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How should cities prepare for floods?

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by

Pengy Yen

on 1 March 2015

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Transcript of How should cities prepare for floods?

How should cities prepare for floods?
Mitigation measures used in Singapore and other cities
Zoning laws
planning the physical development of the land and its uses.
specify the areas where residential, industrial , commercial or recreational activities may take place.

high-value devt

low-value devt
costly devt and

not costly to dev
fetches high income

and brings in less income
Benefits
cities are likely to suffer less economic losses
creates green spaces to help reduce impacts of flood damage
Challenges
development is limited as only certain land uses are permitted
competition for land uses makes zoning difficult as people may not abide by the recommended land use
Regulation - Zoning
Disaster Preparedness -
forecasting and warning systems
Regulation
Investment in infrastructure
Preparedness measures

A zoning map of Eagan City, Minnesota, USA
buildings are built some distance away from the river
low-value devt such as a park
embankment along the Rhine River in Cologne, Germany
Regulation - Elevated properties
Singapore
No flood history - 300 mm above the adjacent road / ground level
Places which experienced flood - 600 mm above ground level
MPL is revised when there is changes to the highest recorded flood.
Imposed on new and existing developments
Investment in infrastructure - levees and floodwalls
Aims
barriers against floods
protects devt against floodwaters

Levees
Raised river banks (natural or man-made)
Floodwalls
man-made structures, made of concrete

Both levees and floodwalls are
built

higher than
the floodplains and rivers to keep out floodwaters

Benefits
cheaper as compared to raising height of the surrounding areas

Disadvantages
Regular maintenance needed, costly for poorer countries
Design of structure is meant to hold back floodwaters up to a certain height, difficult to predict a higher flood level
Raise or elevate properties to a certain height
Minimum platform level (MPL)
Will revised MPL when there are changes to the highest recorded flood
Levees
Floodwalls
Investment in infrastructure - Channel Improvement
Bt Timah Canal, Singapore
before and after expansion
close monitoring, systematic process of data collection and analysis
allow accurate forecast and issue warning

monitor water levels in river channels, canals, tide levels in seas and surrounding weather conditions
Flood events
weather forecast
how?
manual monitoring systems
technology such as GIS tools and remote sensing data
benefits
provides useful information so that there is time to take action and minimise flood damage

disadvantages
some cities do not have the expertise / technology / money to collect accurate data and make accurate forecast
Refers to changes made to the river channel / canal to
increase its capacity to hold water; or
enable the water to flow quickly

How?
widen and deepen the channel
straighten

Benefits
allows moderate or high value devt to take place on the land next to the river channel

Disadvantages
poses a problem for rivers in the downstream
costly
water level sensor in Singapore
Preparedness measures - evacuation drills
a plan to evacuate a large population in the shortest possible time
people practice the steps to leave a place in a safe and orderly manner during an emergency

benefits
people know what to do when a flood warning is received
allows cities to improve their evacuate plans

challenges
not everyone takes drills seriously
Full transcript