Sediment Characterization and Monsoonal Impact on Beach Morphology at the Three Beaches along the Karachi Coast, Pakistan

Sediment characteristics plays important role in the determination and functioning of coastal ecosystems. The present study is an attempt to evaluate the variability in sediment characteristics of the three beaches: Clifton, Sandspit and Buleji, at the Karachi coast. The samples were collected during pre-monsoon and south-west monsoon seasons to evaluate the seasonal differences. The sediments of the three sites showed variations in moisture content, organic matter and grain size. The highest mean moisture (27.17%) and organic contents (3.5 %) were recorded from the sediments of Clifton. The maximum fraction of sediments (> 80 %) consist of fine to very fine sand at all studied sites. The sediments of Clifton were high in very fine sand fraction and low in coarse sand fraction as compared to Sandspit and Buleji. The sediments of all the three studied sites are moderately sorted, negatively coarse-skewed and showed leptokurtic distribution. The studied beaches of Clifton, Sandspit and Buleji shows dissimilarity in sediment characteristics as indicated through Cluster and PCA analysis. The monsoonal influence on sediment characteristics was also observed at all the three studied beaches. The strong wave action during SW monsoon season results in the deposition of the coarser sediments at the high tide level thus increasing the steepness of the beaches.