General Santos City could suffer the same tragedy that hit the northern Mindanao cities of Iligan and Cagayan de Oro, which experienced enormous destruction and still rising casualties brought by tropical storm Sendong in December.

Like many urban centers in the Philippines, the city’s river banks have become favorite settlement areas of urban dwellers, most of them informal settlers.

In General Santos, three major river systems – the Buayan on the east, Silway at the middle and Siguel on the west – are heavily populated at the mouth end where these eventually spill into Sarangani Bay.

The Silway River, particularly, poses the greatest risk among residents who have settled on both sides of the river banks along the villages of Dadiangas West (2007 population: 18,253) and Labangal.  The heavily silted and quarried river also happens to cut across the city in half.  In addition, the dead creek of what used to be Makar River, barely two kilometers west of Silway, runs smack into the heavily populated Purok Puting Bato of Barangay Calumpang (pop 67,832).

Labangal is the third largest village in the city with a population of 57,769 (2007 census).

Flash floods in recent years have already destroyed several houses on both sides of the eroding river banks of Silway and Makar prompting city disaster officials to declare several areas as danger zones.

Three river systems could cause massive flooding in General Santos City.

The city’s loose sandy loam soils make a perfect candidate for severe flash flooding as the city is yet to put in place a comprehensive drainage system.

Most of the city’s catch basins have already been converted into subdivisions (Bula, Lagao and San Isidro) while many agricultural lands have been converted into residential areas putting further strain on the city’s inadequate drainage system.

With a low pressure area continuing to build up east of General Santos City as of Monday (January 2), the specter of flashfloods looms over the city.

The last major flooding in the city occurred in 1971 when the tail of Typhoon Yoling brought heavy rains and strong winds in the city.

Back then the population of the city was barely 150,000.

Today, General Santos City has an estimated population of at least 700,000, more than quadruple when Yoling flooded low lying areas in the city forty years ago.

General Santos City Mayor Darlene Antonino Custodio had already ordered city disaster officials to prepare for any major weather disturbance in the aftermath of Sendong.

On December 30, two weeks after Sendong devastated northern Mindanao, geologist and University of the Philippine professor Mahar Lagmay said General Santos could suffer the same fate as Cagayan de Oro because of the similarities of their topographies.

At 10 a.m. January 2, Weather Advisory 3 of the country’s weather bureau announced that at 8 a.m. the LPA was estimated based on satellite and surface data at 860 km East of General Santos City (5.8°N, 133.0°E)” while wind convergence is affecting Eastern Visayas.

More than 3,000 are said to have perished when Sendong slammed across northern Mindanao.  More than 100,000 people fled their homes and are still in evacuation centers.  It was the worst flooding to hit Mindanao in recent memory.