Climate change adaptation for Guwahati's flash floods

The deluge in Guwahati is the result of a lethal combination-large excess rainfall over a short duration due to climate change impact and accumulation of the city's storm-water drainage problems. The tragic death of four construction workers in a landslide and the occurrence of landslides at multiple locations of the hills in the capital city have sounded the alarm bell of a catastrophe waiting to happen. The district-wise rainfall distribution data from the Hydromet Division of India Meteorological Department show that the Kamrup (Metropolitan) district received "large excess" rainfall with 142% more than normal rainfall on Monday and 62% above normal (large excess) from June 1 till June 13. The actual rainfall in the metropolitan district on Monday was 21.3 mm against normal rainfall of 8 mm which partly explains having flooding of large areas of the city, including main thoroughfares. Waterlogging in city localities following heavy showers is a recurring problem and has become aggravated due to changing rainfall patterns. Experts have cautioned that climate change and global warmings are a reality and cities, towns and villages across the globe will have to brace for climate extreme events like large excess rainfall resulting in a flash flood or worsening annual floods or large deficit rainfall resulting in draught condition or heat wave. The solutions that were evolved to address problems like urban flooding, and flash floods in a city like Guwahati urgently required to be adjusted to changing climatic conditions to ensure their sustainability. Discharge capacities of the city's drainage network need to be reassessed and climate change impact like large excess rainfall should be factored into stormwater drainage solutions. Desilting of natural drainage systems like Bharalu and Bahini rivers, wetlands like Silsako, Borsola, Sarusola, Deepor Beel, Khonajan which serve as reservoirs of rainwater run-off cannot remain limited to a pre-monsoon exercise but needs to be carried out round the year to prevent worsening of the flash flood situation in the city. Conservation and restoration of the river and wetland system in the city requires clearing all kinds of encroachment and obstruction but preventing re-encroachment remains a challenge for city authorities. Huge taxpayers' money spent on desilting exercise go down the drain due to unabated cutting of hills by unauthorized construction of dwelling houses and other construction activities. However, lessons are not learnt from the recurrence of landslide tragedies and repeated warnings by city authorities against hill cutting and unauthorized construction continue to be ignored. Large sections of the city's workforce, who are unable to take houses on rent, encroach the hills or wetlands for low-cost housing solutions which is a hard reality that cannot be ignored. The expanding city's life will come to a standstill without this workforce and therefore alternative low-cost housing solutions such as multi-storeyed subsidized apartments for low-income households living in the hills and part of the city's workforce can put an end to the encroachment of the city hills. Due to rampant cutting of hills, the natural drainage channels for rainwater runoff get blocked and large excess rain adds extra weight to the earth while cutting of slopes quickens the process of sliding of huge landmass under accumulated weight by disturbing the stability. Disaster management for the city also calls for vulnerabilities of the city hills in a multi-disaster situation like the simultaneous occurrence of rainfall and earthquake given the fact the city is in a high seismic zone. Unless the natural drainage of stormwater runoff to the city drain network is ensured the landslides will continue to squeeze the city's drainage system, both manmade and natural, reducing their discharging capacities to a minimum. Besides, clearing of greeneries and forests in the hills for housing needs has exposed large tracts of land which are more prone to landside during excess rainfall. Key stakeholders like Guwahati Municipal Corporation, Guwahati Metropolitan Development Authority, Guwahati Development Department, Kamrup (Metropolitan) administration, Water Resources Department, and Soil Conservation Department holding frequent consultations with experts can help update the solutions already offered or implemented to be sustainable given changing climatic conditions and in tune with city's growth and expansion. The present mess of artificial flooding is also the result of an irresponsible act of throwing plastic bottles and other plastic wastes by some city dwellers into drains, Bharalu and Bahiniriver as well as in the wetlands as those plastic wastes clog the drains and water channels. The imposition of heavy penalties can act as a deterrent against such irresponsible acts and has become an urgent need of the hour. The proposed phasing out of single-use plastic is expected to help improve the situation but will require strict enforcement by the administration as self-enforcement and awareness among the city residents. The problems of flash floods and waterlogging in the city are already known, and solutions have also been evolved and applied. Understanding the climate change impact of erratic and large excess rainfall events is critical to making Guwahati climate-resilient and sustainable.