Heavy rains and floods

We hope all of you have recovered from this week’s heavy rains and floods. What can we all do to prevent future rains and floods from causing loss, damage and harm? How can we tame the rains and avoid destructive floods in the future?

So much rain can be harvested effectively, especially for communities with problematic water supply. Trees, aside from absorbing carbon dioxide and providing oxygen for people, are important for conserving water. Trees protect us from the downfall of rain; they absorb and store rainwater which reduce runoff and sediment deposit after storms.

Sadly, so many trees have been cut to give way to housing and other commercial use. Time to rethink deforestation and implement tree planting in our communities, especially in the uplands.

Effective, functioning drainage systems also have to be responsibly installed and regularly monitored. Proper waste disposal and management will go a long way to avoid flooding and to create a healthier, more secured environment. Responsive service-oriented governance and political will and everyone’s crucial participation can ensure better rain, flooding and other disaster management.

Can we all get ready and work together to more effectively manage heavy rains in the near future? Can we also get ready for other types of disasters and threats this early? Eco-advocates Atty. Golly Estenzo-Ramos and Lito Vasquez of CENRO, Cebu City shared about the 249-page report of  the Sinkhole Assessment Team of the Mines and Geosciences Bureau, Central Visayas ( MGB-CO) titled "Karst Subsidence Hazard Assessment and Ground Penetrating Radar (GPR) Survey in the Upland and some Lowland Urban Barangay of Cebu City" presented during a workshop last March 30 at the Sinulog Hall, Rizal Public Library. Together with the report came a disk with 49 files labeled "Subsidence Threat Advisory," representing advisory on specific locations, the type of hazard(s) and recommendations for 49 upland/rural and some urban barangays of Cebu City.

As an example, in a March 30 letter, the MGB urged the barangay captain of Talamban to “kindly advise your constituents to initiate readiness and measures (including the MGB recommendations) for this identified geohazard (in the following locations: Sitio Cadauhan, Family Park, Sitio Banhica and Highway 77 that have sinkholes ranging from 0.5 to 70 meters classified as cover subsidence and one solution type and at the Talamban National High School and Elementary School with classrooms that exhibited staircase cracks and the wall and floor foundations already with signs of active subsidence and based a tabular cave system and buried sinkhole exists). Please be informed that increase in rainfall, lowering of water table, strong earthquake will increase subsidence activity. Your office is encouraged to contact your City Disaster Risk Reduction and Management Office/Council to plan for any emergency and preemptive evacuation as soon as possible. Adaptation measures for affected communities should also be upgraded.”

MGB recommendations for Sitio Cadauhan, Family Park, Sitio Banhica and Highway 77 included: 1) vigilant monitoring of signs of sinkhole/cave collapse and subsidence in the areas identified by concerned barangay officials. Presence of tension cracks that are widening and/or progressing and circular ground depressions that are subsiding, especially after heavy rainfall and flooding should be monitored and reported immediately to city authorities and CDRRMO; 2) Extra vigilance by residents during heavy, continuous rains brought by typhoon or monsoon rains, especially if areas with identified sinkholes are flooded. Runoff is recommended to be diverted away from sinkholes; 3) Report sinkhole and/or cave collapse to city authorities/CDRRMO. Sinkholes should not be covered unless recommended by authority, especially if subterranean river or creek is noted beneath. This will result to ponding of subterranean river/creek and induce subsidence in the immediate vicinity; and 4) Dwelling units should be made of light materials. Two-storey concrete structure is not advisable in areas near sinkholes and cave system with spalling roof. Avoid infrastructure development on top of cover-subsidence sinkhole. Residents should be vigilant in monitoring for the presence or propagation of wedge cracks on walls of structures, bulging walls and depressions or bulging on floors and/or ground in the area

For the Talamban National High School and Elementary School, the following  recommendations are worth urgent, immediate action: 1) as these buildings are no longer safe for school children and not suitable to be utilized as evacuation centers, expert opinion of  the geotechnical and structural engineers should be sought immediately as the school exhibit cracks. The subsurface geological conditions should be considered in rehabilitation of  these buildings and demolition as an option if cracks are progressing at a fast rate laterally and vertically; 2) Vigilant monitoring of signs of sinkhole/cave collapse, and subsidence as well as tension cracks that are widening and/or progressing, and circular ground depressions that are subsiding, within or near the school? especially every after heavy rainfall and flood events is needed, and to be reported, immediately to city authorities/CDRRMO; and 3) In case of sinkhole and/or cave collapse, cordon off the area and report situation immediately to city authorities/CDRRMO.

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