Grain Size Characterization of Lagoonestuarine System: Eastern Coast, Sri Lanka

Grain size distribution and textural parameters are spectacles to interpret the sediment movements and depositional processes of lagoon estuarine systems that are intermittently open in flood control measurements. A spatial grain size distribution study was carried out to investigate the morphologically controlled sediment movement and deposition of the lagoon estuarine system of the Eastern coast, Batticaloa, Sri Lanka with a specific emphasis on inlet management. A total of 51 surface sediment samples of the lagoon estuarine system of Batticaloa were collected and analyzed for grain size distribution and textural parameters. The results revealed that a marked relationship between lagoon estuarine morphology and the mode of the particle size distribution with respect to the sediment deposition and inlet flows. Statistical parameters are further confirmed from the grain size distribution curves which indicate that the sediments of beach and inlet associated areas have medium to coarse size positively skewed platykurtic nature. However, barrier deposits and shaded areas have medium size negatively skewed leptokurtic nature. The prominent sediment components of barrier deposits and shaded areas as well as beach and inlet associated areas reflect the morphological transition of lagoon environment to estuarine environment. The subordinate components of sediments show two different depositional environments indicating inlet changes. The inlet opening and the closure depends on the intensity of river flux and marine processes. The grain size distribution and morphology parameters of studies samples show a clear relationship which indicate both anthropogenic and natural processes control the changes of inlet of the lagoon estuarine systems.