Search

The north Chennai coast, on the east coast of India, experiences severe erosion caused by waves, and an area of the beach about 600 m wide has eroded over the past 120 years. To protect the seafront, natural stones were dumped by government agencies along the coast for a distance of about 6 km, and in the process, a short beach pocket 400 m long was left unprotected for various reasons. Because the property of a chemical factory located in this 400-m stretch of beach pocket suffered damage caused by erosion, and because the need for a wide beachfront was stressed by local fishermen, an alternative method of protecting the beach was suggested. The proposal involved construction of an S-type rubble sea wall about 100 m long on the southern end of the beach pocket. This paper discusses the numerical model studies conducted to determine the configuration of the S-type rubble sea wall and its effectiveness in beach protection. The model studies suggested a length of projection of 14 m with a radius of curvature of 310 m for the S-type sea wall to achieve the desired performance. Field studies conducted on the 40-m-wide and 400-m-long beach pocket with the 100-m-long S-type sea wall indicate that the sea wall is effective in protecting the beach. [ABSTRACT FROM AUTHOR]

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 +0.02×106 m3 as obtained from beach profile measurements while the model gave a value of +0.014×106 m3. 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 −0.14×106 m3 while the model gave a value of −0.154×106 m3. 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. [Copyright &y& Elsevier]