von Tung Wai Kiong Derek (Mr) N/A Vor 9 Jahren
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Social Impacts refer to the effect of an event on the well-being of people.
Clean water supply may be disrupted due to damaged water pipes.
Sewage may also leak contaminated water supplies.
1) Injuries
People may be injured by objects and debris washed along by fast-moving floodwaters.
2) Spread of Diseases
When people are caught in the flood for a long period of time they may suffer from hypothermia.
Water supplies may be contaminated by chemical spills from factories. People who drink contaminated water may get cholera.
Stagnant water may cause mosquitoes to breed spreading malaria and dengue fever.
3) Loss of lives
Floodwaters may cause buildings to collapse killing people.
Floodwaters may cause damage to property or even sweep houses away.
People may have to go to emergency shelters and stay there for long periods of time while trying to rebuild their homes
Channel Improvement refers to changes made to the river channel or canal to increase its capacity to hold water or enable water to flow quickly.
River channels can be deepened or widened so that they can carry more storm water away.
Levess and Floodwalls are barriers against floods and protect development from floodwater.
Levees = raised river banks which can be natural or man-made.
Floodwalls = structures made of concrete (man-made)
Both levees and floodwalls are built higher thatn the floodplain and rivers so that they can help keep floodwaters out.
Monitoring systems have to collect and analyze information before a forecast is made.
Monitoring in Singapore is done through water level sensors in canals and drains to get water level measurements at regular intervals. Cameras can also be installed to take photos of water levels.
Based on the information collected, areas that are likely to flood can be identified and flood warnings can be issued.
Cities have large populations. During emergencies, cities need to have a plan to evacuate large number of people in the shortest time possible.
Evacuation drills help people practice the steps to leave a place in a safe and orderly manner.
The drills create awareness and reduce panic during a flood
Regulation refers to a rule or a law enforced by an authority and which states how something should be done.
Elevated properties = raised properties to a certain height. (Eg. Slopes / Steps)
Minimum platform level in Singapore is 300mm if that area has no history of flooding.
Minimum platform level in Singapore is 600mm if that area has history of flooding.
Zoning is the planning of physical development of land and its uses. (Eg. Residential, Industrial, Commercial, Recreational)
Flood-prone areas are zoned low-value developments. It does not cost much to develop and has activities that bring in less income. (Eg. parks , fields)
Economic Impacts refer to the effect of an event on goods and services being produced, sold and bought.
Trucks are not able to transport gasoline from terminals to gas stations.
Disruption of energy supply can affect factories as they cannot produce goods.
Damaged power line may also affect factories as they cannot operate with lack of electricity.
This may result in loss of employment and income for individuals and companies.
Transport infrastructure refers to facilities such as roads and railway tracks.
Transport infrastructure can become impassable because they are submerged or damaged during a flood.
Cities have to spend alot of money repairing the damaged infrastructure.
People are unable to travel to work and tourist are discouraged from visiting the city leading to a reduction in productivity, employment and profits.
Floods can damage machinery and equipment as they are submerged by flood waters.
Factories are unable to operate at full capacity and suffer economic losses.
Companies may also lose profits and have to spend money buying new equipment.
People may also lose their jobs.
Floods are overflows of large amounts of water onto land that is normally dry.
Flash floods take place suddenly and last for a short period of time. Water levels rise quickly.
Causes of flash flood: heavy rainfall
Coastal and River floods can also cause flash floods. (Sudden rise in water level)
River floods occur when water in the river rises and overflows its banks.
Causes of river floods: snowmelt, heavy rainfall, dam failure.
Coastal floods occur in areas along the coast.
Coastal floods are caused by intense storms such as tropical storms and cyclones.
Causes of Coastal Floods: Storm Surges , Tsunamis
Example of man-made structures = dams, levees.
A dam/levee is a barrier across a river that helps to store water. Failure of such structures creates a sudden release of all the water into the rivers causing rivers to overflow its banks.
Storm Surge is a sudden rise in the sea level above normal high tide conditions.
When there is a storm, strong winds push water towards the coast and create huge waves.
Ice / snow forms in winter when temperatures are low. In spring, when temperatures are high, the ice/snow melts.
The melted ice/snow flow into rivers and increase the amount of water in the rivers.
If the river cannot contain the water from the melted snow/ice, it will overflow its banks flooding the surrounding area.
Characteristics of Rainfall
1) Rainfall Intensity: rate at which rain falls, measure in millimeters per hour.
2) Rainfall duration: how long the rainfall last.
3) Rainfall frequency: probability of occurrence of rainfall.
Note: Rainfall of high intensity, duration and frequency = high chance of flooding.
Sea level is the average height of the sea surface.
Cities that are located in low-lying areas (below the sea level) are more prone to floods.
Water bodies are significant accumulations of water. (Eg. Oceans, seas, lakes, rivers, reservoirs)
Cities that are located near water bodies or have a river running through them are more prone to floods.
Permeability refers to the ease of which water can infiltrate the ground.
Vegetated surfaces are more permeable unlike concrete surfaces which are impermeable.
More concrete surfaces leading to higher surface runoff when there is rain making cities more prone to floods.
Channel capacity refers to the volume of water that can be held in a channel or canal without overflowing.
Floods occur when there is too much rain and the capacity of the canal is exceeded.
Canals are important in cities as there are many concrete surfaces resulting in alot of surface runoff. The canals help to remove surface runoff from the city preventing floods.
