UP professor on study linked to Monterrazas de Cebu: ‘Not yet finished’

CEBU, Philippines – After Monterrazas de Cebu developers Mont Property Group cited a study to prove their property did not worsen flooding caused by Typhoon Tino (Kalmaegi) in November 2025, a professor of the University of the Philippines in Diliman Institute of Environmental Science & Meteorology (UPD IESM) told Rappler on Tuesday, April 21, 2026, that the full study was not yet done.

Dr. Mayzonee Ligaray, head of the UP IESM’s Environmental Hydrology Laboratory, made the clarification as speculation over who conducted the study spread on social media.
On Sunday, April 19, actor Slater Young shared a link to the UP study and his statement on the November 2025 flood that devastated Barangay Guadalupe in Cebu City — a tragedy that was linked to the uphill developments of the Monterrazas de Cebu.

“That tragedy was real and it deserves real answers. Not speculation, not misinformation,” Young said.

Based on findings of the UP IESM Environmental Hydrology Laboratory in their hydrologic assessment of the Guadalupe and Kinalumsan River Basins, Monterrazas’ retention ponds helped mitigate flash floods in areas near the property.

The lab compared flood simulations wherein the Monterrazas property did not exist, existed but had no retention ponds, and existed with the retention ponds.

The researchers, in their assessment released on March 2, 2026, said that Typhoon Tino (Kalmaegi) was an extreme rainfall event that brought 428 millimeters of rain to Cebu within 24 hours of the weather event.

“Simulations show that [Monterrazas’] retention ponds reduced peak runoff by approximately 70% to nearly 100%, depending on rainfall intensity and available storage, and up to 99.74% of excess rainfall was retained or delayed during the event,” their assessment read.

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Lab’s clarification

Ligaray explained that the assessment of the Guadalupe and Kinalumsan River Basins was still the first of other assessments to be conducted for the laboratory’s study of Cebu’s watersheds.

“It’s really a desktop study and of course, just like any other research, it can still be improved to really see what’s happening. If this was a full-scale project to really investigate this, there has to be river profiling, really checking the watersheds,” the professor said.

In research, a desktop study reviews existing and accessible data about a subject and is considered to be a preliminary form of investigation.

Ligaray stressed that their study intends to look at “watershed dynamics” and collective factors that contribute to heavy flooding scenarios in areas located near watersheds.

“It’s really about the management and the planning of the watershed itself. Iyon ang gusto naming i-emphasize doon, although, hindi kasi namin na-input ‘yong recommendation kasi nga hindi pa siya tapos,” the professor added.

(That is what we want to emphasize, although, we haven’t inputted our recommendation yet because it’s not yet finished.)

How study was conducted

Ligaray said that the study did not receive any funding and was conducted by the UPD IESM laboratory independently using available maps from the National Mapping and Resource Information Authority (NAMRIA) and international data sources.

The laboratory used tools like the Hydrologic Engineering Center River Analysis Software (HEC-RAS) and the Soil And Water Assessment Tool (SWAT), and rainfall data sets from JAXA Global Rainfall Watch to look into the watershed processes.

“These models, especially SWAT, are data-intensive models so we really need to collect data from national government agencies, land cover maps, elevation maps, supported topography, soil maps and climate data,” Ligaray said.

In the process of the assessment, he added, the laboratory only requested the Mont Property Group for the design of the Monterrazas’ detention pond systems.

Ligaray stressed that there still needs to be more investigations into the quality of the detention ponds, citing their lack of resources to conduct on-site inspections.

“Without taking any biases, we’re just going to assume that [the retention ponds] are working perfectly which is the limitation of our study. If we’re going to publish this, we’re going to put that in the scope of limitations,” Ligaray said.

More work to do

According to the head of the UPD IESM lab, there was still more work to be done before a clear assessment of what happened to the watersheds during the Typhoon Tino (Kalmaegi) event could be made.

“On our [social media] post, we mentioned that the study was still ongoing because we’re finishing all the other rivers and for us, what was really most affected was the Mananga River and Cotcot River,” the professor told Rappler.

Ligaray said that if they could be provided with external data on the detention ponds and probable malfunctions, they were willing to make adjustments to their models. Detention ponds are meant to temporarily store runoff water.

It can be recalled that the Laudemir Salac, the Central Visayas regional director of the Department of Environment and Natural Resources (DENR), revealed during a Senate blue ribbon committee hearing on November 14, 2025, that two out of 17 retention ponds in the Monterrazas property collapsed, which later contributed to the heavy floods that hit Barangay Guadalupe during Typhoon Tino (Kalmaegi).

The DENR’s initial findings pointed out that there were sediments found in the Monterrazas’ detention ponds’ waterway due to the uncontained surface runoffs from the development within their project.

“A lot of people are already asking for the article but we still can’t provide that since it’s still ongoing,” Ligaray said.

The professor added that they will welcome any form of support from those interested in the study, especially since most of their work is funded by their own personal contributions and limited government grants. 

In a statement sent to Rappler on Tuesday afternoon, April 21, the Mont Property Group said that they cited the UP laboratory’s assessment in recent statements because it was a public study, adding that they merely provided site data, which include but are not limited to detention pond sizes and locations, and area maps.

“As far as Mont knows, the study for the Guadalupe area is complete (as those are the areas indicated in the study), but we were also told that the study for the rest of Cebu is still ongoing,” their statement read. – Rappler.com