Flooding Flashcards
What are Floods
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
Situations where flooding can occur
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
Why does flooding occur
- 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
- 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
- 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
- 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
- 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
What are the economic impacts of flooding
- 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 - 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 - 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
What are the Social Impacts of Flooding
- 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 - 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 - 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 - 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 - 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
Explain Forecasting and Warning systems as a preparedness measure
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
Explain the Advantages and Disadvantages of Forecast Warning systems
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
Explain the evacuation drill as a preparedness measure
A form of preparedness measure where people practise the steps to leave a place in a safe and orderly manner during an emergency
Explain the Advantages and Disadvantages of the evacuation drill
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
Explain Land Zoning as a Mitigation Measure
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
Explain the Advantages and Disadvantages of Land Zoning
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
Explain Elevating Properties as a Mitigation measure
Properties are elevated or raised to a certain height to prevent floodwaters from entering properties during a flood event
What are the advantages and disadvantages of Elevating Properties
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
What is the background of flooding in Singapore
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
What were the physical conditions affecting drainage in Singapore
Flatlands with low lying coastal areas
Affected by high tides
Increase storm water runoff from urbanisation
Climate Conditions - Average annual rainfall: 2350mm