The final phase of our revolves around visiting chars, sandy river islands, on the Ganges and Brahmaputra River. Chris and Dan are making measurements of soil salinity and moisture and spectra of the soil reflectance, while Liz and I collected samples for OSL dating and understanding the OSL properties of the river sediments here. This entails a mixture of driving around the country and spending time on small country boats and walking around the chars.
Geohazards in Bangladesh
After helping Chris an Dan with soil salinity and reflectance measurement, Humayun, Liz and I moved onto the smaller M.B. Mewl to sail through the Sundarban Mangrove Forest to service our GPS station at Hiron Point.
Humayun, Liz and I headed to Khulna in SW Bangladesh a day after Chris and Dan. Along the way, we stopped at our sediment compaction meter for surveying and removing the GPS, and getting feasted by the family that hosts the system.
I’m back in Bangladesh with a small team after a year and a half away. One different is a police escort as a result of the attacks last year. We start by successfully sampling river sediments to correct the date of an earthquake that caused a river to shift over 3,500 years ago. We also will be fixing broken equipment, visiting the ever changing rivers and hopefully meeting with the public and government officials about the earthquake hazard.
A new film takes viewers from the eastern highlands of India to the booming lowland metropolis of Dhaka, the capital of Bangladesh–and explores an ever-more detailed picture of catastrophic earthquake threat that scientists are discovering under the region.
Despite the miserable weather and ongoing rain, we constructed a wooden structure to hold the GPS receivers, solar panels and other electronic equipment between the three wells. We worked out how and where to mount the antennas and had parts made to accomplish it. Although I had to leave before it was completed, the team persevered through the storm and now we will be monitoring ground subsidence and sediment compaction in the Mississippi Delta.
This summer I am in the Mississippi Delta in southern Louisiana helping to install an updated version of the compaction meters that we have in Bangladesh. The environment is quite different and we have arrived in the midst of an historic storm. Luckily for us the brunt of the storm is NW of us. So far, we are still able to work between the rain above and the mud below.
We finished our work at the river transect. Now we had one more sample to collect. Alamgir had arranged for drillers at this new site, but they were delayed because of a knife fight between two villages over some property.
The success of the tube wells for drilling and obtaining samples was a great boon to our field program. We drilled three additional tube wells to complete a five-well transect across the abandoned river valley. When we date the samples, we will find out if the river switched position suddenly, possibly from an earthquake.
The resistivity testing was hampered by bad roads and flooded fields. The augering was proving similarly difficult in the thick muds of the abandoned channel. It was time to change to our alternative plan: drilling with tube wells. That worked better and we had turned a corner.