegetation removed from slopes - less interception - water moves quickly to rivers .a dam could burst meaning nmore water in river channel flooding river & land.famers who pough up & down slopes instead of around the hillside -channels created by pough allow rain water t travel faster . tarmac in urban areas rainwater cannot soak into ground runs to drains causes rivers t flood
removal of vegetation is classed as human & physical cause of river flooding It is humans that remove vegetation . But this stops the physical process of interception
Effects of river flooding on people
explain how urbanisation & deforestation causes rivers to flood
urbanisation - building of towns the ground is covered in tarmac & concrete -cannot soak up rainwater so it flows straight t drains & rivers -causing flooding
Deforestation - Removal of trees means less interception takes place so there is more surface run off floods
EXAMPLES -Explain the afects of river flooding
BULGARIA river Danube flood 2006-2 mill people affected/ 20 killed by flood as their homes were destroyed.. Large areas of farmland destroyed leaving food shortages . road impassable bridges & train lines washed away .
Mexico 2007 river Grijaiva - 1 mill people affected 70 % state under waterall crops destroyed , sand bags rond La Venta Archeaological Site
** remenber people & environment factors - IMPORTANT
pREDICTION & PREVENTION
Building Design -houses protected Sockets high up walls , doors light weight can be moved upstairs , concrete floors instead of wood , yaht vanish on wooden skirting proctective against water . property built on stilts
Planning - flood risk assessment has to be carried out in certain areas b4 PLANNING PERMISSIOIN GRANTED. 2010 a new law passed all new housing in flood risk areas be resisstant t flooding . Defra departm for environment food & rural affairs responsible for deciding which areas going t be defended & funding avail yto help prevent flooding .Forcasting Met office FORECASTS FLOOD WARNINGS TV RADIO weBSITES - RING FLOODLINE Education govern provide info via websites flood watch - codes advising public what to expect & do .