MANILA, Philippines - An official of the Department of Environment and Natural Resources (DENR) in Region 8 yesterday urged officials of five municipalities in Leyte to pass an ordinance banning all mining activities near the Bito watershed, found to have a high risk to natural and man-made hazards.
The Bito watershed is the source of income and water of the Leyte towns of Javier, MacArthur, Abuyog, Mahaplag, and Baybay. It has an area of 14,706.55 hectares categorized as timber and agricultural lands.
A study conducted from 2009 to 2010 by Edilberto Nasayao, regional technical director for research of the DENR’s Ecosystems Research and Development Service in Region 8, together with Emma Germano and Severino Lacandazo Jr., found the Bito watershed to be highly vulnerable to flooding and landslides.
“This is because the soil in the area is more of andesitic (dark grayish rock like that of Mt. Andes) and basaltic (a dark gray to black dense to fine-grained igneous rock) composition,” the researchers said.
The researchers identified 10 types of soil, which they labeled from A to G. Of these types, G is the most dominant, accounting for 45.97 percent of the land area.
“This soil type has a steep slope which explains the presence of many streams caused by high volume and velocity of excess water,” they said.
On the other hand, soil A is at risk of erosion because of its steep slope, the researchers said. “It is also dry. Therefore, once plants on these soils are removed, landslides would eventually happen,” they said.
Another factor that could trigger landslides and flooding is the topography of the area, the researchers said.
“More than 50 percent of the area is steep slope. Climate also plays a role. The northern part of Leyte falls under Climatic Type II which means that rain is evenly distributed throughout the year,” they said.
Citing data from the Philippine Atmospheric, Geophysical and Astronomical Services Administration, the researchers said the average rainfall per month from 1997 to 2007 in northern Leyte was 2,512 millimeters.
“This is lower than the 4,100 mm rainfall per month 15 years ago. Excessive rainfall due to typhoons can cause water upsurge and flooding,” they said.
The Bito watershed, the researchers said, is also located in the eastern portion of the Sinistral (left-inclined) Philippine Fault, a major continental fault that bisects Leyte. “This means that an earthquake could affect the watershed anytime,” they said. - By Helen Flores
