Evolution of the fluvial landscape in the Mahasthangarh region (Bangladesh) over the last 2000 years: contribution of satellite images and geomorphological studies to the history of paleoenvironment
Résumé
In Bangladesh, paleoenvironmental studies with regard to human settlements remain unusual. For the site of Mahasthangarh located in northwestern Bangladesh, a pioneering work was conducted by Christine Jacqueminet and Jean-Paul Bravard in the 1990’s. They carried out a first study on the geoenvironment of Mahasthangarh. This ancient city has been built on the eastern margin of the Barind Tract – a Pleistocene elevated alluvial terrace – along the Karatoya River. Nowadays, the Karatoya is a small river but in the historical times it was a tributary of the Tista River, a major river of North Bengal. According to written sources and ancient maps, the Karatoya has undergone many changes over the past 2000 years and especially over the
last two centuries. In addition, some parts of the site appear to have been damaged by floods according to archaeological findings. After a gap of almost 25 years, the geomorphological studies have restarted to provide new data on the environmental changes recorded in the region
of Mahasthangarh during the last 2000 years in relation to the human settlement.
This presentation will introduce the preliminary results of this second phase of research that is focusing (i) on the analysis of satellite images to identify the fluvial paleoforms and the ancient drainage network in the current landscape; (ii) on geomorphological operations conducted in the field (with a sedimentary record) to define the processes, the causes and the chronology of the fluvial changes.