Key idea: Surpluses within the hydrological cycle can lead to flooding, with significant impacts for people.

Key concepts:

Causality= the varying causes of flooding

Systems= how weather systems are linked to the causes of flooding

Resilience= the ability of places to respond to floods and their impacts

Groundwater flooding= Flooding that occurs after the ground has become saturated from prolonged heavy rainfall

Surface water flooding= Flooding that occurs when intense rainfall has insufficient time to infiltrate the soil, so flows overland.

Flash flooding= A flood with an exceptionally short lag time- often minutes or hours

Jokulhlaup= A type of glacial outburst flood that occurs when the dam containing a glacial lake fails

What causes meteorological flooding?

What meteorological

factors cause flooding?

The causes of meteorological flooding

Storms and flash flooding: Occasionally, dramatic floods occur following intense torrential storms.

These are called flash floods and are often associated in the UK with extreme rainfall events in

summer months. The intensity of the rainfall exceeds the capacity of the river to cope with the

amount of water- and flooding results. In September 2016, flash flooding caused travel chaos in the

UK, as thunderstorms deposited almost ½ a months rainfall in hours.

Monsoon rainfall: This occurs across South and Southeast Asia between May-September. In July,

2016, heavy monsoon rain in the Philippines led to flooding, landslides and evacuations in villages

just to the NW of the capital Manila.

Snowmelt: Flooding can occur when snow melts and the resulting water cannot infiltrate into the

soil or ground surface. In the winter of 2013, Norfolk police flooding caused by melting snow and ice,

after very mild, wet and windy weather caused rapid thawing.

Understanding weather synoptic charts

Do you know what the symbols on this chart mean and what weather is brought as a result?

As a group annotate your map with any understanding you may have.

Understanding weather synoptic charts

Watch the series of clips and examples from BBC Bitesize and the Met Officeadd annotations to your maps.Next: Using the information you have collected (you may visit the web sites again on your devices) complete the synoptic map worksheet.

Flooding - examples

For each of these examples, you need to read through the geo factsheet and

highlight the key points. You need to formulate notes in your book which helps

you to explain why the floods occurred in these places. Be sure where

applicable that you make sense of the synoptic chart that is shown.

1) Moonsoon Rain- Pakistan

2) Prolonged rainfall- UK

3) Snowmelt- Bangladesh

L11- To know the human causes of flooding and to understand the socio-economic effects of flooding

Human causes of flooding

In pairs discuss how humans

cause floodingUbanisation Deforestation

Floodplain drainageFlooding mis-management

Human causes of flooding

Task: Using the information cards: Write notes on the causes of flooding under the 4 main headings.

Ubanisation Deforestation

Floodplain drainageFlooding mis-management

Deforestation reduces interception and evapotranspiration,

resulting in greater volumes and rates of surface runoff, which

ensures that precipitation reaches river channels faster,

creating more flashy hydrographs. Furthermore, deforestation

and intensive crop-growing expose soil to greater rates of

erosion, increasing river sediment load and deposition within

channels: this reduces the capacity of the river to carry water

and increases the likelihood of flooding. Eg. deforestation in

Nepal and Tibet is known to be increasing the frequency and

magnitude of floods in Bangladesh from the Ganges and

Brahmaputra rivers.

Urbanisation causes a number of changes that also increase

flood risk. Eg, the expansion of impermeable surfaces such as

roads, roofs and patios increase the rate of the surface runoff

into rivers via the urban drainage system. River lag times are

shortened by urban drainage systems, which aim to transfer

water efficiently into watercourses so that streets do not flood

or have standing water. In addition, bridges and culverts -

underground channels designed to divert river water under

infrastructure such as roads - often reduce river capacity.

Floodplain drainage is common in developed countries to

provide land for agriculture and to expand urban areas. The

drainage process reduces the natural storage capacity of the

floodplain, especially where natural wetlands are lost. The

land may shrink as it dries out, getting lower and thus even

more susceptible to flooding.

Flood mismanagement - alterations at one point in a drainage

basin can cause negative consequences further downstream.

In most cases, flood management by hard engineering is

designed to reduce the frequency of floods. Hard engineering

includes the building of embankments (artificial levees) to

increase channel capacity, but it may simply operate by

transferring the discharge to unprotected areas or choke

(narrow) points downstream.

Effects of flooding- The UK

Watch the clips and note down in the effects of

flooding.

Effects of flooding- Pakistan

Effects of flooding

Using the information from the clips, write down the effects of flooding under

two headings. Use the PDF to help you add in any additional info.

Socio-economic

Environmental

Next to each effect you write about, in brackets put the case study/studies that

this relates to.

Exam question

With the help of figure 2, explain why the floods occurred in Pakistan in August 2010 (4 marks)

Exam question

With the help of figure 2, explain why the floods occurred in Pakistan in August 2010 (4 marks)

Exam question

Using examples, discuss the impact of flooding on people and the

environment (15 marks)

Resources:

Peer Assessment

The text must be used for marks to be awarded, There should be

reference to the intensity of the rain and the implications of this - with

reference to the impact on surface runoff and the speed the water

reached the river, the impact of the levees - increasing capacity but

also the scale of the flood, a problem exacerbated by the amount of

material being carried by the river, deforestation encourages rapid

runoff in the areas near the source and provides added sediment for

the channel, leading to reduced capacity. 4x1 or 2 x (1+1)

WWW

EBI

Peer Assessment

The text must be used for marks to be awarded, There should be

reference to the intensity of the rain and the implications of this - with

reference to the impact on surface runoff and the speed the water

reached the river, the impact of the levees - increasing capacity but

also the scale of the flood, a problem exacerbated by the amount of

material being carried by the river, deforestation encourages rapid

runoff in the areas near the source and provides added sediment for

the channel, leading to reduced capacity. 4x1 or 2 x (1+1)

WWW

EBI

Understanding synoptic weather chartsWhat are the circular lines and what

do they show?

What is an occluded front and what is

the weather like?

What do these symbols mean?

What do they H and L mean? What

are the numbers showing?

What is the weather like in a trough?

What are the weather like around the warm and cold

fronts?

Other key facts