Flooding Flashcards

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1
Q

What are Floods

A

Floods are natural disasters caused by the overflow of water from its normal course, which leads to submerging of land
Floods can happen anywhere in the world and can range in size from local to regional and even continental scales.
It can happen due to weather and climate

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2
Q

Situations where flooding can occur

A

Weather related flooding - This type of flooding occurs due to heavy rainfall or snowmelt, causing rivers, streams and other bodies of water to overflow their banks
Coastal flooding - This type of flooding occurs due to storms or hurricanes, causing a surge of water to inundate coastal areas
Climate Change - Climate change is causing sea levels to rise, which can exacerbate coastal flooding. Climate change can also affect the frequency and intensity of extreme weather event, such as heavy rainfall

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3
Q

Why does flooding occur

A
  1. Heavy rainfall is the simplest cause of flooding. When there is too much rain or it happens too fast, there just isn’t a place for it to go. This can result in floods like flash flooding
  2. Storm surge and tsunamis also cause flooding. Storm surges from hurricanes and other tropical systems can cause sea levels to rise and cover normally dry coastal areas in several feet of water. Tsunamis on the other hand are giant waves caused by earthquakes or underwater volcanic eruptions. As these waves move inland, they build height and can push a lot of water inland in coastal areas
  3. Channels with steep banks are also to blame for flooding. Flooding often occurs when there is fast runoff into lakes, rivers and other channels that feature steep sides
  4. Lack of vegetation can cause flooding. Vegetation can help slow runoff and prevent flooding. When there is a lack of vegetation, there is little to stop water from running off and overflowing riverbanks and stems. Very typical in urban areas
  5. Melting snow and ice is another common reason for flooding. When a large amount of snow and/or ice melts quickly, it doesn’t have somewhere to go except low-lying areas
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4
Q

What are the economic impacts of flooding

A
  1. Damage to machinery and equipment
    - Machinery and equipment may be submerged or damaged by floodwaters
    - As a result, factories are unable to operate, and this causes them to suffer economic losses
    - Companies may lose profits and have to spend money buying equipment
  2. Damage to transport infrastructure
    - Transport infrastructure may be submerged or damaged by floodwaters
    - As a result, people are unable to travel to work and tourists may not want to visit this area
    - This causes an overall reduction in productivity, employment and profits
  3. Disruption to energy supply
    - During a flood power lines may be damaged. This causes power outage to occur and leads to the lack of electricity
    - As a result, companies and factories are unable to operate. This leads to the loss of employment and income for individuals and companies
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5
Q

What are the Social Impacts of Flooding

A
  1. Injuries and loss of lives
    - Fast moving floods waters can cause buildings to collapse
    - Objects and debris are also washed along by fast-moving water
    - As a result, people and livestock are swept away and it can cause injuries and deaths
    - People may get caught in the flood for too long, it can cause people to suffer from hypothermia
    - People can also drown if the water levels get very high
  2. Affects emotional and mental health
    - Loss of homes or livestock due to floods can cause mental stress to people
    - Loss of loved ones or family members during a flood can cause emotional distress to flood victims
  3. Spread of diseases
    - During a flood, water supplies may be contaminated by chemical spills, this cause people to be exposed to contaminated drinking water which results in the spread of cholera and dysentery
    - Stagnant pool of floodwater encourage mosquitoes to breed and this leads to more cases of malaria and dengue fever
  4. Homelessness
    - Floodwaters can damage property and sweep houses away. This can cause people to lose their homes and be displaced and have to evacuate to emergency shelters
  5. Disruption to clean water supply
    - Floodwaters can damage waterpipes and this can cause disruption to water supply
    - Water supply may also be contaminated due to burst sewage pipes
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6
Q

Explain Forecasting and Warning systems as a preparedness measure

A

Water levels in river channels and canals, tide levels in seas and surrounding weather conditions are monitored regularly using manual monitoring systems and technology

The information collected is then analysed to make a flood forecast on the areas that are likely to be flooded

Subsequently, flood warnings are issued to the public via social media, television, and radio so that people can take necessary precautions in advance

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7
Q

Explain the Advantages and Disadvantages of Forecast Warning systems

A

Advantage: This provide useful information so that there is time for people to take action to minimise flood damage
Disadvantage: However, some cities may not have the expertise and technology to collect accurate data and are unable to make accurate flood forecasts

Named Example: Singapore
Water level sensors are placed in canals and drains to gather data about the changing water levels at regular intervals

Weather instruments are used to monitor the tides and weather conditions on a daily basis

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8
Q

Explain the evacuation drill as a preparedness measure

A

A form of preparedness measure where people practise the steps to leave a place in a safe and orderly manner during an emergency

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9
Q

Explain the Advantages and Disadvantages of the evacuation drill

A

Advantage: It involves people moving to safe locations by following instructions given by trained personnel and practising first aid. It creates awareness among the people and reduces panic during a flood event. It will enable the government to improve their flood evacuation plans
Disadvantage: However, limited participation from the public will reduce the effectiveness of the city’s evacuation plan

Example: Singapore
Public Utilities Board has provided a public advisory on what pedestrians, motorists, residents and business owners can do in the event of a flash flood

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10
Q

Explain Land Zoning as a Mitigation Measure

A

Zoning laws specify the areas where residential, industrial, commercial or recreational activities may take place. Flood-prone areas are often zoned as low-value developments such as parks and fields for recreational activities so that fewer economic losses will be incurred in the event of floods

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11
Q

Explain the Advantages and Disadvantages of Land Zoning

A

Advantage: It creates space for green areas such as parks and fields which help reduce the impact of flood damage
Disadvantage: However, zoning may limit the development of available land because only certain uses are permitted. It is also difficult to carry out because of competing land uses and people may not abide by the recommended land use

Example: Eagan City in Minnesota, USA. Areas near the flood-prone Minnesota River are used for low-value developments such as the Minnesota Valley National Wildlife Refuge and parks.

industrial zones and residential zones are located further away from the river so that factories and houses may be safe from floods

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12
Q

Explain Elevating Properties as a Mitigation measure

A

Properties are elevated or raised to a certain height to prevent floodwaters from entering properties during a flood event

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13
Q

What are the advantages and disadvantages of Elevating Properties

A

Advantage: Properties are protected from flood water up to a certain height
Disadvantage: However, it is challenging to implement because of the increased cost of development. The appearance or access to building may be badly affect. Floodwater may exceed the minimum height at which properties are raised

Example: Manila, Philippines
Some residents lift their houses far above sidewalk level to delay the entrance of floodwaters. They also build upward, adding additional floors to their homes, though this requires a strong foundation

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14
Q

What is the background of flooding in Singapore

A

High rainfall and dense urbanisation in 1970s and 1980s
High tides and low-lying coastal areas
Singapore has made many efforts since 1960s to build an effective storm drainage network
Prone to flash flood - A flood which follows within a few hours of heavy or excessive rainfall, dam or levee failure

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15
Q

What were the physical conditions affecting drainage in Singapore

A

Flatlands with low lying coastal areas
Affected by high tides
Increase storm water runoff from urbanisation
Climate Conditions - Average annual rainfall: 2350mm

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16
Q

What were the impacts of flooding in Singapore

A

Damage to properties and loss of lives
June 2010, Orchard Road, Bukit Timah, 100millimeters of rain in 2 hours
Floodwaters up to 30cm deep
100 shops and 48 vehicles damages along Orchard Road
868 insurance claims ensued totalling 23 million dollars

17
Q

Explain Elevated properties as a strategy to manage flooding in SIngapore

A

Properties are elevated or raised to a certain height to prevent floodwaters from entering properties during a flood event
In Singapore, the Minimum Platform Level is imposed on the new and existing development. A series of slopes and steps are built to meet MPL requirements
In areas with history of flooding will have an MPL of 600mm or otherwise 300mm

18
Q

Explain the benefits and challenges of Elevated Properties in Singapore

A

Benefits: Properties are protected against floods
Challenges: Challenging to implement because of increased cost. May have insufficient resources to develop the area to the MPL. The flood may exceed 600mm and still lead to damage of properties

19
Q

Explain Channel Improvement as a strategy to manage flooding in Singapore

A

Changes made to the river channel to increase its capacity to hold water or to enable the water to flow quickly
River channels and canals can be widened and deepened so that they can carry more storm water away
This prevents water from flooding or overflowing
A section of Bukit Timah canal was widened and deepened to increase channel capacity

20
Q

Explain the benefits and challenges of Channel improvement to manage flooding in Singapore

A

Benefits: Make it possible for moderate value and high value developments to take place on the land adjacent to river channels and canals
Challenges: May create a problem upstream or downstream of the improved area

21
Q

Explain the SMS Alert System as a strategy to manage flooding in Singapore

A

This system allows information on water levels in drains and heavy rainfall to be available to the public
Each subscriber receives alerts triggered from water sensors located along drains and canals
Example: Stamford Canal, which runs through Orchard Road, has 7 water sensors. When it rains, the sensors monitor water levels every 2 minutes. When water levels hit the 75% mark or 90% mark, the sensors will trigger the sending of an SMS alert to subscribers

22
Q

Explain the benefits and challenging of the SMS alert system in Singapore

A

Benefits: Allow users to prepare in advance
Challenges: Only activated to send out alerts when water sensors along the drains and canals in areas susceptible to floods reach the 75% to 90% mark. By the time the SMS alert service is activated, it might be too late for members of the public to be too later for members of the public to be prepared for the flash floods
Can only subscribe to 1 location

23
Q

What is the Current Situation regarding flooding in Singapore

A

In April 2020, PUB was appointed the national coastal protection agency to lead, coordinate and explore whole-of-government efforts to protect Singapore’s coastlines
Mean sea level around Singapore is projected to rise up to 1m by 2100
Sea levels could rise up to 4m or 5m if we take into account the compounding effects of mean sea level rise of 1m and phenomena such as:
Daily tidal activity (high tides and low tides occur twice daily)
Storm Surges. On average, Singapore experiences 2 to 4 storm surges each year
Land Subsidence due to plate tectonic movements

24
Q

How will climate change and rising sea levels affect you

A

If we ignore climate change and the threat of sea level rise, Singaporeans could face devastating consequences in the future
Iconic landmarks in coastal areas such as East Coast Park and Changi Beach Park could be flooded
Essential services, including transport networks, could be affected

25
Q

How exactly are we combatting the threats of Rising Sea Levels

A

To cater for long-term sea level rise, the minimum land reclamation level in Singapore was raised from 3m to 4m above the Singapore Height Datum in 2011

About 70% of Singapore’s coastline has been protected against coastal erosion by measures such as concrete seawalls and rock revetments.
Mangroves, coral reefs, rocky shores, and seagrass meadows, can complement man-made solutions in protecting out coastlines

Besides helping to dissipate wave energy at the coastlines and prevent coastal erosion brought about by storm surges and rising sea levels, they can also help to enhance biodiversity and create a better living environment