Morphological changes of a developing sandbar along the shoreline of Sonadia Island, Bangladesh between 1972 and 2006 using remote sensing

Abstract

In a dynamic coastal environment, the morphology of a sandbar is anticipated to change regularly, particularly when there is a large annual sediment supply. The study explored the nature and magnitude of a developing sandbar's morphological changes between 1972 and 2006 in Sonadia Island, Bangladesh, using five different satellite images. The sandbar's changes across the shoreline were calculated using field survey data and manual-drawing outlines of overlaid maps. The study revealed continuous and rapid morphological changes of the sandbar along the Island's shoreline. The net annual rate of shoreline displacement ranges between 3.94 m and 7.79 m during the period. These might directly result from the Island being exposed to huge wave and tidal action and excessive sediment supply around the Island. Transect 3 represents the sandbar's head and appears to be the most active zone with the most significant annual shoreline displacement of 22.00 m. The sandbar's far end around Transect 7 is more stable with a yearly shoreline displacement of 0.50 m. Changes were more drastic between 1999 and 2006 than between 1972 and 1999. These rapid changes after 1999 could indicate that the sandbar is becoming increasingly vulnerable to anthropogenic changes and the adverse effects of sea-level rise.

Geochemical characteristics of shoreline sediments from the Bay of Bengal, Bangladesh: Implications for provenance and source‐rock weathering

“…Several studies of the sediments of Sonadia Island have been conducted, including grain‐size analysis (Hoque et al, 2013), assessment of morphological changes of sandbars by means of satellite images (Hoque et al, 2021), and measurement of the distribution of heavy metals and selected trace elements in the sediments (Kabir et al, 2018). Because no systematic petrographic and geochemical studies (combined major oxides, trace elements and REEs) have been made about island sediments in the Bay of Bengal, Bangladesh, we examined the petrography and bulk geochemistry of shoreline sediments near Sonadia Island to investigate their compositional maturity, provenance and source‐rock weathering.…”

“…Sonadia Island is an extended part of Moheshkhali Island, separated by some khals (canals) and ditches (Hoque, Chowdhury, Uddin, Alam, & Monwar, 2013). Sonadia Island is far from the present-day delta building in front of the Bay of Bengal (Hoque, Chowdhury, Chowdhury, & Uddin, 2021); however, the investigated shoreline near Sonadia Island (Figure 1) receives large amounts of sediments from the highland region through tidal current/circulation processes. Sediments are generally fine-grained with a nearly symmetrical grain-size distribution in the upper shore region, but coarse-grained and with a coarsely skewed grain-size distribution in the middle and lower shore region of Sonadia Island (Hoque et al, 2013).…”