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Why are these cities more prone to floods? (Channel capacity (City's…
Why are these cities more prone to floods?
Height of land above sea level
Sea level
refer to
mean
sea level
mean sea level
avg height
of sea surface at a site over a
long
period of time
mid pt
btwn mean low tide and mean high tide
Cities located on
low-lying lands
, esp those
below sea level
,more prone to floods
E.g. Amsterdam, Netherlands
lie
several m below
sea levels
Flood mitigation
have helped
reduce
likelihood of floods in these cities
Proximity to water bodies
Water bodies
r sig accumulations of water
such as oceans, seas, rivers, lakes & reservoirs
Cities located
near water bodies
, such as
coastal cities
or cities wif a
river
running thru
E.g. Manila, Philippines
lies at the
mouth
of the
Pasig river
flows thru
centre
of Manila, connects Laguna de Bay to Manila Bay
city's
proximity
to river makes it more prone to
river floods
Permeability of surface cover
Permeability
refers to the
ease
wif which water can
infiltrate or seep
into the ground.
Concrete surfaces
impermeable
water is
unable
to infiltrate into ground
Leads to
↑ surface runoff
, ↑ likelihood of floods
Vegetated surfaces
more
permeable
allow water to
infiltrate
ground more
easily
As cities expand, natural vegetation may be
removed
and
replaced
wif concrete
↑ in surface runoff
in a rain event bc concrete surfaces are
impermeable
Cities wif
↑ proportion of impermeable surfaces
may be more prone to floods
Channel capacity
Refers to
vol of water
that can be
held
in the
channel
of a river or canal
w/o overflowing
Floods may occur when there is
too much rain
& capacity of channel is
exceeded
E.g. Sungei Pandan Kechil, SG
channel capacity could :red_cross: cope wif
runoff
frm heavy rainfall
lead to
flash flood
City's ability to drain water away
quickly
is v. imp bc it has a
↑ proportion
of built up areas
Concrete areas
in built up areas
impermeable
↑ amounts
of surface runof during rain event
network of canals
is built to
remove
surface runoff
canals and river must
cope
wif
↑ surface runoff
or flood will occur
Cities wif
better network of canals & river
, wld be able to drain surface runoff
faster
↓ likelihood
of floods
impt to ensure channels r
well-maintained
so that they can function at their
best
E.g. PUB, SG
improve
SG
drainage system
against heavy rain & floods
drainage works
and
widening
and
deepening
of major canals
(Rochor)