Lesson 8

Question 1

What is Groundwater flooding?

Answer 1

Flooding that occurs after the ground has become saturated from prolonged heavy rainfall.

Question 2

What is Flash flooding?

Answer 2

A flood with an exceptionally short lag time - often minutes or hours.

Question 3

What is a Jokulhlaup?

Answer 3

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

Question 4

What is Surface water flooding?

Answer 4

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

Question 5

Why is fresh water flooding a problem?

Answer 5

Freshwater flooding affects over one third of the world’s land area, especially on the floodplains of rivers. In addition to a number of meteorological causes of flooding, human actions can also increase the flood risk by altering physical factors.

Question 6

What meteorological factors cause flooding?

Answer 6

Flash flooding in Sardina Island 2013
River flooding in UK
Monsoon

Question 7

What are the impacts of flash flooding in Sardina Island 2013? (4)

Answer 7

18 deaths
$1.14 billion in damage
Thunderstorms resulted in flash floods
Prolonged rainfall caused a series of mid latitude depressions over the same place which caused river flooding.

Question 8

What are the impacts of River flooding in UK? (2)

Answer 8

Mid latitude depressions brings 2 bands of rain.
Ground absorbed some water at start but through flow and groundwater can’t transfer water quick enough as it becomes saturated.

Question 9

What are the impacts of Monsoon? (5)

Answer 9

Seasonal changes in prevailing winds.
India and SE Asia very heavy rain fall.
Moist air from SW Indian Ocean flows over India and Bangladesh bringing a humid climate.
July 2015
103 deaths 
1 million effected

Question 10

What are the circular lines on a synoptic weather chart and what do they show?

Answer 10

Isobars, show lines of equal pressure measured in Millibar (Mb).

Question 11

What do the H and L mean on a synoptic weather chart and what do they show?

Answer 11

High and Low pressure. They show how much pressure is in Millibars

Question 12

What is the difference between the way warm and cold fronts are presented?

Answer 12

A warm front is shown with a red line and red semi-circles and a cold front with a blue line and blue triangles.

Question 13

What is weather like around a cold front?

Answer 13

Cold air follows a cold front resulting in fair weather

Question 14

What is weather like around a warm front?

Answer 14

Warm air follows a warm front resulting in moist air masses rising above cold air masses as it condenses to form clouds bringing rainy weather

Question 15

What does the occluded front mean on a synoptic weather chart and what does it show?

Answer 15

Cold fronts tend to move faster than warm fronts and over time they can catch up with each other and create an ‘occluded’ front. This is shown as a purple line with a purple semi-circle and triangle next to each other. The air trapped between a warm and cold front is called a ‘warm sector’ and we often see low cloud and patchy light rain associated with this type of air.

Question 16

What does a trough mean on a synoptic weather chart and what does it show?

Answer 16

Black lines that have no semi-circles or triangles are called ‘troughs’ and mark areas where the air is particularly unstable. We tend to see showers associated with this type of air.

Question 17

How does urbanisation cause flooding?

Answer 17

More impermeable surfaces increase surface run off into rivers. River lag times are shortened by urban drainage systems which aim to transfer water effectively into water courses so streets don’t flood. Underground channels are designed to divert water under infrastructure (reduce risk).

Question 18

How do floodplain drainage cause flooding?

Answer 18

Common in developed countries to provide land for agriculture and to expand urban areas. Drainage processes reduce the natural storage capacity of flood plains. The land may shrink when it dries out, more susceptible to flooding.

Question 19

How does flooding mis-management cause flooding?

Answer 19

Alteration at one point can cause further problems down stream. Hard engineering to reduce frequency and embankments to increase channel capacity but they may transfer the discharge to unprotected areas down stream.

Question 20

How does deforestation cause flooding?

Answer 20

Reduces interception and evaportranspiration resulting in greater surface run off so precipitation reaches rivers faster. Greater rates of erosion increase river sediment and deposition which reduces the capacity of water that can be transported by rivers.

Question 21

An example of where deforestation is causing flooding?

Answer 21

Nepal in Bangladesh

Question 22

Where is relief rainfall common?

Answer 22

UK

Question 23

When does relief rain fall occur?

Answer 23

When the prevailing wind picks up moisture from the sea and when it reaches the coast it rises over mountains and hills forcing it to cool and condense forming clouds. When forced over mountains it is forced to drop moister (rain). Once over the mountain, the air drops (warming). This gives it a greater ability to carry moisture so there is little rain for the other side of the mountain (Rain shadow).

Question 24

When does frontal rain fall occur?

Answer 24

When 2 air masses meet (one warm, one cold). The lighter warmer less dense air is forced to rise over the denser cooler air. Warm air starts to cool and condense forming clouds and bringing moderate rain fall (precipitation)

Question 25

When does convectional rain fall occur?

Answer 25

In high pressure areas as the sun heats the surface in the day which causes heat to rise. Heavy rainfall in afternoons. When heat rises it cools and condenses which forms clouds. Afternoon big clouds which have formed all day. Thunder clouds and large amounts of condensation occurs as rain is formed. Convection tends to produce towering cumulonimbus clouds which produce heavy rain with thunder and lightning

Question 26

Case studies for flooding? (3)

Answer 26

Monsoon rain Pakistan (2010-11)
Prolonged rainfall UK (2015-16)
Snow melt Bangladesh (2004 and 2007)

Question 27

Impacts of Monsoon rain Pakistan (2010-11)? (4)

Answer 27

Crops destroyed
1/5 of land flooded
schools danged
Live stock killed

Question 28

Impacts of Prolonged rainfall UK (2015-16)? (3)

Answer 28

16,000 properties flooded
3000 families put in alternative accommodation
Accountancy business KPMG lost £5 billion

Question 29

Impacts of Snow melt Bangladesh (2004 and 2007)? (4)

Answer 29

Over 1000 deaths.
crop land destroyed
10.5 mil people displaced
Water born diseases spread