Ewidence Rewision (Flooding)

Question 1

A natural factor of flooding is rainfall. Substantiate this with examples.

Answer 1

✮ The highest rainfall intensity in Singapore recorded in Singapore since 1957 occured on 19 January 2004, when 81mm of rain fell in an hour.
✮ On 23 December 2011, 153mm of rainfall was recorded over 3 hours in Singapore and led to flash floods.

Question 2

A natural factor of flooding in temperate countries is snowmelt. Substantiate this with examples.

Answer 2

✮ Rapid snowmelt and continuous rain resulted in high water in the cities of Hagen and Schwerte in 2011.

Question 3

A natural factor of flooding is storm surges. Substantiate this with examples.

Answer 3

✮ Typhoon Usagi caused a storm surge in 2013.

Question 4

A human factor of flooding is failure of man-made structures.

Answer 4

✮ In August 1975, the Banqiao Dam failure in China resulted in flooding in downstream villages so 26, 000 people died. A further 204000 people died from the famine and diseases caused by floods
✮ In 2005, Hurricane Katrina hit New Orleans and caused the levees and floodwalls to fail. Major flooding took place and over 100, 000 homes and businesses were destroyed.

Question 5

Height of land above sea level determines how likely a place will flood. Substantiate this with examples.

Answer 5

✮ Some cities in the Netherlands such as Amsterdam, Rotterdam and The Hague lie several metres below sea level and are prone to floods.
✮ However, flood mitigation measures have helped to reduce the likelihood of floods there.

Question 6

Proximity to water bodies determines how likely a place will flood. Substantiate this with examples.

Answer 6

✮ Manila, Philippines, which lies at the mouth of Pasig River, is more to prone to floods than other cities who are further away from the river.

Question 7

Channel capacity determines how likely a place will flood. Substantiate this with examples.

Answer 7

✮ In September 2013, the channel capacity of Sungei Pandan Kechil, a canal along Ayer Rajah Expressway in Singapore, could not cope with the runoff from heavy rainfall, leading to flash floods.
✮ Hence, in November 2013, PUB announced that it would start work on 36 projects to improve Singapore’s drainage system in the following 12 months on top of 170 ongoing projects.

Question 8

Flooding causes injuries, spread of diseases and loss of lives. Substantiate this with examples.

Answer 8

✮ In the United States in 2013, there were 60 fatalities and 25 injuries due to flash floods, and 22 fatalities and 8 injuries due to river floods.

Question 9

Flooding causes homelessness. Substantiate this with examples.

Answer 9

✮ Nearly 1.5 million people in New Orleans were displaced or left homeless by Hurricane Katrina in 2005. Emergency shelters and trailer parks had to be set up for flood victims.
✮ The severe property damage was caused by floodwaters and strong winds brought about by the hurricane.

Question 10

Flooding causes a disruption to clean water supply. Substantiate this with examples.

Answer 10

✮ From July-September 2010, Pakistan experienced very heavy rainfall. It resulted in floods that affected >20 million people- the worst since 1929. The floods destroyed houses, submerged farmland and damaged infrastructure in urban and rural areas.
✮ Water supply and sanitation facilities in affected areas incurred US$38 million worth of damages. These include damages to pump houses, storage tanks and water pipes.
✮ Hence, water supply was disrupted in many areas.

Question 11

Flooding causes damage to machinery and equipment. Substantiate this with examples.

Answer 11

✮ In 2011, the Thailand floods caused about a $3 billion loss in productivity and in damage to machinery to the manufacturing industry, damage that was highly extensive

Question 12

Flooding causes damage to transport infrastructure. Substantiate this with examples.

Answer 12

✮ In August 2014, heavy rain hit parts of Serbia and Bosnia, causing floods that destroyed roads and bridges in both countries, slowing down rescue and relief workers trying to reach the affected areas.

Question 13

Flooding causes disruption to the energy supply. Substantiate this with examples.

Answer 13

✮ Downed power lines and debris block the road in the aftermath of Typhoon Haiyan on (10) November 2013 in Tacloban, Philippines.

Question 14

Zoning can be used to reduce the effects of floods. Substantiate this with examples.

Answer 14

✮ Areas near Minnesota River which are prone to floods are used for low-value developments such as the Minnesota Valley National Wildlife Refuge and parks.
✮ Beyond the zone of low-value developments is the zone of industrial areas. Residential zones are located furthest away from the river so houses may be safe from floods.

Question 15

Elevating properties can be used to prevent floods. Substantiate this with examples.

Answer 15

✮ In Singapore, in areas with no flood history, the minimum platform level (MPL) is 300mm above ground level.
✮ In areas which have experienced floods, the MPL is 600mm above the highest recorded flood level.
✮ An existing development can meet the MPL requirement by building a slope or a series of steps.

Question 16

Levees and floodwalls can be erected to prevent floods. Substantiate this with examples.

Answer 16

✮ In Sacramento, United States, the Sacramento River flows south and drains into San Francisco Bay. Starting in the 1870s, several kilometres of levees have been built along Sacramento River to protect the surrounding land from flood.

Question 17

Channels can be improved to prevent flooding. Substantiate this with examples.

Answer 17

✮ In Singapore, a section of Bukit Timah Canal was also widened and deepened to increase the channel capacity in March 2013.

Question 18

Forecasting and warning systems can be put in place to mitigate the effects of flooding. Substantiate this with examples.

Answer 18

✮ In Singapore, water level sensors are placed in canals and drains to gather data about the changing water levels at regular intervals.
✮ The sensors can be equipped with cameras to take photographs of the situation in canals.
✮ Monitoring of the tides and weather conditions is also carried out daily with the aid of equipment.
✮ As of 2014, PUB has more than 170 water level sensors located around Singapore

Question 19

Evacuation drills can help to mitigate the effects of flooding. Substantiate this with examples.

Answer 19

✮ An evacuation drill was held in Marulas, Valenzuela City, Philippines on 14 June 2013.
✮ In 2013, a flood catastrophe exercise was held in Britain to test Britain’s emergency services. It involved 10000 people from the police to prison officers and equipment from helicopters to hospitals.

Question 20

Permeability of surface cover, evidences:

Answer 20

Nothing! “5” for you!