Geohazards in Bangladesh
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 seismologist Michael Steckler keeps us up to date on the work.
Prior to the late 1700s, the Brahmaputra River flowed farther east by up to 100 km. It then switched, or avulsed, into a straight north-south route, possibly triggered by an earthquake in 1787. The small river whose course it usurped was called the Jamuna River. Now, below the avulsion point where what is now the Old Brahmaputra deviates from the present course, the Brahmaputra is called the Jamuna. The last two days were upstream of that location. Now we are downstream of it and thus on the Jamuna River. Our first stop was Sirajganj. This town is protected by a stone embankment. The river has been migrating to the west, threatening the town. As a result, the embankment now protrudes into the river. When I was here in 2011 I saw several collapses along the embankment and my class
saw them repairing it in 2012. They now have a lot more riprap at the base to protect it.
We drove along the embankment, a nice promenade, to the ghat and got a fast boat. Chris had picked out an area with a lot of diversity, so we could efficiently do our sampling. We checked our notes and found the char that had joined to the very large stable island was not the one we visited in 2005. That char was now a thin sliver. We stopped at the head of Katanga Char, only 2 years old, where the high ground was stabilized by grasses and people were growing peanuts and rice on the flanks. We then crossed a channel to the tail of the next char to the north. Here, what had been a grass-covered highland had been
ravaged by the river. Tufts of grass that had help on were surrounded by large scours over a meter deep. The little remnants had the same teardrop shape as the larger chars. Here and on another small char, we were able to collect all the samples we needed. We headed for the ghat and our hotel with an outside chance of taking their boat to the char I visited with my students last year. However, before arriving, we finally found green coconuts for sale. We had been searching for days for green coconuts. The seller cuts off the top with a machete, inserts a straw and you drink the refreshing coconut water. Afterwards, he splits it and you can eat the coconut jelly, not yet matured into the coconut meat. To add to our enjoyment,
Chris also found a shop selling the wasabi potato chips he had been searching for. With the extra stop and the slow check-in process, we abandoned visiting the char, but it was still early, so we went into Tangail for some shopping, although we found most shops closed as it was Friday.
For our last stop in the field, we continued south to the confluence, where the Jamuna meets the Ganges to form the Padma River. There are ghats for crossing the Padma and for crossing the Jamuna. We went to the later, which is smaller now that there is a bridge over the Jamuna. As the chars shift, so does the ghat. We had to walk for the last ½ km to the rental boats as Babu’s van could not go. We started at the southern end of Shivayala Char, a large char at least 30-40 years
old. However, the southern end had been eroded and then grew back. Where we were was only few years old. From there we went to the next, newer char for examining and sampling as it showed a lot of variety on the satellite imagery. That done, our next stop was a piece of fluviotourism, the confluence or actual meeting point of the Brahmaputra and Ganges Rivers. We stopped upstream and walked down the long narrow char. There were huge scour pits from the turbulence of the two rivers meeting during the monsoon. The point where the tow rivers met wasn’t as clearly defined as in 2005, but we waded around and found it our final group photo. Our work was done and it was time to return to Dhaka for some final meetings and a last hartal, and then home. As usual here, many things did
not go as planned, but with some adjustments, everything we planned got done.
We left the pleasant house in Kushtia to resume our nomadic existence. We spent a full day driving to northern Bangladesh. We will now work our way downstream stopping at multiple places along the Brahmaputra River. Finding little traffic, we drove past Rangpur, where we will be staying to the Tista River, a tributary of the Brahmaputra. While it is a large river during the summer monsoon, today it was a shallow stream with exposed sandbanks and people growing crops in the middle of the channel. Chris decided the hour we had before sunset was enough time, so we climbed down the embankment and hired a boat to cross the river. It was shallow enough that we saw children wading across and Chris got out and walked the rest of the way, followed by the chidren. Water diversion projects upstream means
there is little water here in the winter. Some exploration, some sampling, some photos and we were done.
We were up early for the long drive to the Brahmaputra. We hadn’t planned on coming this far north, so we didn’t have maps of this years arrangement of the river. I found two possible places for boat hires and ended up choosing Chilmari as the place easiest to get a boat. When we got the to river agound 11am, we found a cliff. Apparently ~1 mile of the coast had eroded here. An old woman chastised us that we should either prevent the bank erosion or give them money so they could move. We learned the boats were a few hundred meters upstream where you could walk down to the water’s edge. Along the way we
passed a group digging up the topsoil along the cliff to sell before it toppled into the river. We could see the cracks where the next pieces of land would be lost.
We bought some snacks for lunch and hired a boat. The fist char (sandy island) was unnamed, but 5 families from Bazradiarkhata Char had settled the north end and started farming, growing squash, wheat and dal. The char was only 5-6 years old. The families still returned to the larger char in the summer and New Bazradiarkhata Char, as we called it, was chest deep in water during the summer. We continued north to Kachkol Char. This char was 8-10 years old. However, it was now attached to Bazradiarkhata Char. The corn, wheat, dal, etc. growing was being farmed by
people from Bazradiarkhata Char. The village we visited were people who only moved there 6 months ago when their village and land on a char was claimed by the river. They were working a paid laborers and did not have their own land to farm. They were concerned that Meredith be careful of the sun so she wouldn’t get burned. They also suggested that if she moved to the char, she could get dark like them. We then went downstream to Bazradiarkhata Char itself. This char was formed during the major 1988 flood when 2/3 of Bangladesh was submerged. Now, 25 years later it had lots of trees homes, crops, an elementary school and an adult education center. We were surrounded by children, particularly Meredith. She could get the girls to pose for her,
but I could not. On the side of the village, there were great sedimentary features and Meredith and I measured a channel for some flow calculations. At all of there sites Chris sampled and documented the sediments and vegetation cover. By now it was getting late, so we left and circled the downstream end of New Bazradiarkhata Char. Newer and still unpopulated, the cut banks showed amazing patterns of crossbedding from the migration of the sand waves that built the char during high water. We explored this end of the char as the sun set over the right bank of the Brahmaputra.
Today, February 21st, is Language Day commemorating the 1952 martyrdom of students protesting Pakistan’s law making “Urdu and only
Urdu the language of Pakistan” when the Pakistan army opened fire. The ultimately successful language movement in the 1950s marked the beginning of the path toward independence. On our drive to Gaibanda, we saw numerous troups of school children heading to their local Shahid Minar, language day memorial, to pay their respects and drop off flowers. In Dhaka people laid numerous fantastic decorations made of flowers.
Gaibanda was the opposite of Chilamari. Here the coastline has grown outward and we had to walk out to the docks. We later discovered that the new land filled in what was the channel we crossed to reach Rosulpur Char in 2005. It is now attached to the mainland. The embayment by the coast is all that is left of the channel. Humayun again hired
a boat and we went south to an area where Chris could see numerous color variations on the satellite image. We found the land has changed substantially from the image of early January. The channel we wanted was too shallow for the boat, so we had a very long walk. A new Landsat image to be acquired tomorrow should be close to what we saw. Where we stopped was Manikkor Char, only 6 years old. The tree covered area to the north was Kashkhali Char, which is 13 years old. We walked towards it and met a farmer. He told us that there was a town and bazaar here 30-40 years ago, but it was lost to the river. When it returned he received land because his grandfather had owned land here. Such is life on the ephemeral chars. We continued walking towards Kashkhali, but wanted to cross to another area. Only Chris
and I walked through the muddy shallow waters of the embayment. In this area, which we called New Kashkhali Char, we met another farmer, but had no translator. Still, he helped us sample.
After finishing sampling, we went north to Rosulpur char that we visited in 2005. We showed the people photos on my iPad, but found that most of our photos were of people who resided there only temporarily due to their land being lost. They now lived across the channel to the east. Still we were welcomed and follow by lots of children and a few people remembered us from 2005. The teacher remembered Chris, but wasn’t sure about me. Overall, the village seems to be doing well with lots of corn growing on the char. We ended early, but then had a long drive to Bogra for our hotel.
We got to Khulna about 5 pm and met up with Chris Small, who was brought from the boat with all the Vanderbilt University people by Bachchu. This is the last segment of my trip. The next day, we went to an area near the compaction site. Chris had analyzed 10 years of MODIS satellite images and just west of the compaction site was an area that stood out for having increasing vegetation over that time. We drove to the site and then continued on the small dirt road that followed the small creek. We went around a bend and followed the road as far as we could with Chris snapping photos the whole way. We talked to locals at two places and the second one had the answer. Most of the rice fields were still fallow, but one area had a pump watering some fields. We walked over and immediately
became a center of conversation. This area had previously been converted to shrimp farming. About 15 years ago the BWDB built and embankment, which was the road we were on. This stopped the tidal flooding of the land inside the embankment. The shrimp company pulled out and as the land was cleared of its salt by successive monsoons, everyone switched to rice farming. That started about 8 years ago and the land has become more productive with time. This is what caused the long-term trend.
On our way out, we stopped at the compaction site. The Scotts had done everything but download the GPS data. Only the mother and youngest son were home. We were welcomed warmly and served cookies and pakan-pitha, a
pastry filled with a dal paste. Then I downloaded the data and visited the wells. We were invited for lunch and told that Mr. Islam would be upset if he knew we left without lunch, but we were already behind schedule. We had to go on to Kushtia near the Ganges. During the long drive, we found out that there was a hartal called for Monday. We had to rework our plans since we had a lot of driving to do that day. It was dark when we got to Kushtia, Humayun’s hometown. We were surprised to find we were staying in his aunt’s house. Only the caretaker was there and we split the 3 bedrooms. Staying in a home reinforced the plan we had come up with. We would need to stay here three nights. An added plus is we’re close enough to hear the protesters singing every night.
For our new plan, we went to the Ganges downstream of Rajshahi and back so we can go locally at Kushtia during the hartal. During the long drive it started raining. We also had trouble finding a ghat (dock) to rent a boat. We ended up driving to the river and then walking out on a semi-attached char (sandy island). The mud was incredibly slippery in the rain, but I only fell once. Chris sampled along the riverbank and then the two of us waded over to the char to sample some more. Chris will measure the spectra of these samples back home to calibrate his satellite analysis. He will be able to distinguish the percentage of different sediment types for each pixel of the satellite image, which we will then use to better understand the changes in the rivers. The chars move around, appear and disappear
every year during the monsoon. Meanwhile, we were getting soaked and called it quits. Good thing we didn’t go out on a boat for hours.
Today, is another hartal (general strike), however, we were able to walk to the Gorai River here in Kushtia. We went to a park where a lot of boats come to take people on rides, but none were here this early. Still, we managed to flag one down and hire it for the day. We went up the Gorai into the Ganges and headed upstream to Ranakor Char. We spent the day visiting three chars (sandy islands), stopping at multiple sites on each. The cold overcast day brightened as it went on. We did sampling and a lot of walking around examining the bedforms and varied sediment deposits. We could see 5 different scales of bedforms from the
chars themselves to the tiny ripples in the lows of larger waves. This area by Kushtia now has numerous chars and they are much more accessible than the ones we tried and failed to visit yesterday. When we returned in the late afternoon the empty park was filled with people.
After the resistivity, I was supposed to go to Khulna to join Scott and Scott on repairing the compaction meters. We have two places with sets of wells where we installed optical fibers. A local person uses a device to measure the length of the fibers each week by shining a laser through the fiber. Unfortunately several on the fibers have broken since we installed them. The Scotts will be repairing them, as well as the usual yearly measurements and data collecting. They went to the northern site first – we saw them heading north while the conclave group was heading south. I was going to join them for the southern site, but their work went so much faster than expected that they finished while I was doing resistivity. Thus there was no need for me to go to Khulna before meeting Chris Small for the river work. I spent the two extra days in Dhaka. I had plenty of people to look up that I didn’t expect to have time to meet.
On the first day, Humayun and I went to the US Embassy to meet with people who couldn’t make it to the conclave due to the hartal. Even the US Ambassador was going to meet us when he took guests to a resort in Sylhet. As Humayun and I passed through several layers of security, we ran into the Ambassador on his way out. We chatted for a few minutes and then went on to our meeting. After making it back to the university for lunch, we went to the Geological Survey of Bangladesh, where my main contact has been promoted to Director General. I showed him our results and we discussed collaborations, particularly on GPS. All around the university women were dressed on yellow, orange and red
saris for the first day of Bangla spring. Finally back to the Ambala Inn where I met up with the Scotts and Doug and all of us went to dinner with Chowdhury, my collaborator from the Bangladesh Water Development Board (BWDB). He has gotten us a huge dataset on the water levels in the rivers and in groundwater wells. Well over a million individual measurement. Water is so central to life in Bangladesh that there is an excellent monitoring system in place that we use to determine the amount of water impounded in Bangladesh during the monsoon. It is over 100 billion tons of water.
The next day, we went to BITWA to try to obtain more detailed information about the tide gauges for examining sea level changes. Tide gauges measure the height of the water relative to the land, but here the land is sinking. We put 2 GPS
to monitor the land subsidence next to tide gauges. That will let us separate the sea level rise from the subsidence. The combined effect has Bangladesh worried about land loss and water salinification. We went meet with the wrong person twice before we finally found the correct person, a woman whose sister had been a student of Humayun’s. It will now be straightforward to get the detailed data. The afternoon was spent working with one of the students from the resistivity training. Sojon wanted to go through everything in detail so he knows how to run the system. Fayaz would have joined us, but he was out filming archeological sites with Doug. The two of them have taken the initiative to be leaders among the group. The 10-minute ride back to the Ambala Inn took an hour. An area just north of the
university has been blocked off because of the peaceful protests against the razakers, the groups that collaborated with the Pakistani army during the revolution and helped them in their killings. The Islamist party’s hartals for the release of their leader has lead to a larger movement wanting the death sentence for him and others. It is Occupy Dhaka. It was very strange to see women dressing in colorful clothing yesterday with headbands calling for death for the razakers. Finally, I arrived and waited for Meredith, the last of our party to arrive from NY for the river work. The bad traffic meant she arrived very late. Doug and I had a last dinner together at 11 pm in a local packed restaurant.
Today I am finally on my way to Khulna with Meredith and Humayun, with Babu as our driver, of
course. I am stuck waiting to get on the ferry across the Padma River, formed by the merger of the Ganges and Brahmaputra. Once across, we will be in the more leisurely and relaxing south to meet up with Chris in Khulna.
After returning from Sylhet, I left Dhaka the next morning for Comilla for 4 days to train a group of Dhaka University students and graduates on operating our resistivity imaging system. Many of the conclave people headed out to the Padma River, formed by the joining of the Ganges and Brahmaputra to do sampling for a remote sensing study of the rivers. I will be doing this later in the trip, but had other plans now. The transects of wells that we are drilling provide detailed vertical records of the sediments, but how do we connect the dots when the wells are 3-4 km apart? It turns out we can do it with electricity. Clay and mud has much lower electrical resistivity (or higher conductivity) than sands. The basic technique it to pound two pairs of electrodes (stainless steel rods) into the ground. We then use a car battery to
send a current between one pair and measure the voltage at another pair. The voltage depends on the rock type between the 4 electrodes. For our system, we have 84 electrodes that can be spaced up to 9 m apart and a long cable in 12 sections to connect them. A sophisticated resistivity device then sends current to one pair and measures the voltage at up to 8 other pairs at a time. The device is programed to do measurements with thousands of different combinations. The result is similar to doing and electrical catscan of the earth showing the distribution of sand and mud.
I came to Comilla with 6 trainees, Fayaz, Sojon, Jia, Rabi, Fuad and Paval. During the 4 days, they will work with me to learn to use the system
well enough to be able to carry out these surveys on their own. For the training site, we came to Comilla where to work around the Lamai anticline. It is the westernmost hill sticking up out of the floodplain. To help interpret the structure creating the anticlines, we need to know the dip, or slope, of the folded beds. This has been roughly done from topography, but the exposed topography is partly eroded. We want to image the boundary between the older Pleistocene sediments of the anticline and the younger Holocene sediments that cover them. Both sediments are similar, but the surface exposed during the last glacial period when sea level was 120 m lower has been altered to clay. This should show up as a dipping layer of low resistivity. We will do 4 lines, two on each side of the anticline to image the dipping beds.
Our first day was short because of the time it took to get here. We laid out a short line with 56 electrodes a short distance south of one of the wells that was drilled on the east side of the anticline. The car batteries we took along were not fully charged, so we hooked up Babu’s van to provide more power. That worked well and decided to use the car to run the equipmet the rest of the days. However, that meant the lines had to be where a car could go. Humayun did not join us because his wife has been ill. That meant we didn’t have a GPS to record positions or track where we were. We managed to use the GPS in my camera to get the positions of the line. We moved to our home for the next few days, the Bangladesh Academy for Rural Development or BARD.
The next day we shifted to the west side the next day. Google Earth became our tool for finding sites. With a USB modem we had slow, but continuous internet. We found a set of fields close to the one of our drill sites. We navigated to it by recognizing buildings, mostly gas stations from Google Earth. The fields were fallow, so we could cut across them. Everything was going smoothly. We finished early and I was able to spend the late afternoon teaching the students. That evening we processed the data for both lines. The first one showed the boundary we were looking for to be very shallow. A river had eroded part of the anticline. Thus we were on top of it and not on the flank. Good data, but it didn’t provide us with a slope. The other line had noise problems from a power line, but clearly showed the layer we wanted dipping ~3° to the west. The system was providing hard data.
We still needed a line on the east. We tried our first site, but Babu’s van could not drive to the line location. On to plan B, a country road on the west side. We drove our electrodes into the fields at the base of the road being careful not to disturb the growing vegetables. The data was marred by some power lines, but showed our layer for part of the line. It lined up well with the previous day’s results. For our final day, we need a good line on the east. I picked several candidates on Google Earth. The first was inaccessible, but I quickly found another road and we did it there. Because they were planting rice, the side of the elevated road was not useable. The top turned to not be that good a place. The data was much worse quality than any of the other sites. Still, it gave reasonable results. Humayun and Doug came out, so we interspersed working on the resistivity line with filming. That line competed our work here and the training and we all headed back to Dhaka. The students were trained and we learned how to select good sites.
Now that the hartal was over, we were free to travel as we wished. We also switched film crews. Doug and Diane from Earth Images are independent filmmakers that make PBS specials. They arrived in Dhaka on the morning of Feb 6 during the hartal, so could not travel here. Humayun arranged for them to be picked up by an ambulance, exempt from the hartal, and taken to the Ambala Inn to wait out the strike. That meant they were able to spend the day walking around getting footage of Dhaka without cars, a rarity. Colorful bicycle rickshaws ruled the road. They left Dhaka in the afternoon when the hartal was dying down and arrived at the Shuktara around 11 pm.
The geology that we saw over the hartal changed our drilling plans. Steve Goodbred was excited enough by what he saw to change the day’s well from the flat floodplain to the back of the anticline. He and the Vanderbilt team went there early in the morning with the AMNH film team to get their last shots before heading to Dhaka. That meant the rest of us had to stay away. Most of the group went to the Sylhet anticline outcrops near the cricket stadium and airport. I later learned that they found clear evidence of rivers cutting through the anticline while it was growing. It caused mud deposits from the ponding on one side and gravels from the steeper slope on the other. I was recruited by Doug for an interview and to take him up to the Jaflong area by the Shillong Plateau so he could film that. Nafisa and Mosher stayed with us. After they watched my interview from behind a
wall, our group headed north. At the site where Nano gave us an overview, I repeated his story with a 3D camera rolling. Nafisa, Mosher and I held conversations about the geology while Doug filmed us over and over. We then went over to the Rangapani River where border guards stopped us and informed us that foreigners were not allowed to film there. After some explanation from Nafisa, they call their superiors and we were OKed. The pits we had seen a few days before were now deeper and the miners had uncovered a large tree trunk and exposed boulders up to 6 ft across. We continued our conversations for the camera until the border guards told us it was time for us to go. Doug still tried to get more footage, including outcrops out of site of the guards until they followed and saw us still going. We left peaceably.
All the filming and multiple takes meant there was no time for Jaflong itself. We rushed back to the Sylhet Anticline in time to catch the drilling before it got dark. Since we only had a short ride back to the hotel instead of a 1-2 hr drive, a car full headed to Sylht City for shopping. As it was the last night of the conclave, we had a barbeque on the deck on the roof of one of the bungalows. They barbequed fish and tandoori chicken along with a host of other dishes and a procured bottle of vodka. An excellent end to the meeting.
The next day it was time to head back to Dhaka, stopping at a few of the anticlines from southern Sylhet on the way. As usual, getting everyone out and the cars loaded up took longer than expected. Nano and Ellie decided to stay another day in Sylhet and then go straight to the airport rather than have a day in Dhaka. Our group was shrinking. Jenn and Sanzida had already left early
because of ill relatives. A few people had canceled because of illness. We were down to about a dozen people heading to Dhaka. However, the defections and splitting of the groups the last few days made the field stops less unwieldy and more efficient. On the way south, we had a quick stop at Sreemongal, where a group from Singapore we are collaborating with put in a GPS. Then we saw tea gardens, a sure sign of an anticline. Tea needs well-drained soils and cannot be grown on the floodplains. However, the first tea plants were on flat land. The rising anticline had uplifted some of the floodplain on its flank, another useful observation. Then we entered the Rashidpur anticline proper. Several stops revealed that the dips of the beds were not preserved, limiting the value of the outcrops. We stopped for lunch in a tea garden and continued on to our GPS station and seismometer at a school in Chunarughat. In
2007 when we installed the site, we found the building we originally selected was unsuitable. It was brick made to look like reinforced concrete. We found this site by driving down the main street of the town on a Friday night. We found this school and contacted the headmistress, visiting her at her home on the weekend evening. The next morning we installed the site. Now on this visit, Humayun and I were again pressed into service for filming, along with a Nafisa, Mosher and Fayaz. By the time it was finished, we had to head straight back to Dhaka. Some quick stops at the next anticline revealed it too had poor outcrop. We then hit some of the worst traffic I had ever seen. The highway into Dhaka, never very fast, was at a standstill. Babu, our driver, turned around and led
us through back streets to alternative routes until we found one that was moving. It was almost 10 pm by the time we reached our hotel and officially ended the conclave and part one of my trip. Still it was extremely successful, pulling together the different groups and changing the direction of our research.
Our experience in in Bangladesh in nothing will go as planned, but somehow we are able to get everything done. Living in this ever changing land beset by numerous natural disasters has made Bangladeshis incredibly resilient and adaptable. This was tested over the last few days – and may continue to be over the next weeks – by a hartal. A hartal is a strike in which transportation is shut down. The party calling it sets up roadblocks and attacks cars and buses on the streets. Bicycle rickshaws and the green baby taxis are OK. This one was called by Jamaat-e-Islami, the largest Islamic party. The reason was that their leader was sentenced to life imprisonment for war crimes during the 1971 Independence War. The religious
parties supported remaining part of Pakistan and are accused of helping the Pakistani Army in killings. Estimates are that 3 million people were killed in the war for independence with Hindus and intellectuals particularly targeted. The leader on trial was specifically accused of killing 12 and assisting in the killing of 369 others. The problem is that the Jamaat-e-Islami is part of the opposition coalition and many believe the trials are politically motivated to take down part of the opposition before the elections later this year.
On Feb 5, there was a hartal called that ran from 6am-6pm. Driving around in our vans was our of the question. Luckily, it was the day to visit outcrops on the Sylhet anticline, where our hotel is. The sites at the airport and cricket stadium
were out of the question. We found out later that there were bombs thrown in Sylhet, although, thankfully, no one was hurt by them. The third area of outcrops we planned to visit were right by our hotel. We walked to the sites situated by the tea gardens and tea factory to see them. They were not the greatest outcrops, but still provided valuable new data and discussions. We returned to the hotel for a late biryani lunch, a step up from the cold packet lunches we’re been having. For the rest of the afternoon, we held discussions around our large poster-sized maps, or relaxed. The Bangladeshi students took advantage of the early night to go into town after the hartal ended. This was also the day that the AMNH team was doing interviews, so we were able to have people walk back and forth to their makeshift studio in one of their rooms.
More serious was when a second day of hartal was called for Feb. 6. The visit of the U.S. Ambassador to Bangladesh to our group was cancelled. But what were we to do now? We were to visit outcrops to the north and one of our drilling sites. After exploring several options, Humayun rented a very small pickup truck. This type of vehicle should be exempt from the hartal. To play it safe, we started our work by continuing along the same small road over the anticline that we walked on the day before. There are no roadblocks on a small country road. We continued the geologic work over the anticline. These young weathered sediments were hard to interpret confidently. However, we did see the dips of the strata switch from towards the south to towards the north
as we went over the crest of the anticline. We crossed where the floodplain sediments lap up against the folded strata. Our excitement about the interactions we are having in the field continues to grow. After completing this part of the drive, we came to a decision point. Would we continue to the main road and risk facing a possible roadblock? Did we want to travel that far on the back of a pickup? In the end, our group split up. The film crew rented a baby taxi and went off to get footage of the countryside. A second group walked back to the road over the anticline to visit more outcrop and pick potential drilling sites. Steve Goodbred was excited enough by what we saw to change tomorrow’s drilling site from the floodplain to the anticline. The interaction
at the conclave was now altering our project plans. It is working. The last group, including myself, continued as planned with the pickup. Not only was there no roadblock, but it was a pleasure to drive through Bangladesh with so few cars on the road and so little traffic. We got to the well site as they reached the maximum depth they could drill. Gas in the sediments impeded the drillers ability to lift the sediments out of the hole. We could see the gas bubbling up. We continued on to Jaintiapur and took a pleasant hike through a new set of outcrops and beautiful views. I personally found the evidence of a long gap in sedimentation 20-30 million years ago puzzling. As darkness fell, we had to leave the solution for another day. But at least the 2-day hartal was over.
Up to now, each group in our Bangladesh project has worked individually on fieldwork in their subject of expertise. Now that our project is now in it’s third year, we decided it was time to get together in the field to integrate our results. A major focus of the project is the interaction of tectonic forces and sedimentary processes. This week, is our opportunity to have experts on each interpreting the same outcops together. We have gathered a group of 9 Americans and 7 Bangladeshis in Sylhet in NE Bangladesh to what we have termed the “conclave”. I guess we have to send up a puff of white smoke if we all agree. Sylhet is an area where the large basement block of the Shillong Plateau and the Dauki Fault that bounds it meets the fold belt of the Burma Arc with its tea garden covered anticlines. It is also has a rapidly subsiding basin being filled with sediments in which the level of the rivers go up and down with sea level. Lots to see through different prisms. On top of the excitement of the conclave, we have a film crew from the American Museum of Natural History with us for the first 6 days to make a video to be shown in the AMNH and other museums about our project and the science we have been working on. After they finish, will we have another film crew from a company that makes PBS documentaries following us.
Everyone is doing their individual fieldwork before or after the conclave. Several of us arrived in Bangladesh just before the conclave, while others drove over from their fieldwork in western Bangladesh and two crossed the border from studying the Shillong Plateau in India. We all arrived and filled all of the rooms in the Shuktara Nature Retreat. For our first day, we headed to the Patheria Anticline with the Madhabkundu Waterfall. While the waterfall was spectacular, if took most of the day to get there. Pulling out maps after breakfast, we spent time discussing the region, slowed by the filming. Then the drivers took a wrong turn that took us and hour out of our water plus another ½ hour to double back via a faster road. It was 2:30 by the time we got there and almost 3:00 when we finally reached the falls. While there were great outcrops, we only had a hour there before having to start back. It was too late to visit our second stop and quite late before our cranky group got back to the resort for dinner. Overall, a disastrous first day.
Having gotten our bad day out of the way early, we had nowhere to go but up. And it did. We headed north toward the border with India and the Shillong Plateau. At the first stop we got an overview and our first view of the 2000 m high mountain and the geology while standing on one of the folds that mark the frontal area of the Dauki thrust fault. Then we went on to the Rangapani River where the large boulders are washed down from the plateau. There is a huge industry in Bangladesh mining rocks and gravel from the rivers along the border. Bangladesh has a shortage of rock that can be used in construction, particularly making concrete. The Indian border is clearly marked by the presence of rocks. On the Bangladeshi side they have all been stripped away and they are digging
pits to mine the rocks from the older river sediments. This results in beautiful exposure of the sediment layers and we scrabbled around in a pit while the workers mined the rocks around us. After a brief stop at the border crossing where trucks bearing rocks enter Bangladesh, we went to Jaflong, where the mining industry is even larger. The amazing thing about Jaflong is that besides being an industrial site with rock mining and noisy rock crushers, it is also a tourist site where people come to see the mountain. There are tourist kiosks, snack stands and guides mixed in with the industry. For us, there were also outcrops of the older strata from before the uplift of the Plateau. Our final stop was a visit to our GPS and seismometer station at Jalfong. Humayun and I were filmed explaining our work there while the others visited the geology exposed on the side of the hill we were on.
Day 3 was an exciting trip up the Shari River. We rented three wooden country boats and sailed up the river, crossing through exposures of sediments of various ages. The originally horizontal layers of strata have been deformed from the tectonics. The dip of the sediments started at 38° then increased to nearly vertical before decreasing back to ~45°. This folding is due to the sediments riding over structures beneath, possibly a fault. We also saw that the oldest sediments were marine and the seceding layers went to estuarine and then fluvial (rivers) due to the increasing amount of sediments coming from the Himalaya. Our boats traveled together and occasionally leap frogged from outcrop to outcrop. Chris Paola, our river specialist, also noted changes in the shape of the river indicating active tectonics. Our group of specialists is coalescing into a team. Meanwhile, we passed other teams of people dredging the sand and gravel from the river bottom using buckets into their boats.
After waking up in the Rupsa River in Khulna, we watched as the Vanderbilt University group studying sedimentation around Polder 32 arrived on Bachchu’s boat. They pulled up alongside and we spent some time catching up with each other’s trips before it was time to hit the road. Our last site is nearly at the northernmost tip of Bangladesh. This one is for tectonics. The 2-km high uplift block of Shillong, is roughly coincident with the Indian state of Meghalaya (Abode of the Cloud). It was the site of a M8.1 earthquake in 1897, although the exact fault that ruptured is uncertain. Our existing GPS indicate that it is moving south at ~7mm/y, but there is a suggestion that it is rotating clockwise, meaning the western end would be moving slower. Our GPS is going in Bangladesh just to the west of Shillong. However, the Brahmaputra River has eroded away the western margin and buried the remnants under sediments. We have to be far enough north to be on the Shillong-Assam block and away from the several faults on its southern side. We settled on the town of Bharungamari. It is literally the end of the road, only a few miles from the Indian border.
So we set off on a 400 km drive. Along the way, we stopped at Kushtia and visited Humayun’s childhood home and met his sister-in-law and nephew. Then lunch and across the Ganges River. At our first flat tire, we has tea in a small shop – Humayun had them pour boiling water on the glasses for us. At the second it was green cocoanuts. The driver switched to the spare tire while Sarah attracted a large crowd of locals. When we finally got to the hotel it was almost 10pm, about 12 1/2 hours after we left the Kokilmoni. At least it is one of the nicer hotels that I have stayed at in Bangladesh.
The next morning was a more leisurely 8am departure. For breakfast, we were joined by Atiqulla, one of Humayun’s fourth year students who is from Bhurungamari. He scouted the site and would lead us there, the local hospital. We squeezed the extra person into the van and headed north. We got there late morning, scouted out the roof and located a site for the antenna and for the receiver. Getting there meant walking through a hallway with beds containing patients at the hospital. It seems we have had two modes during this trip, either start very early and then have breakfast at noon, or have breakfast first and then have lunch after 4pm. This was the latter. You could tell we were getting worn out. We were having more trouble keeping track of some of the small screws and tools we needed. We started running out of anchors for attaching cables to the wall. Still, we got it done, although it is not our prettiest site.. However, Humayun did a great job with the grounding rod, having a channel cut in the concrete apron around the building, running the wire through a conduit and then recementing over it.
By the time we were done, it was 3:30 and the hospital administrator and some of the staff came to see the site. By the time Humayun finished explaining th purpose of the GPS, we were more than ready to get some lunch. What I didn’t know was that we were invited to Atiqulla house for lunch. We went to the house of his extended family, parents, siblings and nieces and nephews where we were served a feast. The five of us ate while the family and a large group of neighbors looked on and chatted with us. We had chicken, squab and beef along with boiled and pilao rice, paratha (bread), vegetables, dal (lentils), and cucumbers. A veritable feast and a good ending for the last GPS installation.
We stuffed our selves and headed back to Dhaka, staying overnight at Bogra, 4 hours away. Along the way we passed celebrations of Durga Puja, the largest Hindu festival in Bangladesh, and lots of cattle and other animals being transported for Eid ul-Azha, the feast of the sacrifice, to be celebrated this weekend. After arriving in Bogra, we celebrated with a beer at the first bar I’ve ever seen in Bangladesh.
We sailed out of the small channel we were anchored in to the Sibsa River and then to the south. We passed the western side of Polder 32 with a good view of the embankment that protects the island then passed into the Sundarbans forest with mangrove trees on either side of the wide river. Hiron Point is close to the mouth of the river where it empties into the Bay of Bengal. Perhaps empties is not quite the right word as the river is tidal, flowing both ways. Moreover, the mud that maintains the Sundarbans probably comes from the sea. The sediment discharged by the combined Ganges-Brahmaputra-Meghna Rivers is swept westward along the coast and some of it is carried inland by tides and storms. How much is still a topic of research. We prepared the equipment in the bow while watching for tigers along the shore. We reached our anchorage after about 8 hours and enjoyed a BBQ on the top deck. Then, at last, an early night.
Just after 6AM we loaded the launch and headed into the channel with the forest station after watching the sunrise. We were accompanied by two armed guards, required in the Sundarbans, although we don’t expect tigers at the ranger station. The first thing we passed was the tide gauge, the reason we are putting the GPS as this particular location. It is well known and its data is available in a global repository for tide gauge data. We landed at the third dock belonging to the forest service. The path to the ranger station proudly announced the Sundarban as a World Heritage Site and through in a couple of caged tiger statues as well. We met the forest ranger and were told that there is no cell phone service, contradicting what we had been told. During the winter there is a weak signal. That was going to be a problem for downloading the data. We headed to the roof and for once, the ladder was already in place.
The roof had a low brick wall around its perimeter. Brick is much weaker than reinforced concrete and not considered stable enough for GPS. Our two foot threaded rod was long enough to get us 5” into the concrete is we drove the long drill bit all the way to the chuck. It would have to do. The GPS went into a secure room with communications equipment. By now our experienced team split into our familiar tasks. Sarah figured out a way to get the cables to the roof by tying them to a rope after going through the wall. After some effort, I managed to drill the wall to the maximum depth. With the poor to nonexistent cell signal, we set up a yagi directional antenna and pointed towards the closest cell phone tower some 60 km away.
We got everything set up, but the cellular connection didn’t work. Next step is to hope that we can establish a connection in the winter and be able to seasonally download the data. Having to return regularly to download the data or come back to set up a radio link would be expensive, although the Sundarbans is a wonderful place. We said our goodbyes and headed back to the M/V Kokilmoni without having seen either a tiger or a crocodile, although we saw a lot of mudskippers, a personal favorite of mine while leaving.
We weighed anchor and headed back north to Khulna. The crew spotted a crocodile, but I missed it while uploading blogs. Going north, we had left the calm of the Sundarbans and returned to the modern electronic world of cell phones and internet. One more GPS to go, but it is in far northern Bangladesh, a 380 km drive from Khulna where we get off the boat tomorrow.
When we finally got to Khulna, the second largest city in Bangladesh, Bachchu, who organized the boat, met us and led us down country roads to where we met our boat, the M/V Kokilmoni, our home for the next few days. It is very large for the four of us and Bacchu, but faster and safer when there is still a risk of cyclones, as hurricanes are called in the Indian Ocean. Luckily the forecast is for 10 days of clear sky and 90° weather. When we got to the dock (ghat in Bangla), a crew from the ship was there with the launch to ferry us and our loads of equipment to the ship. After stowing it all away, dinner at a reasonable time.
The Kokilmoni sailed down the channel to near the location we will install our GPS on Polder 32. Back in the 1960s, Bangladesh (then East Pakistan) constructed embankments or polders around much of the low-lying coastal region. The region is crisscrossed by numerous interconnecting rivers separating the land into islands. The government built embankments around many of them to protect them from flooding. However, they also prevented the sedimentation necessary to maintain the land. Without either flooding or sediment, the sediments compacted and the land subsided so that it is now 3-4 feet below the land outside the polders that continue to get sedimentation. This set the stage for Cyclone Aila in 2009 and the storm breached the embankment in multiple places. Initial repairs did not hold and the island was submerged for most of two years. What should be done for the poldered areas in the face of continued sea level rise is a major question. Our GPS will provide much needed data on the rate of subsidence.
Polder 32 is a main focus site of a large project funded by ONR, the Office of Naval Research. This project looks at not just the physical side of the balance of sea level rise, subsidence and sedimentation, but also the local population’s interaction with the environment and their potential response to disasters, such as temporary or permanent migration. In fact, social scientists make up the most of the project. The lead institution of this project is Vanderbilt University and there is a group of them here at Polder 32, too. Unfortunately they are on the opposite side of the island, so we were unable to meet up. Neither of us had the few hours to spare to sail over to the other.
Anyway, we again prepared the GPS equipment into the night, then work up early to install the GPS. At least on the Kokilmoni, there was tea and cookies to help us cope with the 6AM start. Plus we had a crew to help carry everything to the site, including a very heavy diesel generator to provide power for the drill. They dropped us off at a dock connected by a bamboo bridge to shore, then moved to a place where they could offload the equipment. They insisted on carrying everything for the 1-kilometer walk to the elementary school we will use.
In May, Dhiman and Steve did an elevation survey of the entire polder and set up a reference station at the school. Then they left the GPS there to get a head start on collecting data with a temporary “campaign” set up. When we got to the roof, we saw the installed antenna, but the GPS had failed. The flimsy portable solar panel could not hold up to the monsoon. Still the data for May and June it go will be valuable and the antenna is already installed. After a discussion with the headmaster about where to put the receiver, we put it in their computer room (solar powered). Just outside is a statue of the Hindu goddess of education as this village is almost entirely Hindu.
We went to work, with our now experienced team splitting up the tasks, with Sarah doing the most technical parts. I drilled the holes in the roof and bolted the solar panel down and secured the antenna cable to the roof. When it was done, we headed back to the ship to head to Hiron Point in the Sundarbans, the world’s largest mangrove forest and nature preserve that is home to 350-400 tigers. And we finally got to eat a lunch at a reasonable time. As a Sundarban tourist boat, the Kokilmoni has very good food.
We spent the entire day traveling to get to Khepupara, not far from the Bay of Bengal. We had heard that there were problems at Mawa Ghat, the ferry crossing of the Padma River immediately south of Dhaka due to siltation on one side and erosion on the other. We decided to head west to Aricha, the shorter ferry ride near the confluence where the Ganges and Brahmaputra meet to become the Padma. Unfortunately, the traffic to get out of Dhaka on the western side was so bad, that it and the longer route lost us more time than using Mawa. We didn’t arrive at Khepupara until after dark even though we started before 6AM. At least after the ferry, we had beautiful scenery of rice fields and forests. I am always glad to get away from Dhaka traffic.
Khepupara is a site where a long tide gauge record shows a very rapid rise of water level implying sinking of the land. However, tide gauges are not designed to be stable over decades, so I don’t trust the rate. We are putting a GPS here to get our own subsidence rate in a few years time. Humayun arranged for it to be installed at the Bangladesh Meteorology Department (BMD) weather radar station. We stayed in their guesthouse, pretty basic accommodations, but it suited us just fine. We walked to a local restaurant for some delicious Bangladeshi food then started preparing the equipment to save time. That took us up to about 11:30 PM with a few short power outages. Then we crashed.
The next morning we started at 6AM to install before breakfast. We went to meet the officials and check out the suitability of the roof of their headquarters building, once a ladder was found. It was reinforced concrete, but the two good corners of the highest roof had a weather vane and anemometer installed. The two back ones had their sky view blocked by a water tank. We went back to the guesthouse and decided that its roof was the better option and had to carry everything back. By the time we finished installing the antenna, the solar panels to power it, grounding rods and lightning protectors, etc. and Sarah checked that everything was working, it was 11AM. Breakfast became brunch for our famished group.
This site took longer, in part, because it will have cellular communications. The three coastal sites we are doing are very remote, particularly the other two that can only be reached by boat. We decided to use cellular modems. Every day UNAVCO in Boulder, CO will be able to call up the GPS and download the day’s data. It will only have to be visited if it stops working. Using solar panels with 2 car batteries to store power, the system is very self contained.
Two down. Next, we drive northwest to get on a boat to take us to Polder 32. An inland island whose embankments to protect the area from flooding failed during Cyclone Aila leaving it underwater for most of two years. Our late finish meant abandoning two secondary items on our agenda. Visiting our compaction meter site to download the GPS data and installing a replacement GPS at Khulna University to replace the one that is no longer working. Humayun will come down here in November to do it himself. While they are close to on our way, we don’t reach the boat until after dark. It is the M.V. Kokilmoni, the boat that I lived on for two weeks last year when we did a month-long seismic cruise on the rivers throughout Bangladesh.
I’m back in Bangladesh for the fourth time in the last two years, my eighth trip overall. It is the first time I’ve been here in October. It is about 90° and sunny. The monsoon is over, but water levels are still high. I have come to install more GPS around the country. With me is Sarah Doelger, an engineer from UNAVCO, an organization that provides technical support for research involving GPS. A number of out GPS stations in Bangladesh are systems on loan from UNAVCO. She has come along because we are establishing stations in remote areas and will use the cell phone system to call the receivers and download the data. I am also traveling around with Humayun Akhter, my partner for many years from Dhaka University, who keeps our network running, and his student Fayazul Kabir. The four of us will be traveling around the country by van and boat to install the stations to monitor tectonics and land subsidence.
As usual, we arrived at 4 AM after a full day or traveling and had to hit the ground running. After a short rest and shower at our hotel, we spent the day unpacking, preparing the equipment and buying the last few items.
Yesterday, was our first installation. We drove east to Comilla University sitting on the last exposed hill of the foldbelt. At a little over 100 ft high, it may not seem like much, but it stands out in a country where half the land is less than 10 ft above sea level. Thanks to bad traffic, it took 4 hours to get there, including a stop for breakfast on an island in the Meghna River. We met with the registrar over tea and cookies, then finally got to work about noon. This site fills a gap in our coverage of the Burma Arc foldbelt, a continuation of the same plate boundary as Sumatra, site of the 2004 M9.3 earthquake and tsunami. Here, the subduction zone is colliding with the largest delta in the world, folding the sediments into a broad set of folds.
Our GPS is measuring the rate of shortening of the foldbelt as strain builds up, possibly towards an earthquake. The antenna was attached to a 2-ft steel rod we cement into the roof of a reinforced-concrete University building. This is our preferred method for a country with almost no solid rock. The receiver, electronics and backup battery were installed in the control room of the large solar panel array just below the antenna. The only hiccup was tapping into their electric system for power and meshing their 2 wire system to our 3 wire system. Their system is not grounded, as we discovered when Sarah got shocked connecting our battery. He fingers have stopped tingling. It took a while to understand what we wanted and in the end we had to ground our system into the lightning protection grounding that we set up. It was all done in about 3 hours and stopped for a well-deserved lunch at about 4 PM on the way home, further hampered by traffic jams.
This morning we packed all our stuff in a large van and are working our way through the traffic to get to SW Bangladesh for the next 3 stations. I am really looking forward to getting out of the city and its traffic and into the calmer countryside.
After finally reaching the Mongla and our boat, we settled into our new home. It is a similar design, but much larger than the one we used in September. As we ate dinner and explored the ship, it started the overnight journey to the southeastern part of the Sundarbans where the wildlife is most plentiful. The Sundarbans is the world’s largest mangrove forest and home of the Bengal tiger. Thus, along the way we picked up two armed guards at the forest station. In the morning, we took a hike along the edge of the forest to Katka beach, with a guard at the front and back. We saw some spotted deer (chital) and arrived at the beach, where untold numbers of tiny crabs made beautiful geometric patterns in the sand with the sediment dug out of their burrows. Much of the group joined in a pickup soccer game where the Bangla Tigers beat the Columbia Lions 4-2. We cooled off with a dip in the sea until it was time to walk back.
In the late afternoon, we had another walk – this time through the mangrove forest itself. First through the more open forest, slipping on mud and avoiding the areal roots of the mangroves. We saw more deer, monkeys and wild boar rushing across the forest. Then we went into denser forest, crossing sites where Bengalis would hide their salt production from the British. Then into the densest part of the forest in single file, close together. If not for the trail, the forest would be impassable. We emerged into a more open forest by a river and a large beautiful tree we climbed over for a group photo. On the way back, we passed some tiger tracks. Since the entire forest is flooded at spring tide, the tracks could not have been older than a week.
Overnight, we shifted to Tiger Point, where most of us arose for an early morning bird and animal watching expedition. We transferred to a small wooden boat, which cut is engine and switched to an oar for the near-silent ride. We saw a multitude of birds including eagles, kites and woodpeckers, but also more deer, wild boar, an otter, a snake and a monitor lizard. Along the waterline at one stretch of the creek were a set of tiger tracks paralleling the river. These had to have been made since the last high tide.
Our final excursion was to two islands that are forming offshore – Bird Island and Egg Island. They first appeared about 20 years ago. Landing on a new part of the island, we walked across it for several hours, starting from a sandy beach devoid of vegetation (but with lots of crabs). We walked across patches where the first grasses were taking root to a more open meadow, following deer tracks for our route. Now we were above the area inundated by the tides. As we continued, the first mangrove trees appeared singly or in small clumps. They were still small, perhaps only 2-3 years old. Finally we ended at the edge of a full-fledged mangrove forest, the oldest part of the island. Then came time for a decision. We could continue working to the very edge of the Sundarbans, but if we turned back immediately, we could reach Chandpai in time to visit some shrimp farms before dark. We choose the latter, skipped the game with the soccer ball that accompanied us, and headed back to the boat. A six-hour trip upriver and our Sundarbans leg would be over.
On Monday, we used the boats of the resort to go visit one of chars (islands) in the Brahmaputra. This char was right beneath the Jamuna Bridge. It was only a small sandy, unpopulated char when the bridge was built. However, the changes in currents due to the bridge helped the island to grow. Five to seven years ago people started moving to the island. Now there are a number of communities on the char. The newest one is in the eastern part of the island where it is growing. The char is moving, eroding on its western side and growing on the east. The “flooding” group immediately started interviewing the residents with the help of the Dhaka students, gathering information on their history of migration and their life on the char. All of them, were very
open and forthcoming. One of them apologizing that she was too poor to offer anything to our large group, but then her husband cut two papaya from the tree next to their house. We tried to refuse, but the next thing we knew, a platter of papaya was being passed around. One of their neighbors proudly insisted on showing me his 6’ x 12’ thatched home.
After the islands, during some free time, a group of students went into nearby Tangail to go shopping, returning with lungis and saris. We all wore then to the evening’s festivities. Under a tent, we feasted on BBQ fish, chicken and lamb while a musical group played both traditional Bengali music and contemporary pop. A strange setting to see everyone dancing to Lady Gaga.
The next morning, we hit the road again. Driving across multiple regions of Bangladesh, crossing the Ganges River and ending in Mongla at the edge of the Sundarbans. Traffic was light in the morning, but a stretch of bad road, a flat tire and traffic took its toll in the afternoon. We lost hours and finally reached Khulna to pick up the waiting Scott Nooner. More trouble with the tires led to us not getting to Mongla until after dark, without any time for visiting shrimp farms or the compaction site. We will have to do it all after the Sundarbans. A lesson in life in Bangladesh, always be prepared to adjust your schedule. Nothing ever going completely as you planned, but somehow it works out fine in the end. A land of improvisation and resiliency.
This semester I am doing something new – teaching a class. The course is in the Sustainable Development program and about the multitude of natural and human-induced hazards of Bangladesh. To help them truly understand what “Life on a Tectonically Active Delta” is like, I have brought them here for Spring Break. Now they will get to see for themselves the geology, environment and people of Bangladesh that they have been hearing about in class. This is a new experience for me, bringing 13 undergraduates and my TA for 10-day trip to the other side of the world, both literally and figuratively. Shepherding them around and being responsible for so many students, rather than a few colleagues and graduate students is a daunting task, and made possible only by the support of Dhaka University. With them, we will see Dhaka, including museums and Old Dhaka, the Brahmaputra River and its ever-changing islands, and the Sundarbans, the world’s largest mangrove forest.
We left on Thursday March 8. I have taken advantage of the large group to transport equipment to Bangladesh. Meeting up a JFK, Scott Nooner and I presented each of them with a box of equipment for Bangladesh and soon the 16 of us with 32 pieces of luggage were on our way. Arriving in Dhaka some 20 hours later at 4 AM on Saturday, our tired group headed to the new Hotel 71 (a tribute to Bangladeshi independence in 1971), stopping for a few sites along the way. After a break for breakfast and showers, we headed off to the Independence War museum where they saw graphic evidence of the events leading up to the bloody break from Pakistan at the cost of 3,000,000 lives. On a lighter note, we were met there by the 9 Dhaka University geology students who will be traveling with us. Then, we all went to the Dhaka University Geology department, my home base in Bangladesh. However, by the time we completed the introductions, and meetings and a visit to the Shahid Minar, we had no time for lunch. We had to get to the dock for our Buriganga river cruise through Dhaka traffic. We would have to settle for snacks on the way. To compensate, we moved up dinner earlier and our hungry group dived into their first Bangladeshi dinner while sailing down river into the wide Meghna River while watching the industrial development and endless brick factories slide by. A relaxing cruise was a great way to start introducing them to Bangladesh after an exhausting journey.
Today, we headed out of Dhaka for the Brahmaputra River, a good thing as a major opposition demonstration is planned for Monday. The 27 of us stopped along the way for the impressive 150 ft. tall National Memorial. Then continued on to lunch at the place we will be staying. There, we were joined by Chris Small, who had arrived earlier, and Hafiz Rahaman, the Khulna University student who works on the compaction meter we installed next to his parent’s home last year. Then across the Jamuna Bridge to Sirajganj, a town threatened by the westward migration of the Jamuna River, as the Brahmaputra is called here. On the spur of the moment, we hired a boat to take us along the embankment, where we could see the ongoing repairs of the collapses from last summer’s floods. Then we walked back, stopping for pictures of the mobs of kids, spontaneous dancing, and a little cricket as we became the highlight of the day. Overall, a great start with many new friendships blossoming between the CU and DU students.
As we headed north to our target areas, we have used any extra time to collect some seismics. We got some near Aricha, then again under the Jamuna Bridge. Today we collected data near Bogra, where the transect of wells that we drilled last spring is located. All three pieces of data show reflectors, including a strong one we think is the bottom of the river valley from glacial times when sea level was 120m (393 ft) lower. It seems to shallow as we go north, which fits with our interpretation.
Having to exchange pilots for every stretch of the river made estimating how far we can go each day more confusing. No, we can’t go that far, then perhaps if we hurry. How fast we can go depends on the ever-changing currents. Each pilot only really knows his own stretch of the river. We make multiple contingency plans. We had to change pilots at a little stop just south of Bogra. That cost enough time, we couldn’t make it to our next stop at Bahadurabad Ghat. Option one was we shoot seismics and then return to this place. While shooting, the pilot agreed that we could then go on to some village on the way. If we stop shooting now, we can make it to Islampur only a little south of our target.
A pattern developed of the crew being overly conservative, correctly not wanting to get stuck in the middle of the river at night, but gradually they work hard to get us what we need and plans change. We initially wanted to start continuous shooting from Bogra north, but even we could tell we could not come close to reaching Bahadurabad if we did that. We got a few critical kilometers and steamed north without shooting to the village where we spent the night. Now, they have become more open to sailing and stopping wherever we are at the end of the day, just in time for our continuous profile. Problem solved.
Last night, Dhiman joined the ship and this morning Rafael and I left to return home. The little village is connected by one of the worst roads in Bangladesh. I will miss when the ship crosses the Dauki Fault during the final continuous shooting upstream on the Brahmaputra to the border. The ship will also collect data going downstream, but the speed over the ground will be very fast, perhaps limiting the quality. However, Volkhard and Tilmann are confident as the speed through the water will not be too high. They do not give up.
Overall the cruise has been a mixture of disappointing data in the east combined with the now very good data coming in in the west. And there is a good chance that tomorrow will bring triumphant images of where the Dauki Fault goes west of the Shillong Plateau. We have cemented our ties to the Bremen group, who have worked offshore for many years, but never entered Bangladesh before. Several joint efforts have developed. Mr. Islam, our guide, has been great. Getting to know the Bangladeshis from Dhaka University, the Geologic Survey and the crew has been harder due to language and my status. Last night we bonded more as we waited together for Dhiman’s very late arrival. I am not so good at languages, nor as exuberant as Tommy. Still, two weeks on an 85 ft. boat brings everyone together.
The Meghna River and its tributaries in NE Bangladesh are very muddy. They carry a lot of water in this very rainy area of many haors, ponds and marshes. The largest is the inland lake that forms every summer. However, as we discovered, the muddy sediment is rich in organic matter and we could not get good data. We only were able to image south of the lake after most of the sediment had been deposited. Despite the problems, we remained optimistic because the Jamuna, as the Brahmaputra is known in Bangladesh, carries mostly sand and silt. However, time is growing short and there is no time to collected data over the entire length of the river. The most important area is in the north, so we must rush upstream to have sufficient time to collect seismics there.
I rejoined the Kokilmoni in Mawa Ghat (port) and the next morning headed up the Padma to the Jamuna. To navigate these rivers, you need a pilot to steer through the many sand bars and channels. That means we sail from pilot station to pilot station and are less free to stop where we want. Yesterday was Mawa to Aricha, at the confluence where the Ganges and Jamuna join to form the Padma. Making good time, we decide to make use of it be deploying the seismic system. This was the test – can we collect good data in the large sandy rivers? Can we deploy and retrieve the streamer in the strong current? The boat slowed to the point of sliding backwards in the current and deployed the equipment. Initially, there was some electrical noise that obscured everything, but we found the source and unplugged it. For the first few minutes we were all squinting at the screen to see if we could see reflectors. Uncertain at first, it soon became clear that we were getting good data and a saw a strong reflector that probably marks the river level at the height of the last ice age when sea level was 120m lower. Success. After an hour we pulled in the streamer and headed to port, satisfied that that we could image here and anxious to head north as quickly as possible.
Today, we entered the Jamuna and are heading north to Sirajganj, just north of the only bridge over the river. Brahmaputra means Son of Brahma, an appropriate name for this mighty river. The river looks different from when I was hear at low water. Then there was exposed sand on the banks of all the islands. More sand then I had ever seen. Now it is all submerged and just the island tops and vegetation are seen. The sand is all below water and shifting, which is why we need pilots. We have made very good time and have only hit one sand bank. Enough time that we are now collecting more data and just passed under the bridge, which has many published borings drilled before construction. These wells will let us correlate our reflectors to actual rocks.
Since we were unable to get the Kokilmoni up to the border on the largest river coming from the Plateau with imaging still difficult, we decided to pull the gear and head downstream on over to the Brahmaputra. We steamed quickly downstream to the one region where we got good imaging. This time we took different channels and once again saw the buried folds at the front to the subduction zone. With two crossing, we will be able to confirm their direction. With this good news, we compromised between the scientists wanting to always continue collecting data and the crew needing to rest. Humayun found a small port off of Araihazar, where I first worked in Bangladesh with the Columbia University Arsenic project and met Steve.
This marks the end of Steve’s time on the cruise. In preparation for his leaving, we held endless discussions on the rest of the cruise, taking into account the need for pilots to navigate the everchanging Padma and Jamuna (Brahmaputra). Humayun, Selim and Babu are also leaving, but a new geologist met us and I will bring Saddam Hossain (no relation) In this small port on the Meghna River east of Dhaka, we had to wade to shore from the launch. Of course, the ride to Dhaka was slowed by heavy traffic, and we arrived at 12:30AM.
The Ambala Hotel felt like home, as we always use it when in Dhaka. Then a whirlwind day of meetings, cups of tea and traffic. The high point was when someone mistook me for a Bangaldeshi – until I opened my mouth. The morning meetings filled through the afternoon, consuming any hope for free time. All meetings in Dhaka seem to be time approximate due to traffic. Then we juggled two dinner invitations by doing appetizers at one and dinner at the other. The appetizers were so extensive, I insisted Steve join me to help eat them. Still, everything went very well, except by the morning Steve was gone, off on his 4:30AM flight home.
During the day I learned that the ship would only make it as far as Chandpur, where they had to arrange for a pilot. Too far for me to join them in the morning. I had to wait until they arrive at their next stop, Mawa Ghat, at the end of the day to switch pilots. Mawa is on the Padma – the name for the mighty combined Ganges and Brahmaputra Rivers. I spent a quiet day in Dhaka working with Humayun and Dhiman, then picked up liquid supplies to keep the scientists happy, and finally the long traffic-filled drive to Mawa. The opposition party has called for a hartal – a general strike – tomorrow, so traffic was extra heavy as there will be no driving in Dhaka tomorrow. Now I am back on the ship hearing their stories of the trip up the Padma.
From our return to Jamalganj, we headed east searching for a river to carry us up to the Indian border across the Dauki Fault. Along the way, we celebrated Steve Goodbred’s birthday. However, even the biggest of the rivers proved too shallow for our boat. We switched to the launch, taking the CHIRP profiler along.
As Nano Seeber described this excursion: “We are navigating the big rivers on the big delta. The seismic reflection profiles are disappointing, but the surroundings are completely captivating. Yesterday we pushed upstream as far as we could on the big boat, then we hopped on our launch and continued north to the Indian border. It rained progressively heavier as we approached the border and the ‘abode of the clouds’ (= Meghalaya). We were one of the many boats traveling the river. Our boat sported a bunch of wet scientists dripping at their noses and their telephoto lenses. The others carry mostly rocks, but some deliver children to school and people to market, an altogether happy scene. Thin long dark wooden boats covered with neatly colored people, vivacious eyes, and umbrellas leaning against the driving rain. The rocks are coming down to build Dhaka city, this fat ugly monster insatiable for people and rocks, getting fatter by the day. As the monsoon feeds the short but energetic rivers of Meghalaya, hard boulders from the ancient rocks
of the Shillong Plateau pour down with the white waters onto the plains and across the border into Bangladesh. There, they are met by an army of small gnarly young people fully engaged into a rock-feeding frenzy. They manage to take from the river so much of its solid deliverance that they alter the morphology. This anthropo-geological action is engineered with technologies dating back to the Egyptians — this is indeed the place to learn how the pyramids were built! We had tea with them, crouching under a tarp stretched about four feet from the sandy bar one foot above the river: a thin layer of human bodies sandwiched between ground water and air-water. We were so crowded under that tarp that light had a hard time getting to the tea kettle at the heart of the circle, but the tea tasted great!”
The tarp-covered restaurant is known locally as an “Italian Hotel” because crouching under the low tarp, you usually sit on a brick, “it” in Bangla. Here, close to the border, we got as good a look at the Shillong Plateau, one of the wettest places on earth, as the downpour would allow. The home of the clouds is appropriately named. In the pouring rain, the closest we got to the Shillong Plateau was a brief stop at a rock crushing facility, where stones of every kind from the plateau were closely examined.
After this wet interlude, we decided to spend our time elsewhere. We are heading south to the one area on the Meghna River where we got good seismic imaging and then to the big rivers, including the mighty Brahmaputra itself.
We have been sailing along collecting data, but so far the data quality is poor due to shallow gas in the sediments. We thought we might have some problems with gas, but the problem is more widespread than we expected. We are now out of the inland summer lake where we met the boat and will soon try profiles up the Indian border where we expect a buried fault. We may pick up a local pilot that knows which ones are navigable. We hope the environment is different enough that we can get good data. A Meanwhile we have been changing the sound source to try to get better data. Depending how it goes, we will continue around here or head to a different part of the country. In contrast, the ship and company is great. Working primarily daylight hours with systems are running flawlessly, we do not have formal watches. It is only for deploying the seismic data and retrieving it that all hands are needed. A small group takes care of maintaining the running equipment. Voldhard Spiess keeps trying different processing to improve the data. We start up at 6:00 AM and continue until around sunset or reaching our target stopping town. During the day, we are continuously having discussions on the science, with each of us bringing different expertise. The data, methods to improve it and where to go are ongoing subjects of discussions. With Steve and Humayun here, we can also plan for future parts of the project.
Last night, we stopped in Jamalganj, where I helped install one of our compaction meters in February. Back then, the river was probably 15 feet lower. A large group came ashore with Humayun and myself to see the site. It is my third time in this now familiar town. Waiting for Aziz, the caretaker, we attracted a large crowd. Walking to the site as darkness fell (and pretty quickly in the tropics), we discovered Aziz had brought a crescent wrench rather than a pipe wrench. With typical Bangladeshi ingenuity, glancing blows with a hammer loosened the cap on the pipe and we were able to retrieve the piezometers and their water level data. We then visited the former jail cell with its massive iron bars where the GPS receiver is and Humayun downloaded that data. Shaheen, Aziz’s son was away in Dhaka, but we retrieved the laptop with the compaction data and copied it, too. The biggest change in the site is that instead of mud everywhere, the site was now covered in green. A small bright spot of success in the trip.
After a great field season last winter, we had an extraordinary opportunity this fall, a research cruise on the Bangladeshi rivers collecting geophysical data. We are using the same technique that Lamont uses on its ship, the R/V Marcus Langseth, but a mini version. The basic idea is to use sound waves from bursts of compressed air to bounce off the layers of sediment below the surface and to record it on a string of microphones towed behind the ship called a streamer. The difference is scale. While the Langseth can tow four 6-km long streamers, we have one 50-m streamer. Our source is similarly reduced. The system we are using, built by Bremen University in Germany, will only see a few hundred meters below the surface, but with great detail. The cruise is taking place on the M/V Kokilmoni, an 85-ft long boat built for tourist cruises of the Sundarban mangrove forest, home of the Bengal tiger.
While the Bremen group and a few of the Americans will stay on the entire 25-day cruise, the rest of us have the opportunity to join and leave the ship during the cruise, something not possible in the middle of the ocean. Due to other commitments and, in part, not wanting to be there for the inevitable problems at the beginning of the cruise like this, joined the ship today, over a week after the scheduled start (less than as week after the actual start). Nano Seeber, Rafael Almeida and myself left Lamont on Monday, Sept 12 and after a long set of flights arrived in Dhaka at 4:00 AM Wednesday morning. We dropped some equipment off at Dhaka University, picked up Humayun Akhter and a student and headed off to find the ship. This was not as easy as we thought. They were entering the area of the Sylhet Basin that floods every year and there were not too many places where car and boat. Talking while driving north, we came up with three places where we could meet. They past the first one hours before we could get the, but worked out a plan for number two, saving probably 5 more hours of driving to get to the third. We drove out to the meeting place on ever-smaller roads finally ending at a port on this vast inland lake. Using cell phone towers, the tall chimneys of brick factories that are now islands and a hospital ship, we finally located each other and they sent their small boat to pick up us. It brought Dhiman and Pritam as well, returning to Dhaka University with Babu, our driver.
Welcomed on board, we got underway following the markings of where the river channel is across the broad expanse of water. Patches of grass, the occasional tree, islands of homes and lines of telephone poles dot the area that will become fertile farmland again in a few months. I’ve known of the flooding worked on calculations about it, and heard stories, but this was the first time I saw it for myself. I’ve always been here in the cool, dry winter-early spring. It is truly amazing and filled with an amphibious population traveling by bus and rickshaw in winter and boat in summer.