Since 2008, Kuala Nerus has undergone rapid urbanization along its coastline, resulting in the loss of sand along the littoral zone. Due to the heavy erosion in 2012 at Tok Jembal beach that migrated to Universiti Malaysia Terengganu (UMT) beach in 2013, the Department of Irrigation and Drainage has implemented a coastal defence project to mitigate erosion by building a series of ripraps/revetments along the coasts. Additionally, breakwaters and groyne structures were built in combination with beach nourishment programme. For the sustenance of the local fishermen community, the Malaysia Public Works Department replaced one of the breakwaters to a jetty-type breakwater at Tok Jembal beach. Shoreline evaluations, beach profile measurements and numerical modelling were used in this present study to identify the effectiveness of combining the coastal defence and beach nourishment programmes. The combination of programmes successfully initiated the accretion of a ~30 m beach dune and created new beaches. However, erosion remains persistent in the beach that was unprotected and exposed directly to the South China Sea. We posit that a combination of coastal defence and beach nourishment programmes can potentially interrupt dynamic coastal processes, especially the current parameters.
The movement of sediment and associated microphytobenthos (MPB) between the upper mudflat and salt marsh in a macrotidal estuary was investigated by comparing the variability of benthic chlorophyll a (Chl. a) and suspended Chl. a during flood and ebb spring tides during the 2015 supermoon event. Sampling was carried out for 4 days in August and September. Flood-tide water carried significantly higher amounts of Chl. a from the mudflat transition zone onto the salt marsh compared to the amount of leaving the salt marsh during ebb tides. Suspended solid loads, suspended Chl. a concentrations, and diatom species composition provided evidence that resuspended mudflat sediments containing biofilm material were transferred onto the salt marsh by flood tide. Significant negative correlations between sediment Chl. a concentrations on the upper mudflat transition zone and Chl. a concentrations in flood-tide water indicated biostabilization of sediments by biofilms reducing sediment resuspension. Mean wind speed had a significant positive effect on resuspending Chl. a from the salt marsh sediment surface into the ebb tide (p < 0.001). The amount of Chl. a being resuspended in flood and ebb tidal waters was significantly correlated with MPB biomass on the sediment surface on the mudflat and salt marsh, respectively. Resuspended diatoms over the mudflat during high tide shared a total of 54.3% similar species with diatoms recorded in flood tidal water over the salt marsh. Diatom taxa characteristic of salt marsh assemblages, and some deposited diatom taxa were resuspended and carried off the salt marsh during ebb tide. Resuspension of Chl. a in both flood and ebb waters was significantly controlled by the tidal range (both significant at p < 0.001). During spring tides, there was a net movement of characteristic MPB mudflat diatom taxa and sediment from the adjacent mudflat to the salt marsh, contributing to the accumulation of material within vegetated marshes during summer months.
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