Purushottam Khatri

Heavy rains lashed the Kathmandu Valley in the early morning of September 6. Over 385 temporary houses built around the banks of the Bagmati, Bishnumati, Hanumante, Dhobikhola, Manohara Rivers faced inundation. More than 232 persons were rescued.  

Many concrete and makeshift houses were worst-hit by the swollen rivers, with muddy waters gushing into the unplanned urban settlements. On the day, the Meteorological Forecasting Division recorded the highest ever 121.5 mm of rainfall in the last 24 hours that eclipsed 84.3 mm record registered on September 12, 2008. That was also the third heavy rainfall in Kathmandu since 1968. The Nagarkot-based station in Bhaktapur also measured 122.4 mm of rainfall on September 6, the fifth heavy rainfall recorded since 1971. 

Engineer Sanjay Kumar Sah says the height of flooding in the Bagmati River at Khokana station had reached 4.7 metres due to rain on September 6. During the monsoon, the water level in Kathmandu normally remains less than two meters. The Kathmandu Valley has witnessed rising level of floods in the major rivers following torrential rains within a short period. Lately, the incidence of floods in the Valley has increased by 0.87 per cent, says Sah. 

The report on Climate Vulnerability and Risk Assessment (CVRA) of the government this year states that the risk of floods is high in Balkhu and other major rivers basins. Forty-eight per cent of the houses built on the banks of rivers are temporary. Only two per cent is made of cement and bricks, the report states. Experts say that the problem is with the construction of narrow and insufficient depth of the rivers and not letting them flow on their natural track. Dams along the river banks have not been constructed in a proper and scientific way. Increasing urbanisation is the main reason for the recent increase in floods in Kathmandu. Runoff coefficient situation has been developing in Kathmandu when the rainfall water could not get chances to saturate onto the land in absence of open areas.

Experts call for assessing the estimated scale works to calculate the highest risk of flooding. When the dam was built on the banks of the Bagmati River, it was necessary to estimate the maximum rainfall that could occur in this area. Constructing limited height and depth of dams on the two sides of the river will just be an act trying to control the natural flow of the river which poses a risk of flooding any time. The solid waste that is thrown along the riverside and sewage has also caused the floods. Riverbed of the Bagmati and other rivers has been rising due to the mud coming from the hills and commercial plotting of land in the hills. 

The CVRA report states that eight per cent of Nepal's territory is at risk of flooding. It states that 26 municipalities and 85 rural municipalities in the country are at risk of floods and landslides due to climate change. Of these, Biratnagar, Lalitpur, Kathmandu, Bharatpur, Pokhara-Lekhnath, Ghorahi and Tulsipur are at high risk of climate change. The more the humans continue to challenge nature, the more climatic events such as rising in temperatures, unnatural changes in rainfall patterns and floods are likely to increase in the years to come.