Vast Flooding in Zamboanga City dealt by the ITCZ

By E.O. Villacampa and I.T. Demetillo

The Intertropical Convergent Zone (ITCZ) prevalence affects the Visayas, Mindanao and Palawan said PAGASA. That would cause inclement weather over the Central Visayas, Eastern Visayas, Northern Mindanao, Caraga Region, and even portions of Soccsksargen and Davao Regions [1].

Prior to this ITCZ, the Tropical Storm Crising [2], later classified as a Low-Pressure Area (LPA), brought heavy rains that inundated several municipalities in Region 9, particularly on the eastern section of the peninsula: Zamboanga Sibugay and some parts of Zamboanga del Sur. Occurrences of landslides and vast flooding were reported on Bayog, Buug, Imelda, Diplahan, Tungawan, and Kabasalan Municipalities last week. Flood occurrences are expected in these municipalities, especially in this type of weather condition. Since those municipalities cover several major river systems such as the Sibuguey River, Kabasalan River, and Tungawan Tigbucay River, their respective tributaries can also cause localized inundations. All of those municipalities (Poblacion Area) cited are located within the floodplains of the said river systems. And with this occurring ITZC, the same areas in Zamboanga Sibugay and Zamboanga del Sur may experience high rainfall, possibly cause floodings, and trigger landslides.

Photo 1 & 2 Vast extents of flooding in Imelda Municipality, Zamboanga Sibugay, houses and government buildings, barangay access roads, and rice fields were underwater over-spillage of the Sibuguey River.
Photo courtesy by Lalaine Bajada Laureano & Footprint Production.

In Zamboanga City, with ITZC in effect, several barangays are experiencing inundations with different magnitudes. Barangays of Sangali, Manicahan, Tugbungan, Tumaga, and Bungiao; Barangays within the City Proper: Tetuan, Guiwan, San Jose, and San Roque experiencing inundations brought from the over-spillage of Curuan River, Bolong River, Manicahan River, Tumaga River, Baliwasan River, and their respective tributaries.

In 2015, the Mines and Geosciences Bureau (MGB) identified the said barangays as highly prone to flooding through Landslide and Flood Susceptibility Mapping and Assessment of Zamboanga City [3]. There are flood generators (river systems) within this City should be eyed especially during heavy-down pours brought such weather condition. These are the Limpaya (Limpapa) River, Patalon River, San Ramon River, Ayala River, Sinunuc River, Baliwasan River, Tumaga River, Cabaluay River, Manicahan River, Bolong River, Mala River, Quiniput River, Curuan River, Vitali River, Taguite River, Lincabagan River and Tigbao River.

In the City Proper, some of the incidences of flooding are not caused by the over-spillage of river systems. Most often caused due to poor drainage system conditions. Such as silted and clogged channels, under construction, incapacitated and undersized drainages, and other possible impairments.

Flooding could be a reiterating incident predominantly during ITZCs, Tropical Storms, LPAs, and other weather disturbances, the same as for landslides. However, these impacts can be minimized through proper mitigation (structural projects), adaptation (relocation or evacuation), and other combined initiatives (risk reduction measures). Moreover, the more significant part is for the individuals to reduce the risk through cooperation.

Photo 3 & 4 (Left) Vast extent of flooding in Barangay Bungiao, the barangay access road, and the portion of a rice field have been underwater. (Right) Residents in Barangay Guiwan are experiencing flooding due to the over-spillage of the Tumaga River.
Photo courtesy by Brigada Zamboanga.
Photo 5 & 6 (Left) Flooding in Barangay Tetuan several residents are affected. The most regarded are structures with low floor levels. (Right) Residents in Barangay Bolong are experiencing flooding due to the over-spillage of the Bolong River.
Photo courtesy by Brigada Zamboanga.

These are the persistent recommendations that should be considered during this weather condition:

  1. Observe the rapid increase and decrease of water levels along the river or creek channel accompanied by the increased turbidity. Report the situation to the proper authorities.
  2. Consider vacating the communities (barangays/puroks/sitios) situated adjacent to minor and major river systems (river basins), its tributaries and its immediate floodplain, as well as the coastal areas;
  3. Avoid residing or vacating along unprotected and unstable road cuts/slopes (both primary and secondary roads);
  4. Consider vacating built-up areas near moderate to steep slopes, especially the ones located atop, in the middle, and at the foot of the slopes and valley sides;
  5. Combination of numbers 1 and 3 – which can be considered critical;
  6. To evacuate, areas are likely to be affected by sheet flooding and localized flooding caused by constricted drainage networks.
  7. Improvement of drainage systems which includes: regular desiltation (the process of removing silt sediments from a body of water) along the river and creek channels, improvement of the width, and lessening the river/creek channel’s sinuosity; removal of garbage, debris, and other structural obstructions, and improvement of drainage capacity and culvert sizes, are some methods that lessen the susceptibility of flooding within the in the area.

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