Protection and Control of Coastal Erosion in India

Erosion prevailing along the vast coastline of India has a long history. Coastal erosion, very of ten, poses a serious problem The nature and degree of protection required for a given coast vary widely depending upon the environmental conditions prevailing in the area. A comprehensive environmental study of the problem is required for developing a suitable solution to any specific coastal problem. In genera I, there wiJl be more than one method applicable to protecting an eroding area Hence, it is very desirabIe to consider both shortterm and longterm effects very carefully before determining the most suitable remedial measure to cernbat erosion problem. In this manual, an attempt has been made to present some of the remedial measures including the guidelines for suitable designs to control coastal erosion with special reference to Indian condinons. While some of the basic information has been presented in the text under various sections, more detailed information has been included separately under six_appendices in the manual. Although the techniques presented in the manual are generally applicable to _ most of the coastal erosion problems, competent engineering judgement, based on experience, is necessary for determining their application to any specific problern. This manual is first of its kind in India. It is intended to be precise and effective .and makes no claim to be exhaustive. Nevertheless, the value of a manual of th is nature, dealing with diverse aspects of coastal erosion and its protection, cannot be denied. The original idea for preparing this manual came from Professor Per Bruun, who has considerable experience of working in Indian conditions for the past fifteen years or so. His major contribution and guidance during the preparation of this manual is indeed greatly appreciated.

I : :~ < ' COVER PHOTO: Anjuna Beach, Goa, India - protruding rocky cliffs offering natural proteetion to pocket beaches ,," 1980 N O Published by National Institute of Oceanography, Dona Paula Goa- 403 004, India Printed at Samyukta Karnataka Press (Job), Koppikar Road, Hubli- 580020, India 1980 N O Published by National Institute of Oceanography, Dona Paula Goa- 403 004, India Printed at Samyukta Karnataka Press (Job), Koppikar Road, Hubli- 580020, India Contents Page Preface I 2· list of Figures iii list of Tables vii Introduction I I General review on causes '·2 Rise of sea level of beach erosion 1·3 Heavy storms, storm surges, wave action and its seasonal effects 1.4 Littoral drift barriers, natural and man-made conditions in India 10 Beach Surveys 19 2.1 Bathymetric surveys 2.2 Sand sampling and analysis 2,2.1 Sand sampling 2.2.2 Sample analysis 2·2.3 Beach fill models 21 21 21 21 2.3 VVave 2.3.1 2.3.2 2.3.3 24 24 19 surveys General VVave measurements Relationship between the visual and the Instru mental data 25 25 2.4 Current and tide surveys 2.4.1 General 2.4.2 Current measurements 2.4·3 long term analysls of current 2.4·4 Tide surveys 2.5 Littoral Coastal I 3·2 drift 25 25 data surveys Protection 26 26 26 27 31 Basic aspects 3· I I Material balance 3·1·2 Beach and bottom profiles 3· 1·3 VVave machanics aspects 31 31 35 Review of coastal protective 36 3.2·1 ~ 2.2 36 measures Natural and man-made coastal protection Pre-re9uisites for coastal protection , 36 40 22 /' ~ 20 18 '2 ~ - Sw r-,