BY MOHAMMAD NUMAAN
India is experiencing a series of extreme rainfall events that have caused widespread destruction, landslides, flash floods and deaths in several parts of the country. The rainfall distribution and intensity have been influenced by various factors, such as the monsoon, the western disturbance, the El Nino-Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and climate change.
The heavy rainfall in North India is primarily due to the interaction between a western disturbance (a low-pressure system originating from the Mediterranean region) and the monsoon trough (a low-pressure zone along the monsoon wind belt). This interaction leads to intense rainfall over regions like Himachal Pradesh, Uttarakhand, Punjab, and Haryana.
Climate change can affect the rainfall in India by altering the temperature, humidity, pressure, wind and cloud patterns over various scales of time and space. Climate change can affect the monsoon by changing its onset, duration, intensity and spatial distribution. Some studies suggest that climate change can delay the onset of the monsoon by increasing the land-sea temperature contrast, which inhibits the northward movement of the monsoon winds. Climate change can advance the onset of the monsoon by increasing the SSTs over the Indian Ocean, which enhances the moisture supply to the atmosphere.
Several areas in Delhi are flooded even as the water levels of the Yamuna River, which rose to an all-time high on last Thursday, are slowly receding. Delhi government shut down schools, colleges, crematoriums, and even water treatment plants yesterday as water from the overflowing Yamuna flooded the national capital.
Punjab and Haryana have also been hit by the rains and are conducting relief work at a brisk pace. According to Haryana government figures, the death count in rain-related incidents has gone up to 16. Earlier, 10 deaths had been reported in the state and 11 from neighbouring Punjab. Authorities in the two states have stepped up relief operations as the weather improved over the past three days. Overall, 14 districts have been affected in Punjab and seven in Haryana.
Floods have also occurred in areas, which were earlier not considered flood prone. An effort has been made in these Guidelines to cover the entire gamut of Flood Management. Eighty per cent of the precipitation takes place in the monsoon months from June to September. The rivers bring heavy sediment load from catchments. These, coupled with inadequate carrying capacity of rivers are responsible for causing floods, drainage congestion and erosion of river-banks. Cyclones, cyclonic circulations and cloud bursts cause flash floods and lead to huge losses. It is a fact that some of the rivers causing damage in India originate in neighboring countries; adding another complex dimension to the problem. Continuing and large-scale loss of lives and damage to public and private property due to floods indicate that we are still to develop an effective response to floods.
The World Meteorological Organisation (WMO, 1976) uses the term ‘Tropical Cyclone’ to cover weather systems in which winds exceed ‘Gale Force’ (minimum of 34 knots or 63 kph). Tropical cyclones are the progeny of ocean and atmosphere, powered by the heat from the sea; and driven by easterly trades and temperate westerlies, high planetary winds and their own fierce energy.
Tropical cyclones occur in the months of May-June and October-November. Cyclones of severe intensity and frequency in the North Indian Ocean are bi-modal in character, with their primary peak in November and secondary peak in May. The disaster potential is particularly high during landfall in the North Indian Ocean (Bay of Bengal and the Arabian Sea) due to the accompanying destructive wind, storm surges and torrential rainfall. Of these, storm surges cause the most damage as sea water inundates low lying areas of coastal regions and causes heavy floods, erodes beaches and embankments, destroys vegetation and reduces soil fertility.
India has the highest mountain chain on earth, the Himalayas, which are formed due to collision of Indian and Eurasian plate, the northward movement of the Indian plate towards China causes continuous stress on the rocks rendering them friable, weak and prone to landslides and earthquakes.
The slow motion of the Indian crust, about 5 cm/year accumulates stress to which natural disasters are attributed. Some landslides make unique, and unparalleled catastrophes. Landslides and avalanches are among the major hydro-geological hazards that affect large parts of India besides the Himalayas, the Northeastern hill ranges, the Western Ghats, the Nilgiris, the Eastern Ghats and the Vindhyans, in that order, covering about 15 % of the landmass.
The Himalayas alone count for landslides of every fame, name and description- big and small, quick and creeping, ancient and new. The Northeastern region is badly affected by landslide problems of a bewildering variety. Landslides in the Darjeeling district of West Bengal as also those in Sikkim, Mizoram, Tripura, Meghalaya, Assam, Nagaland and Arunachal Pradesh pose chronic problems, causing recurring economic losses worth billions of rupees. A different variety of landslides, characterized by a lateritic cap, pose constant threat to the Western Ghats in the South, along the steep slopes overlooking the Konkan coast besides Nilgiris, which is highly landslide prone.
Cyclones are the most devastating among the natural hazards when viewed in terms of their severity, frequency of occurrence and areas of destruction. The coastal regions of India both in the east and west coasts are severely battered almost every year, causing heavy loss to both life and property. Poor man’s dwellings and low rise buildings are seen to be the most commonly affected during a cyclone.
The materials and methods of construction practices significantly go a long way in contributing to the cyclonic resistance of these low-rise buildings. Depending on the availability of the local materials and the local economy of the region, thatch, Mangalore or country tiles, asbestos or metal GI sheets and reinforced concrete are generally used as roof cladding materials. Similarly, mud, clay, stone and bricks are generally used as wall cladding materials.
(The author is a freelance columnist)
DISCLAIMER: The views and opinions expressed in this article are the personal opinions of the author.
The facts, analysis, assumptions and perspective appearing in the article do not reflect the views of GK.