Weather and Tourism

Weather and tourism

Key Stage 2 Geography & Literacy
This activity can be used to revise ways of examining texts to find out information, asking questions to guide research.

What effect does the weather have on tourism?

Overview

This lesson aims to use childrens’ previous learning about mountain climates in to identify how the weather affects the activities and tourism in different mountain localities.

Children will work in small groups and use a range of holiday brochures to find information to complete worksheets.

Objectives

Children should learn:

that varying weather conditions can have a significant impact on life in an area
to use secondary sources

Lesson plans

Activity

The lesson is introduced using slide one. The children talk in pairs about holiday destinations.

Where would they like to go on holiday in the winter?
Where in the summer?
Is the weather important?
What type of weather would they need?
Where in the world would they like to go?
Brainstorm a list of holiday activities, for summer or winter, in a mountain environment using slide 3.

Using slide 4 model how to find information, using holiday brochures and previous knowledge to complete the table for one locality.

Children will be working in small groups and using a range of holiday brochures and books to research types of tourism in a mountain locality they have studied in this unit. Differentiated worksheets can be used to record findings individually. Some children may need support to find information in brochures.

Groups can present their findings to the class.

Plenary
Display slide 5 and use photos to discuss the positive and negative impacts of tourism on mountain areas.

Lesson resources

Holiday activities slideshow.

You will need:
Holiday brochures for locations in this unit.
Library resources
Tourism worksheet (High ability).
Tourism worksheet (Low ability).

Web page reproduced with the kind permission of the Met Offic

Water Cycle Lesson

The water cycle

Key Stage 2 Science/ Geography

Overview

In this series of activities children will be using what they have learnt earlier about evaporation, condensation and reversible changes of state, to build up the water cycle from first principles.

The slides and the water cycle experiment will provide opportunities for children to extend their knowledge and to ask questions.

The practical activities will allow children to demonstrate their learning in a fun and creative way.

Objectives

Children should learn:

that water evaporates from oceans, seas and lakes, condenses as clouds and eventually falls as rain.

that water collects in streams and rivers and eventually finds its way to the sea

that evaporation and condensation are processes that can be reversed to interpret the water cycle in terms of the processes involved

Lesson plans

Activity one

Water cycle in a bowl experiment

Activity two

Children work in small groups to describe the water cycle in a variety of ways:

  • Designing a poster of the water cycle
  • Making a cartoon strip of the water cycle for a drop of water
  • Writing and performing a water cycle rap
  • Completing the water cycle word search
  • Each group shares their work with the rest of the class during plenary.

You will need:

  • Paper for posters
  • Paper for cartoon strips
  • Reference books

The water cycle wordsearch

The water cycle wordsearch answers

Web page reproduced with the kind permission of the Met Office

Some Background information.

For teachers the water cycle in depth.

The Water Cycle

The water cycle

The water cycle is the process by which water travels from the Earth’s surface to the atmosphere and then back to the ground again. It is a constant process with the same water going through the cycle over and over again.

The diagram below shows the different parts of the water cycle.The water cycle

The Earth’s water

Nearly all (about 97%) of the Earth’s water is contained in the oceans. A tiny amount is locked away as ice sheets and glaciers. This leaves a very small amount which travels around in our water cycle, although it may not always seem this way on wet days.

Stages of the water cycle

Stage 1

The first stage of the water cycle is when moisture from the sea and plants is lifted into the atmosphere. As the sun beats down it warms the oceans, rivers and lakes. This causes the water to rise into the air as water vapour. This process is known as evaporation. A tiny amount of moisture is also released from trees and plants. This is known as transpiration.

Stage 2

As the water vapour rises in the atmosphere, it cools and condenses, forming clouds. This process is known as condensation. It is the same process that makes you see your breath on a cold winter morning. The clouds will then produce rain or snow (known as precipitation) which returns to the Earth’s surface as water. The cycle then starts all over again.

Stage 3

Only about three quarters of the rain which falls back to Earth lands in the oceans. This is much less than leaves in the first place. The remaining water makes only a slow return to the oceans. Most is locked up in glaciers and icebergs and can take several thousands of years to complete its cycle. In tropical areas the process can take just a few hours.

The remaining water runs slowly overground, seeps into the ground or is taken up by plants as the cycle begins again.

Importance of water

The water cycle is vital for making sure rain falls around the world. People depend on it for drinking water for themselves and their animals and also for growing their food. Droughts caused by a lack of rain affect many parts of the world causing famine and many deaths.

Activities

Why not try making your own mini water cycle. Check out our Water Cycle in a Bag experiment and our water cycle in a bowl demonstration.

Measuring a puddle

What you will need:

  • A puddle
  • A piece of chalk

Choose a day then there has been rain overnight and the rest of the day is expected to be dry, warm and sunny.

Choose a puddle and first thing in the morning use a piece of chalk to draw around the puddle. A few hours later go back and draw around your puddle again. Repeat this several times during the day.

You should find that the puddle slowly shrinks during the day as the water evaporates.

For teachers – water cycle in depth and a water cycle lesson 

Web page reproduced with the kind permission of the Met Office

Snowflakes

Snowflake facts

How does snow form?

Snow crystals form in clouds when the temperature is below freezing. They are made by water droplets freezing onto ice particles. As an ice crystal falls through the cloud it bumps into others and becomes a snowflake. This processing of bumping into others, along with some melting and re-freezing helps to form their complex design. The air that the snowflake falls through has to be below freezing otherwise the snowflake will melt and turn to rain.

What do snowflakes look like?

Snowflakes are always six sided and it is thought that no two are ever the same. The shape and form of a snowflake depends on the temperature and amount of moisture within the cloud. Snowflakes can be divided into six main shapes, plate (flat), stars, column, needle, dendrite (lacy) and capped column. When it is very cold the snow is very fine and powdery and the snowflakes are quite simple in design, normally rod or needle shaped. When the temperature is closer to freezing point (0 degrees Celsius), the snowflakes are much larger and more complex in design, such as a star.

The Snowflake Man

An American photographer called Wilson A Bentley spent much of his life looking at snowflakes and taking pictures of them. He developed a huge collection of several thousand photographs of snowflakes and was nicknamed ‘The Snowflake Man’. In 1925 he was quoted as saying: “Under the microscope, I found that snowflakes were miracles of beauty; and it seemed a shame that this beauty should not be seen and appreciated by others. Every crystal was a masterpiece of design and no one design was ever repeated. When a snowflake melted, that design was forever lost.”

Snow facts

It is recorded in the Guinness Book of World Records, that the world’s largest snowflake was 38 cm wide and 20 cm thick. This occurred at Fort Keogh, Montana, USA on 28 January 1887.

The tallest snowman ever made measured 34.63 metres and was made by residents of Bethel, Maine, USA. It took 14 days to build, finally being completed on 17 February 1999. Nicknamed Angus, he had vehicle tyres for his mouth and trees for arms.

Why not make your own pretty snowflakes.

Follow the instructions below. You might need a adult to help you with the cutting out.

Fold your paper in half

1) Take a large square piece of white paper and fold it in half to make a triangle.

Fold your paper in half again

2) Fold your triangle in half again, corner to corner, to make a smaller triangle.

3) + 4) Your triangle now needs to be folded in to three. Fold the two sides across each other, making sure both sides are equal. It should look like diagram 4

Diagram 3
Diagram 4

5) Cut straight across the bottom of the paper to make a triangle with a straight base like the one below.Cut straight across the bottom of the paper to make a triangle with a straight base

6) Now you can make random cuts to make your own snowflake pattern.

Web page reproduced with the kind permission of the Met Office

Rainbows

Rainbow facts

RainbowRainbows are beautiful arcs of colour in the sky.

They occur when it is raining and sunny at the same time.

To see one you have to stand with your back to the sun.

The sun gives off light. The light we can see is called ‘white light’. But this white light isn’t actually white at all, it is made up many different colour wavelengths.

The main colours are red, orange, yellow, green, blue, indigo and violet. These seven colours are called the colours of the spectrum. The longest wavelength is red and the shortest is violet.

Memory aid for rainbow coloursMany people use the phrase ‘Richard Of York Gave Battle In Vain’ to help them remember the colours of the rainbow.

Separating the colours

Prism separating colours

To separate these seven different colours from the white light, you can use a prism (a triangular-shaped piece of glass).

The prism separates the white light into the different colour wavelengths by bending each light ray at a different angle and so separating the colours. The separation of white light into different colours is called ‘dispersion’. When the prism bends each light ray, this is called ‘refraction’.

So the reason we get rainbows in the sky is because the raindrops act like lots of tiny little prisms. As the sun shines white light through the sky, the raindrops separate it into the seven main colours, forming a rainbow.

Activities

Why not try creating your own phrase to remember the colours of the rainbow?

Why not draw your own rainbow and then colour it in? Try to use the right colours in the right order.

Web page reproduced with the kind permission of the Met Office

Mountain Environments

The mountain environment and weather data

Key Stage 2 Geography
How does the weather compare in each of these places?

 

Overview

This series of lessons aims to use a cross-curricular approach to geography and mathematics, to extend children’s knowledge of mountain environments, and their skills in collecting, presenting and interpreting data.

In activity one the children use a range of secondary resources, including the internet, to collect the latest weather data for three mountain environments, using worksheet 1 to record findings.

Activity two focuses more closely on climates. Climate slides can be used to introduce the main activity which is an investigation using the internet to find climate averages for the past 30 years. Children collect and present data as bar graphs and interpret their findings in terms of similarities and differences between places using differentiated worksheets.

 

Objectives

Children should learn:

about weather patterns in different parts of the world
to use secondary sources
to use ICT to access information

Lesson plans

Activity one

Collecting weather data using the internet
Children work in groups to collect weather data for three mountain localities related to their studies earlier in this unit.
They will need to use the internet to collect the data which, if possible, should be from that day’s latest weather reports.

Worksheet 1 can be used to record their findings.

Plenary
Groups can share their findings and discuss similarities and differences in weather between localities.

Note: When the latest weather data for a specific location is not available, children can use atlases to find the nearest towns and cities for which the latest weather data is available.

Lesson resources

PDF document containing photos of mountain localities being studied.

PDF document containing worksheet comparing latest weather data.

You will need:
Atlases
Internet access for groups
latest UK weather forecast.

Activity two

Comparing mountain climates
Using slide 1 as a starting point, ask the children to imagine they are going to visit the places in the photographs and that they need to think about the clothes they need to pack for each of the locations. Children can work in pairs to describe types of weather they might experience at low and high altitudes and make notes.

Allow time for children to share their ideas and discuss any questions arising from the exercise.

Using slides 3 to 10 introduce the class to climates and encourage children to think about factors that affect climate in different parts of the world.

Split the class into ability groups and introduce investigation task. Ensure each group investigates a different locality. Use worksheets 2, 3 and 4 to record data and plot graphs.

Plenary
Allow each group to present their findings and discuss with the children the similarities and differences between the weather in each of the mountain environments.

Compare bar graphs of rainfall for the different mountain environments and ask the question ‘is the driest time to go on holiday the same in all these places?’

Mountain climates slideshow- PDF document containing a set of slides for use with activity 2.

You will need:
Internet access for groups.

PDF document containing worksheet on Kathmandu (Low ability)

PDF document containing worksheet on Capel Curig (Middle ability)

PDF document containing worksheet on Cusco (High ability)

PDF document containing worksheet for any location within the UK

Link to the World Weather Information Service for Cusco.

Link to the World Weather Information Service for Kathmandu.

Link to the Met Office mountain weather forecast for Snowdonia (Capel Curig).

Web page reproduced with the kind permission of the Met Office

Measuring Temperature; Keeping Warm

Keeping warm

Upper Primary Science, Geography and Maths
Using a thermometer

Overview

In activity one, children will be introduced to thermometers and their uses, and have the opportunity to practise taking temperature readings using thermometers with different scales. They will link the measurement of temperature to how hot or cold things are.

In activity two, children will take careful readings of outside temperature during the day and try to explain findings in terms of weather conditions. Only a short time is needed at hourly intervals to take the temperature readings throughout the day.

Objectives

Children should learn:

to use a thermometer to make careful measurements of temperature, using standard measures.
that temperature is a measure of how hot or cold things are and that something hot will cool down and something cold will warm up until it is the same temperature as its surroundings.
to explain temperature and temperature changes using scientific knowledge and understanding

Lesson plans

Activity one

Introduction to using thermometers
Using slides 1 and 2 the children discuss uses of thermometers and are taught how to handle thermometers safely. They are then given a selection of thermometers to handle and examine.

Teach the children how to read the thermometer scale using the thermometer ITP.

Activity
Have containers of water at different temperatures ready, positioned so that all the children will be able to take temperature readings during the activity. Tell the children they will be practicing taking temperature readings for each container of water and the empty container which will be at room temperature. Remind the children that care will be needed when measuring the temperature of very hot water. Children record their measurements using the measuring temperatures worksheet and note the time. They will take a second reading an hour later.

While waiting to take the second reading, use the rest of the slides to practice reading temperatures, discuss temperature as a measure of how hot or cold things are and predict what will happen to the temperature of the water in the containers (the water will cool down or warm up to reach room temperature).

This will be a good time to introduce activity two, using slides 9 and 10 in preparation for starting the activity at 9a.m. when planned.

Plenary
Ask the children to measure the temperatures again and complete the worksheet.

Lower ability groups will need support to take temperature readings and complete the worksheet.

Lesson resources

Using a thermometer slideshow

You will need:
Containers of water at different temperatures including below room temperature and an empty container at room temperature.

Measuring temperatures worksheet

Activity two

Measuring the outside temperature
Place a thermometer in a safe place outside in the shade, away from direct sunlight.

Children take temperature readings at every hour and record them, using graph with or without scale.

Plenary
When children have completed all readings and constructed their bar graphs, discuss the results and ask children questions about their findings.

Ask the following:

What was the temperature at 9am?
What was the temperature at playtime?
How did the temperature change during the day?
What was the warmest time of the day?
Can you explain why the temperature changes during the day?

You will need:

Slides 9 and 10 from using a thermometer slideshow (above)

Outside temperatures worksheet

Outside temperatures worksheet(without scale).

Web page reproduced with the kind permission of the Met Office

Handling Data and Measurements

Handling data and measurements

Key Stage 2 Mathematics
Handling data and measurements

Overview

Children measure the outside temperature at the same time on each day for a week. They use ICT to record the temperature each day, in a suitable data handling program. At the end of the week they use the program to display the results on a bar chart. They answer questions such as:

On which days was it warmer than 15 degrees?
What is the difference between the temperature on the hottest day and the temperature on the coldest day?

Objectives

Children should learn:

to read, to the nearest division and half-division, scales that are numbered or partially numbered. Use the information to measure and draw to a suitable degree of accuracy.
to answer a question by collecting, organising and interpreting data.
to use ICT to create a bar chart.

Lesson plans

Activity

Mental starter
Use slide 1 to ask questions about the temperature data.

Main teaching
Use the thermometer ITP, to teach the children how to measure temperature to the nearest degree.

Using slides 5–9 go through temperature, rainfall and wind speed measurements.

Tell the children they will be keeping a weather diary for one week and measuring the outside temperature at the same time every day.

If you have a weather station at school show them how to measure the wind speed and rainfall. Otherwise, show the children how to find the information using the latest weather data on the internet.

Demonstrate how to record the temperature each day in your chosen data handling program.

Lesson resources

Keeping a weather diary (Temperatures) slideshow.

Link to the Met Office latest weather forecast for the UK.

Main activity
Children measure the outside temperature in groups at the same time every day for one week and complete their individual weather diaries.

On the last day, when all the information has been collected, using ICT, children record the temperatures for the week in the chosen data handling program and use the information to display as a bar chart, which can then be printed.

Your own weather diary worksheet.

You will need:
Access to computers or laptops

Plenary
Using slides 10–14 ask the children to answer questions with the help of their bar charts. Can they think of any other questions to ask? What does the chart tell us about the weather during the week?

You will need:
Slides 10–14 of keeping a weather diary (Temperatures) slideshow (above)

Web page reproduced with the kind permission of the Met Office.

Poems and Songs

Poems and songs about the weather for children and schools

There are lots of songs and poems about the weather. Why not practise singing the ones here on this page? Or you could make up your very own song using your favourite weather words!!

TIPS: Tapping your fingers on a table sounds like raindrops, stamping your feet sounds like thunder, blowing sounds like the howling wind and you could even make shivery noises for the cold!!

Poems


Rain & Sun
Christina Rosetti


Wind
Christina Rosetti


Rain
Robert Louis Stephenson


Raindrops
Anon

Wind Poem 2
Wind Poem 2
Christina Rosetti

We also like the following poems by more recent poets – see if you can find them in a poetry book!

Anything from The Book of Clouds Juris Kronbergs
The More it Snows A.A. Milne
Snowflakes Helen Moore
Snow Alice Wilkins
Winter Ocean John Updike
Winter Morning Ogden Nash
It s never Fair Weather Ogden Nash
Fog Carl Sandburg
Winds light to disastrous Spike Milligan
Storm Roger McGough
Rain George MacBeth
Glass Falling Louis MacNeice
Clouds Aileen Fisher
The Fight of the Year Roger McGough

Floods

Flooding may result from a large amount of rain or from rapid thawing of snow and in coastal regions may also be caused by a storm surge or a combination of high tide and high river level. The consequences of flooding are often disastrous but there can also be beneficial effects of flooding.

Download Floods Fact File

Storm surges

Storm SurgeStorm surges are mainly caused by the effect of the wind on the sea, not changes in atmospheric pressure. The effect of wind on the sea surface is known as wind stress. The wind stress on the surface of the sea causes the water level on a coast to rise if the net transport of water is towards land and to fall if it is away from land.

Many coasts are at risk from storm surges and these include the Atlantic side of the United States, the Bay of Bengal area around India, Thailand and Indonesia, the coastal areas of the Netherlands and eastern England coastline. At the head of the Bay of Bengal large storm surges (up to 4m in height) are initiated by hurricane force winds coupled with low pressure tropical cyclone systems. Fortunately for the UK surges large enough to bring about catastrophic flooding of these North Sea coasts are experienced only a few times each century, and improved sea defences should stop all but the most extreme surges. On the Indian sub-continent, especially near the mouths of the River Ganges, death tolls from storm surges caused by tropical cyclones have been huge. In 1970, for example, more than 200,000 died when such a surge struck the area. Here, as in other places where storm surges occur, the sam

Examples of storm surges in the UK and their effects


A FerryFlooding of the Thames on 6th -7th January 1928 highlighted the need to find ways of forecasting storm surges. However, the real push to investigate storm-surges was on 31st January and 1st February 1953, when, a surge exceeding 2.7 metres at Southend in Essex and 3.5 metres in parts of Holland killed 307 people died in eastern England and 1,800 in the Netherlands. The storm that caused the 1953 surge was among the worst to hit the UK in the 20th century. Before the storm’s low pressure and storm-force northerly winds raised water levels in the southern North Sea, hurricane-force winds blew down more trees in Scotland than were normally felled in a year; and a car ferry, the Princess Victoria, on passage from Stranraer in Scotland to Larne in Northern Ireland, sank with the loss of 133 lives. Only 41 of the passengers and crew survived. Nowadays, surges are forecast with considerable accuracy and storm-surge barriers are in place in the most vulnerable places in the Low Countries and eastern England, one of them on the Thames a (south of Greenwich).

The effects of pressure on sea level

The Thames BarrageWhen pressure falls by one millibar, sea level rises by one centimetre. Thus, a deep depression can cause sea level to rise 60 or 70cm above the level predicted purely on the basis of tidal theory. The pressure-induced rise in sea level caused by a tropical cyclone can be much greater, maybe a metre or more.

Flash flooding

FloodingOne of the most energetic and destructive of all weather systems are tropical cyclones. The hurricane-force winds can reach 50m/s and torrential rain falls from their towering cumulonimbus clouds.flooding The winds can cause disastrous surges on coasts and the downpours of rain can cause serious flooding. Power and water supplies are disrupted, buildings are damaged, crops are destroyed, people and livestock are drowned, bridges collapse, roads and railways are undermined or blocked by debris, and beaches are scoured. Tropical cyclones nearly always leave behind a trail of destruction and misery.

Flash floods are exceedingly dangerous. When water cannot percolate into the ground, it runs off the surface as it would from impermeable concrete. This is particularly so when the ground is very wet or when baked hard after a hot dry spell. Potholers can be especially at risk, such as on 24 June 1967, when five drowned in Yorkshire. The water which fell in a heavy thunderstorm after a spell of dry weather ran off rapidly into underground streams and caverns at Mossdale. The rise in water levels below ground was too rapid for the potholers to scramble to safety.

Floods resulting from persistently wet weather and thawing of snow case studies

Raining In terms of water flow, the Mississippi is the sixth largest river in the world. Its annual average flow rate is 14,000 cubic metres per second and it discharges into the Gulf of Mexico 580 cubic kilometres of fresh water per year. The greatest flows occur in the period March to May and the least in the period August to October. A large proportion of the United States is drained by this river.

To protect against flooding, which would otherwise occur frequently, the Mississippi River is constrained by levees (embankments) all the way from the State of Missouri to the sea. This barrier, much of it concrete, has isolated the river from a lot of the surrounding countryside, but without it and other means of dealing with excess water in the river, low-lying cities such as New Orleans could not exist.

Tragically, some of the levees around New Orleans were breached on 29 August 2005 when they failed to withstand the battering imposed by the waves and a storm surge generated by Hurricane Katrina. Flood depths reached six metres in places and more than 1,000 people died.

Despite levees, spillways, reservoirs, pumping stations and other constructions, flooding does still occur. The flood-control system proved incapable of containing the flood of 1973, for example, and again proved inadequate in the summer of 1993, when abnormally high rainfall over central parts of the United States caused extensive flooding of the upper and middle Mississippi and lower Missouri rivers. The city of St Louis was particularly badly affected. Discharges of water from the Mississippi into the Gulf of Mexico in the late summer of 1993 were abnormally high. A study using satellite imagery showed that water from the Mississippi spread out far and wide off the States of Louisiana, Texas and Alabama. Indeed, some of the Mississippi water passed through the Florida Strait into the Atlantic.

There was rain, more rain and even more rain in northern California soon after Christmas 1996. From 29 December 1996 to 4 January 1997, depression after depression from the central Pacific brought rain to northern California. As the air was unusually warm, a consequence of the precipitation was that large amounts of snow melted. During the week of the storms, 61 cm of rain was recorded. Significant flooding occurred in northern California and southern Oregon and 43 counties were declared disaster areas. Flooding occurred rapidly because soils became saturated and amounts of snowmelt were large. Flood-control reservoirs could not cope, as their storage capacity was no more than moderate because of near-normal rainfall and run-off prior to the onset of the severe weather. Levee failure occurred on several rivers.

After the United Kingdom’s snowy winter of 1947 came the thaw. In many parts of the British Isles in February and early March 1947, deep drifts of snow, some five metres or more deep, caused villages and hamlets to be cut off for days on end. Then, on 10 March, warm air and rain edged into south-west England and advanced across the British Isles. By 13 March, floods were widespread. Vast areas of Fenland, the Severn Valley and other parts of Britain were submerged. At Selby, Yorkshire, three-quarters of all the houses were under water. A severe south-westerly gale on 16 March drove water ahead and caused dykes in the Fens of eastern England to burst. Warm air and rain are much more effective at thawing large quantities of snow than sunshine. The albedo of old snow (proportion of light reflected) is about 55%. The albedo of fresh snow is about 80%.

On 9 and 10 April 1998, just before Easter, prolonged heavy rain fell over a wide area of Wales and central England. In the Midlands of England, there was serious flooding, with Northampton and Leamington Spa badly affected. In these Easter Floods, as they have come to be known, 4,500 homes were inundated, five people died and the estimated cost of the damage exceeded £350 million. The culprit was a slow-moving depression centred over Brittany. North of it, lying east-west across the Midlands, there were two parallel fronts which were almost stationary, producing prolonged heavy rain that fell on a catchment that was already saturated.

snowflakeIn coastal regions, flooding may be caused not only by a storm surge but also by a combination of high tide and high river level. An example of the latter occurred in South Wales in 1979. On 26 and 27 December of that year, falls of rain exceeded 100mm in many places, especially over the hills. Extensive flooding occurred on the 28th. Cardiff was badly hit when the River Taff in spate met a high tide from the Bristol Channel. Hundreds of homes and offices near the city centre were inundated. Flooding with sea water is bad enough, not least because the salt in the water is left behind when the water evaporates, but the flooding in Cardiff on this occasion was particularly unpleasant, as the water welled up into streets and houses through the sewers.

Health Risks after Flooding

A RatIn many parts of the world, there are serious health risks after disastrous flooding. Mosquitoes, flies and other insects may become more abundant than usual, as the filth, debris and stagnant water left by the floods provide suitable breeding conditions. Consequences may include out-breaks of typhoid, dysentery and encephalitis. Rats and mice displaced from their natural habitats may find conditions to their liking in houses, sheds, barns and other buildings.

a snakeIn some parts of the world, snakes also become a problem after flooding, as they, too, are displaced from their natural homes by the water. Quite often, they appear inside houses. However, snakes can be beneficial, as they help to reduce populations of rodents.

Beneficial Effects of Flooding

The NileSome of the most fertile land in the world lies beside rivers, the Nile valley being the classic example. For thousands of years, the people of Egypt have relied upon the waters of the Nile to overflow their banks every year, carrying with them fertile silt that makes agriculture possible. The flow of this river is nowadays controlled by means of the Aswan High Dam, an operation that can have its advantages and disadvantages. Salinity levels in the Nile Delta have increased, for example, because the outflow of fresh water from the river is much less now than before the High Dam existed. On the other hand, availability of water from the lake behind the dam, Lake Nasser, has allowed water levels downstream to be maintained in drought years, thus benefiting agriculture when in olden times crop failure and famine might have occurred.

A River ValleyThe Ganges Delta is another place where flooding brings benefits for agriculture. Here, every June to October, the waters of  the Ganges, Brahmaputra and other rivers overflow and inundate the countryside. There is, however, no equivalent of the Aswan High Dam to control the waters of the Ganges Delta. Sometimes, crops are destroyed, hamlets ruined and humans and animals drowned.

In some arid regions (e.g. Namibia and central Australia), floods occur very occasionally. When they do, glorious displays of flowers follow. In these areas, seeds can lie dormant for many years and germinate (grow) very rapidly when the rains come.

A TreeThe heavy rains brought by tropical cyclones can help revive crops and replenish water supplies. Sometimes, fruit trees have flowered and borne fruit a second time after the passage of a cyclone. Sometimes, floods have flushed away mosquito breeding areas. There is a danger, however, that residual pools of water will, in turn, become mosquito breeding areas.

MetLink - Royal Meteorological Society
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