P

eople living near rivers on the slopes of Mount Merapi in Yogyakarta and Central Java are bracing for lahar, volcanic mud flows, over fears the incoming rainy season will dislodge the millions of cubic meters of volcanic debris from last year’s eruptions that have settled in the river beds.

On Thursday, hundreds of families in Magelang, Central Java, were forced to flee their homes in the late afternoon as lahar began to flow in the rivers near their villages. However, they returned to discover that the rivers had not burst their banks as they had feared.

However, the floods forced local authorities to close the road connecting Yogyakarta and Magelang for about two hours.

“This is just the beginning of the rainy season and more lahar is expected to come and is predicted to last for about three months,” Cabibullah, a volunteer working with Merapi eruption victims, said on Friday.

Habib of Sabrangkali village, Blongkeng, Ngluwar, Magelang, said that the lahar flood on Thursday had not hit residential complexes in his region but had flooded the riverbanks of the Putih River, which flows from the peak of Merapi. However, a number of temporary bamboo bridges along the river were destroyed.

“We are expecting bigger lahar floods this year,” said Sungkono, head of Jumoyo subdistrict, another area hit by lahar, in Salam district, Magelang.

He said that an estimated 18 million cubic meters of volcanic material from Merapi had settled in the Putih River, and that heavy rain could dislodge it, causing a devastating lahar flood.

Merapi erupted in epic fashion last October and November 2010, spewing more than 150 million cubic meters of volcanic material, massive amounts of which settled in the mountain’s rivers, up to 15 kilometers down stream.

The following floods destroyed hundreds of houses and dozens of bridges as well as hundreds of hectares of crops in Magelang and Sleman regencies.

In West Sumatra, floods affecting 70 percent of South Pesisir regency have killed three people and severed transportation with neighboring Bengkulu.

One person was reported missing and 52,000 others were displaced.

Ade Edward, a manager of the disaster mitigation agency said that high rainfall since Wednesday had caused almost all 12 rivers in the regency located on the western coast of Sumatra to overflow.

“These are the kinds of river flash floods in which water is held back. The overflowing water inundated thousands of houses in up to 2 meters of water,” Ade said on Friday.

Ade said that around 70 percent of the evacuees returned home as of Friday after the water had begun to recede. Although heavy rain came again, they did not cause the river to overflow.

He said that 300 aid packages containing blankets, food and household equipment had been dispatched and were expected to reach disaster locations within four or five hours. Distribution had been slowed down by the damaged road network, he said.

Flash floods still continue to haunt the western region of the mountain, although the government has carried out normalization projects along the 12 rivers, Ade said.