Irrigation and Drainage Systems 3: 205-206, 1989. © 1989 Kluwer Academic Publishers. Printed in the Netherlands.

B o o k Review

Brookes A. 1988. Channelized Rivers. Perspectives for Environmental Management. New York: John Wiley & Sons Ltd. ISBN 0 471 91979 9 According to the author, this book is intended to give a view about the state-ofthe-art in the field of scientific research related to the physical, biological and morphological effects of the channelization works on rivers, in order to improve the management of such rivers in the years to come and provide guidelines for future research programmes. The book consists of five parts, progressively developed into nine chapters. The first part (Chapters I and II), is a general introduction of the subject, followed by a presentation of conventional engineering methods and their practical limitations. Chapter I starts with a short historical background of channelizations from the most remote days to our times, made first to provide protection against floods and then, because of other reasons linked to the social development and needs (improvement of agriculture, industry, navigation, etc.). It has only been in the last decades that mankind has become aware of the negative effects of many of these works on the environment and that public opinion has raised against their uncontrolled construction. Illustrated with a number of case studies Chapter II gives a detailed description of the conventional channelization works (resectionning, realignments, embankments, diversion channels and so on) as well as their pros and cons. The second part (Chapter III), shows how a specific legislation has been developed in the different countries during the last twenty years to protect the environment against deterioration caused by channelization, and provides examples of methods used in the assessment of physical, ecological and aesthetic impact in the most advanced countries (USA, Denmark, Great Britain, etc.). The following chapters cover and analize in detail the physical (morphological), biological and downstream effects of such works and the readjustment and recovery process of the fluvial environment after channelization, frequently interrupted by conservation and maintenance operations and manifest the need to research on the factors that affect the environmental balance in the downstream and surrounding ecosystems. In Chapter VII, Mr. Brookes presents an analysis of the Revised Construction Methods and the results of various studies which offer some alternatives to mitigate the negative effects of the conventional constructive methods described in Chapter I. The in-depth study of biological factors involved in channelization originat-

206 ed new specialities such as "biotechnical" and "geomorphological" engineering to offer less detrimental alternatives to riverine ecosystems management. It is also stressed to regard the river basin as a whole and consider all activities carried out in it from an overall point of view. Likewise a detailed study of the Revised Conservation Methods is conducted: biological recovery, aquatic weed selective clearance and dredging, channel darkening, etc. Chapter VIII further develops the previous chapter and presents techniques to attenuate the ill effects of channelization works on rivers as well as to increase their internal resistance to their adverse effects and to accelerate the recovery processes. It includes also a description of devices and instream structures aimed to help for the natural formation o f pools and riffles and of other methods to restore substrate primitive conditions. Chapter IX is a sort o f epilogue where the author provides a series of considerations on the future perspectives of channelization works and underlines once more the conflict between the engineering works that affect rivers and nature conservation, stressing the lack of awareness in most of the countries of the negative effects of such works and insists in the need to establish legal provisions for environmental protection. Mr. Brookes wonders if the channelization works do not constitute an antithesis to the environment and refers to famous scientists who support different points o f view. However it remains true that all structures do not produce necessarily negative effects and that the degree of deterioration depends on the length of the reach affected by the works, the type of work and the consideration given to biotechnical aspects. From all this a growing need results for increased participation of scientists and experts on environmental aspects who must work, hand by hand, with civil and other engineers in all works affecting the environment in order to anticipate consequences and to advise on how to avoid the detrimental ones. Mr. Brookes concludes his book stressing the need to keep strengthening hydraulic and geomorphic research, to publish handbooks and to give guidelines for a correct rivers channelization policy. In addition he includes a bibliography with more than 800 references to support arguments stated in the book, as well as two alphabetical indexes (by authors and by subjects), to facilitate any consultation on any question. This book, rich in practical data, references and specific suggestions based on real cases, is a genuine consultation book and can be extremely useful not only to engineers involved in channelizing works, but also to other technicians, specialized in environmental matters, since it provides with a vast variety of practical solutions for water ecosystems and for the whole watershed protection, without neglecting the execution of the works required for the welfare and development of mankind.

Madrid, Spain

Jos6 A. Ortiz F.-Urrutia