Tropical Storm Kristine

The tropical depression was named Kristine by PAGASA when it entered the Philippine area of responsibility on October 20, 2024, part of an elongated weather pattern called trough that extended eastward towards Guam. Named Trami by the Japan Meteorological Agency, it intensified into a tropical storm and made landfall in Divilacan, Isabela on October 23, 2024, and emerged over the coastal waters of Ilocos Sur the following day. Signal No. 2 was raised by PAGASA for parts of Luzon and included the Bicol provinces of Camarines Norte, Camarines Sur, Albay, Catanduanes, and Sorsogon. A red alert warning was issued for Bicol by the Office of Civil Defense, which initiated the Charlie protocol, its highest status of emergency readiness, because of the anticipated impact of the storm.

Bicol Region, especially Naga City and several nearby areas, experienced severe flooding and damage due to Tropical Storm Kristine. Heavy rainfall, strong winds, and widespread flooding in Camarines Sur, forced the local government to declare a state of calamity. Floodwater surged in low-lying areas of Naga and neighboring places such as Cadlan, Pili, and towns such as Baao and Buhi. In Del Gallego, two spillways overflowed due to heavy rains, causing strong currents. Because of high-level flooding, river-like conditions occurred on streets and residential areas, such as in Camella Del Rosario as the Yabo River swelled. Homes and vehicles were reported as submerged, resulting in the evacuation of thousands.

In Albay, which was also under a state of calamity, flooding was reported in Polangui and Malilipot. Floods washed away homes in Libon. In Guinobatan, a road was closed due to a landslide. In Tiwi, the Taqui River at Nagas in Oas cut off the national road and landslides were reported in nearby barangays. In Albay, the Public Safety Emergency Management Office oversaw evacuations and provided temporary shelters and food assistance. The threat of landslides and lahar flows from Mayon Volcano, exacerbated by torrential rain, posed additional risks to residents.

The situation remained critical across Bicol, including the provinces of Camarines Norte, Sorsogon and Catanduanes, where likewise flooding and landslides were reported. Efforts by local governments and volunteer organizations were focused on ensuring safety and managing emergency shelter and supply needs. Hundreds of roads and bridges were rendered impassable. The Office of Civil Defense reported that 379,000 people in Bicol were displaced with many seeking refuge in evacuation centers, churches, hotels and private homes.

The topography and hydrology of Bicol

The severe flooding and extreme weather patterns that impacted Naga City and the surrounding areas of the Bicol Region are closely tied to the region’s unique topography and mountainous landscape. The Ragay Hills, Bernacci, and Taobtaob mountains along the west coast contribute to significant rainfall accumulation, as these formations tend to trap moist air masses coming from the sea, intensifying rainfalls during storms. These mountains, combined with the region’s chain of volcanoes, including Mt. Isarog, Mt. Iriga, Mt. Masaraga, and the highly active Mt. Mayon—create complex water runoff patterns that can amplify flooding during extreme weather events.

Bicol River starts from Lake Bato, 6 meters (20 ft) above sea level, in the slopes of Mt. Iriga and Mt. Mayon, and flows 94 kilometers (58 mi) downstream to its estuarine mouth at San Miguel Bay. The volcanic chain shapes the local hydrology. As rain from Tropical Storm Kristine poured down, the mountains collected and channeled the water into rivers and tributaries that feed the Bicol River. This process led to rapid surges in the rivers of Pawili (Pili), Anayan (Pili), and Yabo (Pili-Naga), contributing significantly to flooding in both rural and urban areas. The possibility of lahar flows from Mt. Mayon, as warned by the Philippine Institute of Volcanology and Seismology (PHIVOLCS), further complicates the flooding situation, adding to the risks for communities situated near these volcanic slopes.

The Bicol River Basin and its Sub-basins

The Bicol River basin in Camarines Sur and its sub-basins, including the Libmanan–Pulantuna Watershed, Tigman–Hinagyanan–Inarinan River Irrigation System (administratively referred to as THIRIS), Naga–Yabo River, Pawili River, Ragay Hills, Waras–Lalo Watershed (Iriga-Buhi), Naporog River (Bato), and Quinali Watershed (Albay), are highly susceptible to flooding due to their geographical and hydrological features.

Here’s how these features contributed to severe flooding caused by Tropical Depression Kristine:

1. Low-Lying Basin Topography: The Bicol River basin is characterized by a low-lying topography with a wide floodplain that is prone to flooding, especially when experiencing prolonged or intense rainfall. The large lowland area in the center of the basin is made up of thick deposits of sand, silt, and clay, suitable to rice production. When Tropical Storm Kristine brought heavy rains this overwhelmed the basin’s capacity, leading to widespread flooding as rivers overflowed into surrounding areas.

2. Converging River Systems: Multiple rivers in the basin, such as the Naga–Yabo, Pawili, and Quinali rivers, converge toward the Bicol River. During heavy rainfall, these rivers add substantial water volume into the main Bicol River, which can quickly reach its capacity. When a storm like Kristine hits, all sub-basin rivers flood simultaneously, compounding the overflow risk.

3. Natural Drainage Constraints: The gentle slope of Bicol River near its mouth at San Miguel Bay slows down the water flow and increases the likelihood of backwater flooding. The shallow and wide tidal flats restrict the available channel for water discharge, exacerbating the effects of tidal levels. High tide and storm surges can cause water levels to rise and accumulate hindering the drainage outflow of river water. This can result in flooding upstream and in the surrounding areas, particularly during heavy rainfall. Furthermore, high sediment loads from upstream erosion can accumulate at the river mouth, further reducing the river’s capacity to drain effectively. This can prolong the flood duration, increase flood depths, and push salt water upstream, affecting water quality and impacting agriculture.

4. Deforestation and Land Use in Watersheds: Areas such as the Ragay Hills and Quinali Watershed have experienced deforestation and land conversion for agriculture, reducing the land’s natural capacity to absorb rainfall. Without this vegetation, more rainwater flows directly into rivers, elevating water levels faster during storms like Kristine. Economic activities, over-extraction of groundwater, and inappropriate land-use practices result in decreasing water quality.

5. Sedimentation: The Bicol River Basin has geologic formations that contribute to serious sedimentation, such as Ragay Hills which have sedimentary formations like limestone, siltstones, conglomerates, and shale. The Bicol plain is made up of thick alluvial deposits of sand and silt. Rivers in the Bicol basin are prone to sediment buildup from upstream erosion, especially in watersheds with degraded vegetation. This sedimentation decreases river channel capacity, causing rivers to spill over their banks more readily during intense rainfall. Eruptions from Mayon Volcano have caused heavy sedimentation in river channels, reducing the flood carrying capacity of rivers.

6. Frequent Typhoon Pathway: Located within the Philippines’ typhoon belt, the Bicol region frequently experiences intense tropical storms. The Bicol River Basin’s alluvial plain near San Miguel Bay floods due to storm surges from slow-moving typhoons. The central part of the basin, from Baao Lake to Bato Lake, and the alluvial plain from Naga City to the river mouth are also flood target areas. The cumulative effect of prior storms, including Tropical Storm Kristine, often leaves rivers and soil saturated, reducing their ability to absorb further rain and increasing the likelihood of flooding. Moreover, the Bicol Region as a whole is prone to droughts, flash floods, landslides, and volcano eruptions.

In summary, the topography and hydrology of the Bicol River Basin, combined with environmental factors and frequent typhoons, makes the terrain highly vulnerable to flooding during severe weather events. Tropical Storm Kristine exemplified how these factors interact to cause widespread and prolonged flooding in the region.

Keeping cities above water

Civic organizations have stepped up to provide immediate rescue and relief operations around the Bicol Region, such as: Angat Buhay, the initiative led by former VP Leni Robredo with Kaya Natin! Movement for Good Governance and Ethical Leadership, a civic organizations composed of public servants and engaged citizens; Tabang Bicol led by the Ateneo de Naga University community; Tarabangan Bicol Disaster Network led by more than 300 community leaders and first responders in 17 municipalities and supported by Tanging Yaman Foundation; and, private initiatives led by entrepreneurs Jetjet Vergara in Camarines Sur and Arik Carranceja in Camarines Norte, to name a few. Many community service advocates are now using #BangonBicol in their social media posts to symbolize their aspirations for hope and recovery in the calamity battered region. But what next?

There are numerous research studies and development plans conducted through the years regarding the Bicol River Basin and how to mitigate the effects of flooding. The scientists behind the body of knowledge accumulated so far are well respected and were from reputable institutions in the Philippines and abroad. One can only wonder how much of their research and policy work have been actually utilized in the day-to-day work of administration of the Bicol River Basin and the preparation for and anticipation of the inevitable – another storm and deluge, resulting in damage and destruction.

Much have been publicized about public and privately funded flood mitigation, irrigation systems development, watershed management, riverbanks erosion control, waterways dredging, drainage and sewer clean up projects, reforestation and forest conservation. The reality is, when storms drop excessive rainfall in the basin, flooding is to be expected. Knowing the low terrain elevation of the cities compared to the point of outflow, human intervention, on the one hand, must simply enable Mother Nature to drain the water quickly from the cities through the river to the bay. On the other hand, communities living in areas vulnerable to flooding must always be in a state of preparedness, with trained volunteers and lead persons, calamity ready centers of evacuation, heavy transport equipment and watercraft on call for moving people and basic necessities, medicines for waterborne diseases, portable power generators for lighting and electronic devices and emergency sustenance for the needy – all to be funded by a combination of local, provincial and national government budgets and less reliant on private donations. In the aftermath of calamities, damages on public infrastructure typically expose shoddy workmanship. The guilty parties involved in these construction projects, whether public officials or private contractors, should be prosecuted to the full extent of the law. A recent meme in social media speaks volumes, “Pagod na kami maging Resilient! Ang kailangan namin ay Accountability!”

Finally, one civic initiative worth mentioning is the Coastal Cities at Risk in the Philippines (CCARP) that seeks to bridge the chasm between science, policy and practice on climate and disaster risk. As featured in The ASEAN Magazine (authored by Joanne B. Agbisit, Associate Editor, October 2023), CCARP operates under the Ateneo de Manila University, Manila Observatory, and its implementing partner, the National Resilience Council. It seeks to help bustling urban centers such as Naga City as they navigate the persistent and intensifying effects of climate impact drivers, such as typhoons, floods, drought, and sea level rise. Dr, Emma Porio who heads the CCARP initiative says, “Resilience, to us, is the capacity to absorb, resist the effects of the climate shocks, and to transform our ways of doing things so that we can proactively tackle the impacts of flooding, typhoons, and all other natural hazards.” 

An anticipatory approach to calamity readiness necessitates reliable, precise, and easily accessible science and technology for people to respond proactively on the ground. it has developed a Resilience Toolkit, an online repository of studies, data, models, discussions, and other resources on climate, social vulnerability, geospatial information, city resilience, and capacity building. The toolkit for disaster and climate resilience is designed specifically for local governments, disaster risk reduction and management offices, and other community stakeholders. CCARP works with the Ateneo Innovation Center to develop and deploy technologies that enhance the disaster resilience of cities. The four areas deemed critical during disaster operations are food, energy, water, and information technology. 

Examples of these technologies include the solar-powered water system that collects rainwater and makes it potable through a triple filtration system. A mobile cloud storage system called Near Cloud can contain digital education resources to ensure uninterrupted learning for children during disasters. CCARP advocates turning local community centers, even schools, into resilience hubs equipped with smart design even before calamity occurs. Community centers can be transformed into shelters that can accommodate many families. It supports nature-based solutions, such as mangrove rehabilitation, reflecting a growing awareness of sustainable practices to mitigate the impact of disasters.

Dr. Porio notes, “We just do what we can do. We cannot solve century-old problems or problems of the world, but we can make a meaningful difference by focusing on what we can do with our talents and knowledge products.” This pragmatic approach embodies the spirit of the CCARPH initiative, demonstrating that while current challenges may be daunting, anticipatory thinking and collective action can pave the way towards a more resilient and hopeful future. 

The featured header image is the map of the Bicol Region featured online in PAGASA/ Flood Forecasting and Warning Systems for River Basins. This article was written by Jojo De Jesus for Dateline Ibalon based on the news coverage on Tropical Storm Kristine by various news agencies (GMA Network, CurrentPH, Manila Times, PhilStar, Inquirer.ph, Manila Bulletin); the PAGASA weather reports; The Bicol River Basin Project: Development of Comprehensive Early Warning System for Agri-Fishery Communities in the Bicol River Basin, authors Ricky P. Laureta et al, March 2021); Problem Tree Analysis for Farm Communities Along the Bicol River, authors Ricky P. Laureta et al, May 2022; A case study for the main watersheds of Bicol River Basin, Ernie Bañares et al, Journal of Hydrology: Regional Studies, August 2024.