Global warming’s irony: More floods, less water supply
Jennifer Rendon (The Philippine Star) - November 28, 2019 - 12:00am

ILOILO City, Philippines — The devastating floods that recently hit Venice are not a farfetched possibility in Philippine cities, a visiting Canadian professor has said.

Gian Yew Gan said as the world braces for global warming, more flooding is expected to happen – but the irony is there could be less supply of water.

His lecture on “Perspectives on Multi-facet Impacts of Global Warming on Earth’s Waters” was delivered during a forum at the University of the Philippines Visayas last Nov. 19.

Gan is a civil and environmental engineer from the University of Alberta specializing in water resources, hydrology, cryosphere, remote sensing and environmental impact of climate change.

“The problem is you can have more rainfall but you have less stream flow,” he said.

Gan has been giving lectures in Asia, Europe and North America. UP Visayas was his first in the Philippines.

By sharing his perspectives on climate change impact, Gan hopes to raise awareness, especially among younger generations.

During the lecture, he presented several slide shows and scientific evidences on the global warming impact and why these changes are occurring.

Global warming is the long-term rise in the average temperature of the Earth’s climate system. It is a major aspect of climate change, and has been demonstrated by measurements of direct temperature and various effects of warming.

Gan said the greenhouse effect plays a key role in all those changes.

He cited as examples the melting of glaciers and sea ice that has never happened before in a significant way.

“All those things have not happened in a thousand years but started to occur in recent years,” he said.

Based on instrumental temperature record, 2016 was the warmest in the last 150 years.

Gan said the melting of glaciers, sea ice and snowpack has significant impact because it signals the change in the water cycle and water supply of certain river basins.

While there are no glaciers in the country, Gan said melting of glaciers will still have an impact because of sea level rise.

“For one thing, it will cause coastal erosion problems. Warmer ocean would likely cause hurricanes, typhoons and so on because oceans carry a lot of energy. There’s more energy in the oceans, more likely that you will get those extreme events that could impact Philippines in a very similar way,” he said.

Submerged cities 

A report by Climate Central indicated that several countries in the world are at risk of being submerged by 2050 due to increasing sea levels caused by climate change.

In the Philippines, major cities in Luzon, Visayas, and Mindanao could potentially be erased from the map as coastal flooding and increasing sea levels may take place in 30 years.

Based on the coastal screening tool of Climate Central, the following areas will be below annual flood level by 2050 – Roxas City, Iloilo City and areas of Iloilo, Antique and Aklan.

Gan said he is not aware of the Climate Central report or the possibility that some cities, including Iloilo, would be submerged 30 years from now.

But he said sea level rises around 3 mm per year “and the rate is increasing.”

“In the past it’s just 1.8mm a year then it went on to 2.0,” he said.

And at the rate it’s going, it could even post 4mm per year, partly owing to the increased melting of ice sheets.

“It may not be completely submerged but more likely, cities will get flooding incidents like what is happening in Venice right now. These things are gonna happen more often and more areas flooded,” he said.

But it’s not just climate change. Gan said land use would also play a vital role.

“If you will build more roads and put more concrete pavements, that will reduce the infiltration loss,” he said, as flooding is more likely with a lot of concrete pavement.

He instead pushed for pavements that are permeable.

Permeable paving is a method of paving vehicle and pedestrian pathways to enable infiltration of storm water runoff. Permeable pavement surface typically includes pervious concrete, porous asphalt, paving stones and interlocking pavers.

While he could not confirm the specific cities that might be submerged, he said increased flooding is always a possibility.

He pointed out, though, that there are small islands in the Pacific Ocean where floods are omnipresent that eventually residents have to move to higher ground.

“In the Philippines, I don’t know the terrain features but small islands, low-lying areas will have more flooding problems,” he said, adding more studies are needed to determine the magnitude of potential danger. 

“If sea level increase is at 3mm per year, in the next 50 years, you’re gonna have 150mm of higher water level. So, this is not that much but it will impact low-lying areas,” he said.

The Philippines will not be impacted much on this aspect compared to countries with snow and glaciers.

As a country, the Philippines can’t do that much, Gan said.

“Simply because this will depend on major players of the world, America, China, India and the rest of global powers,” he said.

After all, global warming is not a local problem.

“There must be a conscious effort of those big players that can do a difference. Small players can’t do that much,” he said.

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