From Barisal to Khulna
A small ferry carries people and motorcycles, with a large new bridge under construction in the background.
Having completed servicing the two GNSS and RSET stations south of Barisal, we are now heading west to Khulna to service the rest of these stations to survey the Ganges-Brahmaputra delta of land subsidence and sedimentation. Many roads in Bangladesh radiate from Dhaka. In southern Bangladesh, there are not many good roads going east-west. This makes driving slow in rural Bangladesh. Near Pirojpur we had to take a ferry across the wide Baleshwar river. From the ferry (pier), I can see the large new bridge that is about to be completed.
Our car ferry approached.
There is a lot of construction going on across the country. With an annual economic growth of 7% for the past 4 years, the country is booming. As Bangladesh transforms from a low-income country to a lower-middle-income country, new roads and bridges, subways in Dhaka and new train lines are all under construction.
RSET team, Ira, Masud, Upal, Pinky, Nahid set up the measuring arm.
About halfway through Khulna, we turned south to our stop in Sonatora, Sharan Hora district. Here, we have installed two GNSS stations. One is located on top of the primary school like many of our other schools and the other is mounted on an RSET pole. RSET (Rod Surface Elevation Table) measures sediment accumulation, elevation changes, and shallow settlement relative to the 80-foot rod we hit the ground.
Loading a rickshaw brings our equipment to the site.
GNSS will measure the absolute motion of the same rod, giving us the deep component of the sink. The two GNSSs here are only 2.5 years old, too short for a reliable rate estimate, but they consistently show about 1mm/year faster sinking on buildings, which is more ingrained than poles.
Our team goes through the GNSS antenna on the RSET mast. Bachchu, Sanju, Upal, Masud, Nahid, me, Pinky, Ira and Chris are still exploring these areas.
Getting here requires another ferry crossing to reach this land on the edge of the Sundarbans mangrove forest. We had to use the road at the top of the embankment to go around the island as the inner road was not suitable for our van. We hired a rickshaw to transport our equipment from the embankment road to the school and then to a nearby open space.
Bachchu’s garden, part that is easy to walk through.
We also met Bachchu, a local farmer who allowed us to put equipment in his rice fields and is a member of the school council. More than two years later, we are both happy to see each other. The school’s first site, SNT1, looks good. Although we lost contact in late October, the receiver continued to log data into December, when the battery was low.
Some local women are harvesting rice.
Then we checked the ground rod. To our relief, it was still in place, but the wires connecting it were cut. We just need to splice a new wire. SNT2, with receiver boxes installed in Bachchu’s garden, works even better. Low battery, but still running. To be on the safe side, we replaced the battery with a new one anyway. Bachu gave me fresh cucumbers as we made our way around the garden’s central pond. The site went surprisingly well, but the RSET team still beat us because we had two GNSS here.
Our car squeezed through freshly harvested rice as we drove on rough brick roads.
We now turn our route back to the main road and drive past the historic city of Bagrat, built in the 1400s, to Khulna. We passed the Psul River, which we sailed a few days later, and entered the city. Since our driver didn’t know Khulna well, we followed Google’s directions to our hotel, which took us down a bad road. We bumped slowly on our way to the hotel. The long drive and stop to Sonatora meant we arrived at 7pm, another 12 hours a day.
Sanju standing next to a working GNSS station. The antenna is behind him, and the electronics and batteries are in a waterproof case.
Our second day location was a long drive southwest. We initially estimated it would take 3 hours to get there, but Google’s misdirection and the last bad brick road meant it would take 4 hours. We ended up getting out of the car and walking to lighten the load on the car. Also, we can go faster than a car can go on this road. Still, the long drive featured a greater variety of rice, shrimp and other crops at various stages of development, and Chris took three times as many photos as the previous three days combined. We can see that the fall rice crop is being harvested while the spring rice crop is still in its seed bed, or just transplanted, and everything in between. The area of this site is mainly Hindu and we passed many temples and shrines.
A local teenager climbed a tree blocking the antenna and chopped down many of the problematic branches.
After walking to the school that doubles as a hurricane shelter, we met with the principal and went to the roof. To our surprise, we found that the receiver was working and still recording data. When we replaced the batteries, we found that one of the old battery cases was separated, so they won’t last long in this world. However, a tall tree grows between the GNSS and the open field with RSET. We wanted to try a new technique here called GNSS-IR (interference reflectometry). It uses the bouncing of the river or now the ground to determine its height below the GNSS antenna. It can give us continuous measurements of subsidence and seasonal changes, but not if trees block the view.
At the local store on the corner, the owner makes tea for all of us.
The principal initially suggested we wait for the power company to trim the trees near the power lines, but eventually a local boy climbed up the tree with a machete and started cutting branches. We were able to get about ¾ of the offending branch; the rest will have to wait for the power company. For the first time, we did well before the RSET team. We had tea and Sanju bought sweets for all the local kids. Then we walked leisurely along the red brick road to the embankment, talking to the farmers along the way. We left the RSET team and returned, stopping for a quick snack around 5pm, just as the RSET team was finishing their work.
A street in Khulna with the kind of green auto-rickshaws we took to the museum.
The RSET team has now completed their land site, but our boat won’t be ready until 7:30pm. We have a site at the nearby Khulna University. We were done by noon. Sanju, Chris and I then went to the Divisional Archaeological Museum to meet with Regional Director Afroza Khan Mita. When we arrived by auto rickshaw, we found here and all her staff waiting in line at the entrance to welcome us with flowers.
Afroza Khan Mita gave me a replica of a terracotta tile as a gift.
She then showed us around the museum and we met in her office for tea and snacks. She organized a webinar series and I got involved in delta eco-archaeology. It includes archaeologists and geologists. With the people I meet in this series, I hope to expand my measurement of settlements to include more archaeological sites. It was a pleasure to meet her in person and we are all excited about the potential collaboration. This conference concludes the third part of my trip. The last part will be by boat to the remaining GNSS and RSET stations.
