Magnitude of floods decreased between 1970 and 2010: Study

The magnitude of floods decreased in most parts of India between 1970 and 2010 as compared to the previous 100 years even as flood intensity increased in northwestern Himalayan and Malabar regions in the pre-monsoon and early monsoon season in the same period, according to a new study based ‘on water flow data from 173 gau-

- ChetanChauhan

The study, “The changing magnitude and timing of riverine floods in India”, published last week in peer reviewed journal, Nature, comes at the time when the flash floods caused by extreme rainfall have caused the death of 148 people in Himachal Pradesh (78) and Uttarakhand (70) since the onset of monsoon on Junel.

The Central Water Commission, India's water regulatory body, has installed gauges, also known as water sensors, across river systems to measure the flow of water for hydrological purposes including flood warning.

The study, by the Indian Institute of Technology (IIT) Delhi and IIT-Roorkee said, flash floods in the higher reaches of Ganga and Indus regions are now happening in the early monsoon period, a change that could have “catastrophic outcomes” since the entire flood management system needs to be redesigned to change in the flooding pattern.

‘A possible reason for higher frequency of early flash floods is climate change induced alteration in the rain-snow transition zone in the higher reaches which could advance spring/pre-mon-soon flood peaks by several weeks in snowmelt-dominated regions, the study added.

‘Another region where the flood intensity has increased (by 8% per decade) during the study period was in the west flowing rivers from Tadri to Kanyaku-mari (Chaliyar, Periyar, Bhara-thapuzha, Vamanapuram, etc.) in the Malabar coast , the result of intense pre-monsoon rainfall.