New Delhi: Heavy rain and landslides may have caused a major river tributary in Kerala's Kozhikode district to split into two branches twice over the past two weeks, intensifying the flooding, water experts said.
The branches later merged downstream, a scientist said, adding that extreme rain is unlikely to cause rivers to change course permanently.
The tributary named Iruvanjippuzha, which merges with the Chaliyar river, split into left and right branches on August 9 and August 14, V.P. Dinesan, a senior scientist at the Centre for Water Resources Development and Management, Kozhikode, said.
Scientists believe this happened because of bouts of intense rainfall upstream and massive landslides that deposited soil, boulders and trees into the river, hampering its natural flow.
"After the split, the tributary's left and right branches flowed through several houses close to the riverbank. This happened in the night; people didn't know what was happening," Dinesan told The Telegraph. "The same thing happened again on August 14."
However, Dinesan said, amid the extensive flooding, the two branches merged downstream about 500 metres from the point where the tributary split. "Once the trees and debris were cleared from the tributary, the direction of natural flow was restored. But the entire area downstream is flooded," he said.
Water resources specialists say that extreme rainfall events are unlikely to change the geomorphology - land elevation and other terrain features - or the courses of rivers permanently.
"The extent of the inundation can change from place to place along the same river," said Subhankar Karmakar, assistant professor at the Centre for Environmental Science and Engineering, Indian Institute of Technology, Bombay.
"So, along some stretches of the river, the floodwaters may flow into low-elevation channels nearby, creating the visual effect of a parallel flow."
Karmakar said quick visual inspections of flooded areas even before the water had receded could be misleading.
Two low-pressure systems that had emerged over the northern Bay of Bengal on August 8 and August 14 had triggered intense spells of rain over Kerala.
Environmental scientists have attributed the floods to the heavy rainfall, Kerala's distinct topography, its network of rivers and the land's loss of capacity to hold water.
Chaliyar is the waterway through which logs were ferried to Kozhikode's Kallai, one of the most important timber trade centres in the world in the late 19th and early 20th century.
Iruvanjippuzha had found a place in popular culture in the mid-20th century when renowned Malayalam novelist S.K. Pottekkat set his Nadan Premam (Love in the Countryside) in Mukkam, a village on the river's banks.
'Severe' calamity tag
The Centre has declared the floods a "calamity of a severe nature" and told Kerala High Court there's no provision to declare a "national calamity" or "national disaster", as demanded by the Kerala government and the Congress.
Focusing on the mammoth reconstruction and rehabilitation tasks that lie ahead, chief minister Pinarayi Vijayan said: "The Centre has cited technical issues against declaring a national disaster but has promised all help."
The death toll since May-end has risen to 376.
