Optimization of a Shore Protection Scheme for the West Coast of India

Abstract

More than 300 km of the 2000 km-long west coast of India are undergoing severe erosion. The economic importance of India’s coastal zone in the States of Kerala, Karnataka, Maharastra and part of Tamilnadu requires that various shore protection measures be investigated to halt the erosion which in some locations exceeds 5 meters per year. Shore protection measures considered were beach nourishment, groin construction and the construction of a rubble-mound seawall. Economic and practical considerations led to selecting the seawall alternative since a source of suitable beach sand was not readily available and the cost of the heavy construction equipment necessary to build groins would have been prohibitive. The shortage of heavy construction equipment, an abundant source of labor and the availability of suitable rock from nearby quarries influence the economically optimum seawall configuration. Hydraulic model tests of the proposed rubble seawall were undertaken to establish the seawall cross-section and to determine the amount of damage caused by various levels of wave attack. The results obtained by an interactive computer program to establish the optimum level of design for the seawall and to determine the most economical cross-section geometry are discussed. The program considers factors such as the size distribution of rock produced by blasting at the quarry, the quarrying costs of producing armor stone of the required size, the cost of transporting and placing the armor stone, and the cost of repairing the seawall in the event design conditions are exceeded.