Rolling in the deep: New equipment surveys Oro River’s depth

For many years, the riverbanks have been home to numerous people and the river itself has helped them earn a living; however, countless lives have also been taken away by the river with the frightful comeback of Mother Nature. With the community’s close relation to the river, the question now is, how deep do you actually this river?

Exploring the uncharted

In positive and resilient response to the aftermath of Sendong, many have made efforts to ward off the destruction of another possible calamity in the city. One of these efforts is the Preliminary Depth Profiling of the Cagayan de Oro River and the creation of its 3-Dimensional depth profile which was spearheaded by Dr. Edgar Allan Po, Engr. Mark Alexis Sabines and Engr. Jan Taat from Xavier University College of Agriculture.

Dr. Po shares that they took inspiration from the idea of exploring the unmapped channel which will possibly help establish calamity preventive measures or devices. “Initially, [Engr. Elpidio] LP Paras initiated a talk with regards to what can be done after Sendong, so this [research] was one of the suggestions. He was willing to fund [it] that’s why we had this particular study.”

With the utilization of technological advances, the researchers were able to map out and construct a 3D depth model of the unexplored void of the Cagayan de Oro River through the use of echo-sounding devices and Global Positioning System (GPS) receivers. Basically, the echo-sounding devices make use of sonar to measure river depth while the GPS receivers determine spatial location.

“Basically we were using a rafting boat, so what happened is we put an instrument on the sides which measures the depth of the river so as we move along we’re picking up depth. Now, to be able to know where that depth measurement is, we used a Global Positioning System,” explains Po.

“So we have a location [and] we have a depth, we were able to map out na dayon [the river].” The team also made use of secondary information necessary for the creation of the 3D model. “The satellite images [of the river] were used to come up with the topography as well as determine the edge of the river.”

The findings

Sailing the river on February 9 and 14, 2012, the research team has conducted the survey and mapped out a total distance of 38.8 kilometers starting from Bubonawan Junction to near the river delta at Barangay Bonbon.

Manifested by the results of the study, majority of the river’s areas with 50.24% is less than 1 meter deep while portions of 1 to 4 meters constitute 45.21%. Visual inspection of the river depth model revealed that most of these portions lie from the Pelaez Bridge to the Maharlika Bridge. Other areas measuring from 4 to 8 meters deep areas comprise 4.07% of the total area studied. These patches of deep sections can be found in areas bordering St. Augustine Cathedral and Paseo del Rio. On the other hand, the deepest part of the river measuring more than 8m and making up only 0.48% lies at the zone beyond Pelaez Bridge.

Other than determining the depth of the river, the research also paved way to a more socially significant observation – Flood Area Forecasting.

With the data generated, flood scenarios were created projecting the possible elevation of water during excessive rainfall. “Flood is a function of the capacity of the river to contain a certain volume of water,” says Po.

The study shows that if a section of the Cagayan de Oro River rises 2, 4, and 6 meters, it will result in the flooding of 164, 211, and 245 hectares (inclusive of the surface area occupied by the river), respectively. The most concrete representation of these numbers is the wrath of Sendong with the flood water rising from its normal level to almost 5m.

Using this information, location-specific early warning advisory can be issued to frequently flooded areas. “The only thing it can do is provide information for future interventions to be conducted.”

First row onward

Mitigating the adverse effects of natural calamities has always been a goal of river and flood related projects; however, it remains an idealistic yet far-fetched aspiration. Despite this, Dr. Po believes that the results of this study will become the springboard for further flood precautionary methods and strategies to surface.

“If you look at the results, you already know where the deep areas are, where the shallow areas are. [If] we want to mitigate disasters in the future… then they will know where to go. That’s basically the contribution of this.”

Po added that the research team has furnished copies of their study and forwarded it to different agencies including the Chamber of Commerce, NEDA and to the Advisory Council of the City Mayor during the term of Mayor Vicente Emano.

With the information acquired in this study, a more powerful weapon is now at hand – knowledge.

In collaboration with the government or with the help of the society in general, any further inquiry on the Cagayan de Oro River and supplementary data and analysis of the River Depth Study will hold immense potential in addressing river mitigation challenges in the city.

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Before any strategy can be crafted to alleviate the impact of flooding, there is always a greater need to explore and examine the spring of the problem – the river. Its structure, its area and its depth are vital factors to better understand its system and its possible adverse effects. If the city yearns to address flood issues and actually leap forward towards risk reduction, there is a need to step back and examine what was left examined over the years.

During the study, as the raft paddles forward acquiring measurements from the river, it does not only pick up depth, but it also lifts up hope and drive to prevent another dreadful Sendong from happening.

References:

Dr. Edgar Allan Po, Engr. Mark Alexis Sabines, Engr. Jan Taat. 2012. Preliminary Depth Profiling of the Cagayan de Oro River.