TD Marilyn and Habagat brought floods in ZC

By El-Jedidiah O. Villacampa and Ian T. Demetillo

On September 14, 2020, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) reported that Tropical Depression Marilyn and Southwest Monsoon (Habagat) would bring cloudy skies with scattered rain showers and thunderstorms over Visayas and Mindanao. In Zamboanga City, there are already several reported flood occurrences caused by the inclement weather brought by these meteorological conditions.

The MGB-9 technical personnel conducted ocular inspections to the identified flood-prone barangays in Zamboanga City. In the duration of the assessment, the barangays along the east coast of Zamboanga City are lightly experienced inundations even with the intermittent rainfall events. Meanwhile, barangays along the west coast are reported to experience flooding, particularly in Ayala and Talisayan area. The occurrence of flooding in the areas mentioned are due to the constriction of natural waterways and the limited drainage system capacity.

Photos 1-A & 1-B. (1-A) As indicated by a resident, the reported flood reached a half meter in height in Zone 8, Barangay Ayala, Zamboanga City. This flooding is caused by this inclement weather condition LPA and Habagat on September 13, 2020. (1-B) Debris carried by high volume water contributes to the occurrence of flooding within the area. As the debris and garbage piled up alongside the road, so the floodwaters drained without restriction.
Photos 2-A & 2-B. Inadequate and incapacitated drainage systems are one of the causes of inundations. Flooding in Talisayan (Old National Highway) areas, particularly along Dumagsa Creek, located in Purok 1, Talisayan, was constricted and clogged. Hence, flooding readily ensue along these areas.

Causes that constrict the natural waterways are the development of river dikes, which narrows down the channel breadth and intensifies the river channel’s sinuosity. Moreover, the limited capacity of drainage systems also caused flooding, such as installing inadequate sizes and numbers of culverts and clogging caused by garbage and other objects.

Improvement of drainage systems which includes: regular desiltation (the process of removing silt sediments from a body of water) along 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 will lessen the susceptibility of flooding within the area.

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