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Thursday, November 17, 2011

Bito Watershed at risk, study shows

Like most of the country’s natural resources, the Bito Watershed, which is located along the so-called Leyte Cordillera is facing serious threats due to physical and man-made factors.

An assessment of the vulnerability of the watershed conducted from 2009 to 2010 showed that it is highly vulnerable to flooding and landslide. 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.

Forester Edilberto E. Nasayao, Regional Technical Director (RTD) for Research of the Department of Environment and Natural Resources-Ecosystems Research and Development Service in Region 8, together with Emma M. Germano and Severino A. Lacandazo, Jr. conducted the study.

The researchers identified 10 types of soil, which they labeled from A to G. Of these types, G is the most dominant occupying 45.97% 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. On the other hand, soil A is at risk of erosion because of its steep slope. It is also dry. Therefore, once plants on these soils are removed, landslides would eventually happen.

Another factor that could trigger landslide and flooding is the topography of the area. More than 50% 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. According to the Philippine Atmospheric Geophysical and Astronomical Services Administration or PAG-ASA, the average rainfall per month from Calendar Year 1997 to 2007 was 2,512 mm. 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.

The Bito Watershed is also located in the eastern portion of the Sinistral (left-inclined) Philippine Fault, a major continental fault that bisects Leyte. This means that earthquake could affect the watershed anytime.

The Bito Watershed has been the source of income and water of five municipalities in Leyte. It has an area of 14,706.55 ha categorized as timber and agricultural lands, sprawling across the municipalities of Javier, MacArthur, Abuyog, Mahaplag, and Baybay. Of the aforementioned area, the biggest portion is timberland, which occupies 9,032.70 ha. The cultivated and grassland area is only 4,132.70 ha. The rest are forested and alienable (habitable and can be or are already titled) areas.

Considering the physical factors that could trigger flooding and landslide in the area, all harmful activities at the Bito Watershed should be avoided before it is too late, RTD Nasayao recommended. An ordinance needs to be passed banning all mining activities in the area to protect the whole population living around the watershed. The local government units of the five municipalities that share the Bito Watershed are therefore called to action. Niño Antonio P. Villalino and Wolfreda T. Alesna, VSU-DDC/VICARP S&T Media Service

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