Coastline Change and Erosion-Accretion Evolution of the Sandwip Island, Bangladesh

Abstract

The study tries to analyze the morphological and hydrological changes and to establish their relationship in the Sandwip Island through the integration of Remote Sensing (RS) and Geographic Information Systems (GIS). The study concludes from the recent 30 years' data that the different parts of the island response different cycle of coastline change associated with hydrological dynamics. The resulted net loss of the coastline is about 6.98 km (0.23 km/y) and the net loss of the coastal area is about 23.99 km2 (0.8 km2/y). The erosion processes (increase in the water depth near shore) were active along the western and the south-western shores. This erosion of the island is facilitated by the steep slope of the bank, high tidal water pressure and loose bank materials. In contrast, the accretions (decrease in the water depth near shore) were taken place in the larger parts of the northern and the north-eastern shores of the island. This is due to the backwash sediment deposition with the favor of gentle topographic slope along shores.

Global long-term observations of coastal erosion and accretion

“…Prominent examples are: (a) the delta of the Mekong river (Fig. 4a–c ), along which several dams were installed in the last decades 23 ; (b) the delta of the Indus river, at the border between India and Pakistan, associated with the exploitation of one of the world’s most extensive irrigation networks 33 , and where the largest erosion is revealed - exceeding 40 km of cross-shore retreat of the coastline (Figs 2c , 5a ); (c) the estuary of the Sittaung river, in Myanmar, where hydropower plants have been installed 34 ; and (d) the Brahmaputra delta 24 . For all the above cases, the effect of the upstream dams is combined with human degradation of the coastal mangrove forests, resulting in enhanced erosion due to the decreased capacity of the estuaries to retain sediments 12 , 15 .…”

Geomatics Assessment of Coastal Erosion Vulnerability: A Case Study of Agadir Bay, Morocco

“…The Linear Regression Rateof-change (LRR) is the slope value of a linear regression line positioned in the scatter plot formed by the distance measurements between all the intersection points of each transect and the compared dimension lines. This attribute, which also reflects the annual rate of change of the reference line along each transect, is interesting for analyzing coastal kinematics over more than three dates, as the calculation method takes into account the evolution of the coastline over the entire period considered, as shown by the results of the study by (Emran et al, 2019) in Bangladesh. Figure 8 illustrates the use of this attribute for a case study based on three shorelines.…”

Technical and Social Approaches to Study Shoreline Change of Kuakata, Bangladesh

“…While there is a net accumulation of sediment (delta building) at the river mouth (Broadus, 1993;Amin, 2008), a substantial amount of sediment is entrained by waves and currents. Sediment replenishment plays an important role in deltaic stability by hindering natural compaction and subsidence (Dixon et al, 2006) and is thus considered one of the main factors in this coastal zone for shoreline changes caused by sea level rise (Amin, 2008;Emran et al, 2019). Along with a gentle slope into the Bay of Bengal, this wide sandy beach area has patches of mangrove trees behind it which withstand the perpetual forces of the tides.…”