Residents of Hacienda Caridad in San Enrique town of Negros Occidental were alarmed after the waters in a portion of the Candaguit River suddenly rose after a loud growling noise was heard by fishermen.
Rex Nebril and Ernesto Suanico, both of Purok Malipayon, Barangay Sibucao, said they were fishing in the river when they felt a mild tremor and heard a loud growling noise about 50 meters from their position.
At first they thought that it was just a large animal taking a dip in the river. But when they approached the area where they heard the noise, they discovered to their alarm that the portion of the river bed – about 35 meters – had risen by three feet. They claimed to have seen smoke seeping out from the cracks.
Bacolod City Disaster Risk Reduction and Management Office (Cdrrmo) head, Joemarie Vargas, said the sudden rise of the river bed may have been caused by the build up of either nitrous oxide gas or methane gas.
Vargas said nitrous oxide gas has the same odor as rotten eggs and it is possible that a large tree might have been swept in the area and eventually buried beneath the river. The gas then built up over years of decomposition until the pressure eventually triggered the river bed to rise.
“It’s like what you see with buried garbage which if put in the ground for too long would eventually create methane gas. However since this was located in the marshland then it is most likely nitrous oxide,” Vargas said.
He added that such incidents are normal and people need not be alarmed, although, he advised San Enrique officials to prevent anyone from swimming in the area where the river bed rose as it is possible that there is still a pocket of gas underneath which could cause it to collapse and create a large sink hole.
Vargas said the town officials should consult geologists to survey the area and assess conditions there.
He also assured the public that the incident was not connected in any way to the volatile state of Kanlaon volcano which is now under Alert Level 2 status.