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How Should Cities Prepare For Floods - Coggle Diagram
How Should Cities Prepare For Floods
Introduction
Cities use a range of mitigation measures to reduce the impact of floods and prevent floods from occurring, such as regulation, investment in infrastructure, and disaster preparedness
To be successful in reducing flood risk, cities need to adopt an integrated flood management approach that involves a combination of mitigation measures. Such an integrated approach would also take into consideration each city's unique characteristics
Regulation
Zoning
A way in which the government plans the physical development of the land and its uses; zoning laws often specify the areas where different activities such as 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; they generally do not cost as much to develop and has activities that bring less income. With the use of zoning, cities are likely to suffer fewer economic losses in the event of floods
E.g. Minnesota, USA and Cologne, Germany
While it is advisable to zone flood-prone areas for activities that will not be as heavily impacted by floods, there is also a need to maximize profits, making the task of zoning difficult
Benefits: Creates green spaces (like parks and fields) which help reduce the impact of flood damage
Challenges: May limit the development of available land as only certain land uses are permitted, also difficult to carry out due to competing land uses and because people might not abide by the recommended land use
Elevated Properties
To reduce the impact of floods by elevating and raising properties to a certain height (e.g. Minimum Platform Level (MPL) in Singapore, can be revised when there are changes to the highest recorded flood level in an area)
Benefits: Developments are protected against floods up to the height of the MPL
Challenges: MPL might be challenging to implement as it increases the cost of development
A rule or a law enforced by an authority which states how something should be done. Examples of regulations include zoning and elevating properties
Investment in Infrastructure
Development of floodwalls and levees
Barriers against floods, protect development from floodwater
Levees are raised river banks which can be natural (made of mud) or man-made
Floodwalls are man-made structures made of concrete
Both are built higher than the floodplains and rivers to keep out floodwater
Flood prone cities, such as Hereford, UK and Sacramento, USA, may build levees and floodwalls to prevent river flooding
Benefits: It is cheaper to build floodwalls and levees to mitigate and prevent floods than to raise the height of the surrounding land
Challenges: Regular maintenance is required to ensure that the levees and floodwalls are strong enough to hold back floodwater, levees and floodwalls are designed to prevent floods up to a certain level; they are unable to prevent floods beyond that level
Channel improvement
Changes made to the river channel or canal 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
They can also be straightened so that water can be carried away quickly
To prevent water in the river channel and canals from overflowing (e.g. in Singapore, a section of the Bukit Timah Canal was widened and deepened to increse the channel capacity)
However, there is a limit to the changes that can be made to river channels and canals
Difficult to carry out when the land next to the river channels and canals is already used for other purposes
A city also needs to improve its network of river channels and canals if channel improvement is to be effective in mitigating floods
Benefits: Channel improvement makes it possible for moderate-value and high-value developments to take place on the land adjacent to river channels and canals
Challenges: Channel improvement may create problems for areas upstream or downstream of the improved area
Disaster Preparedness
Evacuation drills
Cities need to have a plan to evacuate a large number of people in the shortest period of time
Form of preparedness measure where people practice the steps to leave a place in a safe and orderly way during an emergency
Creates awareness amongst the people and reduce panic during a flood event
Involve people moving to safe locations, following instructions given by trained personnel, and practicing first aid
PUB, Singapore's national water agency, has provided a public advisory on what pedestrians, motorists, residents, and business owners can do during a flash flood (to save lives and reduce damages to properties during a flood)
Benefits: People are educated on what to do when a flood warning is received, cities will be able to improve their flood evacuation plans
Challenges: Limited participation reduces effectiveness of the drills
Forecasting System
May be put in place to reduce flood risks (forecasting and warning system)
Needs monitoring (systematic process of collecting and analyzing information to identify changes) for accuracy
A forecast, which is a statement about the way things will happen in the future, is made based on the information collected. A warning needs to be issued if the situation is serious
Monitoring: Water levels in canals, drains, and river channels; Tide levels in the seas; Weather conditions
Forecasting: Flood events, weather forecast
Can be done with: water level sensors equipped with cameras to take photographs of the situations, equipment to monitor tides and weather conidtions daily, manual monitoring systems as well as technology (remote sensing techniques, geographic information systems (GIS) to map flood-prone areas for close monitoring) in flood monitoring and forecasting
Flood forecasting can be made to identify the likely flood areas affected by a flood event
Following this, a decision would be made if flood warnings should be issued to the public
Benefits: A forecasting and warning system provides useful information so that there is time for people to take action to minimize flood damage
Challenges: Cities may not have the required expertise and technology (accurate data and flood forecasts)
Cities can take further steps to reduce the harm caused by floods; being warned of possible floods is important in reducing the flood impact, and people can also be trained to be prepared and to know what to do when a flood occurs