Floods and global warming

It is distressing to hear that so many countries have been devastated by recent floods and mudslides causing deaths, loss of homes and property, crops, infrastructure and displacement of people

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[Floods]

*Sri Lanka
  Affected areas - Central, Northern,
  Eastern provinces
  Homeless people - Over 541,000
  persons were displaced
  No of deaths - 23
* Brazil
  Affected areas - Rio de Janeiro,
  San Paulo States
  No of homeless - 4,600
  No of deaths - 471
*Philippines
Affected areas - one third of provinces
No of homeless - 400,000
No of deaths - 42
*Australia
Affected areas - Three-fourth of Queensland State
No of affected - 200,000
No of deaths - 35

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Flooding in Sri Lanka has resulted in deaths of about 23 persons during a week of monsoon floods in the Central, Northern and Eastern provinces especially Batticaloa and Trincomalee once severely bitten by terrorism. Over 541,000 persons were displaced and had to take shelter in 275 camps set up by the Government, bringing the total number of displaced persons to about 1,081,000.
Sri Lanka depends on monsoon rains for purposes of irrigation and generation of power but the seasonal, relentless downpour caused deaths and damage to homes, crops and infrastructure in low-lying areas and mountainous regions.

Disaster zone

In Brazil, the heaviest rainfall in 44 years caused mudslides and floods that swept away homes, killing nearly 471 persons and leaving 4,600 homeless in Rio de Janeiro and San Paulo states.

Heavy floods left vast tracts of Queensland State under water. Picture courtesy: Google

In Philippines, 42 persons had been killed as a result of on-going torrential rains and landslides rendering about 400,000 homeless. About one-third of the Philippines' 80 provinces were reported to be affected. The damage to crops and infrastructure was estimated to be around one billion pesos (US $ 20 million).
Australia faced the most damaging floods in the State of Queensland including the capital city Brisbane. Nearly 70 towns and over 200,000 people were affected and the damage initially was assessed at Australian $ one billion. Three-fourth of the State of Queensland was declared a disaster zone. Over 35 persons were killed by the floods and nine persons were reported missing. The floods of Queensland wiped off billions of Australian dollars from the national GDP. Floods will also cost the supermarket chains tens of millions of dollars.

Flash flooding

The Queensland disaster was followed by floods in the Victorian State and more than 50 communities in Western and Central Victoria were affected as a result.
Prime Minister Julia Gillard has announced a plan to raise $ 5.6 billion for flood damage and to reconstruct Queensland by scrapping not-so-important capital expenditure projects and imposing a one-off 12-month flood levy that cuts in gently on incomes over $ 50,000 but rises steeply on incomes over $ 100,000. Floods are not always caused by heavy rainfall but by seawater flooding, tidal flooding, run-off rivers and dams and especially flash flooding due to defective and inadequate urban drainage.
It is true that floods have both negative and positive results. Floods can bring relief for people in drought-stricken areas whose crops and livestock are affected by shortage of water and can be a natural way for wetland regions, swamps and native waterways to survive.
They will also reduce high salt levels in lagoons and land-locked lakes.
The long history of floods shows that the largest known floods of the Quaternary Period (about 1.64 million years ago to the present) resulted from breaching dams formed by glaciers or landslides. The late-Pleistocene Missoula floods in the Pacific Northwestern United States were some of the largest ever to have occurred on earth. The Lake Bonneville flood of about 14,500 years ago resulted from nearly 5,000 cubic kilometres water spilling out of the Great Basin into the Snake River drainage.

Climate change

In general, larger river basins produce larger floods.
Floods mainly occur due to rainfall and some do occur due to snowmelt, rain-snowmelt and snowmelt/ice jam. Floods on large rivers from ice jams result from break-up jams in which dislodged river ice accumulates at river bends forcing bonding upstream and rapid release of water when the ice dams breach.
During the second half of the 20th Century, largest floods have occurred in Zaire (Congo River basin, Russia (Amur) and (Ob-Irtysh), Chad (Chari), Australia (Murray), Bangladesh (Ganges) and (Brahmaputra), Senegal (Senegal), Vietnam (Mekong) and Kazakhstan (Amu Darya).
The problem we face today is that most countries are obsessed with climate change, dryness brought about by global warming due to human activities which result in warm to hot temperatures, severe droughts and rising sea levels.
The belief that the earth would become increasingly parched has prompted most countries to impose water restrictions to conserve water.
Construction of dams across major rivers to store water for future use to ward off dry seasons consequent on less rainfall has made them almost dangerously full in times of torrential rains and flooding.
The recent floods clearly show the flawed notion of releasing water from the dams before they breach almost at the same time as flash flood waters enter the river system effectively contributing to the deluge.
This belief in anticipated droughts and parched land to which most countries cling on leads to building on areas normally subject to flooding which becomes almost the first easy target of rushing flood waters.
Nevertheless, it is hard to fix the blame on any government or institution for this highly complex natural disaster.
It is really a war against nature which, of course, has the power to override man and have its own way.
Courtesy - Daily News - Dr Mathu H Liyanage