The Mighty Cagayan River

By Fred F. Castañeda, R.A. November 18, 2020


The Cagayan River, also known as “Rio Grande de Cagayan”, is the longest River in the Philippines about 520 kms long. It flows in a northerly direction from its head waters in the Province of Nueva Viscaya through the Provinces of Quirino, Isabela and Cagayan Valley to its mouth in the Babuyan Channel dividing the Town of Aparri into its West and East baranggays. The Cagayan River basin is bounded by mountain ranges, the Sierra Madre on the East, Cordillera Central on the West, Caraballo-Maparang on the South and the Babuyan Channel on the North. It has many tributaries and the major tributary rivers are the Pinacanauan, Siffu-Mallig, Chico, Ilagan and Magat River. Magat River is the biggest of its tributaries. Historically, the Cagayan River served as one of the major ports of the Galleon Trade during the Spanish Colony at Aparri. In the early periods, the Cagayan River was used as the main thoroughfare of transportation to Manila. The Cagayan River is the lifeblood of the Cagayan Valley, a fertile land that produces a variety of crops including rice, corn, bananas, coconut, citrus and tobacco.

CURRENT USES OF CAGAYAN RIVER- the following are current use of the River:

  1. IRRIGATION-it provides much needed water for farmlands in the basin. As of 2005 study, it provides irrigation for about 206,511 hectares of rice fields and 135,540 hectares of corn fields. Unfortunately, not all farmlands in the Region are irrigated.
  2. QUARRYING and MINERALS- the River Bank is the source of sand and gravel for concrete aggregate. Small scale mining for gold panning is undertaken in the tributaries of the rivers in the province of Quirino and Nueva Viscaya. Manganese and Chrome are found in the province of Isabela and Cagayan.
  3. TOURISM-Kayaking, River Rafting, White Water Rafting, River Trailing and Swimming are favorite activities along the River. Bancarera (boat race) is also undertaken at some areas of the River. During the first week of July, fluvial parade for the Lady of Piat is conducted. Aparri has a Ferry River Tour to certain locations within the municipality along the river basin to visit locally produce products.
  4. TRANSPORTATION-Landing Ports exist along the River for cargo and passenger transport. In Aparri, we have the Furugganan Landing, Toran Landing and Macanaya Landing. Ferry Boats link Aparri and Claveria to Fuga Island and Camiguin Group of Islands. Passenger Ports are available in Callao Norte, Lasam and Gattaran. Private ports exist in Nassiping, Guising, Lapogan and Centro Sur. Public Ports are also available in Dungao and Abariongan Ruar linking Sto.Niño to Gattaran. In the Province of Isabela, municipality of Benito Soliven, Public Ports are located in Yeban Sur, Maluno Sur and Maluno Norte. In the Province of Quirino, a mini Port is located in Nagtipunan.
  5. FISHING-the river is the principal source of freshwater fish and shellfish such as Ludong, Unnok, Balinggasa, Tulya, Kabibe and Aramang.
  6. HYDRO-POWER-the Magat Dam, one of Asia’s biggest Dam, located along the Cagayan River’s tributary river in Magat, Isabela is the source of electric power for the Magat Hydro-Electric Plant that has the capacity to provide 360 megawatts of electricity powering the Luzon grid and contributes electricity to Manila and suburbs.


The Philippines has a tropical climate that is mostly hot and humid. The Climate can be divided into two seasons, the Dry Season (November to May) and the Wet Season (June to October) although with climate change, summers had been extending into June and July. The Philippines is in the Typhoon belt and is prone to dangerous storms during the Wet Season. The summer monsoon brings heavy rains to most of the archipelago from May to October. Annual average rainfall ranges from as much as 5,000 millimeters (197 in) in the mountainous east coast section of the country, to less than 1,000 millimeters (39 in) in some of the sheltered valleys. Monsoon rains, although hard and drenching, are not normally associated with high winds and waves.

In the Region, Typhoon normally strikes during the month of July to December for an average of about 8 times a year. In the 2006 study, the basis rainfall is 2,600 mm. It varies from less than 2,000 mm in the lowlands to more than 4,000 mm in the mountainous areas. The Cagayan River discharge capacity, based on the 2006 study, is 2,000 cubic meters per second in the Downstream Area (Tuguegarao to the estuary). This capacity is less than the 2-year probable flood estimate of 6,400 cubic meters per second; hence this causes frequent flood occurrences.


During rainy season and typhoons, additional water runoff comes from nearby mountain ranges that flows into the tributary rivers and into the Cagayan River. The forest cover of the Cagayan River basin, based on the Lower Cagayan Flood Control Study in 2001, was estimated at 41%, a decrease from the 42.3% in the 1987 Master Plan Study of the whole basin. The Forest Register also shows that 38% of the total forest area is old-growth forest and 60% is residual forest. The principal cause of forest destruction is the continued expansion of slash-and-burn farming and legal and illegal logging activities. Vegetation slows down the flow of water and increase infiltration and storage in upland. Thinning of vegetation contributes to the water runoff and erosion.

Increased sedimentation due to erosion and the collapse of mountain slopes are carried into the Cagayan River. In the upper Magat River Basin including the Santa Cruz River, Balilim River and Santa Fe River, the earthquake of July 1990 increased land collapse and sediment deposits. Land collapse and basin erosion have increased tremendously the sediment deposit in the Magat Dam estimated at about 188 million m3 in 1999 or 67.8% of the Dam’s storage capacity based on the Japan International Cooperation Agency (JICA) 2002 study; hence, reducing its capacity. Heavily silted waterways made rivers shallower. Eroded soil carried by water run off constantly add silt into the Cagayan River decreasing its depth.

River bottlenecks-the Cagayan River has areas of bottlenecks and constricted sections in the Magapit Narrows. They are in the areas of Tupang, Nassiping in Alcala and Magapit in Lal-lo. These hinders the flow of water to the Aparri Delta causing backwater and meandering in the River Channel in the upstream. However, the 2001 JICA Feasibility Study did not recommend widening of the Magapit Narrows based on simulation test conducted. Economic and Environmental issues were also considered.

Meandering Channels upstream of Magapit Narrows-the effect of the rising of the water caused by the constricted Magapit Narrows resulted to the shifting of the River course from its original alignment extending from Alcala to Tuguegarao City. This meandering produced gentle slope gradient of the River bed thus retarding the floodwater flow.


During typhoons and rainy season, the majestic Cagayan River that provides lifeblood and character to the Region is abruptly changed into a monster engulfing life and property as it floods the valley. Lives and millions in cost of products and livelihood are lost. Subsequent health hazards follow after the flood. Although the Region prepares and anticipates yearly flooding, the November 12, 2020 flood was so immense and unexpected since there were no direct Typhoon in the Region. Magat Dam was about to overflow and opened its 7 gates. This additional volume of water spilled into the Cagayan River and exacerbated the flooding.

The extent and severity of damages of the November 2020 Flood had magnified the people’s concern for a more enduring protection against flooding. This Cagayan River Flooding issue is not a Regional Problem anymore but a National Concern. The immediate support from authorities and people from other Regions are worthy of awe and gratitude. However, we need a more permanent solution to the constant flooding of the Cagayan River. This solution to be effective must include the 4 provinces of the Region (Nueva Viscaya, Quirino, Isabela and Cagayan Valley) including Apayao, Kalinga, and Ifugao of the Cordillera. These 3 provinces were formerly of Region 2.


  1. CREATE ONE AGENCY. There are 4 major Provinces and many municipalities affected by this flooding in the Region. The extent of flooding severity differs in parts of the Region as per the 2006 study. To provide a single source of management, a CAGAYAN RIVER AUTHORITY must be created to oversee the implementation of the Flood Mitigation Program. This Agency can serve as the governing body of current government and or private agencies in the Region dedicated to work in the Cagayan River such as DENR, NIA and others. Additionally, it will oversee the National Irrigation Administration-Magat River Integrated Irrigation System that manages the Magat Dam and all proposed Dams, and other work planned for the Region. There must be one authority to coordinate release of water from the Dam and alert all concerned parties in the Region. Current protocols must be reviewed and coordinated with input from all Provincial representatives in the Region. Any work associated with all the Tributary rivers that may affect the Cagayan River must be approved by this agency. Flood Control Work, to include Forest Management, Irrigation, Watershed and related work must be under the supervision and management of this Agency. This should unify and reduce different government agencies performing different tasks unknown to other Agencies in the region.
  2. REVIEW OF PAST STUDIES AND RECOMMENDATIONS; CREATE A COHESIVE PLAN FOR THE REGION. There had been many studies and proposals made about the Cagayan River Flood Mitigation. Past studies include the following:
  3. 1987 Cagayan River Basin Flood Control Master Plan.
  4. 2001 Feasibility Study on the Lower Cagayan River Flood Control
  5. 2006 Cagayan Valley Flood Mitigation Master Plan, Censal Year 2006-2030
  6. Project ReBuild. ReBuild is for “Resilient Capacity Building for Cities & Municipalities to Reduce Disaster Risks from Climate Change and National Hazards.” This was a 3-year Project (2013- 2016) by the Climate Change Commission (CCC) under Mr. Henderson Alvarez as Commissioner and with funding and administrative assistance from the New Zealand Aid Program (NZAP) and the United Nations Development Program (UNDP). Launched July 2013 and agreement among parties signed in Tuguegarao City.

The 2006 Study included a detailed report with projects scheduled yearly and tied to funding shared by the Region’s respective Towns, Provinces and the National Government. The work is far reaching as it includes municipalities within the Cagayan River Basin. It addressed solutions regarding Limited Water Supply during Dry Season-during rainy season much water is available and dry up during the Dry or Summer Season months. This 2006 Master Plan, addressed projects from the upper land to the lower land, dykes and river edge protection, River dredging, watershed at all tributary rivers, forest management, small water impounding projects (SWIP), Small Farm Reservoir (SFR), multi Dam projects at Matuno, Tumauini, Siffu, Alimit, Mallig and Kalipkip Rivers. These studies where money and resources were invested are useless if not implemented. The proposed CAGAYAN RIVER AUTHORITY should review all previous studies and proposals to mitigate the river flooding and create a single Plan for implementation.

  1. CREATE FUNDING. No Program can be successful without a transparent & concrete commitment to provide funds for its implementation. The 2006 Study identified shared Yearly Funding among the Region’s Provinces, Municipalities and the National Government. Short-Term and Long-Term Work are scheduled based from availability of funds. The Funds should be managed by one entity; hence, the proposed Cagayan River Authority. The Flood Control Plan can be structured so that projects to protect and provide growth and revenue in the Region can be prioritized. This increase in revenue in turn will shore up yearly budget for Long-Term work. The National Government and the Regional Provinces can reach out to other countries for support and/or Joint Projects. This can be a part of the government’s “Build Build Build” or “PPP” Programs.
  2. EVERY MUNICIPALITIES SHARE RESPONSIBILITIES-Consequently, flooding mitigation is a shared responsibility of every one, every barrios and municipalities. We need to review our Town’s Storm Drainage System, our Town Water System, Sanitary and Sewage Disposal System. Do we have adequate Storm Water Retainage Basin in frequently flooded areas? These are all tied to how we connect to the river. We also need to review our Building and Zoning Codes as it affects how we construct structures with property drainage and materials suitable for constant typhoon and flooding. New Developments, Residential and Commercial must be more sensitive in the provision of proper site drainage and for larger development the provision of a Storm Water Retainage Pond if possible. We must provide proper site drainage to all public structures such as schools and gymnasiums used as temporary refuge during flooding and emergencies.

“One life lost is one too much”. How many more season will the people of the Region suffer? We need a united effort of all the Region’s Governors, Senators and Representatives to raise this issue with Congress and the President of the Philippines. Many studies had been made-it’s time to put it into action. It will take years to implement it but it is so worth it to finally resolve this flooding issue. I see a future with an Aparri Seaport, an International Maritime Trade, a busy throughfare along the Cagayan River plying all its Region’s Provinces and a robust growth of business along the river’s basin. The Mighty Cagayan River can truly be the lifeblood of the Region when we can control its temperament.


  1. Cagayan Valley Flood Mitigation Master Plan CY 2006-2030. RDC2 Resolution No. 02-045 by the Regional Development Council II, Tuguegarao City, February 2006.
  2. Water Quality Management in the Context of Basin Management: Water Quality, River Basin Management & Governance Dynamics in the Philippines by Vicente B. Tuddao, Jr. PhD, Executive Director, River Basin Control Office, DENR, September 21, 2011
  3. Flood Forecasting & Warning System for River Basins; The Cagayan River. by Philippine Atmospheric, Geophysical & Astronomical Services Administration (PAGASA), March 12, 2016
  4. Longest River in the Philippines by Kenneth Kimutai, World, July 24, 2018


Fred F. Castañeda is a Registered Architect in the United States and the Philippines. He graduated Cum Laude at the College of Architecture, National University, Manila on full academic scholarship and was a Top Notcher in the 1971 Architectural Licensing Exam in the Philippines. Prior to immigrating to the United States, he was the Principal of A.F. Castañeda & Associates, Manila, Philippines and was a member of the Faculty of the College of Architecture, National University, Manila. He recently retired as the President of Castaneda Architect, P.C. in New York City. An inactive member of Philippine Institute of Architects, American Institute of Architects & National Council of Architectural Registration Board. He enjoys his retirement with family in New York and Florida.

Leave a Reply

Your email address will not be published. Required fields are marked *