NAMRIA: Metro Manila's sea level rising almost 3 times the global average

The sea level around Metro Manila rose by 8.40 millimeters a year from 1901 to 2022 - around three times the global average, according to the National Mapping and Resource Information Authority (NAMRIA).

NAMRIA Division Chief Dennis Bringas presented the data during a coastal engineering summit at the Mariano Marcos State University in Ilocos Norte on August 15.

“We have records to show like in Manila, (the sea level) is increasing pero what we did was to segregate ‘yung old historical data saka yung nangyayare ngayon,” Bringas said.

The NAMRIA's data showed that from 1947 to 2022, the sea level increased by an average of 13.20 millimeters yearly.

When urbanization began in 1965 until 2022, it increased by 14.40 millimeters a year.

“So kung tignan natin ‘yun, mas mataas pa - 14.4. That’s the start of urbanization in Manila. So I’d like you to know na itong 1947 at itong 1965, may 1 millimeter difference,” he noted.

Bringas said this difference was part of the "coupling effect" or the sea level rise and land subsidence.

Among the factors that contributed to this were:

• Groundwater, oil, and gas mining
• Water impoundment or channelization
• Vegetation clearance or deforestation
• Other activities affecting the hydrological cycle including pollution, climate change, deforestation, landscape changes, and urban growth

Bringas also presented data from tide stations in the provinces. In Legazpi, the rate of increase in the sea level is 6 millimeters per year, while Cebu is below the average with 1.2 millimeters per year, and Davao is under the global average of 3.60 millimeters per year.

The study showed that the coastal sea level rise or fall depended on the strong influence of other local factors such as geographic location, climate pattern, ocean dynamics, and varying geologic forms and settings.

“Most of the sea level trends from Tide Gauges (TG) in the East, North, and South of the Philippines showed sea level falling, because or the short period or TG observations or less than 19 years that is dominated by El Nino occurrences, while TGs with long periods of observation (of more than 19 years) exhibit a sea level rise,” NAMRIA said. — DVM, GMA Integrated News