Shore Processes And Shoreline Development (1919)

SHORE PROCESS AND SHORELINE DEVELOPMENT BY DOUGLAS WILSON JOHNSON ASSOCIATE PROFESSOR OF PHYSIOGRAPHY, COLUMBIA UNIVERSITY FIRHT EDITION NEW YORK JOHN WILEY SONS, INC. LONDON CHAPMAN HALL, LIMITED 1919 ii l ililiiiwbliitiMiMiiiii vlr iilii 11 1 - Si A PREFACE THE present work was born of a need experienced by the author in connection with his shoreline studies. In the course of a critical examination of the arguments supposed by many to demonstrate a progressive subsidence of the Atlantic coast of North America within historic time, it developed that in respect to certain of these arguments agreement between students of the problem could not be reached because there was not sufficient agreement as to what features are normally characteristic of a stable coast, and what features are peculiar to coasts which are rising or subsiding. No work existed which combined with an extended analysis of the forces operating along the shore, a full and systematic discussion of the cycle of shoreline development and such further discussion of the modifying effects of changes of level as would enable one to differentiate stable, rising, and subsiding coasts. It seemed necessary, therefore, to enquire somewhat fully into the fundamental principles of shore processes and shoreline de velopment for it would not be profitable to add to the already overburdened literature on changes of level another essay which should merely add quantitatively to the volume of evidence pre viously discussed by many earlier writers, and again assert as the correct interpretation of that evidence conclusions which some geologists and geographers accept and others reject. Profit could come from the study only in case thediscussion of principles was such as to bring geologists and geographers into substantial agree ment as to what shore features are, and what are not indicative of changes of level. Once this measure of agreement was reached, I could not doubt that a critical analysis of the arguments supposed to prove the progressive subsidence within historic time of the coast of southeastern Canada, the Atlantic coast of the United States, and certain other marginal areas of the continents, would demonstrate to the impartial and critical student the inadequacy of those arguments. I therefore set myself the task of bringing together the results of shoreline studies published in different languages, of analyzing and criticising the conclusions reached iv PREFACE where this might appear to be profitable, and of presenting a digest of those fundamental principles which should prove to be best established by the independent work of different students and best supported by my own field observations. At the s me time I purposed to develop somewhat fully certain important aspects of the physiography of shorelines which have hitherto received little consideration. The magnitude of the task proved to be greater than antici pated, partly because of the wide divergence of expert opinion regarding the mariner in which shore processes operate, and partly because of the great volume and scattered distribution of the writings dealing with the subject. It was, indeed, the desire to relieve others who might have occasion to study shore processes and shoreline forms, of the burden of duplicating the work involved in my undertaking which first suggested to me the desirability of placing on record, in compact form fortheir use, the results of my enquiry, even where these results did not relate to the original problem of coastal subsidence. The present volume is the con crete product of this desire to render a service to my fellow students. The engineer will find in the chapters on waves and currents a summary of the widely conflicting opinions and observations re lating to those most puzzling forces with which he has to deal...