Last of two parts
MALAYBALAY CITY (MindaNews/31 December) – Weather bureau PAGASA issued storm signal number 2 for “Sendong”. In the Philippines, however, most people only become restless when storm signals reach number 3 or higher, which explains the general complacency even when the storm was about to make a landfall. As noted in the first part of this article, storm or typhoon signals are forecasts of wind velocity.
Unfortunately, it wasn’t the wind that caused the floods in Northern Mindanao but the unusually high amount of rainfall.
PAGASA said “Sendong” brought 180 mm of rain in less than 24 hours. According to Al Tongco, a Geographic Information System specialist at Oklahoma State University, this means that about 254 million cubic meters (= 1414.44 sq km x 180 mm) potentially fell on the city’s watershed. For 24 hours, this volume ballooned to 6 billion cubic meters.
Tongco said that since Cagayan de Oro’s watershed neck at downtown is only 6 km wide and 12 km long, flooding was inevitable.
“Rushing flood waters could rise to more than 3 meters (= 254 million cubic meters / 6×12 sq km) in downtown CDO,” he added.
Besides, he said, the city had to contend also with the floodwaters coming from the watersheds of the rivers other than the Cagayan de Oro River that pass through its other coastal barangays.
Cagayan de Oro’s topography as a narrow floodplain, along with the bitter memory of the January 2009 floods that displaced thousands of families, should have prompted the city officials and planners into examining the applicability of their disaster preparedness and mitigation measures, if any were in place.
As can be gleaned from Google Earth maps, the city is at the receiving end of water from parts of Misamis Oriental and Bukidnon, mainly from Mount Kitanglad Range and the province’s northern towns of Libona, Baungon, Talakag and Manolo Fortich, and partly from Mount Kalatungan Range. Some of the water that drains down to the city may also come from Lanao del Sur since it shares boundary with Talakag town in Bukidnon.
Tongco estimated Cagayan de Oro’s watershed at 141,444 hectares or 1,414.44 sq km. Mount Kitanglad Range alone has a total land area of at least 47,000 hectares, although water from its southern portion drains towards the Pulangi River.
A three-dimensional presentation of Cagayan de Oro and its watershed would reveal that the city is like a trough.
“Unfortunately, most residences are within this trough,” MindaNews reader Willie Jones B. Saliling said in an email. He said this is one case of how urban planning can render people vulnerable to risks.
Saliling, agricultural engineer from Kabacan, North Cotabato said that land use in the uplands may also have altered the hydrology within the watershed of Cagayan de Oro. Logging and erosive agricultural activities, he said, make water flow faster putting lowland inhabitants at the constant mercy of floods.
As for Davao City, Saliling also did not discount the possibility that real estate development and quarrying on top of the Matina floodplain had contributed to the floods in June. “But I guess the biggest contribution came from the agricultural plains in the north.
A larger watershed is needed to impound such large volume of water to flush the floodplains,” he, however, said.
He further noted that Iligan City’s topography also makes it flood-prone, without dismissing the significant contribution of logging in its watersheds to the disaster.
“There are two watersheds that drain to Iligan, one that has an area of approximately 65,000 hectares and one with around 7,800 hectares (estimated only through GE Path). The bigger watershed drains water from as far as Talakag in Bukidnon and Kapai and Tagoloan II in Lanao del Sur. The smaller watershed drains partly the towns of Tagoloan, Baloi, and Pantaran in Lanao del Norte. All of these watersheds drain into an area approximately 1,500 hectares within Iligan proper. It is like having two large buckets pouring their contents to a very small one,” he explained.
These data and other technical information can be obtained from the Department of Environment and Natural Resources, NAMRIA, and even nongovernment organizations and academic institutions that are into hydrology and mapping related activities. But one may wonder if the local government units have made great use of these data.
As for long-term solutions to the periodic flooding in the lowlands, Saliling suggested negotiating “proper land use” in the uplands, although he admitted it would be an uphill battle.
Saliling’s suggestion is anything but new. Years ago, environment groups and some development planners had proposed a similar scheme. In many forums, the late Dr. Antonio Sumbalan, who served as Bukidnon’s planning and development coordinator, said that those in the lowlands that benefit from the environmental services of a preserved forest – e.g. water distribution firms, plantations – should invest in its conservation by giving socio-economic incentives to upland communities. He said this is the surest way to encourage upland dwellers to protect the forests.
The Aquino government, for its part, has directed local government units to embark on a “regreening program” and ordered a log ban. But these approaches, though desirable, cannot be expected to produce results in the immediate future. Climate change caused by the phenomenon of global warming has reached a stage where carbon sequestration measures such as reforestation can no longer roll back or contain its impacts. The impacts are no longer a distant fear but are already an unfolding reality.
The imperative is to make local communities resilient against climate change through appropriate adaptation and mitigation programs to avoid natural hazards from becoming catastrophes. Local governments must take the lead in this effort by ensuring that poor families are settled in safe areas, investing in flood protection and mitigation, and creating and updating databases on local watersheds, land use and hazards.
Moreover, there should be efforts to translate technical weather information into a language easily understood by the people. For its part, PAGASA can start by clarifying that storm and typhoon signals refer to wind velocity, which has nothing to do with floods.
The aftermath of “Sendong” tells us that an accurate rainfall forecast and an understanding of the risks involved would have saved many lives. It was not the wind but the waters that killed the victims. (H. Marcos C. Mordeno/MindaNews)
