Morphological response of the Pussur River, Bangladesh to modern-day dredging: Implications for navigability

Abstract

Mongla Port is the second gateway of Bangladesh, situated at the bank of the Pussur River some 131 km upstream from the Bay of Bengal. In this study, the available hydrographic survey charts of Pussur River were collected from Mongla Port Authority (MPA) and analyzed to assess the trends of morphological changes at the potential sites. The causes of navigation problems, previous interventions of MPA, dredging history of the river, and effectiveness of dredging was analyzed. It is found that in the upstream portion of the navigation route at the MPA jetty area and its approaches was slightly scour-prone from 2010 to 2013; however, after capital dredging in 2014, the channel was found highly siltation-prone, having a rate of 0.1–0.6 m/year between 2015 and 2017. Before dredging the channel, the Inner bar area (downstream of Mongla Port) did not show any significant change in the bed topography between 2010 and 2013, however, a high backfilling rate (up to 1.5 m/year) was observed after the capital dredging. The channel was sufficiently deep and quite stable from Joymonirgol to Hiron point. The current navigational channel at the outer bar (at the mouth of the river) is silted by 0.1–0.25 m/year. Reduction of upstream flow, numerous shipwrecks at different positions, and human disturbances were identified as the causes behind the navigational problems in the river route.