Beach-dune complexes are dynamic systems and fluctuations in its hydrodynamic conditions facilitate the exchange of sediments between onshore and offshore seasonally. The present study focuses on sediment texture within the beach-dune systems corresponding to an arcuate and a straight beach of Bakkhali and Talsari region, respectively. Multivariate statistical approach has been used to identify the end members and their proportion contributing to the grain size composition of the beach-dune system. To support the end members with a meaningful geological significance, discriminant analysis for depositional environments and CM plot for its dynamics are substantiated. The beach-dune system of Bakkhali shows appreciable homogenization of samples as compared to the Talsari region. In the Bakkhali beach an average of 0.238 m/year erosion and average rate of accretion is 0.423 m/year while in Talsari beach it is 0.238 m/year and 0.302 m/year, respectively. The end-member (EM) modelling showed relatively high contributions of medium- to fine-sand (ranging similar to 2.0 to 3.5 Phi) along with a minor amount of fines. Our study clarifies that grain size population exerts the primary control on erosion-accretion whilst hydraulic effects of wave and wind contribute to its spatial distribution. Since the particular size is lost from the system which needs to be replenished otherwise it disturbs the beach equilibrium. This study also bears its importance for beach nourishment as the end member analysis serves as a guide to replenish a beach with the required types of sediment grain sizes and search for its specific source areas. This work will also pave the way for advanced coastal resilience programs and climate adaptation planning and provide a platform for policymakers, technological innovators, the industry and researchers for coastal hazard mitigation and will ensure decision-makers regarding the execution of the plans on the ground.
Sinha, S; Mondal, SK; Mondal, S; Hansda, S; Patra, UK
Deciphering grain size populations and hydromorphological characteristics of the beach-dune system of East Coast of India: implications to coastal resilience and hazard mitigation
Environmental Earth Sciences