by Greg Deligero
With 30 men, women and children dead and at least another four people still missing, the flash flood that rampaged through Talomo district Tuesday night was without doubt the most devastating in Davao City’s history in terms of human suffering and damage to property.
Along with harrowing tales told by survivors, it was readily apparent that the tragedy had singled sprawling subdivisions and settlements that border the Matina River in the barangays Matina Pangi, Matina Crossing, Matina Aplaya and Talomo proper.
These are the downstream areas of the Matina River Watershed, one of the seven watersheds of the city.
A watershed is a stretch of land marked off by topographical features such as a ridge or mountain range, along which rain is caught and drained into a body of water like a river. Technically, a watershed encompasses the area that extends from the uplands to the downstream areas or lowlands, and the coast. Watersheds are also known as ‘river basins’ or ‘catchments’.
The flood path
Making up the upland portion of the Matina River Watershed are barangays New Valencia, Biao Guianga, Biao Escuela, Ula, Matina Biao and Tacunan. The ground and surface waters from these areas drain into the Matina River.
The river’s headwaters start from barangay Langub and flow to Catalunan Grande, Matina Pangi, Matina Crosing, between Talomo proper and Matina Aplaya and finally find their way to river’s mouth and the Davao Gulf.
Days before the flood, torrential rains in the upland portion of the watershed made it “super saturated” according to city planning and development coordinator Roberto P. Alabado III, citing field reports generated by his office.
So, by late evening of Tuesday, the swollen river meandering system started to overflow its banks, thus triggering a devastating flash flood that wrecked havoc on properties, killed at least 30 people mostly children, washed out makeshift houses and affected at least 12,000 families.
“We had never witnessed a flood of such magnitude,” said Julina Lutche, 45, a resident of NHA Bangkal.
Rainfall
The Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) has no record of rainfall specific to the Matina River Watershed. The agency has only two Agromet Observation Stations to measure the rainfall in the city, one in the Davao International Airport which is within the Sasa Creeks Watershed and another in Bago Oshiro in the Talomo River Watershed.
For the entire month of June, the average daily rainfall in the city measured at the Sasa observation station was pegged at 8.1 millimeters while in the Bago Oshiro station it was t 15.97 millimeters. Rainfall is measured through the use of rain gauges. Rainfall amounts are estimated actively by weather radar.
The Bago Oshiro station is adjacent to the Matina River Watershed.
Last June 28, the night of the disaster, the rainfall in Sasa was recorded at only 8.0 millimeters while in Bago Oshiro it was 60 millimeters. The following day, the rainfall in Sasa was a mere 3.9 millimeters while in Bago Oshiro it had reached 66.8 millimeters.
Impact
Alabado shrugged off arguments that the flash flood was the end result of the development activities in the upland areas, saying that the city’s zoning ordinance is very explicit in prohibiting development activities in the upland except for agriculture and agro-forestry.
He maintained that only less that 20 percent of the entire Matina River Watershed area were residential and commercial developments which are located mainly in the lowland.
“Most of the upland areas remain green as these are still farms and forests. We develop area where flooding may occur, but development did not contribute to the flooding. It was an act of nature, a hundred-year flood,” said Alabado.
As for future development projects, he said the city government will put restrictions in areas susceptible to flooding.
“We have to know how much development (investment) they will allow, particularly flood control development. If we are not convinced, then we will deny their applications,” he said.
As for present structures, Alabado said they will urge the owners to put up flood-proof structures akin to houses and buildings in the lahar-hit areas in Luzon. “They have to build sturdy structures and devise ways of effective flood-proofing,” he added.
Alabado said the city government is also bent on fast-tracking the integration of a geo-hazard map into the zoning ordinance which is expected to be enacted by October.
“We will amend the Comprehensive Land Use Plan and integrate this geo-hazard map into the zoning ordinance,” he said.
The geo-hazard map, a document which Davao City secured some years back, turned out to be a mere advisory for developers. It was not strictly integrated into the requirements set for these developers before they start and implement projects like housing or for commercial purposes.
“If we integrate this in our zoning ordinance, developers would have to abide with our requirements, especially if they are to develop a property classified as moderately or highly susceptible to flooding or landslide.” he added.
The geo-hazard map clearly identifies and classifies areas which have low, moderate, and high susceptibility to flooding. This way, developers and even property owners will have an idea of how secure the property is from potential danger or disaster.
It is also the role of government to assure the safety of the people by providing them right information about the risks and hazards in residing in a particular community.
However, given the information from the government, it then becomes the responsibility of owners of the property to protect themselves aginst possible disasters.
