- India
- Aug 16
India records 6,808 deaths due to hydrometeorological calamities in 3 yrs
• According to a written reply in Lok Sabha, the ministry of home affairs informed that 6,808 people lost their lives in the country over from 2018-19 to 2020-21 due to hydrometeorological calamities such as flash floods, landslides and cyclones.
• During 2020-21, a total of 1,989 deaths were reported by the states and UTs. As many as 2,422 lives were lost in 2019-20 and 2,400 in 2018-19.
• During the current financial year 2021-22, the first installment of central share of State Disaster Response Fund (SDRF) amounting to Rs 8,873.60 crore has already been released in advance to all states on April 29, 2021.
Rainfall triggered landslides
• According to Geological Survey of India (GSI), during the monsoon period, landslides occur in almost all landslide-prone areas, some of which are disastrous leading to loss of lives in the country.
• In most cases, these are triggered by extreme rainfall events or cloudbursts.
• These types of fatal landslide events are common almost every year, mainly in the Himalayan States, in the Western Ghats and Konkan areas.
• When the rainfall becomes incessant and much higher than the threshold amount, major landslide events occur, which can cause loss of lives.
• The primary responsibility for disaster management rests with the state government. The concerned state government undertakes relief measures in the wake of natural disasters including flash floods, cloudburst and landslide from the State Disaster Response Fund (SDRF) already placed at their disposal in accordance with the government of India’s approved items and norms.
Floods
• India is one of the most flood-prone countries in the world.
• Out of the total geographical area of 329 million hectares (mha), more than 40 mha are flood-prone.
• The principal reasons for flood lie in the very nature of ecological systems in this country, namely monsoon, highly silted river systems and the steep and highly erodible mountains, particularly those of the Himalayan ranges.
• Most of the floods occur during the monsoon period and are usually associated with tropical storms or depressions, active monsoon conditions and break monsoon situations.
• Floods occur in almost all river basins in India. The main causes of floods are heavy rainfall, inadequate capacity of rivers to carry the high flood discharge, inadequate drainage to carry away the rainwater quickly to streams/rivers. Ice jams or landslides blocking streams, typhoons and cyclones also cause floods.
Types of Floods
• Flash Floods: Floods occurring within six hours, mainly due to heavy rainfall associated with towering cumulus clouds, thunderstorms, tropical cyclones or during passage of cold weather fronts, or by dam failure or other river obstruction. This type of flood requires a rapid localised warning system. Flash floods occur due to high rate of water flow as also due to poor permeability of the soil. Areas with hardpan just below the surface of the soil are more prone to floods as water fails to seep down to the deeper layers.
• River Floods: Floods caused by precipitation over a large catchment’s area, melting of snow or both. Built up slowly or on a regular basis, these floods may continue for days or weeks. The major factors of these floods are moisture, vegetation cover, depth of snow, size of the catchment’s basin, etc.
• Coastal Floods: Floods associated with cyclonic activities like hurricanes, tropical cyclones, etc generating a catastrophic flood from rainwater which often aggravate wind-induced storm and water surges along the coast.
• Urban Flood: As land is converted from agricultural fields or woodlands to roads and parking lots, it loses its ability to absorb rainfall. Urbanisation decreases the ability to absorb water two to six times over what would occur on natural terrain. During periods of urban flooding, streets can become swift moving rivers, while basements can become death traps as they fill with water.
• Ice Jam: Floating ice can accumulate at a natural or human-made obstruction and stop the flow of water thereby causing floods.
• Glacial Lake Outbursts Flood (GLOF): Many of the big glaciers which have melted rapidly and gave birth to the origin of a large number of glacier lakes. Due to the faster rate of ice and snow melting, possibly caused by global warming, the accumulation of water in these lakes has been increasing rapidly resulting in sudden discharge of large volumes of water and debris and causing flooding in the downstream.
Structural Measures to Tackle Flooding
Embankments
This has been one of the major structural approaches in which the river is restricted to its existing course and prevented from overflowing the banks. Usually embankments are constructed with earth but at some places masonry and concrete walls are also used. However, divergent views have emerged concerning the effectiveness of embankment. Studies have pointed out some of the problems such as poor congestion in protected areas, silting of rivers which not only means rising river bed level and consequent decrease in carrying capacity but also depriving neighboring agricultural land from fertile soil and groundwater recharge. There have also been concerns on the issue of embankment capacity to withstand erosion.
Dams, Reservoirs and other Water Storage Mechanism
Dams, reservoirs and other water storages, both natural and man-made, are effective means for reducing the flood peaks in the rivers.
Channel Improvements
The aim of channel improvements is to increase the area of flow or velocity of flow or both to increase carrying capacity. Normally this measure involves high cost and there are also problems of topographical constraints to execute such a measure.
Drainage Improvement
This aims at construction of new channels or improving capacity of existing channels to decongest and prevent flooding. However, what is important is to ensure that such an approach do not cause congestion and flooding in downstream areas
Diversion of Flood Water
This involves diverting all or part of flood water into natural or artificial constructed channels which may be within or outside the floodplain. The diverted water may or may not be returned to the river downstream. Usually effective to prevent flooding around cities.
Catchments Area Treatment
The aim in this approach is to provide protection to catchment areas through measures such as afforestation which minimise siltation of reservoirs and silt load in the rivers. This can be a very useful approach to control flood peaks and suddenness of run offs.
Seawalls/Coastal Protection Works
The construction of seawalls and other such work, try to prevent flooding from sea water. These are highly cost intensive apart from the fact that complexity of sea behaviour and other environmental aspects should also be considered.
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