‘Key bridges could be badly damaged by another jolt’Major bridges in earthquake-prone Kathmandu Valley have been found to be very vulnerable to seismic impact, raising suspicions whether they will be able to withstand another jolt like the 2015 Gorkha Earthquake.
Major bridges in earthquake-prone Kathmandu Valley have been found to be very vulnerable to seismic impact, raising suspicions whether they will be able to withstand another jolt like the 2015 Gorkha Earthquake.
As many as 32 out of the 145 major bridges in the Valley could be severely damaged if a 7.8 magnitude earthquake were to rock the Capital, according to a study conducted by the Ministry of Urban Development (MoUD) in collaboration with the Japan International Cooperation Agency (Jica).
The study, which has analyzed post-earthquake scenarios at three different ground intensity levels (slight, moderate and heavy) in a 7.8 magnitude earthquake, has bad news for Kathmandu.
While 32 bridges might be severely impacted in the event of a 7.8 magnitude earthquake with heavy ground intensity, the number of bridges expected to be affected in case of a moderate and slight ground intensity stands at 11 and two respectively.
According to Suman Salike, senior divisional engineer at the MoUD, a project entitled Seismic Risk Assessment for Kathmandu Valley studied different aspects of the
city and drew three different scenarios.
The study has stated that there are 145 motorable bridges in the Valley, among which 62 come under the purview of the Department of Roads. Only 45 bridges have been built with reinforced concrete pier foundation.
“Since bridges are a vital lifeline in adverse situations like an earthquake, it is important to strengthen them at the earliest possible,” Salike said. He added that the project had come to this conclusion after thoroughly studying the outer structure and frame of bridges. “Major bridges may even collapse if timely measures aren’t taken.” Ryoji Takahashi, consultant to the Disaster Management Administration, Jica Contractor, said that a number of precautionary steps can be taken to ensure that the bridges are least impacted even in the event of a severe earthquake.
“Such bridges can be retrofitted. Major pillar bases
too can be jacketed,” Takahashi said.
According to the Post-Disaster Needs Assessment (PDNA) prepared by the government, a portion of the Strategic Roads Network was completely damaged or washed out by the 2015 Gorkha Earthquake. The document stated that the total estimated damage in the transport sector amounted to Rs4.6 billion.
Likewise, the recovery need for the construction of bridges impacted by the earthquake alone stood at Rs803 million in the fiscal year 2015-16 and Rs1.87 billion in the fiscal year 2016-17.
Saroj Pradhan, head of the Bridge Division, Department of Roads, told the Post that they had carried out a study of the damage caused to bridges by the Gorkha Earthquake, and that they had initiated preventative measures based on its findings.
“Bridges within a 100 km radius of the epicentre Barpak were assessed and several measures were taken to strengthen them,” Pradhan said. He added that factors like increased mobility of people and vehicular traffic besides the risk of earthquake had made it necessary to strengthen the bridges.
“The findings of the MoUD and the Japanese consultant will be helpful in our bid to enhance the safety of bridges.” Four teams mobilized by the Department of Roads had examined more than 400 different bridges.
Kathmandu has been identified as one of the riskiest cities for seismic disasters in the world. The MoUD, based on a scientific test carried out in the different parts of
the Valley, stated that the southern belt of Kathmandu was highly vulnerable to seismic risk.