"With these more expensive instruments, we can measure the sinking of the delta to better than 1 mm/year. All deltas are sinking. What is important is the balance of sea level rise, the land sinking and the sediment filling the space. In the Mississippi Delta, sea level rise and subsidence outpace sedimentation, so Louisiana is losing land at a rapid pace. Here in Bangladesh, there is enough sediment, but it is distributed differently than the subsidence; we are measuring where it is keeping pace and where it is not."
"We have co-located our GNSS with RSET-MH (rod surface elevation tables-marker horizons) that measure elevation change and sedimentation rates. Together, they provide an estimate of both deep and shallow subsidence, to help us understand how it varies with depth and where the land is keeping up with sea level rise and subsidence. Right now, the RSET team is far ahead of us since we had to return to our site at Barishal University before heading west to Sonatola, a small village on the edge of the Sundarbans Mangrove Forest, about four hours away. With all the bridge building going on here, we only needed to take one car ferry to get there."
High-precision GNSS instruments are being deployed across Bangladesh’s delta to measure subsidence rates to better than 1 mm/year. Deltas universally sink; resilience depends on the balance among sea-level rise, land subsidence, and sediment deposition. The Mississippi Delta experiences sediment deficit relative to sea-level rise and subsidence, causing rapid land loss. In Bangladesh, overall sediment supply is sufficient but deposition patterns do not match subsidence locations, producing spatial variability in elevation change. Co-locating GNSS with RSET-MH installations yields combined estimates of deep and shallow subsidence and sedimentation rates. Polders prevent sediment entry and often leave enclosed land lower than adjacent unpoldered areas.
Read at State of the Planet
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