Earthquakes, floods, sea-level rise and sudden shifts in river courses threaten many of the 150 million Bangladeshis living in the low-lying Brahmaputra River delta. Scientists from Lamont-Doherty, Dhaka University and other institutions have begun a five-year project to understand the hazards and the possible hidden links among them. Lamont geophysicist Michael Steckler keeps us up to date on the work.
Geohazards in Bangladesh
Construction in the Swamp
The weather is miserable, but there is no let-up in the forecast. However, we seem to be in a local area of less rain, and more importantly no lightning. The worst weather is in northern Louisiana. They are getting 15-20”. While waiting for a break in the weather, we assembled some of the wooden planks into walkway sections. As the rain let up a little, we finally decided to go for it and head to the site. We loaded up the mudboat, and Don and Keith took a load over to lay down the walkway. Don is the technician
for the fiber optic system and Keith is a UNAVCO GPS engineer. Tim is a professor specializing in geodetics, while I have experience with subsidence on a variety of scales, including our GPS and compaction meters in Bangladesh. When they returned, we followed with more of the supplies. The wooden walkway allowed us to only sink up to our ankles instead of our knees in the mud. Carrying the supplies out, we started construction
on the structure that will hold most of the equipment—solar panels, GPS receivers, batteries, modem. Sinking the six 4×4 columns into the mud was tough, but less so than we envisioned. After that, we managed to get most of the structure built while Don worked on the compaction meters. We were completely soaked, but got a satisfying amount done. Returning to camp, we spent the rest of the day planning, buying more supplies, and dinner. Our biggest question mark is how to attach a GPS antenna to the reference rod that goes
down 37 meters to the bottom of hole 1. The size of the rod and the standard thread size for GPS equipment do not match. Adapters are not readily available. Tim and I wanted to install GPS antennas on both the reference rod and the upper casing, but it is not clear whether the two antennas will interfere. We decided against putting two on the same well, but may add it later if feasible.
The next day, the weather remains lousy, but we are still in a pocket of less rainfall
than much of Louisiana. We started out soon after sunrise. All the rain meant that the planks sank farther into the loose mud than the day before. By now, walking in thigh high muddy water all the time is usual. We split into different tasks. Tim and I mounted the solar panels, Keith set up the GPS antenna mounts and Don redid the compaction meter electronics. Later Keith and I set up the receivers and batteries while Tim and Don redid the conduit connecting the compaction meters to our control platform. Tor Tornqvist and John, a
graduate student from Tulane University, visited us in the morning and went back to the camp via a pirogue, a small Cajun boat. As time went on, the rain lessened. Best weather we’ve had. We are working well together. Hardship makes for good bonding. By 2 p.m., we had finished all we could do today and called for Mark to take us back.
We decided we needed a machine shop to make the adapter, which needs to be stainless steel. That is not possible until Monday morning. The rest of our needs we could get at a hardware store. After
lots of discussion about the plans, Tim delayed his flight home. Don will decide at 10 a.m. tomorrow morning if he needs to delay his flight. The aim is for everything but the reference rod to be done by midday tomorrow. If so, Don can leave. Keith will stay to the end, to set up he reference rod. Since so little is left that needs manpower, now that the major construction is done, I will leave as scheduled tomorrow morning. We are approaching completion of the site. While I hate leaving before it is completed, I have other commitments and this group can easily do the work without me. We will shortly have two extremely sensitive compaction meters and three GPS receivers to monitor ground subsidence and sediment compaction. If we can get more funding, we will install another optical fiber in the middle depth hole and another GPS. Meanwhile, we have the world’s best compaction meter in one of the world’s worst sites for fieldwork and solid ground.
P.S. Don delayed his flight and Sunday and Monday the group finished everything. A machine shop built the missing parts on Monday and Keith, as the only one remaining, will install it Tuesday. Success, despite the weather.