LEGAZPI CITY, Dec. 26 (PNA) –- Bicol local authorities are now equipped with maps that will enable them to pinpoint specific areas where to focus disaster preparedness and mitigation measures for “zero casualty” during natural calamity situations.
The maps, technically prepared by the Mines and Geosciences Bureau (MGB) of the Department of Environment and Natural Resources (DENR), are now in the hands of Municipal Disaster Risk Reduction Management Councils (MDRRMCs) -- particularly in 83 of the region’s 107 municipalities classified as highly vulnerable areas.
Latest to receive the maps are all the 11 municipalities in Catanduanes, an island province by the Pacific Ocean with no pronounced seasons but regularly visited by typhoons.
The MGB identifies the island as most landslide-prone province in the region based on a study it has conducted.
The study says that Catanduanes’ landslides are mainly because rock formations in the province are already old and have already cracked.
Its mountainous terrains are covered with thick soil that erode during heavy rains due to the past commercial logging activities wherein illegal cutting of trees still happens until now.
The maps in hard copies accompanied by “soft” or digitized copies from where local disaster authorities could identify zones prone to natural hazards such as earthquake, storm surge, rain or earthquake-triggered landslides, tsunami, flood and liquefaction.
These are in 1:50,000-scale, Arlene Dayao, the MGB regional technical director, on Thursday said.
The maps determine flood hazard susceptibility zones based on the geomorphological analysis of land forms and the fluvial system.
Information on flood occurrences, flood depths, duration of inundation as well as topographic information supported the geomorphologically-based flood, Dayao said.
On liquefaction, she said, there are no reported occurrences based on several field interviews.
However, zones of different liquefaction potential were derived based on the geomorphological analysis of the study area following previous studies.
Landslide hazard susceptibility zones, on the other hand, were derived through qualitative map combination using lithology, geomorphology, slope gradient and fault distance.
The Global Information System (GIS) was used in the map with combination and subjective weights were assigned to each unit in the parameter map.
The maps also delineate areas of possible ground settlement through the analysis of the geomorphological lay of the study area, the sub-surface soils and the ground water levels, according to Dayao.
Another set of maps, in 1:80,000-scale of the same hazards but covering the entire island of Catanduanes, was also given to the Catanduanes provincial government for use by the Provincial Disaster Risk Reduction Management Council (PDRRMC), she said.
These geohazard maps, whose preparation and distribution are under the government’s Ready Multi-hazard Mapping and Assessment for Effective Community-based Disaster Risk Management Project, are designed according to their geographic and tectonic settings with emphasis on areas highly exposed to natural hazards, she said.
The project is funded by the Australian Aid Program through the United Nations Development Program (UNDP) and the National Disaster Risk Reduction and Management Council (NDRRMC).
It is being implemented nationwide, particularly in 29 of the country’s 79 provinces that have been determined to be of greatest risk to disasters, especially those along the eastern seaboard that include Catanduanes, Dayao said.
With these materials on their hands, she said, it would now be the responsibility of the respective DRRMCs of each local government unit in Bicol to deduce from the multi-hazard maps, particularly the digital version, the risks being faced by each of its barangays so that the vital information could be properly communicated to village officials and residents.
Other Bicol towns that already have these maps in possession are this city and the two other Albay cities of Ligao and Tabaco and all the province’s municipalities -- Camalig, Daraga, Guinobatan, Malinao, Malilipot, Tiwi, Sto. Domingo, Bacacay, Rapu-Rapu, Jovellar, Manito, Oas, Libon, Pioduran and Polangui.
Albay’s three cities and the towns of Camalig, Daraga, Guinobatan, Malinao and Malilipot have some of their barangays listed in the maps as highly vulnerable to floods and lahar flows because of their proximity to Mt. Mayon, with some sitting within the permanent danger zone.
The other towns far from the volcano have their own risk factors such as Tiwi, which plays host to the 350-megawatt geothermal energy complex being run by Chevron; Rapu-Rapu, an island town where the Korean-owned Rapu-rapu Minerals, Inc. (RMMI) operates a polymetallic project through open-pit mining; and Manito, site of the giant geothermal field of the Energy Development Corporation.
Oas, Libon and Polangui are also listed as flood-prone areas, being part of the Bicol River Basin (BRB) -- a vast wetland covering various towns of Albay, Camarines Sur and Camarines Norte.
In Camarines Sur, those towns mapped as geohazard areas are Baao, Balatan, Bato, Bombon, Buhi, Bula, Cabusao, Calabanga, Camaligan, Canaman, Caramoan, Gainza, Libmanan, Magarao, Milaor, Minalabac, Nabua, Ocampo, Pamplona, Pasacao, Pili, Sangay, San Fernando, Sipocot, Siruma and Tinambac -- all within the BRB.
The other Camarines Sur municipalities are Lupi, Ragay and Del Gallego that are called the railroad towns of mountainous terrain whose forest covers have perished due to logging and other environmental-destructive activities.
The rest listed are Buhi, Garchitorena, Goa, Lagonoy, Presentacion, San Jose and Tigaon -- all upland-coastal areas threatened by floods and landslides.
The cities of Naga and Iriga, both in Camarines Sur, are also listed as flood-prone, being parts of the BRB.
In Camarines Norte, all the 12 towns -- Daet, the capital town; Jose Panganiban, Labo and Paracale, the mining towns; and Basud, Talisay, San Lorenzo Ruiz, Vinzons, Capalonga, San Vicente, Sta. Elena, Mercedes all, mountain areas pestered by illegal logging -- are geohazard sites, according to the MGB mapping.
In Sorsogon province, the maps identify Sorsogon City, the provincial capital, and 12 of its 14 towns -- namely Bulan, Bulusan, Barcelona, Casiguran, Castilla, Gubat, Irosin, Juban, Magallanes, Matnog, Prieto Diaz and Sta. Magdalena.
All these LGUs have portions that are considered risk areas, according to the MGB.
Down Masbate, the mapped risk areas are the city -- which is the provincial capital, the gold- mining town of Aroroy and the coastal municipalities of Cataingan, Balud, Cawayan, Dimasalang, Placer and Uson -- all within the province’s mainland. (PNA) FGS/DOC/CBD/UTB