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Allen Hazen ( -1930)
"Flood Flows. A Study of Frequencies and Magnitudes. By Allen Hazen, D.Sc. New York: John Wiley & Sons, Inc.; London : Chapman & Hall, Ltd. [Price 20s. net.]
This book appears at a most useful time, written, as it is, by one of the leading authorities in the United States. Readers will regret that this eminent engineer is no longer with us, his death having occurred on July 26 of this year. He leaves behind him, however, in his last book, a record which will, we believe, endure, and it is seldom, if ever, we have come across such successful attempts to collate known records with the avowed purpose of predicting maximum flood flows in the years to come. The records used by Mr. Hazen are those of the United States Geological Survey Department, and of the Miami Conservancy Board and, most valuable of all, those of his own firm, Messrs. Hazen and Whipple.
We are pleased to note that no river is too small to come under consideration, quite considerable attention, for instance, being paid to a river as small as the Little River, Mass., whose catchment area is only 48J square miles. The book, of course, deals with the larger rivers of the American Continent, but we specially wish to emphasise that here is an American engineer who considers the smaller problems as worthy of attention as the larger. This is justified by the conclusion to which he comes, namely, that given similar geological and climatic conditions, the general behaviour of a river to a small scale is the same as the behaviour of its larger brethren.
After a brief introduction, the book passes on to the definition of flood quantities of which, of course, there are many factors, requiring, therefore, very specific definitions. The reader will appreciate this when the terms dealt with include such expressions as the “ one per cent, chance flood.” The author then proceeds to discuss the best way of plotting flood flows, and comes to the conclusion that all the graphs or curves are best plotted on logarithmic paper, with the object of endeavouring to bring the different observations into a straight line curve. It is a pleasing feature of the book that in these curves quantities are not shown by cubic feet per second, but as ratios to mean flood. Although too complicated to endeavour to explain in these brief notes, twenty years’ experience in Mr. Hazen’s office has shown that there are three coefficients operating in a river which can be obtained from data over a period, the longer the better, and these coefficients are explained. They are termed “ the coefficient of flood,” “ the coefficient of variation,” and “ the coefficient of skew.” It is evident how very careful the author is to proceed with caution in his method of research, for he points out that one exceptional flood, occurring in a short period of records, greatly upsets the calculated forecasting curves.
Chapter IX is, perhaps, the most valuable of all in the book, giving, as it does, a whole sequence of flow flood curves of many American rivers, of which the biggest is the Columbia River, with its 237,000 square miles of catchment area. This chapter also concludes with an interesting map showing the geographical grouping of records with the values of the three coefficients for the rivers in the different areas.
The book then goes on to deal with cases of specific floods and lays down the different ruling* factors to be considered in estimating flood flow. The duration of floods being, of course, important, the author discusses the question of detention reservoirs, both natural and artificial, and explains their action in checking the floods and their influence on the different coefficients, special reference being naturally made to the research work of the Miami Conservancy Board. One of the interesting facts which emerges is that the Mississippi floods have been doubled as to flood rise by the building of the protecting levees, which, therefore, never appear to be really high enough or strong enough. The author inclines, it may be imagined, to a preference for “ short-circuiting ” bends in rivers. Of course, as we have seen in other books, this does not always have the beneficial results hoped for, and the general result seems to be that each case must be dealt with on its merits.
The author divides river catchment areas into three portions:—
(1) The river bed proper;
(2) Ground above this liable to flooding;
(3) Ground above all floods.
He does not find from his researches that floods in the United States have appreciably increased, but considers that the damage done becomes greater and greater as the middle area becomes encroached upon by cities and development estates.
Although his researches take cognisance of floods which occur in say 1, 10 or 100 years, he does not find that there is any definite cycle of any flood of any particular class. The effects of land drainage are discussed, but do not appear in America to affect the run-off of any river materially, and the effects of afforestation are also thoroughly discussed.
It is a pleasure to read an author so keen on his subject, and the book, in itself, is a classic of its type. As far as the sale of technical books go, the work should succeed in this country, and it ought to be brought to the notice of members and officials of all the new Catchment Area Boards now being formed under the Land Drainage Act, as also to the new Inland Drainage Boards, which are to emerge from the existing Commissioners holding authority under the old Land Drainage Act of 1861. To such bodies and their officers, the book represents a fund of assembled and collated information.
As Mr. Hazen was the first to introduce the study of probability into hydrological questions, and his death having occurred quite suddenly, at the age of 61, at Miles City, Montana, from a heart attack, we desire to pay our tribute on this side of the Atlantic by briefly recording his professional career. Mr. Hazen’s work, of over 30 years, brought him first into touch with sanitary engineering, following his graduation from the New Hampshire College of Agriculture and Mechanic Arts. He was actively associated with the sewage-disposal problems of the City of Boston, and with the water filtration plant at Lawrence, where special precautions were taken in connection with the outbreak of Asiatic cholera in America. He was in charge of the sewage-disposal plant at the World’s Fair at Chicago, in 1893, and after a protracted visit to Europe for purposes of study, he undertook the design and construction of the filtration plant for Albany, New York. After 1904, however, Mr. Hazen devoted a great deal of his time to the subject which is dealt with in his book now under review. He was a member of the American Society of Civil Engineers, and was held in high respect by engineers on both sides of the Atlantic."