Geography Paper 1.3

V-shaped Valleys

the valley has steep sides and narrow bottom it is V-shaped, the stream winds around ridges or spurs of land which jut into the river valley. These are called interlocking spurs

River processes

Abrasion - where sand and pebbles are dragged along the river bed, wearing it away

Hydraulic action - where fast flowing water is forced into cracks breaking up the bank over time

Attrition - where rocks and stones wear each other away as they knock together

Solution - where rocks such as limestone dissolve in acid rainwater

Solution - dissolved chemicals are carried along in solution, invisible to the eye

Suspension - tiny particles of sediment are carried in the rivers current

Traction - large stones are dragged along

Bedload - heavier material is carried along the bottom

Waterfalls and gorges

Waterfalls occur when a river crosses a bed of more resistant rock, erosion of the less resistant rock underneath undercuts the hard rock above it, the rivers energy creating a hollow at the foot of the waterfall known as a plunge pool, the less resistant rock eroding again more rapidly by abrasion and hydraulic action creating a ledge which overhangs and collapses so the waterfall takes up a new position, leaving a steep valley or gorge

The valley shape has changed from a V-shaped valley to a U-shape. They are usually flatter here

The river flows faster than it did in the upper course even though it has a gentle gradient because of the greater volume of water so erodes laterally

This is where it deposits most of the sediment, starting from the heaviest so when the river floods over the flood plan fine sediment forms layers of alluvium which is fertile

Meanders

The water in the river flows naturally in a corkscrew pattern, this is the helical flow. This sends the rivers energy to the sides where the fastest current (thalweg) is forced to the outer bend where it undercuts and erodes the bank to form a river cliff. Then the helical flow transports sediment from the outer bend ton the inner bank where the slower moving water deposits sediment. Continued erosion causes a narrow neck between meanders leading to the neck being cut through creating a new channel and a easier route for water. The old meander then becomes an oxbow lake when deposition seals the ends seperating it from the river

The river at this point is wide and deep flowing over a gentle gradient carrying large volumes of water. This area floods easily. There are embankments next to the river (levees) these are formed where sediment and clay builds up beside the river as the flow is slower. Later on the river meets the sea (estuary) where water is taken out to sea

Long and cross profiles

Long profile - at source there is a steep gradient and at the mouth there is a gentle gradient

Cross profile - Upper course: Steep sides, narrow bottom. Middle course: Flood plain begins, sides quite steep. Lower course: Almost flat, wide, flood plain with gentle sides

Leaves and branches catch rain (interception)

If the ground is hard or very wet the rain flows overground called surface run off

Rain soaks into the ground called infilteration

Some water continues into solid rock to form groundwater, which flows very slowly

A mixture of surface run off, throughflow and groundwater flow feeds into the river

Permable rock - allows water to infilterate

Impermable rock - water cannot infilterate

Rock and soil type

Permable allow water in so is absorbed easily so surface run off is rare. Impermable rocks allow surface run off meaning the water reaches the river more quickly. Pervious rocks and porous rocks have either joints or gaps in the rocks so allow water through

Rainfall

Antecendent rainfall is rain that has already happened so the ground may already be saturated so more rain will flow off as surface run off towards the river. Heavy continual rain or melting snow means more water will flow into the river

Land use

In urban areas, surfaces like roads do not allow water to soak into the ground so runs into drains and spills into the river. In rural areas, ploughing up and down hillsides creates channels which allow rain water to reach rivers faster, increasing discharge. Deforestation means less interception so rain reaches the ground faster so it is likely to become saturated and surface run off will increase

Relief

Steep slopes means the rainwater is likely to run straight over the surface before it can infilterate, whereas on gentle slopes it is the opposite

Weather Conditions

Hot, dry weather can bake the soil so when it rains the water cannot soak in so runs off the surface straight into the river. High temperatures increase evapouration rates from water surfaces, reducing discharge. Long periods of extreme cold weather can lead to frozen ground so the water can't soak in

Hydrographs

When water enters the river, discharge increases (rising limb). The gap between peak rainfall and peak discharge is the lag time. The falling limb tends to be a gentle slope. Changes in land means that water may get their faster so the lag time decreases

What caused the rain?

Warm air mass picked up moisture as it crossed the Atlantic, the air was forced up higher ground. The air cooled and the moisture condensed into heavy rain and the weather front stopped over Cumbria. The eastern side was relatively unaffected because most of the rain had already fallen

What helped to cause it?

The ground was already saturated, the steep slopes of Cumbrian mountains helped water run rapidly into rivers.

What factors cause flooding?

Heavy rain and rapidly melting heavy snowfalls, building particulary on flood plains increases the area of impermable surfaces reducing infilteration and increasing surface run off and the destruction of natural environments e.g. Deforestation as it increases the rate of run off

Effects

1300 homes were flooded and contaminated with sewage

Many businesses flooded causing financial and economic issues for locals

4 bridges collapsed and 12 were closed because of flood damage

1 man died

Responses

The government provided £1 million to help clean up

The Cumbria flood recovery fund was set up to help victims

Network rail opened a temporary railway station in Workington

The 'Visit Cumbria' website provided lists of recovery services and trade

Flood Codes - 3 codes are used:

Flood alert

Flood warning

Severe flood warning

Causes

Heavy rainfall - 900mm fell in July

Low land country

Melting snow from glaciers in the Himalayas

Effects

2000 deaths

25million homeless

100,000 caught water-borne diseases

Flooded fields reduced growing of rice, prices rose by 10%

Responses

Infrastructure destroyed

Other governments provided food, water and medical aid

International charities funded rebuilding homes

Some homes have been built on stilts so they're less likely to be damaged by floods

Build flood banks - raise the banks of the river so it can hold more water. Relatively cheap, one off cost

Straightening and deepening the river - Straighten the river channel to speed up the flow, dredge so it is able to carry more water. Dredging would have to be done every year and is an expensive method

Dams and reservoirs - trap and store water and release in a controlled way. Very expensive and means huge changes to the ecosystem

Flood walls - build around settlements, industry or roads. Expensive and looks unnatural, is effective if flood is not to extreme

Storage areas - Water is pumped out of the river and stored in temporary lakes. Effective but needs large areas of spare land

Barriers - The barrier is raised when a high tide or flood is forecast. Very expensive and may need to be replaced in the future.

Flood abatement - change the land use upstream. Slows down the flow of rainwater into rivers

Flood proofing - design new buildings or alter exisiting ones to reduce the flood risk. It is expensive to alter current buildings

Flood plain zoning - different uses are allowed, depending on the distance from the river. Land closer to the river being used for grazing and more important buildings further in

Flood prediction and warning - monitor river levels and rainfall and use the information plus weather forecasts to predict flooding. They issue warnings and produce Flood maps

Washlands - parts of the flood plain that are allowed to flood. Washlands cannot be built on and usually used for sports pitches or nature reserves

Water facts

The amount of water used per household has risen by 70% over the last 30yrs - due to the introduction of appliances like washing machines and dishwashers

Only 66% of houses owned a washing machine in 1972 but by 2010 the figure was 94%

Water is mostly used for washing, flushing the toilet and washing cars

The average person in the UK uses 150 litres a day compared to Africans 47 litres and Americans 578 litres

Water stress

Areas of deficit do not have enough rainfall or water, areas of surplus have more water than needed

Increasing demands

The UK's population is growing and is expected to increase by 10 million in 2023

More people means more houses and larger amount of water needed

By 2020 the demand for water could be about 5% higher than it is today

Temperature rise due to global warming means there will be drought and water shortages being more frequent in the UK, especially the south

Fact file

Based in Northumberland and is 12km long and 52 metres deep. It is the biggest man-made reservoir in Europe. It was built to meet the increase in water demand. It is also a water-transfer scheme (water is transferred from one area to another)

Benefits & disadvantages

Major tourist attraction

1.5 million trees were cut down to build it

The north-east has the most reliable water supply in  England

The water is used to generate hydroelectric power at Kielder Dam

It was expensive - £167 million to build

How can we be more sustainable?

Increase the use of rainwater harvesting and grey water recycling

Make new homes more water efficient

Install water meters in all homes

Reduce water leakage from pipes and reservoirs

Share water supplies when there is a surplus

Charge more for water to encourage people to use it in a sustainable way

Make appliances like washing machines and dishwashers more water efficient