Open Forum
New Delhi, 22 September 2017
Urban Floods
COMMON GLOBAL CRISIS
By Dr S. Saraswathi
(Former Director, ICSSR, New Delhi)
Mumbai, Chennai, Bangalore or Delhi -- urban
flooding has become a common recurring factor in pre-monsoon and monsoon
periods thus providing flood news throughout the year. It is no consolation to
read worse reports of heavy flooding even in Florida or Texas in the most
advanced nation, the US. Comrades in distress cannot afford to stop with sharing
their bitter experiences, but should pool
their tested strategies to restrain urban flooding which has become
an inevitable global phenomenon in recent decades.
A global analysis based on an exhaustive
study of river systems across 160 countries shows signs of changes in stream-flow patterns causing
intense flooding in cities and smaller catchments and drying up of countryside.
Intense rainfalls overwhelm infrastructure, however expanded and modernized, and
cause frequent urban flooding.
Climate studies, on the other hand, have
found that climate change caused by global warming is the major reason behind
heavy rainfall and extreme weather conditions and climate events with changes
in frequency, intensity, spatial extent, duration, and timing.
A projection by the UN State of World
Population indicates that by 2030, over 50 per cent of the total world
population will be residing in urban areas. Asia is said to be fastest in
urbanisation where population in cities which was 37 per cent of the total is
likely to grow as 50 per cent by 2025. World Bank reports that five countries --
India, China, Indonesia, Nigeria, and the US will lead this surge and India would see fastest
growth of urban population.
India’s urban population constituted 10.8 per
cent of the total population in 1901 and increased to 31.1 per cent in 2011. In
the decade between 2001 and 2011, the growth was nearly 4 per cent. The
increase is due both to expansion of existing cities as well as growth of new
cities and towns.
The term “urbanisation”, technical definition
apart, raises different images of transformation of villages into cities. The
process of urbanisation that can contribute to urban floods involves human
intervention in natural environment. It includes man-made modifications of
natural landscape in which paving and building is an important part. In this
process, the natural soil, which can absorb water, is removed. Extremely clean
and well-laid concrete roads constructed in cities of western countries are highly
attractive and manifest affluence of the place, but they hardly provide a shield against flood. They cannot
swallow rainwater which the old rugged rural roads can easily do. There is a
direct correlation between increasing urbanisation with paved and impervious roads
and flooding of cities by rain.
Concretisation of roads is a luxury in India,
but use of asphalt and cementing of
pavements with slabs are common. If well-laid roads can cause flood, one can
imagine what would be the effect of deliberate drying up of ponds and canals to
raise high rise buildings for residential, commercial, and administrative
purposes. Urbanisation in catchment areas can actually induce flood where there
was previously no such possibility. Much worse is conversion of river beds and
canal banks as garbage dumping sites reducing space for natural water flow.
Demand for housing due to continuous
migration from rural areas has led to enormous growth in building construction
at any available space. Rapid urbanisation increases the extent of flooded area
and water depth even with no change in the quantum of rainfall. Correlation
between urbanisation and urban flooding being a proven fact since 1970s, urban
flooding everywhere has become a
separate theme for identifying time-specific causes, impact assessments, and
required remedial measures.
There is rapid rise in urban flooding in the
past 15 years which itself is
illustration of potential ill effects of green-house induced climate
change. Many Indian cities seem to be vulnerable to flooding.
Three
main factors are behind urban
flooding – meteorological resulting from
weather factors like heavy rainfalls;
hydrological depending on presence or absence of overbank flow channel networks
and occurrence of high tides impeding drainage;
and deliberate human
interventions like changes made in
land-use pattern and rapid urbanisation without sufficient
infrastructure. In the first two
also, human activity is indirectly present. Some problems are common whether it
is Houston or Chennai.
India has many companions in Asia in
promoting urban flooding. The number of cities in China affected by floods has
more than doubled since 2008 despite the fact that major rivers have remained stable. In 2003, over 200 cities in China were
swamped at some point due to urban sprawl that took place faster than
construction of drainage. The massive flood in Yangtzi River in the late 1990s
was initially considered a rural problem overlooking the
urban factor that was present even at that time.
The importance of urban drainage was lost in
the concentration placed on concretisation of urban land. Construction of dams
to store water from national and international rivers received priority and changing the natural course of
water and introducing diversions became part of development. As a result, rainfall
for just two to three hours is enough to flood many roads in urban China.
Chinese cities have expanded rapidly some of
them directly on flood plains. Reclamation of rivers and lakes for development
projects has gone on vigorously. There are over 150 sunken underpasses in
Beijing alone inviting flood after even moderate rain.
Countries most prone to urban flooding
include low-lying Netherlands, Surinam, Bahrain, Gibralter and Hong Kong. In
South Africa, flooding of urban areas has become a regular geographical event
every year. Low-lying Jakarta in Indonesia, where a number of rivers and canals
cross, is described in a study as presenting a “never endless” history of
floods. The Philippines exposes flaws in urban planning.
On top of all, hundreds of cities in the US have faced severe flooding and
still face flood threats. The list of
vulnerable cities includes New York, Boston, Chicago, Detroit, San Francisco,
Miami besides whole States in southern US.
The recent Houston flood is said to be a design problem.
While flooding of Mumbai is a regular event,
flooding of Chennai in 2015 was a rare event for which the residents were
totally unprepared. It threatens to become a regular event as urban expansion
is continuing vigorously while necessary infrastructure is hopelessly lagging
behind. Bangalore seems to follow
Chennai model of expansion.
Flood disaster in all these places is
man-made caused by unplanned urbanisation and unregulated encroachments.
Vertical growth of inner cities is disproportionate to the existing sewerage
and storm water drain network. Violation of building rules is common as
deviations are accepted as normal. It is hardly realised that the policy of
regularising irregular constructions amounts to inviting disasters.
AMRUT (Atal Mission for Rejuvenation and
Urban Transformation) has been launched in 2015 to improve urban infrastructure
in 81 cities in five states. It aims at enhancing basic infrastructure
including water supply and sewerage connections in the cities taking up urban
improvement as an integrated work. It is expected to eliminate the side effects
of rapid urbanisation. SMART city project is also going on vigorously. These
projects have to aim primarily at making cities liveable and free from
development-induced disasters like floods.---INFA
(Copyright, India
News & Feature Alliance)
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