river landscapes

examples of hard engineering defences

• groynes

• seal wall

• gabions/ rock armour

what is a groyne

wood barriers prevent longshore drift, so the beach can build up

advantages and disadvantages of groynes

• beach is still accessible

• no deposition further down coast= erodes faster

what is a sea wall

concrete walls breakup the energy of the wave. has a lip to stop waves going over

advatages of disadvantages of sea walls

• long life span

• protects against flooding

• curved shape encourages erosion of beach deposits

what are gabions/ rock armour

cages of rocks/boulders which absorbs the wave energy protecting the cliff behind

advantages and disadvantages of gabions

• cheap

• local natural can be used to look less strange

• will need replacing

examples of soft engineering defence

• reprofiling or beach nourishment

• costal realignment or managed retreatment

• sand dune regeneration

what is reprofiling/ beach management

beaches built up with sand , so waves have to travel further before eroding cliffs

adaptations and disadvantages of reprofiling/ beach management

• cheap

• beach tourists

• need replacing (after storms)

• offshore dredging damages to sea bed

what is costal realignment/ managed retreat

low value areas of the coast are left to flood/ erode

advantages and disadvantages of coastal realignment/ managed retreat

• reduce flood risk

• creates wildlife habitiats

• compensation for land

what is sand dune regeneration

encourage sand dune to grow- this builds up the height of the beach

advantages and disadvantages of sand dune regeneration

• reduces flood risk

• creates wildlife habitats

• cheap

• long life span

• protects from flooding

what is precipitation

moisture falling from clouds as rain, snow or hail

what is interception

vegetation prevents water reaching the ground

what is surface run off

water flowing over surface of the land into rivers

what is infiltration

water absorbed into the soil from the ground

what is transpiration

water loss through leaves of plants

what are physical cause of river flooding

• prolonged and heavy rainfall

• relief

• geology

what is a human cause of river flooding

land use

how does prolonged/ heavy rainfall cause flooding

long period of rain causes soil to become saturated leading to runoff

what is geology

impermeable rocks cause surface runoff to increase river discharge

what is relief

steep-sided valley channels water to flow quickly into rivers causing greater discharge

what is land use

tarmac and concrete are impermeable. this prevents infiltration ad causes surface runoff

how are interlocking spurs created

as the river lack energy here it erodes downwards and therefore avoids areas of hard rock bending around them

where are waterfalls and gorges found

upper-course formation

how are waterfalls formed

river flows over alternative types of rocks

rivers erode soft rock faster creating a step

further hydraulic action and abrasion form a plunge pool beneath

hard rock above is undercut leaving cap rock which collages providing more material for erosion

what are the characteristic of the middle course of a river

here the gradient gets gentler, so the water has less energy and move slower, the river begins to erode laterally making the river wider

what stage of the river are meanders and ox-bow lakes found

middle course of a river

how are ox-bow lakes found

step 1- erosion of outer bank forms river cliff, deposition inner bank forms slip off slope

step 2- further hydraulic action and abrasion of outer banks, neck gets smaller

step 3- erosion breaks through neck, so river takes the fastest route, redirecting flow

step 4- evaporation and deposition cuts off main channel leaving an ox-bow lake

how are formation of floodplains

as meanders migrate they erode laterally creating a flatter valley floor getting higher after each flood event due to deposition of silt

how are levees formed

levees are formed during fllod events, the heavist materails are deposited first near the channel edge creating a higher bank either side of the channel

what are positive of floodplains and levees

nutrient rich soil makes it ideal for farming, flat land for building houses

how are estuary’s formed

salinity increase towards the sea. sediment can be sourced from the river and the sea here. it is tidal so both costal and river processes can occur in an estuary.

how are mudflats created

mudflats are created in low energy areas (usally at the mouth)

soft engineering river management schemes

• afforestation

• floodplain zoning

• flood warnings

• river restoration

hard engineering river management schemes

straightening channels, embankments, deepening or widening river/ flood relief

what is afforesation

plant trees to soak up rainwater and intercept rain reduces flood risk. increases lag tome

what is flood plain zoning

allow/ not allow building on flood prone areas- or allow some uses that allow for flooding

what is flood warning

use of technology to warn people

what is river resotratoin

create natural widening rivers that would naturally slow water down increasing lag time

what is straightening channel

increases velocity to remove flood water but can cause flooding downstream

what are embankments

heightens river so flood water is contained but if it collapses flooding worsens

what is deepening or widening river

to increase capacity for a flood, can cause flooding elsewhere

what is a dam and reservoir

temporary storage of water to lengthen lag time- if it collapses then a major hazards happens

what is peak discharge

is the discharge in a period of time

what is lag time

is the delay between peak rainfall and peak discharge

what is rising limb

the increase in river discharge

what is falling limb

the decrease in river discharge

what is watershed

an area of land that separates water flowing different rivers (edge of river basin)

what is confluence

the location where two rivers join

what is vertical erosion

when it erodes down

what is lateral erosion

erosion side to side

characteristics of upper course

• lots of friction

• very steep gradient

• V-shaped valley

• low velocity

characteristics of middle course

• meanders

• sediment is smaller

• U-shaped valley

characteristic of the lower course

• less friction

• high velocity

describe how the river channels may change as it goes downstream

rivers change in many ways as they travel downstream. for instance, in the upper course vertical erosion occurs creating V-shaped valleys. whereas, in the lower course erosion occurs laterally creating U-shaped valleys. another example of changes occurring in river as they travel downstream is friction increasing, causing the sediment to decrease

what is erosion

erosion is the wearing away of rock and soil found along the riverbed and banks. these rock particles are carried downstream

what is hydraulic action

the force of the river hitting against the bank- causing cracks. pressure weakens and wears banks

what is abrasion

rocks carried along by river wearing down the bed/ bank- sandpapering effect

what is solution

dissolved particles in the water

what is attrition

rocks smash together making them smoother and rounder

examples of erosion

• hydraulic action

• abrasion

• solution

• attrition

what is transportation

rivers carry or transport the rivers material its bed load somewhere else

examples of transportation

traction, saltation, suspended, solution

what is traction

the rolling of large materials along a riverbed

what is saltation

sediment bouncing along the riverbed

what is suspension

light particles carried by the current

when does deposion happen

deposition occurs during a flood when a river bursts its banks. the sudden increase in friction as the water floods over the land reduces velocity causing deposition. this creates a river bank feature called a levee

where does deposition occur

around the inside of river bend and at river mouths this is due to the velocity of the river reducing, this means that it cannot carry the load

what material is depostied last

the lightests material

which course of the river sees the most deposition

lower course

what is a levee

embankment either side of the river channel, formed naturally by sediment deposited during a flood

what is a floodplain

flat area of land either side of a river which is regularly inundated with water during a flood

where is an estuary found

at the mouth of the river

what is river flooding

when the volume/ discharge in a river rises it bursts banks and the water runs on the land. this usually happens after heavy rainfall- which often occurs during winter periods

examples of land use

deforestation, urbanisation

how does deforestation cause flooding

reduces interception, increases surface run off

how does urbanisation cause flooding

they take away soil and replace with concrete, creating impermeable environment

what is a hydrograph

a graph that shows how the discharge responds to the storm event

what are lianas

vines/trees that use other trees as support allowing these plants to reach the forest canopy to obtain sunlight needed for survival

how waxy and pointed tip leaves help trees

• flexible base

• water doesnt sit on leaf- otherwise algae would grow blocking sunlight

• allow excess rain water to run off

what are buttress roots

they are large, wide roots which provide stable bases, they are often found in rainforests with poor nutrients in soil.

they only grow tiny distances into the ground to tap nutrients from the thin layer of topsoil where most of the nutrients are concentrated