Littoral sediment transport and shoreline changes along Ennore on the southeast coast of India: Field observations and numerical modeling

Abstract

The newly constructed port in 2001 at Ennore, on the southeast coast of India near Chennai, with breakwaters on either side (north and south) has been causing large-scale changes in nearshore morphology. Beach profiles and shoreline positions along 25 km coastline of Ennore were measured at regular intervals during 2001–06 to understand the sediment transport patterns in the region. At the same time the results of wave hind-casting and wave transformation modeling were incorporated in LITDRIFT model to compute the sediment transport rates along Ennore coast. The model results are compared with the sediment transport values obtained from beach profile measurements. The performance of the model at different locations within the study area with variable wave conditions has been examined. The annual net sediment loss (−) versus accumulation (+) were estimated for two smaller study areas (cells) containing ten regularly spaced beach profiles numbered from north to south, BP1-5 in cell I and BP6-10 in cell II. For the cell I region, which is protected by the Ennore shoals and where human interference is minimum, the annual net sediment supply is + 0.02 × 10 6 m 3 as obtained from beach profile measurements while the model gave a value of + 0.014 × 10 6 m 3. For the cell II region where there is large human intervention by way of Ennore port development and breakwater construction, the annual net sediment movement as obtained by the beach measurements is − 0.14 × 10 6 m 3 while the model gave a value of − 0.154 × 10 6 m 3. It is found that the performance of the model is satisfactory and the model may be used successfully to study sediment dynamics along any coastline provided one has detailed understanding of the coastline orientation, nearshore topography, cross-shore bathymetry and prevailing annual wave climate. Based on the sediment transport data and beach profile measurements the beach and shoreline changes for transect locations BP-1 to BP-10 are also critically examined in this paper.