Mapping flood hazards goes hi-tech

UNIVERSITY of the Philippines president Alfredo Pascual (left) and Science Secretary Mario Montejo inspect the instruments that will capture images of river basins for flood forecasting. E.I. REYMOND T. OREJAS

CLARK FREEPORT—Capt. Francisco Cadenas, a pilot of 35 years, and Christopher Cruz, a geodetic engineer, made a historic flight to the Pampanga River basin on a Cessna 206 from the Clark International Airport on Nov. 22.

With Cadenas in control of the plane and Cruz in command of the Light Detection and Ranging (Lidar) instruments, the Philippines has entered an era of modern flood hazard mapping and simulation on 18 major river basins to save lives and property whenever disaster strikes.

The mission of Cadenas and Cruz was laid out by President Aquino to find a “long-term solution to all the death and destruction wrought by natural hazards,” said Science Secretary Mario Montejo shortly before the maiden flight took off at 4 p.m. on Nov. 22.

The project’s second plane followed, heading as well to the Pampanga River basin.

The Aquino administration has given priority to disaster risk reduction in the country. According to the Belgium-based Center for Research on the Epidemiology of Disasters, the Philippines is the third most disaster-prone country in the world and among the most frequently visited by natural hazards in the last 10 years.

Montejo said the Lidar, which had been installed in the plane after its passenger seats were removed, is flown at an altitude of 1,000 meters or beyond and acquires high resolution images that can be processed into three-dimensional (3D) maps of the 18 major river basins, including watersheds in the country.

“These fine resolution maps will be processed further to make more accurate flood models that will be the basis to warn communities in advance of potentially deadly floods,” he said.

“The flood models can be so detailed that residents can find their houses [in the maps],” said Dr. Enrico Paringit, program head of DREAM (Disaster Risk and Exposure Assessment for Mitigation) by the University of the Philippines’ National Engineering Center.

DREAM, done on a grant from the Department of Science and Technology (DOST), is tied to the agency’s Nationwide Operational Assessment of Hazards (Project Noah).

Lidar, which relies on amplified light to rapidly take images, originated in Germany, Canada and the United States. “Its application has rocketed in the last 10 years but this is, so far, the first Lidar project of the Philippine government,” Paringit said.

It is the “most effective technique to accurately measure elevation and depth for flood modeling,” he said.

The Lidar project, to be completed in two years by 50 Filipino experts, mostly from UP, costs the government P1.6 billion. It leased the two aircraft from the Asean Aerospace in Clark after undergoing bidding.

Montejo thanked the British Embassy in Manila and the British government’s environmental agency for sharing its expertise with the project.

UP president Alfredo Pascual said the project was very important to the university because it “makes true the mandate [of the state university] to assist the government.”

DOST officials said the catchment area of the 18 river basins that would be mapped, at 105,631 square kilometers, is one-third of the country’s total land area.

The flood models would be included in the Project Noah website and integrated in existing systems such as the Pampanga River Basin Flood Forecasting and Warning System (PRBFFWS). The PRBFFWS, located in the City of San Fernando in Pampanga, has water sensors and rain gauges that feed real-time data to computers.

Paringit said the first rough flood model of Marikina City was tested during the southwest monsoon rains in August.

According to a project briefing, the 3D maps can be used for forest inventory, environmental monitoring, infrastructure planning, fault line mapping, archaeological surveys, agricultural assessment, government revenue management and postdisaster damage assessment.

Montejo said policies were being discussed in terms of data use and access. The images may also be used to find out what would happen if gates of certain dams are opened, he said.