Onshore barrier affects sediment deposition in a subtropical mudflat

Abstract

Onshore barrier in the intertidal area is reported to influence coastal geomorphology, sediment dynamics, and erosion and accretion processes. The present study describes sediment texture and deposition pattern, and shore profile of a tidal mudflat located in the Kutubdia Island of Bangladesh. A physical barrier in the form of concrete ring structure was placed on the mudflat of experimental site and the control site was 50 m away without any barrier. The texture of sediment was mostly medium silt (45.3%) in leeward side (= the side facing away from the tide/wave action) of the barrier. Whereas, coarse silt was dominant in the control (35.2%) and seaward side (31.2%), followed by medium silt (25.1% and 29.0%, respectively). The proportion of fine sand was higher in the control (18.4%) and seaward side (16.1%) than that of the leeward side (6.1%). Because of the barrier, there was noticeable sedimentation on mudflat as demonstrated by increased elevation of shore profile in the leeward side, 23.3 cm vs. 3.6 cm in the control. Sediment deposition was, however, varied due to susceptibility to erosion depending on grain size distribution, e.g. the fine deposits had greater erodibility than the sandy deposits. These results suggest that barrier on mudflat could bring a positive change to the sediment profiling and shore morphology, and thus help stabilizing the eroding shoreline.