A study of seasonal longshore transport direction through grain-size trends: An example from the Quilon coast, Kerala, India

Abstract

The longshore transport direction in relation to the pre-monsoon, monsoon and post-monsoon seasons was studied, utilising the textural parameters of the foreshore sediments along a 41 km stretch of the Paravur-Purakkad coast in Kerala. The seasonal grain-size variation and sediment budget along the coast was also examined. This coast was divided into two sectors viz., southern and northern, based on the variation in the sediment type and a change in the orientation of the coastline. The sediment transport direction deduced from both statistical methods and field measurements are in agreement for the southern sector, signifying the availability of sediment for transport; in contrast, in the northern sector, no correlation was found except during the premonsoon season. The reason given for the obscured direction of sediment transport is the possible removal and transportation of the beach sand to the near-shore shelf during the monsoon and post-monsoon seasons, and also mining activities. The deposition of winnowed material from the southern sector, on to the beaches of the northern sector may be responsible for the northerly-oriented current during the pre-monsoon season.