CITY OF SAN FERNANDO --- Ten barangays in Arayat and Magalang towns located near the footslope/flank and periphery of Mt. Arayat are still in danger of landslide and flash floods if heavy downpours hit the area, Mines and Geo Sciences Bureau warned.

In Magalang, the possible barangays in danger are Barangays San Vicente, Ayala, Sto. Nino, San Agustin and Turo while in Arayat town, the barangays in high risk situation are Barangay San Juan Baño, Gatiawin, Palinlang, Balite, Turo Lapaz,

MGB Geohazard Finding in Magalang
Based on the findings along the northwestern part of Mt Arayat specifically the side of Magalang, it was concluded hat three main drainage systems are potential delivery channels for landslide materials.

These are evident due to the presence od breached portion or scarps along the northern summit of Mt. Arayat These drainage systems are the Takwi, Kinanawan and Bundalian Creek affecting Barangay Ayala, San Vicente and Turo Magalang of Magalang, Pampanga, respectively.

However the possible degree of debris flow in Bundalian Creek is small compared to Takwi and Kinanawan Creek because of its lower headwater’s elevation and no recent evidence of breached portion was observed during the survey.

In Takwi and Kinanawan Creek, because of their breached portion along their headwater and observed landslide along its slope, the possibility of debris flow affecting the downstream portion is imminent or looming and far more critical.

As observed possible artificial damming could also happen along the upstream of these creeks, because of their steep slope gradient or v-shaped creek channel.

This was evidently observed along on the upstream of Takwi Creek near the dam where two large boulders of rocks obstruct the flow of water downstream. When cut logs or even uprooted trees along with other large boulders clogged the middle portion of these creeks, this could create artificial damming in the area. Aside from being landslide prone, these creeks can also be affected by flashflood thus affecting the areas on the downstream portion.

The other major drainage systems affecting Barangay Sto Niño and PAC (San Agustin) specifically Punto Creeks, Pulong Bulo Creek, and one unnamed intermittent creek could help trigger flashflood and sheet flooding on its downstream.

Minor slides could also happen along Sto Niño and Turo Magalang as mentioned above. However the distance of the communities along its footslope which is estimated to be 500 meters to 1 km could minimize the damage it might contribute. Added considerations are that the headwater elevations of these creeks are not high.

The MGB team also observed kaingin and illegal logging activities on the surveyed area.

Geohazard Study in Arayat
Geohazard assessment in the periphery of the Mt. Arayat showed that there are creeks and natural drainage that are potential delivery channels of landslide materials and debris flow. The breached portion of the summit had exhibited weakness and there are manifestations of active landslides in the form of rock fall and translational slides.

As exhibited by Sapang Maeyagas, the segment of the creek in the upstream portion are susceptible to artificial damming based on the nature and configuration of the creek channel usually exhibiting a v-shaped channel with steep slope gradients. Accumulation of water in the upstream was exacerbated by the occurrence of big trees and boulders piling up to form an artificial dam along the active channel.

The creeks are also prone to flashfloods in the upstream and would spread as surface run-off when it reaches the break in the slopes and when the slope gradient gradually becomes moderate. Sapang Oliva, Telatalaga Creek and the other active creek channels in Mt. Arayat showed similar characteristics as the Sapang Maeyagas.

The creeks should be cleared of debris and obstructions which could start the build-up of dam structures along the channels. If the water could pass freely along the channels, pore pressure on the unstable banks and unconsolidated materials along the path of the creeks would be lessened. A water impoundment structure was located in Telatalaga Creek as well as fully grown trees along the creek channel.

There was an abandoned treasure hunting site in the upstream portion of Telatalaga Creek where potential for artificial damming is evident .

Recommendations
. As the results of these findings, the MGB has recommended the following to minimize and mitigate the impact of possible landslide and flash floods in the area: A good warning system and warning signs must be formulated and established by the local government units in these barangays.

The people must aware of this system and the hazard both rain-induced and flooding that may affect them during rainy season. Dry runs/drills must be carried out to determine their readiness and awareness to avoid confusion during actual emergencies and disaster.

Construction and development of communities directly on the path of the creeks should be avoided. Areas defined as possible landslide debris accumulation zones must be declared as permanent danger zones. Should there be communities present in these high risk zones, the communities must be informed of the looming and impending danger that they are facing.

There should be a regular monitoring of these mentioned creeks that are active and potential delivery channels of landslide materials and debris flow especially during the rainy day periods and unusually heavy and prolonged precipitation associated with typhoons and monsoon rains to prevent flash floods and artificial damming along the creek channels.

Constriction of the natural flow of these creeks especially man-made must be prevented to avoid possible cause of artificial damming that may cause flashflood on its downstream.

Areas define as possible debris accumulation zone must be declared as permanent danger zone and houses should be prevented to be constructed on those areas.

Cutting of trees, charcoal making and kaingin activities in the classified natural forest park should be controlled or stop if it will not be prevented to preserve the natural forest condition and minimize the human-induced activities which contribute to the destruction of the natural environment.

The LGU should request PAGASA for the installation of rain gauges on strategic locations as well as training of responsible residents who will man the devices. The location of the rain gauges must be secured from vandals and possible damages.

The Barangay Disaster Coordinating Council should be active and always ready in times of emergencies. A communication system must be established in the barangays for proper information dissemination, appropriate and on time response, and coordinated action the fastest way possible.(Joel P. Mapiles)