River migration in the Philippines presents a serious hazard to its bridges. According to a Prevention Web article, “Monitoring moving rivers: Analysing threats to critical bridges in the Philippines,” hydrometeorological threats or extreme events like flash floods, coastal flooding, landslides, and severe rainfall are among the causes that trigger rivers to migrate in the Philippines.
While some rivers are stationary across the landscape for many years, many rivers in the Philippines are exceptionally dynamic, making bridges and roads close to rivers particularly vulnerable.
The Philippines location in the typhoon belt within the Pacific Ocean region makes the country highly exposed to tropical storms.
An average of 20 storms enters the Philippines, with 6 to 9 making their landfall, according to PAGASA. Strong typhoons can cause floods and landslips, destroying houses, livelihoods, and critical infrastructures.
An international team of researchers analyse the threats and monitor river migration in the Philippines with satellite images from Google Earth Engine (GEE). The GEE platform offers an extensive catalogue of satellite images that is accessible. The team analysed satellite images of rivers and bridges in the Philippines between 1988 to 2019 to identify and detect any river changes over this period.
Of the 74 bridges that the researchers examined, half of them show a substantial river migration that can pose serious risks to infrastructure if not managed. The other half remained relatively stable or showed minimum river migration.
Researchers also observed diversity in river behaviours, and with different rivers adjusting in various ways. River migration is not only a local event but could extend beyond the bridge’s area.
According to researchers, sometimes local site inspection fails to capture this information and recommends using satellite imagery as a low-coast approach in river monitoring investigation and inform future placement of bridges.
Other critical infrastructure next to rivers like road, rail, and pipelines can also use satellite imagery to manage risks from all climate change threats and natural disasters.
PHOTO CREDIT: Aerial view of Jones, Isabela, Philippines by P199 – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=22454896. The photo has been cropped to suit the website’s image size requirement.
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