Disaster and Environment: Floods, GLOFs, drought and desertification

Floods and glacial lake outburst floods

Floods recur in India every monsoon, and many of their causes are environmental: loss of wetlands and flood plains that once stored water, deforestation and soil erosion in catchments that silt up river beds, and paved cities that send rain straight into drains. This chapter looks at disasters from that environmental angle; the hazard science is in the Geography chapter on disasters.

Source: PIB, Ministry of Jal Shakti, 1 August 2024 (Release 2040173). These are the 1980 commission’s figures, not a current survey.

Mains 2024: Flooding in urban areas is an emerging climate-induced disaster. Mains 2024 Discuss the causes of this disaster. Mention the features of two such major floods in the last two decades in India.

Mains 2020: The interlinking of rivers can provide viable solutions to the multi-dimensional inter-related problems of droughts, floods, and interrupted navigation. Mains 2020 Critically examine. A balanced answer weighs these gains against submergence of forests, loss of river ecology and displacement.

A glacial lake outburst flood (GLOF) happens when water held behind a glacier’s moraine or ice suddenly breaks out. As glaciers retreat, such lakes form and grow. The Central Water Commission monitors 902 glacial lakes and water bodies from June to October every year: 477 with a water spread above 50 ha and 425 of 10 to 50 ha (PIB, 8 August 2024).

After the Teesta-III hydroelectric dam collapse in October 2023, the CWC decided to review the design flood of all existing and under-construction dams vulnerable to GLOFs, and GLOF studies were made mandatory for all new dams with glacial lakes in their catchments. A Committee on Disaster Risk Reduction under NDMA, with six Himalayan States/UTs, has identified high-risk glacial lakes for expeditions and early warning (PIB, 8 August 2024).

Drought, land degradation and desertification

Drought is a slow-onset disaster: it builds up over months and its effects last long after the rain returns. When dry spells combine with over-grazing, deforestation, poor irrigation and soil erosion in drylands, land loses its productivity. This is desertification. It is land degradation, not the spread of existing deserts.

Land degradation in India (ISRO Space Applications Area Centre atlas)

Measured values: SAC atlas as cited in MoEFCC’s National Action Plan to Combat Desertification and Land Degradation through Forestry Interventions, 2023 (PIB, 7 August 2023, gives 97.84 million ha). Target: PIB, 9 September 2019.

Water erosion is the biggest process of degradation (11.01% of the geographical area in 2018-19), followed by vegetation degradation (9.15%) and wind erosion (5.46%). Rajasthan has the largest share, followed by Maharashtra, Gujarat and Karnataka (National Action Plan, 2023). At the 2015 Paris COP India joined the Bonn Challenge pledge to restore 13 million ha by 2020 and 8 million ha more by 2030; at UNCCD COP14 in 2019 it raised the 2030 pledge from 21 to 26 million ha (PIB, 7 August 2023).

The UN Convention to Combat Desertification aims to promote effective action through innovative national programmes and supportive international partnerships, and is committed to a bottom-up approach, encouraging the participation of local people; it has no special focus on South Asia and North Africa (Prelims 2016: 1 and 3 only).

Government of India encourages the cultivation of sea buckthorn because it helps in controlling soil erosion and in preventing desertification, and it has nutritional value and is well adapted to cold, high-altitude areas; it is not a rich source of biodiesel or valuable timber (Prelims 2012: 1 and 3 only).

Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables plants to resist drought and increase absorptive area, tolerate extremes of pH and resist disease infestation (Prelims 2013: 1, 2 and 3).

Dryland programmes have changed hands over time. In the official key, none of these pairs was correct: Drought-Prone Area Programme with the Ministry of Agriculture, Desert Development Programme with the Ministry of Environment and Forests, and National Watershed Development Project for Rainfed Areas with the Ministry of Rural Development (Prelims 2014: None).

Mains 2020: The process of desertification does not have climatic boundaries. Mains 2020 Justify with examples. Mains 2026: Discuss the role of aeolian processes in desertification and land degradation. Mains 2026

Mains 2016: In what way micro-watershed development projects help in water conservation in drought-prone and semi-arid regions of India? Mains 2016 Small check dams, contour bunds and trenches slow runoff, recharge groundwater and keep soil in place.