Excessive sand mining threatens 'Sabo' damns
Sri Wahyuni, The Jakarta Post, Yogyakarta
Sand excavation activities on the rivers at the base of Mount Merapi in Central Java are now threatening Sabo (lava control) dams constructed along the rivers to control the flow of hot lava from the volcano, a researcher warns.
"If nothing is done about it, I'm afraid it will damage the Sabo constructions, and once the volcano erupts, lava could destroy hundreds of hectares of rice fields and housing areas around Mount Merapi," said Sabo researcher Hariyadi Djamal of Yogyakarta Water Resources Research Institute of the Ministry of Settlement and Regional Infrastructure.
Speaking on the sidelines of a one-day international symposium on sediment-related issues in the Southeast Asia region in Yogyakara Wednesday, Djamal said that his research institute had noted that some 14,000 cubic meters of sand was being quarried from the base of Mt. Merapi every day.
"The amount of sand quarried should be reduced to a "safe" level. Otherwise, it will not just destroy Sabo dams but also cause degradation of the Progo River, where most of the tributaries end up," said Djamal, adding that his institute had yet to conduct a study on the acceptable amount of the quarried sand.
Sand quarry activities near a Sabo dam construction in Jurang Jero (Magelang, Central Java) and Kaliboyong (Sleman, Yogyakarta), for example, once damaged censor wires used to monitor and measure the rainfall and flood levels.
"It has yet to cause damage to the construction but it will if nothing is done about it," Djamal said.
According to Djamal, the negative impacts of sand dredging in the rivers near Mt. Merapi could in fact be reduced by providing tight control on it.
He particularly urged local governments to ban sand dredging near Sabo dams.
"The safe areas for taking sand from the base of Mt. Merapi is several hundred meters on either side of the dams, and should not exceed five meters below the base of the dams," he said.
An integrated coordination among related government and non- government institutions including the sand quarrying companies, according to Djamal, was needed to control and help reduce the negative impacts of dredging.
A Japan-sponsored Yogyakarta Sabo Technical Center has from 1972 to 1998 built 13 Sabo dams, of between six to 11 meters long in the Merapi area as well as in the regions of Magelang and Klaten (Central Java) and Sleman (Yogyakarta).
During the eruptions in 1992, 1994, and 1998, Kaliboyong Dam 6 was instrumental in diverting the lava from flowing to and damaging Kaliurang resort and other northern regions of Yogyakarta. The Kali Lamat and Kali Putih dams were also hailed for protecting the southeastern regions of Magelang.