As Typhoon Bising and the southwest monsoon bring persistent rains, the Department of Environment and Natural Resources - Mines and Geosciences Bureau (DENR-MGB) has listed 986 barangays vulnerable to possible flooding and rain-induced landslides.

In an advisory dated July 4, but was only released on Sunday, July 6, the agency reported that a total of 986 barangays are being monitored, with 287 in Region I and 699 in other regions.

“As of July 04, 2:00 AM, the LPA developed into Tropical Depression Bising. It is expected that TC Bising will intensify tomorrow, July 05, into a Tropical Storm,” DENR-MGB said.

“Bising is forecasted to re-enter the Philippine Area of Responsibility (PAR) on Sunday morning, July 06, and is expected to intensify into a Severe Tropical Storm on Monday, July 07.”

Due to expected worsening weather conditions, the agency warned that the rainfall threshold for the Ilocos Region has been lowered because of reports of heavy antecedent rains that could cause oversaturation of soil and slopes.

“In areas classified with moderate flood susceptibility, the LGUs must implement pre-emptive evacuation if floodwaters are about to reach 0.5 meters,” the agency said.

“Deploy DRRMO personnel who will monitor the rapid decrease/increase of floodwater level from active river systems.”

For areas with high to very high flood susceptibility, the DENR-MGB urged local officials to enforce pre-emptive evacuation protocols, especially for households located near active river systems, and to strictly avoid flashflood-prone areas.

“Riverbank erosion and slope undercutting by rivers are common mechanisms that induce flood-related landslide. Hence, for households situated along riverbanks, pre-emptive evacuation protocols must be enforced,” the agency noted.

On landslide risks, the DENR-MGB advised that any incidents of seepage should be reported immediately to local authorities, as these are signs of an imminent landslide.

“Barangays classified under high to very high landslide susceptibility must be closely monitored for early signs of landslide such as: tension cracks at the crown, tilting of trees or fences, ground subsidence, and seepage,” it added.

The agency said residents must not be allowed to return to barangays and areas where a landslide has occurred until authorities confirm it is safe.

“Preferably, the LGU should enforce pre-emptive evacuation for residents living near a stream or a channel with low embankment, especially if the barangay experienced persistent rainfall and have experienced past incidents of debris flow.”

The DENR-MGB explained that in areas where recent landslides have occurred, local government units may install warning signs and carry out slope monitoring.

“Temporary closure of roads that traverse identified landslide-prone areas should also be considered. The LGUs / Provincial Governments may opt to temporarily close roads to all forms of vehicles, until such time these areas are deemed safe,” the agency stated.

According to the department, the Abulog, Abra, Cagayan, and Agno Rivers across Regions I, II, and CAR are among the key waterways identified for intensified monitoring.

“These systems are not likely in their normal water level/conditions because of recent typhoons, hence water can easily overtop their riverbanks and inundate peripheral communities,” DENR-MGB said. 

“Hence, evacuated residents should not be allowed to return to their homes, considering the threat of another tropical cyclone. Lastly, residents remaining in these areas are recommended for forced evacuation.”