Sea Level Rise and Land Subsidence
On May 26, 2024, Cyclone Remal made landfall in southwest Bangladesh. Storm surges up to 3 m breached levees, flooding and contaminating farmlands. Approximately 0.8 million people were forced to evacuate their homes, 45% of standing crops were damaged, and $500 million was lost in assets and infrastructure. (BRAC Sit. Rep., 2024)
Quantifying Sea-level Rise, Land Subsidence, and Sedimentation
In the face of climate change, flood hazards from cyclones like Remal will be amplified by sea-level rise and land subsidence (See figure to the left). At the same time, some hazards can be mitigated by natural sedimentation that builds up the land surface. One of the greatest challenges in projecting hazards comes from the land subsidence, which can vary significantly across the coastal zone. Our team is overcoming this challenge by quantifying sea-level rise, land subsidence, and sedimentation across southwest Bangladesh, using state-of-the-art field and modeling technologies in collaboration with BRAC, Dhaka University, and Louisiana State University.
Click the image to the left to see a larger version.
Subsidence map
Measurements of subsidence are made with a network of different devices. Most subsidence comes from compaction as water is squeezed from sediments as they are buried. Because each system is anchored at different depth, they each measure a different amount of subsidence. We are using numerical modeling to integrate the measurements to better understand the distribution of subsidence spatially and with depth.
Explore full resolution map to see how subsidence varies across Bangladesh
Field Work
To make our subsidence measurements, we have traveled to Bangladesh to install, maintain, and repair our equipment. These include continuously recording GNSS systems (i.e., GPS), mostly installed on the roofs of buildings. Many of these are co-located with surface elevation tables (SETs) in conjunction with Louisiana State University. We independently surveyed geodetic monuments and investigated the sinking of historic sites. We also operated a optical fiber strainmeter measuring sediment compaction across six depth intervals until the instrument was destroyed by riverbank erosion. Detailed descriptions of our fieldwork are available on the Columbia University Climate school blog, State of the Planet: Geohazards of Bangladesh.
