Grain size distribution of modern beach sediments in Sri Lanka

Abstract

Grain size distributions are widely used to describe sedimentary geochemistry, depositional environment, and sediment transportation. The objective of this study is to analyze grain size distributions of modern sandy beach sediments in Sri Lanka. Sediment samples (n = 90) were collected from beach berm, representing the entire coastline of Sri Lanka. Grain sizes were determined by the dry-sieving method. Statistical parameters such as mean size, sorting, skewness, and kurtosis were calculated using GRADISTATV9.1 software for all the sieved sediment samples. Grain size variations (108.2 – 609.8 µm) show that Sri Lanka mainly consists of medium sand, whereas the northeast part of the country mixes with fine sand due to the influence of Bengal fan sediments. The variations of skewness (-0.229 – 0.446) and sorting (1.305 – 2.436) indicate symmetrical distributed moderately sorted samples. These variations specify a moderate energy depositional environment/wave action around the coastline of Sri Lanka. In addition, grain size analysis confirmed relatively high and low energy deposition environments on the west and east coasts, respectively. Accordingly, the west coast is more vulnerable to coastal erosion compared to the east coast of Sri Lanka. Therefore, this study provides the baseline grain size distribution data that can be used in decision-making for coastal zone management by mitigating beach erosion.

Environmental impacts of shore revetment

“…The revetments can result in less suitable nesting area. They possibly force the sea turtles to stay away and lay eggs in a lower section of beach berm, which is more susceptible to erosion and inundation [ [82] , [83] , [84] , [85] ]. Revetments and seawalls were shown to have adverse effects on sea turtle nesting, where fewer turtles emerged onto beaches in front of revetments and returned to the water without nesting when compared to adjacent beaches [ 86 , 87 ].…”