425 
 M82 
 
HOUSE OF REPRESENTATIVES, UNITED STATES 
 COMMITTEE ON AGRICULTURE 
 
 A EEPORT 
 
 ON 
 
 THE INFLUENCE OF FORESTS ON CLIMATE 
 AND ON FLOODS" 
 
 BT 
 
 WILLIS L. MOORE, LL. D., So. D 
 
 Chief of the U.S. Weather Bureau 
 
 Note. — When Professor Willis L. Moore was before the Committee on Agriculture 
 of the House of Representatives in 1909, to explain the estimates for the 
 Weather Bureau, a discussion arose as to the influence of forests on climate 
 and on the run-off of water. Professor Moore stated that he was then mak- 
 ing some studies on the subject which might lead to some definite conclu- 
 sions, and he was requested by the chairman of the committee to continue 
 these studies and make a report when they were concluded. This has been 
 done, and the report submitted by Professor Moore, which follows, is printed 
 by direction of the committee. 
 
 WASIIIXtiTClX 
 GOVERNS KXT 1 'M \ ; I \ ( J OFFICP: 
 
 r,ii(i 
 
Cornell University 
 Library 
 
 The original of tiiis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924000432777 
 
THE INFLUENCE OF FORESTS OX CLIMATE AND ON 
 
 FLOODS. 
 
 By Wans L. Moore, LL. D., Sc. D., Chuf U. S. Weather Bureau. 
 
 INTRODUCTION. 
 
 One of the most important problems before the American people 
 to-day is the protection of their natural resources against either the 
 preed of those who would monopolize them for their own individual 
 benefit or those who, while well meaning, would through ignorance 
 destroy our heritage and leave posterity poor. 
 
 In tlie discussion of matters concerned with the conservation of the 
 natural resources of the nation, some of which may involve the 
 expenditure of hundreds of millions of dollars and the employment 
 for years to come of thousands of public officials, a consideration of 
 the relation of forests to climate, floods, and low water is vitally 
 important. 
 
 VVliile much has been written on this subject, but little of it has 
 emanated from meteorologists or from those in the public service 
 who have been actively engaged in the forecasting or river stages, 
 both of high and of low water. In the prosecution of such duty these 
 officials have become acquainted with the physical facts involved in 
 the problem and are therefore well fitted to speak on the relation of 
 such facts to stream flow. 
 
 THE AUTHOR ACKNOWLEDGES A CHANGE OF OPINION. 
 
 It has frequently been stated that forests control the flow of 
 streams, both in high-water stages and in low-water stages, and that 
 the climate is so materially affected by the cutting away of the 
 forests that droughts have largely increased and that the well-being 
 of future generations is seriously menaced. It is my purpose to 
 present facts and figures that do not support these views, some of 
 which, especially those that pertain to the flow of streams, were held 
 by me up to a "few years ago — until a careful study of our own and 
 other records and of tlio incidents of history caused me to modify my 
 opinions. I sliall eiHieavor not to be dogmatic, but rather to present 
 the reasons for the conclusions that I now entertain, with, so far as 
 1 i!;v Iv, .-'.j; Mi;il und Idsforical evidence to sustain them. And 1 
 iv-fTve t'lf- n'.:lil in chi.ii'j-c (jr -till further morlify my views if the 
 pr; s<-'iit. 'wii I'f i!''V\' l:ir!s and fiirnif- render such a course logical, 
 all'! d') not en idr)' thai 1 hiiall ;-tulti[y myself in so doing. 
 
 3 
 
» HIE ixFi.rExn: of forests ox climate axd o^r floods. 
 FO!;"srs su()i-i.i) be protected. 
 
 There are so many reasons ^v\\y forests should be protected by the 
 state and the nation and economically conserved in the interests of 
 the whole peo]ile tliat it is doing an injury to a good cause to attempt 
 to brmg to its support the false reasoning"and mistaken conclusions of 
 enthusiasts, no matter how well meaning they may be or how devoted 
 to high and lofty purposes. 
 
 Conservation of national resources is national econom}', just as 
 conservation of private resources is personal econom}'. But whether 
 personal economy is beneficial or harmful to the individual and his 
 children depends upon the extent and nature of that economy; and 
 the same thing is equally true of a nation. Conservation that pre- 
 vents the practical use of individual or national resources is like 
 unto the economy of the timid servant that hid his master's talent 
 in the earth, and in large measure deserves the same condemnation. 
 
 There should be neither wasteful use of resources nor that greatest 
 waste of all, total disuse of them, but that economical use which in 
 the end will have jielded the greatest good to the greatest number. 
 
 Preservation of the forests, cutting wisely, but never more than 
 they reproduce, enables us to draw from a perpetual supply a certain 
 quantity of material for buildings, for furniture, and for fuel. But 
 of course the forested land yields not a handful of wheat nor of com 
 and mal'es hut a wretclied substitute for the pasture upon which to feed 
 milch cows and heef cattle. These conflicting interests, the pleading 
 of the poor man's chiklren for bread and meat and the cry of the 
 country for the lumber that only a woodland can furnish would, if 
 there were no other interests to modify the result, somewhere find an 
 inevitable balance. But just as the body is more important than 
 its raiment, so, too, is 'its food more important than its shelter; and 
 therefore in every country the general tendency, with growth of popu- 
 lation, is to con r ai fori st lands into cultivated fields, and this tendency 
 should not be discouraged unless it can be shown that deforestation has 
 augmented drougliis and floods, and I believe that it can not be soshown; 
 I believe that forests should he preserved for themselves alone, or not 
 at all. 
 
 The average virgin forest is wasteful as a source of lumber and of 
 fuel. It is only here and there that a tree is found of proper growth 
 and suitable species for first-class material. As a lumber producer a 
 forest of this kind is analogous to a cornfield planted in scattering 
 hills here and yonder, instead of being cultivated throughout its 
 extent and planted with that regularity and closeness of spacing that 
 will produce the maximum yield. If the expense is not found to be 
 too great in comparison with the return, forests should be cultivated 
 with the same care both as to species and as to distribution, and pos- 
 sibly, too, as to rotation, that the intelligent farmer uses in planting 
 his fields. In this way returns equal to what we now get could be 
 secured from a mucli smaller forested area, and there can be no valid 
 objection to decreasing the area where homes and a weU-fed people take 
 the place of irild nnln'oh and the vrildrrness. 
 
 It is found that in some limited areas where the forest is cleared 
 awiiv, till! soil, owin;.' to its nfiturc and slojie, will not admit of suc- 
 cess!' u'l ciiltiviition. It niav v, ash so badly under heavy rains as to 
 become unfit even for reforc-^ting. In others, owing to the nature 
 
THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 5 
 
 of tlie siirfiice, cultivation is impossible. These are fit places for 
 lociil control, provided such control is commercially feasible, but not 
 for national control, unless it can be demonstrated that the conditions 
 at these places materially affect the navigability of streams or harmfully 
 affect the climate of the continent at large. 
 
 The great value of forests as fuel producers is admitted on every 
 hfind, and because of the growing cost of coal their importance in 
 tHs particular is likely to increase rather than diminish, and of course 
 without them the woild would be deprived of that beautiful building 
 m^aterial which from the earliest ages it has used so freely and regarded 
 &si indispensable, but which in the future may be used in a less ratio 
 &a the use of noncombustible materials, like concrete, stone, and 
 st eel, becomes more general, and certainly their use will increase. No 
 niason in addition to these can be needed to justify an immediate and 
 vigorous effort on the part of individuals, and especially on the part 
 of goverimients, to teach and to insure the wisest national use — that 
 is , wisest use when both the present and the future are properly con- 
 si dered — of all existing forests, and also where and how best to secure 
 other forested areas. 
 
 Nevertheless additional reasons are urged, and in some cases urged 
 as the paramount reasons for forest conservation, which will not 
 stand the test of investigation. 
 
 EFFECT OF FOREST ON CLIMATE. 
 
 It is often said that the climate of a given place depends upon the 
 e3:tent and proximity of wooded areas; that the number of rainy days 
 and the total amount ot rainfall are modified by change of forest 
 ejctent; that the depth of floods, the shallowness of low water, and 
 ti e regularity of flow are all profoundly modified by changing the 
 proportion of fields to forests in the watershed. 
 
 Now, the extent and even the nature of these influences is not a 
 matter, as often is implied, of universal agreement. In regard to 
 change of climate, regardless of the cause, trustworthy records of 
 temperature, of rainfall, and of other meteorological elements do not 
 cc>ver a sufficient range of time to furnish all the data necessary for 
 a statistical solution of this problem. However, there appears to be 
 plenty of evidence that there have been times in the remote past 
 when the salt seas both of Asia and of America had surfaces of greatly 
 increased size over those that now exist. There is evidence also that 
 in certain of tliese regions trees once grew more abundantly than is 
 now the case.kThis, however, must not be taken as proof thatihere 
 has been a decrease of rainfall due to destruction of the forests/ It 
 is true that the forests have diminished— in some cases wholly van- 
 ished—and it is also true that the evidence strongly supports the 
 assumption of a decrease in rainfall, and therefore, of course, of a 
 grciter or less change of climate; but this decrease of precipitation 
 mi^rlit better be regarded as the cause rather than as the result of 
 till" l»arren condition of the soil. There is no evidence that the for- 
 ests were ever more extensive in Alaska and in other high-latitude 
 cuiiiiiiios thiin thev now arc. Nevertheless, in these countries, too, 
 JK^l :i< in arid rc<rions of tlie great continents, there is evidence of 
 tl!< .-.line slow, long-period climatic change— a decrease of precipi- 
 tation or an increase of temperature, or both— a change that can 
 
6 THE INrLTJENCE OP FORESTS ON CLIMATE AND ON FLOODS. 
 
 not be due to deforestation. This evidence consists in the slow irrejj.u- 
 lar retreat (followed once in a while by a slifjht advance) and diminu- 
 tion of the glaciers, which phenomenon is said to be universal regard- 
 less of latitude, of longitude, and of elevation, and which appears to 
 have been in more or less steady progress with, however, occasional 
 temporary relapses of one or another magnitude since the culmina- 
 tion of the great ice age. In fact, we can reasonably say that ^ye 
 are even yet in the ice age — a vanishing age to be sure, but one not 
 wholly gone — and, j'urther, that U'Jiatever raarked climatic changes ta.lce 
 place they are essentially universal and not local. i 
 
 Prof. William J. Humphreys, Ph. D., Johns Hopkins, professor of 
 meteorological physics, Linited States Weather Bureau, says: 
 
 These universal slow climatic changes that for thousands of years have been modi- 
 fying the glaciers and changing the inland seas might very well have led to exten.si ve 
 forest destruction; but that it itself was the effect and the destruction of the trues 
 the cause seems most unlikely. ) 
 
 DESICCATION IN ASIA. 
 
 In this connection I would refer to the opinion of Mr. Ellsworth 
 Huntington, B. A. of Beloit and M. A. of Harvord. For four years, 
 1897-1901, he was the President's assistant and instructor at Euphra- 
 tes College, Harput, Turkey. He explored the canyon of the Euphia- 
 tes River in 1901 and was awarded the Gill Men[iorial by the Rojal 
 Geographic Society of London. He was research assistant in the 
 Carnegie Institution, of Washington, and was a member of the Pu.m- 
 pelly expedition to Russian Turkestan in 1903-4. He spent one and 
 one-half-years in Turkestan and Persia and a like period in India, 
 China, and Siberia as a member of the Barrett expedition. He has 
 been instructor in geography at Yale since 1907. He explored the 
 Lop basin in Chinese Turkestan, whose length is 1,400 miles and whose 
 maximum width from north to south is 400 miles, embracing an aiea 
 as large as that portion of the United States east of Lake Michigan 
 and north of Tennessee. Most of the basin is desert. In an article 
 in the Monthly Weather Review for November, 1908, dated at Ynle 
 University, November 10 of the same year, he says: 
 
 The Lop basin contains abundant evidences of climatic changes, and has been dis- 
 cussed in detail by the writer in "The Pulse of Asia." Throughout the basin the 
 amount of vegetation has greatly decreased in recent times without the intervention 
 of man. On the lower slopes of the Kuenlun Mountains the dissected condition of 
 numerous deposits of loess shows that a cover of grass prevailed at no remote date, but 
 has now disappeared. In the zone of vegetation plants of all kindsshow signs of a 
 process of drying up which has been in progress for centuries. Tamarisk bushes stand 
 upon mounds from 5 to 60 feet high, a sure sign of the lowering of the level of ground 
 water; poplar forests which once extended for scores of miles now form wastes of 
 branchless dead trunks like gaunt gray skeletons; and beds of dead reeds cover hun- 
 dreds of square miles, fit has often been asserted that the destruction of forct^ts has 
 been the cause of the diminution of rainfalQ In the Lop basin the opposite appc.ir3 
 to be the ca^e; the supply of water has diminished, and therefore the forests have died. 
 ■Rainfall unquestionably controls forestation, but neither in the Lop basin nor in other 
 parld of rcmral and western Asia is there any good evidence that forests have an 
 apiirfr-iabie effect unoa rainfall. 
 
 Anolher ieipdiianl line of evidence is found iu the relation ol rivers to the de ert 
 of Taklaniakan and io ruin-^ of aueient dwellin-.^ Ou the south .-iide cf tlio Lop ba ui, 
 from Kholun eastwiinl to l.up Xur, the writer exaniituil seventeen streams wlneh arc 
 worthy of notice, because of their si/e (jr brc.v>;-c ilicv supiH'rf oases. All but f. ur 
 conio to an end in the zoni' of veiri'ta'ion, wii.re they spread out and 'Iwapjiear en er 
 naturally or because used for irrigation, lieuce it i-= nupossible to del eruuno whether 
 
THE I^'FLUEXCE OF FORESTS ON CLIMATE AND ON FLOODS. 7 
 
 . r r.it they have dci-roa^od in loiiirth. At the lower ends of the other four, old channels 
 ire unmd lined with dead forests, whii.-h ])rove that the streams once extended from 
 S to -5 milea farther than is now tlie case before finally becoming swallowed up in 
 (he eand. 
 
 FORESTS IN EVIDENCE AFTER STREAMS HAVE DRIED UP. 
 
 The fact that dead forests stand long after the streams have receded 
 see77is to prove that they are the last to disappear rather than the first, 
 and therefore that their removal did not precede the drought but rather 
 that the forests ceased to exist when the rainfall became deficient. 
 Lnmistakable evidence is found of the existence of extensive forests 
 in Arizona and New Mexico, where only the petrified trunks of trees 
 now remain. It can not be said that man removed these forests and 
 brought on the drought. 
 
 LOCAL CLIMATIC INFLUENCES OF FORESTS. 
 
 One may conclude from the evidence gathered from many sources 
 that summer temperature is slightly less in the forests and in their 
 neighborhood, especially to the leeward, than it is in corresponding 
 cleared sections. Forest temperature is also slightly higher during 
 cold weather than is that of open fields, due presumably to the inter- 
 ference of the trees, even when of the deciduous type, with free ground 
 radiation. 
 
 The increase of winter temperature, however, is not equal to the 
 decrease of that of summer, the season during which most vegetation 
 needs .ill of the heat it can get; and, therefore, it happens that, wooded 
 areas may slightly retard the growth of crops in their neighborhood, 
 as if 5>iid to be the case in the uplands of Mauritius. 
 
 Witli regard to the eS'ects of forests on rainfall, I quote the follow- 
 in_' fi'im recent writings of Prof. Cleveland Abbe, who is the senior 
 professor of the Weather Bureau and a member of the National 
 Academy of Science. He says: 
 
 It is a pity that the errors of past centuries should still continue to be disseminated 
 lot! 2 after scientific research has overthrown them. It is easy to start false theories and 
 t.j believe them, because they are generally simple and plausible, but long years of 
 ■work are necessary before we get at the secrets of nature. In this day and generation, 
 the idf-a that forests either increase or diminish the quantity of rain that falls from the 
 clouds is not worthy to be entertained by rational, intelligent men. 
 
 Gauges exposed over forests universally catch more than gauges 
 exposed at the same elevation in the open. Professor Abbe explams 
 this as follows: 
 
 Tlio main tnjublo consists'in the assumption that the water caught and measured 
 
 i" •!:'■ r;'in pauLMjcorreetly represents the rainfall. Perhaps the most interesting ob;er- 
 
 v.i'i'jh- iiearij];,' directly on this question are tho-e made by Brandis and Blanford in 
 
 h iia. '.. iiere rain Kau^es were placed Ijoth on the ground and above the tree tops at 
 
 '),'- h^.-ijiit of GO feet in well-watered rej.'ion-. Thehi^'h fjau'/os in the forest rerorded 
 
 i j.f-r ' ' 'it ^'ri_\itcr catch than those at the same hei;,'lit in the open fields, and the low 
 
 •.-1 ..'■ - ',1 the ^Touiid in cleared .-puce- in the forc-t lmvc 2 jjcr cent (rr' atcr c;itf h tlian 
 
 o|i' ,■! Iiimls. But tlie-e li 'urc- do ii'.t prove tluil the fore.-t received more 
 
 lij- clear ;iri.as, :illhoiiL'h at fir t -i_'ht tlj' y would .-i-cin to confirm th;it idea. 
 
 i I.I. , it llic I'orc-t L'iini"-' were b'-it r -hcli<.r.;d from the v.'ind than tliO (piicn- 
 
 . . ..ii.'c- ;ind thi.H c.iii-ed tlietn to catrh a l.irj. r )irHi,ortiori of ttie r.iiii thut fell. 
 
 ,j ■. ;■ 'c h:i - -.;\ i-r.d ,-.;iirce- of err'.r tluit niM-t be- Ci-.-e-i i-Ml' d ani'i ailo\'.i-d fi"T, 
 
 :i.' ■ I ■ ii-oroIo-.-ical a|)piir;;!.u-. -•• f'.i.d v, c may not u e ciiide and inij)cr[(;ct 
 
 (■ c|ii.. L ,,f llic- V. ind in dirniiii-liii.j the f ,,icli r,[ the ram 'jmvji- lia- lrc(|uiMitly 
 
 ( ' ,. '.. -I.i;.;ated -iiice the fir-t -tudie- b}' .Mil.le in l^I!l, and llie Jjre-ent slate of OUT 
 
8 TUE INFLUENCE OF FORESTS OX CLIMATE AND ON FLOODS. 
 
 kiiov^i-Io(lcnwa.-ro-aviiiriiiL:!ysiimmarizoa * * * in 1SS7 in an Appendix to Bulletin 
 ' • P"'>'i^ H'd by the Fnrivtry l>ivi-i..ii, United States Department of Agriculture. 
 Tins Bulletin, edited by 1'.. K. l-'ernow, "the father of American forestry," recounts 
 the various metliod.-i appropriate to the determi;-..uion of the true amount of precipi- 
 t.itiou, and it^ bearing on theories of forest inliueneos. 
 
 It appears that in ordinary rainfalls we have a mixture of large and email drops of 
 water descending with various velocities that depend on their size, density, and the 
 resistance of the air. Particles of hail descend even faster than drops of water, but 
 flakes of snow fall more slowly. When the wind strikes the side of a rain gauge the 
 deflected currents move pa.<=t this obstacle more rapidly, and there is an invisible layisr 
 of wind above the open mouth of the gauge, whose horizontal motion is more rapid than 
 that of the wind higher up. Some of "the lar,-er falling drops mav descend with a 
 rapidity sufficient to penetrate this swiftly mo-iini: layer of air, biit the slower ones 
 will be carried over to leeward and manyVill miss the gauge. The resulting loss of 
 rain will depend upon both the horizontal velocity of the wind and the vertical 
 velocity of descent of the rain. _ 
 
 The fact that the deficit increases with the velocity of the wind (which ia less over 
 the forest) has also been proven in a different way, Viz. by shielding the gauge from 
 the wind, when the deficit becomes greatly reduced in value. Professors Henry, 
 Nipher, Boemsteln, Hellmann, all of them eminent investigators, agree in this con- 
 clusion. 
 
 Of two gauges exposed at the same elevation above the ground, 
 one over the open fields and the other over a forest, just above th« 
 tops of the trees, the one over the forest will catch considerably moij'e 
 ram, because the friction of the trees reduces the velocity of the winjd 
 and it does not rush across the open end of the gau^e ■with the same 
 speed that it does across the gauge over the open fields. ; 
 
 The influence of a forest upon the rainfall is therefore only ap- 
 parent; it may increase or diminish the catch of the gauge, but not the 
 quantity of rain falling from the cloud. 
 
 Professor Abbe further saj*s : 
 
 Tf gauges are raised up year by year, the deficit increases; if gauges in open fields 
 become surrounded by growing trees or higher buildings, the deficit decreases. .The 
 climate has not changed, but the errors of the record have done so. Those who wifih 
 to restore the good old times before the forests were cut down, when rain and snow 
 came plentifully and regularly, have only to lower and shelter their rain gauges atd 
 snow gauges and, presto, the climate has chans-ed to correspond. 
 
 When rain is falling on a forested region, about 2o per cent ia temporarily held far 
 above the ground on the leaves and branches of the trees. In thia minutely divided 
 condition, exposed to the action of the wind, the drops evaporate freely, so that the 
 forest atmosphere becomes saturated and decidedly less moisture^ reaches the grouiid 
 to be absorbed in the forest humus than on an egual volume of soil outside the fore&t. 
 A special climate is therefore maintained within a forested area. The temperature 
 is lowered and the relative humidity is increased, but there is no evidence that this 
 local forest climate extends outside the forest or affects exterior conditions to any 
 important extent. Of course, the climate under a tree or a tent or within a houue 
 differs from that outside, but these are local mattere quite foreign to the broad ques- 
 tion, Do forests affect climate?' 
 
 The climate within a house is not the climate of the whole city, nor is the climate 
 of a ravine that of the surrounding fields. One thermometer or rain gauge iii the 
 open air does not give the climate of a State or watershed. The various and restricted 
 uses of the word "climate" have led to our confusion. 
 
 LOCAL TEMPERATURE DIFFERENCE.5 DUE TO CHARACTER OF SOIL 
 
 COVERING. 
 
 As tlie result of iiiv('sti;:;atiuns bezun in "Wisfonsin by the author 
 ovf-r fifLoca ^-(■)l^s vj:n and continuf-'l durin;,' the pa~t throe or four 
 yeiirs \iy Vn<':. Henry J. Cox, of the Wf-^ithcr Biiroaii, we hayo, found 
 t};:it Hiir[.ri-in/ i^ -nils iirc obfjiini-d rn f.vo suri'a<(.-s of jiroriscly llio 
 siMDO lovcl on injja'-''nt liojil,, r.no <T t.'--!.a cuvori'd with tliii'k xc^t)- 
 tation and tlie otlier covered 2 in'.ii'.s deep with .saud. We hu\e 
 
10 THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 
 RECORDS OK PRECIPITATION SHOW NO MATERIAL CHANGE. 
 
 The records of precipitation of the United States Weather Bureau 
 do not show that tlicre has been any appreciable permanent decrease 
 in the rainfall of any section of the United States. There are un- 
 doubtedly periods covering a number of years of continued deficiency 
 in precipitation for certain districts, but at the same time other dis- 
 tricts may show a corresponding increase. One of the best and long- 
 est records of precipitation of the eastern part of the country is that 
 madeat New Bedford, Mass., by Mr. Samuel Rodman and his son, 
 coyering the period from 1814 to within a year or so ago, a period 
 of about ninety-five years. The following table shows the annual 
 amount of precipitation during each year of the above-named period, 
 from which one can see for Himself the variations in the amounts 
 from year to year, by the ten-year period, or make other comparison: 
 
 Table 1.— Annual precipitation at New Bedford, Mass., for the period, 1814 to 1908. 
 
 Year. 
 
 Amount. 
 
 Year. 
 
 Amount. 
 
 Year. 
 
 Amount. 
 
 Year. 
 
 Amount. 
 
 Year. 
 
 Amount. 
 
 1814 
 
 43.08 
 
 1833 
 
 42.62 
 
 1852 
 
 46.14 
 
 1871 
 
 49.60 
 
 1890 
 
 61.69 
 
 1815 
 
 40.78 
 
 1834 
 
 45.12 
 
 1853 
 
 39.47 
 
 1872 
 
 47.66 
 
 1891 
 
 47.83 
 
 1816 
 
 44.13 
 
 1835 
 
 47.21 
 
 1854 
 
 63.82 
 
 1873 
 
 51.70 
 
 1892 
 
 42.83 
 
 1817 
 
 43.33 
 
 1838 
 
 42.83 
 
 1855 
 
 41.00 
 
 1874 
 
 49.34 
 
 1893 
 
 50.27 
 
 1818 
 
 40.77 
 
 1837 
 
 39.07 
 
 1856 
 
 37.09 
 
 1875 
 
 48.33 
 
 1894 
 
 43.89 
 
 1819 
 
 39.66 
 
 1838 
 
 38.28 
 
 1857 
 
 43.30 
 
 187« 
 
 42.18 
 
 1895 
 
 41.63 
 
 1820 
 
 41.32 
 
 1839 
 
 44.38 
 
 1858 
 
 44.03 
 
 1877 
 
 47.04 
 
 1896 
 
 47.73 
 
 1821 
 
 45.64 
 
 1840 
 
 45.59 
 
 1859 
 
 51.43 
 
 1S73 
 
 50.56 
 
 1897 
 
 50.96 
 
 1822 
 
 41.78 
 
 1841 
 
 50.60 
 
 1860 
 
 39.73 
 
 1S79 
 
 42.31 
 
 1898 
 
 62.60 
 
 1823 
 
 59.89 
 
 1842 
 
 39.06 
 
 1861 
 
 46.46 
 
 18S0 
 
 40.07 
 
 1899 
 
 44.34 
 
 1824 
 
 47.34 
 
 1843 
 
 50.67 
 
 1862 
 
 43.32 
 
 18.81 
 
 39.10 
 
 1900 
 
 44.99 
 
 1825 
 
 38.09 
 
 1844 
 
 40.73 
 
 1863 
 
 45.10 
 
 1882 
 
 41.38 
 
 1901 
 
 51.84 
 
 1826 
 
 54.77 
 
 1845 
 
 48.06 
 
 1864 
 
 40.96 
 
 18S3 
 
 43.51 
 
 1902 
 
 45.42 
 
 1827 
 
 62.90 
 
 1846 
 
 34.51 
 
 1865 
 
 46.01 
 
 1884 
 
 54.99 
 
 1903 
 
 47.49 
 
 1828 
 
 39.04 
 
 1847 
 
 43.91 
 
 1866 
 
 40.30 
 
 18S5 
 
 36.81 
 
 1904 
 
 50.08 
 
 1829 
 
 65.41 
 
 1848 
 
 40.74 
 
 18S7 
 
 47.11 
 
 1886 
 
 49.85 
 
 1905 
 
 41.30 
 
 1830 
 
 64.66 
 
 1849 
 
 36.42 
 
 1868 
 
 56.32 
 
 1887 
 
 51.77 
 
 a 1906 
 
 43.09 
 
 1831 
 
 61.18 
 
 1850 
 
 62.67 
 
 1869 
 
 49.94 
 
 1888 
 
 55.07 
 
 1907 
 
 42.32 
 
 1832 
 
 49.31 
 
 ISol 
 
 51.61 
 
 1870 
 
 47.16 
 
 1889 
 
 52.71 
 
 1908 
 
 38.61 
 
 o The record lor New Bedford ends with the year 1906; annual amounts for 1907 and 1908 are for Fall R .ver. 
 Mass. 
 
 The average fall for ten-year periods from 1814 to 1908, inclusi^-e, 
 indicates that while the rainfall during the past few years has besn 
 considerably less than the average, it has not been less than has 
 occurred in numerous previous years — notably from 1814 to 181 9, 
 from 1833 to 1839, and from 1860 to 1866. _ Further investigation 
 shows that for the first fifty years of the period the average annual 
 rainfall at that point was about 46 inches, while during the Iftst 
 forty -five years the annual fall has increased to more than 47 inches. 
 This indicates that instead of a diminishing rainfall we have the evidence 
 that, if there is any variation at all in the 'pred'pitation, it is a slight 
 increase for this region. 
 
 Figure 1 graphically shows the average fall for ten-year periods, 
 namely, from 1814 to 1908, inclusive. 
 
 We will now move our inquiry to a part of the Middle West where 
 there has been no (Icforestation. Here there has been a growth of 
 planted hodLre rows, of trees along highwaj's and fence linos and 
 about places of habitation, and the virgin soil has been broken and 
 made more permeable to the rainfall. 
 
Tilt: I-\I-LUEXCE OF FORESTS ON CLIMATE AND ON FLOODS. 11 
 
12 THE I^•FLUE^'CE OF FORESTS OX CLIMATE AND ON FLOODS. 
 
 In Kansiis during the last fiftv voars records of rainfall have been 
 made onh' m the eastern part of the State. In the western part of 
 the State a single record has been made, viz, at Dodge City, extending 
 back to 1S75. Likewise in Nebraska, the record for North Platte is the 
 only one that extends back to the early seventies. The mean annual 
 rainfall at Dodge, Kans., for tlie entire period of observation is 20.8 
 mches, and at North Platte, Ncbr., IS. 7 inches. 
 
 Considering the record for the last thirty years only, since it is 
 convenient to subdivide that number into periods of equal length, 
 the mean becomes for Dodge, 21.3 inches, and for North Platte, 19 
 inches. I have also had computed the average rainfall for three 
 additional s(;ations in Kansas, three in Nebraska, and one each in 
 Iowa and ilissouri for the last thirty years, to see whether the con- 
 clusions reached from a consideration of the Dodge and North Platte 
 data are of local or general application. The averages in periods of 
 ten years each appear in the following table, from which it may be 
 clearly seen that the first and the last ten years were periods of 
 fairly abundaiit rainfall and that the middle ten years was a period 
 of deficient rainfall. It will be further seen, and this is the impor- 
 tant point in the discussion, that there is practically no difference 
 between the rainfall of the first ten years and the last ten years. 
 Three of the ten stations show that the last ten-year period "had a 
 slightly greater rainfall than the first, but the difference is so small 
 that it is really immaterial. The remaining stations show a slightly 
 less rainfall in the last ten years than in the first. This table shows, 
 therefore, that the rainfall has neither increased nor diminished by 
 amounts worthy of consideration. \ 
 
 The heavy rains of 1906, and also the yeai' previous, were common 
 to all that vast stretch of territory west of the ninety-fifth meridian. 
 It was not a local phenomenon centered in western Kansas and 
 western Nebraska, since equally heavy rains fell in Colorado, Utah, 
 western Texas, Oklahoma, New Mexico, Arizona, Nevada, and cen- 
 tral and southern California. The explanation of the heavy rains can 
 not be attril)utcd to local conditions of soil and moisture, since, as 
 has just been stateil, the heavy rains were common to the arid and 
 mountain regions of the Southwest where very little agriculture is 
 practiced. 
 
 Mean rainfall at the stations named. 
 
 Stations and periods of observation. 
 
 For the 
 
 full 
 period of 
 observa- 
 tion. 
 
 For the thirty years, 1877-1906, In periods 
 of ten years. 
 
 First. 
 
 Second. 
 
 Third. 
 
 ilean. 
 
 Dodce, Kins., lS7o-100<; 
 
 Xof.h Pld'T.., Xfbr., lS7.V]0f)(i 
 
 ID'Ji" ''f'!]'!' ';'■'* Kan-: ISTi lO'^i 
 
 Inches. 
 2U.8 
 1S.7 
 37.1 
 2^.2 
 30. 
 .31;. 4 
 30.7 
 .31.5 
 3.'.. 1) 
 35.0 
 
 Inches. 
 22.8 
 20.1 
 39.1 
 20.3 
 33.4 
 35.1 
 37.6 
 30.1 
 37.1 
 35.4 
 
 Inches. 
 18.4 
 17.2 
 35.5 
 2r,.4 
 29.2 
 39.2 
 25. 
 29.2 
 32.3 
 31.4 
 
 Inches. 
 22.7 
 19.8 
 38.1 
 31.3 
 31.9 
 30.7 
 27.9 
 29.8 
 39.5 
 35. 1 
 
 Incites. 
 21.3 
 19.0 
 37.6 
 
 f; r,, , '.■,.fjr ']^r''-l'">*' 
 
 28.0 
 
 M -.n:;.r ' .m. Kmj.,., 1 - >- l'"wi 
 
 .31.5 
 -.17.0 
 
 ()r .f.^ Vi or lS71-l'i"'. 
 
 cO.i 
 
 >..':. :■:,. .-.'.br.. I'-r--!')';'. 
 
 (JT' ''■'. Mo \-'^i-\'i'f 
 
 J1.7 
 
 ;«.3 
 
 K<';' '.•- lov.a lS7-'-r>'/. 
 
 ;i4.3 
 
 
 
THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 13 
 
 f 1 
 
 
 Ihchu 
 
 ^ ' - J- - 
 
 
 IB3A 
 
 t ::::::::. 
 
 
 less 
 
 1, :../.._ 
 
 
 /ese 
 
 T" i 
 
 
 ia37 
 
 -;' ::S:;: 
 
 
 /esa 
 
 1 
 
 
 1839 
 
 '":; — 
 
 'i 
 
 1840 
 
 "n" 
 
 Z._ 
 
 I8AI 
 
 
 
 ^ A 
 
 la^z 
 
 -;' " 
 
 7' 
 
 /8i3 
 
 -- - ' - ? 
 
 
 /«4* 
 
 ,._ -,- 
 
 
 184-5 
 
 
 
 
 _____ _ s ^ 
 
 
 
 2 -_ s 
 
 
 is'ie 
 
 / 
 
 !=;; 
 
 IBA-9 
 
 ^' _._ __ 
 
 "s. 
 
 laso 
 
 
 ! 
 
 
 'i'" '"s. ::_ : 
 
 ^ 
 
 
 
 
 
 I 
 
 -"7 ie54 
 
 f -_ — - __ 
 
 7 ' 1855 
 
 \' ::::::: 
 
 
 
 -s • 1357 
 
 _L_ " 
 
 
 . ? 
 
 L__ - \!^Sr- 
 
 C^' 
 
 
 
 
 
 : _. _.:) 'ssz 
 
 
 ^1 1363 
 
 ""^S. 
 
 
 "■-S,. _ _ 
 
 ~ ' . . '1865 
 
 
 
 — ' '" y~~ " ::__ . , 
 
 ___ .:--=L^_._Li||7 
 
 
 J.-,).-- I'ttj 
 
 
 _,^' \ie69 
 
 ^^ 
 
 ,'- [4|;e. 
 
 _ _ _ ^ ^ 
 
 \I37/ 
 
 ^>. ._ - . ---_ 
 
 * 1 leiz 
 
 — __^^--- - -- 
 
 _ .. _ MS73_ 
 
 ■^s 
 
 ^ iia74 
 
 — - "" [" "" : :: : 
 
 
 2 
 
 \ leis 
 
 
 y 1 ie77 
 
 - - - 
 
 
 ""s^ 
 
 
 - -- -^ 
 
 " / 1 /eao 
 
 — -- -- ^ 
 
 
 " "" " ;; 
 
 
 
 
 _ ^^_3- 
 
 
 / 
 
 
 jt :::::: __-- 
 
 V, iieas 
 
 3s" 
 
 
 " " _|_--s, 
 
 
 1 ^v 
 
 'Mi^ 
 
 
 -<-- ;°;; 
 
 1 '^' 
 
 
 '^^ I 
 
 
 — ^r-^^^^- - - ----- ---^ 
 
 / , ._ ll._ !6-'.-'J 
 
 _„ .^___. -) _ j- 
 
 1 1 , 
 
 -'-'1 '^- 
 
 - T\ . i._, -. -- 
 
 ,...\,v...±tl. 
 
 _ ' ~ ■ - ^-1 
 
 
 \M--"^ 1 
 
14 THE INFLUESTCE OF FORESTS ON CLIMATE AND ON FIX)ODS. 
 
 The annual fluctuation in procipitation for two fliffcrcnt parts of 
 the United States, viz, New England and the Ohio Valley, is L'rapliic- 
 ally shown in li^'ure 2. The New England curve was constructed from 
 the data for Boston, New Bedford, and Providence, at which points 
 fairly accurate rainfall measurements have been made dating bark to 
 1836. The Ohio Valley curve is based upon rainfall measurements 
 made at Marietta, Portsmouth^ and Cincinnati. 
 
 The_ heavy horizontal Hnes m the diagram represent the normal 
 precipitation. The amount that the actual fall of any year exceeded 
 or fell short of the normal may be found by noting the intersections 
 of the curved hnes with the smaller horizontal hnes, whose values are 
 given in inches on the left margin. If periods of heavy and hght rain- 
 fall alternated regularlv, the hnes of departure from the normal 
 (the curved line) would rise and fall in a series of bends or inflec- 
 tions precisely as the temperature rises and falls with the alternation 
 of day and night. Reference to the diagram itself will best show how 
 closely the rainfall of the two regions approaches any sort of periodic- 
 ity. The Ohio Valley curve is more symmetrical than that of New 
 England, and there appears to be a rough periodicity of about nine 
 years in it. Thus there were periods of heavy rainfall about 1837, 
 1847, 1858, 1866, 1875, 1882, and 1890, and of drought in 1839, 1856, 
 1863, 1871, 1878, 1886, and 1895. 
 
 A comparison of the two curves illustrates the fact elsewhere 
 referred to that the rainfall over a region so large as the L'nited 
 States is not by any means uniform in its distribution. Thus the 
 period of relatively light rainfall in New England during 1880-1883 
 was one of heavy rainfall in the Ohio Valley and elsewhere in the 
 great interior valleys. Likewise in 1878 there was heavy rainfall in 
 New England and light rainfall in the Ohio Valley. 
 
 In New England, where deforestation hegan early in our history and 
 h,as been extensive, the mean of the fluctuations in the rain curve is a 
 steady rise since 1836 wp to a few years ago^ and in the Ohio Valley, 
 where the forest area has been greatly diimmshed, there is no decrease 
 of rainfaU shown by the average of the fluctuations of the curve. These 
 facts are important and can not be successfully aisputed. 
 
 GOVERNMENT RECORDS VERSUS RECOLLECTIONS OF OLDEST INEABI- 
 
 TANTS. 
 
 It is the duty of the United States Weather Bureau to publish 
 information with regard to climatic conditions; and in this connec- 
 tion I would call particular attention to the fact that the goverrmient 
 records are in a class separate and distinct from the recollections of 
 the oldest inhabitants, which are entirely untrustworthy, no matter 
 how truthful the persons intend to be. These recollections do not 
 justify the claim that the forests have increased precipitation, for it is 
 almost the universal opinion of the maturer man that the climate is 
 milder and that the snows are less deep than when ho was a lioy. lie 
 remembers tlie long tramp to the little rod schoolliouso in snow knee 
 deep, but lie fails to take into ccmsidoration the fact that a snow knee 
 deep to a boy of nine years of ago is no inconvenience to a man of six 
 feet two. liujuau rofoUeetion can only recall from the diiii pa?t 
 unusual storms — conditions that were abnormal, and these al>nor- 
 maltics are what the man of fifty or sixty years to-day believes to 
 
THE IKFLVKKCE OF FOI;i:^TS OX CLIMATE AND OK" FLOODS. 15 
 
 havo li(-(Mi tlie avoraij;,' wIkmi ho Mas youns;. In other words, the 
 mdiviihial rcM'^Uectidu sho\il(l be cfivcn little weight in determining 
 a matter tliat requires eareful cnleiilation and the preservation oi 
 accurate daily records before anything like safe conclusions can be 
 reached. 
 
 THE EFFECT OF FORESTS OX FLOODS. 
 
 I have always held to the opinion that the cutting away of forests 
 has had little or no appreciable effect on the amount of precipitation 
 or on the general temperature. But until recent years I did believe 
 that deforestation hacf an important and beneficial effect on the con- 
 servation; that is, on the economical use of the rainfall, and that 
 forests restricted the run-off. But study and investigation have 
 caused me to modify my views. 
 
 Professor Abbe says: 
 
 The cultivated soil outside the forest, when plowed and broken open down to a 
 depth of S inches, acta as a sponfje to retain water quite as well as does the ordinary 
 humus of a forest, especinlly when we consider that under a forest less rain actually 
 enters the humus. In fact such measiu'ements as have been made show that the 
 amount iii water that is eventually given up from the forest humus varies but little 
 from that given up in the course of time by the unforested, cultivated soil. The total 
 run-off ir im the two regions does not eventually differ greatly, but it does differ in the 
 spf ed . However, it may be neither the amount nor the speed of run-off from the soil 
 that determines the occurrence of river floods. We must distinguish between the 
 soil run-off and the river run-off. When water has once entered the river channel its 
 movements are determined wholly by the force of gravity, the curvattu-e, the section, 
 and the slope of the channel. Floods may occur in every small tributary and yet 
 these waters may so enter the main channel as to produce only a gentle rise through- 
 out ir- whole lensth. At other times the smaller elementary floods may conspire and 
 produce a specially disastrous flood in the main channel. Therefore the occurrence 
 of di-astrous floods does not depend on rainfall alone or wholly on soil run-off, but 
 equally and principally on the relative times at which floods occur in the individual 
 tributaries, and the tiine required by them all to reach and combine at any given 
 point in the main channel. 
 
 This is a tangled problem, since the result must depend upon the 
 slope of the ground; the nature and condition of the soil; the nature 
 of the forest, whether deciduous or evergreen; the nature of the gen- 
 eral climate of the place, whether it has cold, snowy winters or rainy 
 ones, and whetlier the spring merges gradually or abruptly into sum- 
 mer; upon the use or treatment of the cleared surface; and probably 
 upon other conditions. 
 
 The foresters are generally in accord in the belief that the forests 
 exercise a marked restraining influence on floods and a conserving 
 influence on precipitation, even if they do not actually increase, by an 
 appreciable amount, the rainfall. On the other side, army and civilian 
 engineers and meteorologists generally believe that the broken, 
 cultivated, permeable soil, which is covered for a greater portion of 
 each vear with millions of the rootlets of growing grasses and cereals, 
 is efjiiidlv as good a conserver of the rainfall as the forest area itself, 
 even tlunigli the latter has the advantage of the deep boring of large 
 roots intirtlie siil>stratum; that tlie evergreen forests prevent the 
 driftinir of tfie snow and at the same time tlicir heavy foli.-ige j)rolects 
 tl:.- -ri'r.v IVom tlie sun and jjeiniits ,t slow melting, which is all 
 ;:',-o!!;''l bvthe l'r)M-1 rover until il is saturated, and tlien w il li ftullier 
 },' ;it tin; v.-uter breaks oui in a flonfi; that the function of de(i<lu()us 
 fi,-, ,. t;-'-'-. i-. to cat'-li the faHii.'j; -now, di-tribute it e'lHally over tlie 
 
 .;, ,,. , ■ -i thus fai-iliiate JI1..1I.- r.!),id Jiiclting by caii-u.'j thcsnow 
 t,, r ', .'vt tw the warm air a greater jneiling surface than it does in the 
 
16 THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 
 
 open, where wind drifts it into banks in the lee of opposing objects 
 and stores it in depressions and ravines, so that it may remain for a 
 considerable time after the evenly distributed blanket has disap- 
 peared from the forests. 
 
 _ It has been shown by Chittenden that in Yellowstone Park and 
 similar mountain regions the forests protect the snow from drifting, 
 melting, and evaporating, while in the open there is much drifting 
 and an early clearing up of those places well exposed to wind and to 
 sunshine; therefore, when warm weather and its rain come on 
 abruptly, and come to stay for the summer, as they do in those 
 regions, the melting of the snow in the forests, because of the greater 
 area exposed, the surface being uniformly covered, is far more rapid 
 than it is in the open where it is badly drifted, and leads to higher 
 freshets and less enduring run-offs. On the whole, it is prohable that 
 forests have little to do with the height offloads in main tributaries and 
 principal streams, since they occur only as the result of extensive and 
 heavy rains, after the ground is everywhere saturated, or when heavy 
 warm rains come on the top of deep snows. 
 
 RUN-OFF AND ABSORPTION. 
 
 Concerning the surface run-off, it appears to be generally held that 
 when the ramfall is small, the dead leaves, the moss, the tangle of 
 undergrowth, and the like, in the forests may modify or entirely 
 prevent flow, and may slightly intensify low-water conditions of 
 summer, while on the cleared surfaces, except that of freshly-cultivated 
 fields, this is not so markedly the case. When the rains are heavy and 
 continued, there is surface flow in the forests as well as in the open, 
 and the two do not materially differ, for it can be shown that the 
 run-off from a smooth surface and from one covered with sticks, 
 dense grasses, or forest, are equal after the rough surface becomes 
 saturated, and it is long after all surfaces have become saturated that 
 flood conditions can occur. 
 
 Because of their open, porous condition sandy soDs and freshly 
 plowed fields are the Dest absorbers, and in general forest ground is 
 thought to be more penetrable to moisture than is that of the cleared 
 fields, except when the latter are freshly broken, but the greater part 
 of the cleared land is either broken and cultivated several times dur- 
 ing the year or else it is occupied by vegetation that exercises either 
 partly or wholly as great a conserving influence as the forest. 
 
 All of these problems could be definitely settled beyond the possi- 
 bility of argument if we had accurate river gaugings from day to day 
 and year to year, together with a full knowledge of the rainfall and 
 of the proportion of the wooded to cleared areas, data that unfor- 
 tunately we do not have. We must, therefore, reason empirically 
 from the best information at hand, and , this insufficiency of data 
 renders less positive tlic conclusions of all investigators, no matter 
 which side or the question tliej' may be on. 
 
 EFFECT OF FORESTS ON FLOODS IN FRANCE. 
 
 An important contribution to this discussion was made in 1873 by 
 Capt. Charles J. Allen, of the Eiiijinccr Corps, U. S. Army, in the 
 translation that ho nindo of oxtmcts from the work of M. F. Valles, 
 whicn treats of tlic inll'itacc of forests on floods and inundations. 
 
THE INTLUENCE OF FOBESTS ON CLIMATE AND ON FLOODS. 17 
 
 This translation contains quotations from the works of M. Bclfjrand 
 and other French engineers, who had made the hydrology of the 
 basin of the Seine a special study." Among other things M. Bel- 
 grand says: 
 
 Thia country comprises all or part of 21 Departmenta, ;a3 follows: Aisne, Ardennes, 
 Aube, Cote d Or, Eure, Eure-et-Loire, Loiret, Mamo, Haute-Mamc, Nievre, Nord, 
 Oise, Pas-de-Calais, Seine, Seine-Inferieure, Seine-et-Mamo, Sommc, Vosges, and 
 Yonne, and comprises an area of about 107,000 square kilometers, nearly equal to 
 the fifth part of the area of country comprising the 86 Departments. 
 
 The most irregular streams, those most subject to rapid rises, are found especially 
 in the Departments of the Yonne, Nievre, and Cote d'Or, and to a less extent in those 
 of the Aube, Haute-Mame, and Aisne. This region is very woody, more so, perhaps, 
 than the rest of France. The most remarkable Departmemts in regard to the regulanty 
 of the water courses which rise within them are tne Eure, Eure-et-Loire, Nord, 01=6, 
 Pas-de-Calais, Seine-Inferieure, Somme, the chalky parts of the Aube and of the 
 Marne, and those portions of the Seine-et-Oise and Loiret in which the limestones of 
 La Beauce abound. The majority of the streams in these countries are subject to 
 slight rises of short duration, their stage of water varying but little. This group of 
 Departments is perhaps one of the most sparsely wooded in France, because the Eure, 
 Eure-et-Loire, Nord, Oise, Pas-de-Calais, Seme-Inferieure, and the Somme have 
 only about one-tenth of their surface wooded, and the plateaus of Ija Beauce and the 
 chalky plains of Champagne are, if we except some recesnt plantations of pine, com- 
 pletely Dare of trees. 
 
 In order to test the question as to the effect of forests im regulating the flow of water 
 JI. Belgrand had daily measurements made from Noveniber, 1850, to May, 1853, of 
 the discharges of the Cousin and of the Grenetierre, which is one of its affluents. Both 
 of these basins are of granite formation, impermeable and otherwise alike, but the 
 first is only about one-third wooded, while the second is «ntirely covered with trees. 
 Notwithstanding this great difierence as regards the extent of forests in each, the 
 results have been the same in both, as is shown by the following account: 
 
 " The regimen of each.is identically the same, although their valleys are unequally 
 wooded. Their waters riae and fall at the same rate, whether in rainy weather or in 
 dry, in winter or in summer; their low winter regimen is more abundant than that 
 of summer. 
 
 "A heavy rain in winter produces in both a sudden flood of greater or less height, 
 but of very short duration, followed by a long stage of toleiably high water; the sudden 
 and high freshets take place in each at the same time." 
 
 The different details concerning the flow of water are, then, exactly the same in 
 the two basins, and yet one is entirely covered with forests, while in the other two- 
 thirds is bare of trees. M. Belgrand has made a number of more detailed observations 
 yet, which show, further, that it is not upon forests but upon cultivated ground that 
 the greatest regularity in flowage is observed. * * * 
 
 In Valles's paper he quotes from a report on the basin of the Eure 
 made by M. St. Clair, engineer in chief, showing the beneficial effects 
 of cleared and cultiTated lands in diminishing by absorption the 
 amount of surface water, as follows : 
 
 All the valleys, even those of least extent, arc cut up by rd\-ine3 which weie often 
 foriLerly the beds of torrents. Within the last twelve years the condition has changed; 
 they are now almost always dry. The cause of this great change, the progre.'s of agri- 
 culture, is generally recognized in the country. The soil has been cultivated more 
 and rendered more permeable; the farmers, reaping more advantiiges from the culture 
 of the ground, and fully aware of the utility of improving it, have, by means of ditches, 
 hedges, and endikements properly located, controlled the flow of -n-ater everyivhere, 
 preventing erosion, causing fertilizing deposits of sediment, and relie\-ing the surf;ice 
 of the ground from the asperities which interfered with cultivation. The wiUers, 
 retarded thus in their flow, have settled in great part through the ground and di?ap- 
 pearf^d before reaching the ravines. 
 
 These acrriculuiral iinprovcnipnts, in a country where land susceptible of cultiva- 
 tion, amounts to nixt\--nno onc-hundr?(ltbs of the area of the country, have, then, 
 reduced the surface (lowage and increased the absorption. 
 
 "Annales des Fonts et Chaussees, annee 1S52, premit 
 
18 THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 
 
 They have rendered less fronuent and Eormidable the frc.-'hct.a, which, in the basin 
 of the Eure, are to be attributed to an excess of surface water rather than to any supply 
 from springs, \( hich latter is almost always invariable. 
 
 The effect upon springs of cutting down forests can now bo easily eliminated. We 
 will divide them into two classes, viz, superficial and subterranean. 
 
 The first issue froai the points of the surface very near to the strata in ■nhich the 
 waters which produce them collect. The second, on the contrary, are found very far 
 below these strata, and the water, in order to find an outlet, traverses frequently long 
 distances underground. 
 
 The first, generally small, pertain indifferently to ibsorbcut or nonabeorbent ground ; 
 but the second, occasionally very powerful, pertain essentially and almost exclu.=ivf-Iy 
 to permeable soils. 
 
 Now, it is indisputable that the continual humidity of the soil of forests is favorable 
 to the first and ought to maintain in their feeble flow considerable regularity. It is, 
 then, very likely that the clearing away of forests and exposing the earth to Alternations 
 of drought and moisture would alter the regimen of these springs; that these would 
 be more abundant in time of rain; that they would decrease in summer and po=sibly 
 be dry for several months in the year. This explains the disappearance of certain 
 springs after the cutting down of forests. 
 
 As regards the second group, which are plentifully supplied by infiltration through 
 the permeable soils, it is' different. 
 
 From the different manner in which, as regards absorption, wooded and cultivated 
 soils act, we see that in the first this faculty is in great part destroyed, while in 
 the second it is increased. To remove standing timber from permeable soils is to 
 restore to them the facility of transmitting the waters which the forest vegetation, 
 whether by the spreading of its roots, by the fall of leaves, or by the compactness of 
 the soil, had taken from them, and it results, consequently, in a more abundant 
 supply of water to the subterranean springs. 
 
 Thus, it is worthy of remark that the most abundant of all of them, especially in 
 seasons of low water, are located beneath the vast ledges of limestone which are alniost 
 entirely denuded ; for instance, those of Cahors and Louysse, in the department du Lot, 
 and the famous fountain of Vaucluse, of which mention has already been made. 
 
 M. Belgrand further says: 
 
 Now these basins, bo remarkably alike, we have; they are those of the Seine in 
 the seventeenth, eighteenth, and nineteenth centuries. Everything in these is alike 
 excepting the extent of the forests, which has steadily decreased, so that if we were 
 in possession of adequate information of some exact measurement'' of the greate.'it 
 inundations during the time specified, we could easily test the correctness of our 
 theories. 
 
 In fact, observations of this nature have been made; they go back to 1615, about 
 the time when French industry began to develop, and when, consequently, the felling 
 of timber to a great extent commenced. 
 
 This places at our disposal an interval of five half centuries. 
 
 In a memoir published in 1814 by the engineer Egault, these observations were 
 compiled, discussed, and arranged with reference to the heights of the most marked 
 inundations. We add to the results collated by them those which have been obtained 
 aince his time and give them in the following table: 
 
 Dates of the Inundations. 
 
 July 11, 1615 
 
 January, 1649 
 
 January, 1651 
 
 March 1,1658 
 
 March, 1690 
 
 March, 1711 
 
 December 25, 1740. 
 
 January, 1751 
 
 November 14, !7ii4 
 
 March 4, 1784 
 
 February 4, 1799.. 
 Januarys, 1802... 
 
 March 3, 1807 
 
 May, 1836 
 
 February, 1850 
 
 Height at 
 
 the bridge 
 
 ofLaTour- 
 
 nelle. 
 
 Meon per 
 hall" cen- 
 tury. 
 
 Fett. 
 29. 
 25. 
 25. 
 2S. 
 24. 
 24. 
 25. 
 21 
 21. 
 21. 
 
 2-:. 
 
 24. 
 21. 
 IS. 
 19. 
 
 4.77 \ 
 
 S.P2 ; 
 
 Feet. 
 
 27. .53 
 2f.. 36 
 2," 34 
 
 2J 42 
 
TJIE IXFLt'EXCi: OF FOliESTS ON CLIMATE AND ON FLOODS. 19 
 
 Thi' lUiluctinns frum this tablo aro etrikiug. The continued docrcapo of the floods 
 f. r o;irh lialf century is reni;irk;Ude. The waters attained a mean height; of 27.53 
 iVvt in the first half of the seventeenth century; they only attained a mean of 21.22 
 f et in the present. According to this, \ve Lavo experienced an amelioration of 
 I '-arlv 6."iti feet, and yet the trees have been steadily and unceasingly cut down, 
 a;ul tlie forests tr.msformed into c\dtivated farms. 
 
 What would we gain, tlien, to-day, I ask, in rewooding our field? It would be 
 bit an unfortunate attempt to restore the old order of things, when the floods of the 
 t.ine nx-e to 29.53 feet above the low stage. 
 
 lu connection Avith tho conclusions reached in this report, as -well 
 :is Avith re'_r.n-j to those reached by the foresters and others who differ 
 fnun my views, I wouUl emphasize the fact that none of us have 
 llood th'ta extendmg over any great period of time, but in Europe 
 ve fortunately have some long-period observations. The preceding 
 pages show the result of observations made by competent engineers 
 during two and one-half centuries m the basin of the Seine, and 
 show that there has been a gradual and constant decrease in the 
 height of floods with the diminution of forests. 
 
 in Germany another long-period record is presented. Mr. Ernest 
 Lauder, chief of the hydrographic bureau of the Austrian Govern- 
 ment, recently made an exhaustive investigation of the records of 
 the Danube, the great river of central Europe. He prepared an 
 exhaustive report on the destructive floods in the Danube that 
 occurred in 1897 and 1899, and in this report traces the history of 
 the floods of the Danube for eio;ht hundred years, taking into account 
 12.5 different floods. His conclusions are that progressive deforesta- 
 tion of the country has had no effect in increasing the frequency of 
 floods or in augmenting their height. Among other things he showed 
 that the flood of 1899, which was a summer flood, was severest where 
 it came from the heavily wooded districts. 
 
 ]iluch has been written about the barren condition of the valley 
 of the Jordan, in the Holy Land, and it is pointed out that great 
 cities and teeming populations once covered the regions now barren; 
 but this does not prove that if there has been a decrease in the rainfall 
 it is due to deforestation, for everywhere in this region are evidences 
 of extensive irrigation that was practised at the time this region 
 was thickly ]>opulated. The date palm, the vine, and the fig tree 
 will grow there as luxuriantly to-day as in the old Biblical days, if 
 artificial irrigation is used, as was formerly done. It is not believed 
 that the cutting of the cedars of Lebanon has had anything to do 
 with the dryness of the adjacent regions. 
 
 At the tenth International Congress of Irrigation, held at Milan 
 in 1905, papers were presented by representatives from France, 
 Gcriiiany, Italy, Austria, and Russia, ki which the writers heartily 
 favored "the protection of the forests and their cultivation. But 
 tliese writers were unanimous in the opinion that forests exercise 
 little influence upon either the high water or the low water of rivers. 
 
 In tliis connection I will quote from Col. H. M. Chittenden, M. Am. 
 Soc ('. E., volume 34, page 944, Proceedings of the Society of Civil 
 Hn/iiiciT^, as follows: 
 
 T ,, ,..,.,.; nil-,- rrii'Tiiled statemont that floods are increa.^ing in frequency and 
 
 ■; , ci,rii[>,T' d '.vith fornu-r time.-', has nothing to sujjport it. 'i'hfre are. it is 
 
 ',,•" , ;;.,,,■- .,..h<-n llui/'l- are iin^re fr';(|ueiit, than at others, and lia^ly conclusions 
 
 II , . I -. ... II al ,■' li times; but, takiiig the record^ year after year for cou-idi r- 
 
 '^i.l';] , ! ii(n-li ill."- ■>'.-nrlh coD.-iderii.'/ i.- ili-co\'crablo. Tlif; e.\ phi rial ion of l)i:~cj 
 jpf-rio'J of lii-h waiiT, like the on.- wav prevailing, must, of course, be Bought in pre- 
 
20 THE I^-FL^"i;^ci: of forests on climate and on floods. 
 
 cipitation. That is ■\vlipro floods cnmc from, and it is very slrnnge that those who are 
 looking so eaprcrly for a cause of thosp floods jump at an indirect cause and leave the 
 direct one entirely untouilied. In the records of precipitation, wherever they exist, 
 will be found a full and complete explanation of every one of the floods that have 
 seemed unusually frequent and eovcre in recent years. 
 
 THE SOURCE OF FLOOD ■\VATERS IN THE UNITED STATES. 
 
 Before one can o;ct a comprehensive idea of the magnitude of the 
 problem involved in the creation of the floods of the United States, 
 it will be necessary for him to first study chart A, which gives a 
 tvpical illustration of the cyclonic storms that frequently form on 
 the Rocky ^Mountain Plateau, either on its northern, central, or 
 southern portions. Under the influence of gravity air flows from 
 regions where the pressure is great toward the regions where it is less. 
 In the case illustrated by this chart the atmosphere, as indicated by 
 the direction in which the arrows point, is flowing from the region 
 marked "high," which is central over the Carolinas, toward the 
 region where the pressure is low, which is central over Montana, 
 and the vaporous atmosphere that rises from the Gulf of Mexico 
 and the adjacent ocean is carried far into the interior of the continent. 
 Conditions similar to these occur many times each month, and as 
 a result the eastern and central portions of the United States are 
 bathed in a succession of rains which, as shown by chart B, gradually 
 thin out and largely disappear on the eastward edge of the Rocky 
 Mountain Plateau, because the currents of air from the Gull' of 
 Mexico do not reach farther inland. 
 
 STATEMENT BY MK. BAILEY WILLIS. 
 
 In the May issue, 1909, of the magazine entitled "Conservation," 
 page 2G2, Mr. Bailej^ Willis makes the statement: 
 
 The moisture which falls upon North America in the form of rain and snow comes 
 chiefly from the Pacific Ocean. A smaller proportion, rising from the Gulf of Mexico 
 and the V.'est Indian seas, falls upon the eastern United States. 
 
 It is true that chart B, giving the normal annual precipitation 
 indicates that the Pacific Ocean furnishes precipitation that is heavy 
 along the immediate coast, but that it is the principal source, as Mr 
 Willis says, of the moisture that falls upon the North American Con- 
 tinent, is not borne out by the facts exhibited by the precipitation 
 chart herein produced and by the inflowing currents of air that are 
 ■showTi on chart A. 
 
 The range of mountains on the Pacific coast intercepts the inflow 
 of the vaporous atmosphere, which is comparatively shallow, and 
 precipitates its aqueous vapor on the windward side of the range, 
 and mainly on the north half of the windward side, because storms 
 seldom enter from the southern half. To be sure, some of the scant 
 precipitation that falls on tho plateau does drift over the tops of 
 those mountains, but tho amount is small. Certain it is that the 
 Paci-fio Ocean lias little influcTicc on tlie precipitation of the eastern 
 half of the I'ltited vSlales, which fact is well uiulcistood hy mctcoroio- 
 gi<"ts; and I i)elievc Unit mo^t of tlieni will join mo in the belief tliat 
 the oniv wav that man could materially all'ecl the rainfaU of the 
 eastern 'half of the United States would ))e to erect a rnoiiiitam barrier 
 
THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 21 
 
22 THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 
 
 10,000 foot hi^li skirting the Gulf and South Atlantic coasts. Of 
 course this is impossible, but if nature had erected it there would ho 
 no question al)out floods in the Ohio and the Mississippi rivers and 
 their tributaries, for there would be neither rivers nor tributaries; 
 just as on the Pacific coast, the rain would fall on the ocean sido of 
 the mountains, and the world's greatest granary would be a barren 
 waste. 
 
 Prof. Frank H. Bigelow, on page 17 of A Manual for Observers in 
 Climatology and Evaporation, says: 
 
 All this distribution of the general circulating currents, and the consequent pre- 
 cipitation, would occur whether there were forests or not growmcj ou the land rna--r j. 
 It may be proper to say that the forests follow the precipitation and do not prened'' it. 
 
 There can be no question but that the action of the sun on tlie 
 waters of the Gulf of Mexico and the adjacent ocean heavily cliaijre 
 the air with water vapor, and that this vaporous atmosphere is 
 carried inland by the circulation of the air in such storms as are 
 described in a preceding paragraph and illustrated on chart A, and 
 that the effect is shown on chart B in the form of heavy precipitation 
 in the region of the Gulf, which gradually shades away toward the 
 Rocky Mountains. 
 
 It IS therefore apparent that the precipitation that causes floods 
 in the eastern half of the United States is from the aqueous vapor 
 that is raised up from the vast waters to the south and southeast of 
 our continent, and that the supply is inexhaustible. Our rainfall, 
 then, is the result of such fundamentally igreat causes as not to he appre- 
 ciably affected by the planting or cutting away afforests, or by any of 
 the operations of man in changing the maracter of the surface covering 
 of the continent, although to statistically and positively settle the 
 question beyond the possibility of argument it would be necessary 
 to have scientific data of temperature, rainfall, and the height of 
 rivers, beginning at the first settlement of the continent and con- 
 tinuing through to the present time. Such records, of course, are 
 not in existence. But the fundamental fact that the precipitation 
 of the United States is due to the great hemispherical circulation of 
 the air, and to the relation of the great bodies of water to land, and 
 the direction of the vaporous-bearing currents, and the trend of 
 mountain systems is something that can be positively shown. 
 
 Mr. Wilhs further says, in the same issue of Conservation, page 
 265, that: 
 
 The mountains are wet because they are high, and they are heavily forested because 
 they are wet. But there is also a reciprocal action of the forests on the wetness, for 
 the radiation from the dark-green expanse is comparatively uniform and promotes 
 frequent and steady rains. Were the mountains bare they would, like the bared 
 sierras of Spain, receive occasional but violent downpours and send down excej.-^ive 
 and disastrous floods, even more disastrous than now. * * * For in so far a.^ we 
 clothe the surface with green crops we lower the temperature of therismgairaiul lavor 
 precipitation on the verdure-covered plain. 
 
 It would be difficidt to either confirm or disprove this stateniont 
 of Mr Willis. Certain it is that the rain is precipitated larjxoly from 
 air masses that exist at a considerable distance from tlio smhieo of 
 the earth, and that the influence that Mr. Wilhs doscrihos is m a 
 thin stratum of air close to the earth. Karoly is this stnUtim satu- 
 rated cvon durini,' the fall of rain. If, then, the. piocosses tluM >^ 
 describes do not bring the an- to the saturation point, aiul it the 
 
TUE IXFLUF.^'CE OF FORESTS ON CLIMATE AND ON FLOODS. 23 
 
24 THE IXFLUEXCE OF FORESTS Olf CLIMATE AKD ON FLOODS. 
 
 nrocipitntiou occurs in tho regions above those afTected by these 
 local suriaec conthtioiis, I am unablo to see how the rain can be 
 either increased or decreased in its amount. Certain it is that most 
 of tho loadinc: inctoorologists of tho world are of the opinion that the 
 rainfall on continents is caused by the fundamentally great operations 
 of nature as described above. 
 
 EROSION. 
 
 iVnother effect of deforestation, that of erosion, is of importance 
 but of unequal importance in different sections. In level countries 
 it makes but Uttle difference in this particular whether the ground 
 is waste, cultivated, o densely forested, while in hilly or mountainous 
 sections the result is different. When the soil becomes well sodded 
 with grass, erosion is little worse in fields than in the woods, but 
 usually the fields are cultivated from time to time, and occasions 
 come when the best of care and cultivation can not prevent the 
 formation of bad gullies that injure both the gullied fields and those 
 of the lower grounds that are overflowed. 
 
 Of course, though, a field ■with an occasional wash yields more 
 food material than the same area covered by a forest of any kind, 
 so that only in exceptional cases — those in which erosion would 
 probably be unavoidaole and ruinous — is this a sufficient argument 
 against clearing away the woods and the planting of crops in their 
 stead, for the time is came when we should not only increase the yield 
 per acre hy wise rotation of crops on cultivated ground, hut clear wp and 
 seed to wheat, com, grcLSS, ana fruits m,iUions of acres that now he idle 
 under brush or forest. In other words, every acre that wiU grow food 
 for the people, and thereby reduce its cost and furnish sustenance 
 for our increasing population and the teeming milHons that are on 
 the way to these snores, should be so employed ; the remainder should 
 
 ijrow timber that should be protected in its growth. Man and beast 
 ove the cooling shade, and the eye is pleased by the beauty of the 
 wooded landscape. Therefore begin with the children and teach 
 them to plant trees along the highways and byways and on the barren 
 spots that will not produce food. Thus may we approach this prob- 
 lem rationally, with the object of gaining the greatest good for the 
 greatest number for the longest period of time. 
 
 BATIO OF THE FORESTED AREA, OR MOUNTAIN WATERSHEDS, TO THE 
 
 TOTAL WATERSHED. 
 
 I am of the opinion that not enough consideration has been given 
 to the relative magnitude of the areas involved in the creation of 
 floods. A flood in any given stream is usually caused by the pre- 
 cipitation over its entire watershed or over those of the major tribu- 
 taries and is affected but comparatively little in a region hke that 
 of tho Oliio basin by the precipitation over the extreme upper reaches, 
 usually tlio forested area, or any othcr_arca that could be reforested 
 without seriously encroaching upon tho rich alluvial plains. 
 
 A criticid exiunination of Cliart C, wluch shows the entire river 
 system of the Oiiio basin and gives tho exact limits of its bound- 
 aries and wliii-U al-ii indicates tlie elevations, shows what a compara- 
 tivclv' sniiiU area in relation to the total catchment basin hcs at 
 
THE INFLUENCE OF FOBESTS ON CXIMATE AND ON FLOODS. 25 
 
 elevations of more than 1,000 or 1,500 feet above sea level. Tliis 
 chart furnishes a conclusive answer to those who behove that floorls, 
 except, of course, torrents in the mountain creeks, are caused by 
 the precipitation on the comparatively small area of the water- 
 sheds at the headwaters of rivers. If it be granted that forests 
 control the flow of streams, and I doubt that they do except as 
 stated above, it will be necessary, in order to have an appreciable 
 effect on navigable or other important rivers, to reforest areas many 
 times in excess of anything that so far have been contemplated. 
 The rugged mountain slopes and tops, where land has little value, are 
 unimportant as flood producers. It will be necessary actually to reforest 
 the lower slopes and valleys where the land is ofareat value and where 
 it should be devoted to agricultural purposes. I can not escape this 
 conclusion. 
 
 ABE FLOODS INCREASING? 
 
 Two papers have recently appeared, in both of which the argu- 
 ment is made that there is a marked tendency toward increasmg 
 flood frequency as a result of deforestation. The first of these 
 
 Sapers in point of time was that of Mr. M. O. Leighton, Chief Hy- 
 rographer United States Geological Survey." The second paper 
 appeared in volume 2, Senate Document No. 676, beginning at 
 page 112, and later as Forest Service Circular No. 176, January 11, 
 1910, under the signatures of Mr. WilUam L. Hall, Assistant Forester, 
 and Mr. Hu Maxwell, expert. \ 
 
 Before entering upon a discussion of these papers I wish to ^draw 
 attention to the following statement in the last-named paper, page 3 : 
 
 * * * Both the Geological Survey and the Forest Service have secured data,b 
 and the results warrant the statement that unmistakably floods are steadily on the 
 increase in some of our most important rivers. 
 
 I wish to remark in connection with this statement that substan- 
 tially all of the data used by the authors of the papers above men- 
 tioned were drawn from the records of the United States Weather 
 Bureau." 
 
 In Water-Supply Paper No. 234 the author has made a diagrammatic 
 arrangement of data composed of annual and decennial means, 
 whereby he shows an apparent progressive increase in the number 
 of flood days at Wheeling, W. Va., and other points, without a pro- 
 portionate increase in the amoimt of precipitation. It appears to 
 me that his argument is defective in at least two particulars. 
 
 First. The flood or danger stage of the rivers at the various places 
 discussed by him was long ago fixed by the Weather Bureau as being 
 at the point where the river either overflows its banks or damages 
 property adjacent thereto. Mr. Leighton has disregarded these 
 points and arbitrarily assumed, for the purpose of his discussion, a 
 
 o Report of National Conservation Commission, p. 95, and Water-Siinplv rain r 
 No. 234. 
 
 !>The italio? Tro mine. (Author.) 
 
 cin Water-Suppiy Pnper No. 234 the imprestiion seems to bo given that the amhor'.-j 
 researches and conchision.i are based on a considcr.ition of river dwchiiriro nuMsure- 
 ments. It i.s proper to state that river dischnrijj.iuoa.^urcmcnts wore lioeun uiuIit ; he 
 direction of the United States Geological Survey in lS9(i and that p;uii;i' roailiiv_-.-i of 
 heights of rivers were begun by the United States Signal Service, now Wcatln-r liureau, 
 in 1874. 
 
26 THE INFLUEKCE OP FOBESTS ON CLIMATE AKD ON FLOODS. 
 
 considerably lower stage in each case, so that his argument fails 
 completely so far as it relates to flood frequency; for example, at 
 WheeUng, W. Va., he assumes a stage of 20 feet, whereas the r)hio 
 at that point is not in flood until a stage of 36 feet is reached. What 
 the author is discussing is therefore not floods as such, but moderate 
 stages of the river. 
 
 "What appears to me to be a second defect in the author's argument 
 lies in his acceptance of the total number of so-called flood days 
 (20 feet or more being a day of flood) divided by the annual pre- 
 cipitation as an indication of flood intensity, since the annual rain- 
 fall, as he himself acknowledges," bears little or no relation to floods. 
 Greater floods may occur during a year of deficient precipitation 
 than during one of excessive annual precipitation if the proper pro- 
 
 Eortion of the rainfall be concentrated over a limited area in a 
 mited time. 
 
 An examination of the data for Chattanooga, Tenn., given by that 
 author, discloses the fact that there has not been any increase in the 
 number of so-called flood days at that place. The average amount 
 of precipitation for each daify river stage of 20 feet or more, as de- 
 termined by him, is almost exactly the same for the two periods, 
 1884 to 1895 and 1896 to 1907, inclusive. But in the number of 
 actual jiood days, as determined by Professor Frankenfield, th& 
 official in charge of the Weather Bureau river and flood service, 
 that is, 33 feet or over (and the river does not reach the danger or 
 flood stage until it stands 33 feet above low water), there was a 
 consideraole decrease in the second period, in harmony with the 
 precipitation. 
 
 I understand that when Mr. Leighton s^jeaks of "the ratio of the 
 annual number of days of flood to annual precipitation," he means 
 the number of days (stage above 20 feet) in each year divided by the 
 total precipitation for the year. Thus, if the number of flood da3-s in 
 any one year is 20, and the total precipitation is 40 inches, the ratio 
 would be 20 divided by 40, or 0.5. These ratios are totaled in 
 eleven-year periods and the average of each period obtained. The 
 average for the first eleven years^ as obtained oy him, was 0.38, and 
 of the second, 0.48, indicating, m his opinion, an increase in flood 
 intensity during the second eleven-year period, as 1 inch of rain 
 made only 0.38 of a flood during the first period, while in the second 
 period 1 inch of rain made 0.48 of a flood. In other words, during 
 the first eleven-year period 1 inch of rain made only 38 per cent of 
 20 feet of water, or 7.6 feet; while during the second period 1 inch 
 of rain made 48 per cent of 20 feet of water, or 9.6 feet. 
 
 This line of reasoning leads to wrong conclusions, as it is certain 
 that the ratios obtained by dividing the number of days that a cer- 
 tain gage reading was reached or maintained by the annual, or for 
 that matter by any other, precipitation, without entering into the 
 problem the exact height of water gives a meaningless result. It 
 appears to me to be a fatal method of reasoning to take sinii>ly the 
 number of days that a stage of 20 foot was ronchod, without roeard 
 to heights above 20 foot. Therefore, if on a cortiiin numl>or oi d:ivs 
 the gage reading was cxactlv 20 foot, one would got prooi.-;ol_v '.\\o 
 same quotient as he would if on the same number of days the ii;i;ic 
 readings were hvrgoly in excess of 20 foot. 
 
 a Pago 22, Water-Supply Paper No. 23-1. 
 
THE IXFLUENCK OF FORESTS ON CLIMATE AND ON FLOODS. 27 
 
 I now come to that part of the discussion in Water-Supply Paper 
 No. 234 which has boon widely quoted by the adherents of the forest- 
 control idea, viz, tlie proposition that, although the flood periods in 
 the Tennessee liavo decreased in later years due to diniinishcd pre- 
 cipitation, the flood tendencies have increased. This idea, like 
 others that have been put forward in this connection, is important 
 if it can be substantiated; and if it is prcn'^en, then it is incumbent 
 upon the author of that paper to show that the increase is duo to 
 deforestation, which he docs not do. I have no data as to the area 
 that has been cleared or that has been allowed to revert to forests, 
 but it can not be great in twelve years. 
 
 This whole matter of the influence of forests upon climate and 
 floods is so important to the nation in planning a correct economic 
 policy for the future that we should move cautiously and be sure 
 that we are building safely and wisely. I am heart and soul with 
 the noble men and women who, as individuals or collectively, are 
 striving to protect and conserve in the interests of the whole people 
 the nation's resources of forest and field and of minerals and water 
 power, and in this opinion I am generally and strongly sustained by 
 the scientific staff or the Weather Bureau. 
 
 With regard to the matters of which this paper specifically treats I 
 wish for the freest, fuUest, and fairest discussion and investigation, 
 with the end in view of correcting error if there be such and of finding 
 common ground upon which all well-meaning persons may stand. 
 Those whose official reports differ from mine I believe to be as honest 
 and as sincere in. their investigations and conclusions as I know 
 myself to be. 
 
 To return to Supply Paper No. 234, referred to above, I quote as 
 follows from page 23: 
 
 The results for the Tennessee basin cover twenty-four years, from 1884 to 1907, 
 inclusive. * * * Summing up the flood-producing rains for the twenty-four year 
 period, it i.' found that the total is 335, of which 313 occurred from December to May, 
 inclu-'ivo, and the remaining 22 during the other portion of the year. It is apparent 
 tLat the number of such rains from June to November is not sufficient to afford a basis 
 of comparison . Therefore only the December to May floods will be considered . * * * 
 On dividing the period covered by these 313 floods equally, two consecutive twelve- 
 year periods are afforded, which give a basis of comparison. The floods in the later 
 period, resulting from a given depth of storm precipitation, are clearly shown to be 
 more severe than in the earlier period. The method of presentation further makes it 
 po?fible to compute the increase in flood tendency due to deforestation in the Ten- 
 nessee. 
 
 »»»♦»« * 
 
 If we now divide the number of flood days by the number of storms the result will 
 be the number of days per storm. 
 
 Days offload per storm. 
 
 
 Perlorl. 
 
 Storms In inches precipitated. 
 
 
 1 to 1.5. 
 
 1.5 to 2. 
 
 2 to 2..';. 
 
 2.5 to 3. .3 to 3.5. 
 
 3.5to4. 
 
 4 to 4. 5. 
 
 4.5 to 5. 
 
 
 
 0.7 
 .1 
 
 0.5 
 
 .0 
 
 2.5 
 2.0 
 
 LSI 2.G 
 2.7 1 3.2 
 
 5 
 
 fi 
 
 S 
 
 8.1 
 7 
 
 I- i't-\''*n 
 
 
 !;u;f jncrr^a-sc 
 
 
 .^'0 
 
 
 
 
 - 17 
 
 V'TIV. 
 
 - 'l.! 
 
 ■' 
 
 V! 1 22 
 
 20 
 
 33 
 
 '1 hi; :i!L"-)inii.- Film of l.hi; iibovc pcrci'ulnjn-H i^ \i<.) ;,ii'l the u,viTa'.,'o is 18.75, v.-hich 
 ti. 111.1 i:;) l.h(- i'lliM.l..s I'f defor<.'.-l;ilio?i ou I'UU-ol'f from IHol to 1907, inclusive. 
 
2S TirF, TXFLUEXCE OF FORESTS ON CLIMATE AND ON FLOODS. 
 
 I invito attention to tho figures given in this table "Days of flood 
 per storm." If the riin-ofl" in the second period was greater than in 
 tho first, duo to deforestation, would not the latter show a uniform 
 and progressive influence increasing as the amount of rainfall in- 
 creased?" How, then, does it happen that a decrease in run-off of 43 
 per cent is shown for rains of intensity 1 inch to 1.5 inches, while m 
 the next higher grade of intensity, viz, 1.5 to 2 inches, an increase 
 of SO per cent is shown ? In the next higher grade, viz, 2 to 2.5 inches, 
 the increase drops to 4 per cent. These results founded, in my judg- 
 ment, on incorrect premises, are both inconsistent and meaningless. 
 To " divide the number of flood days by the number of storms " gives 
 no valuable quotient, for the gage readings selected as floods are 
 not floods, but only moderate stages, and no account is taken of the 
 actual height of the water, and ^diile the conclusion is reached that 
 there is an increase in flood intensity of 18.75 per cent in the Tennes- 
 see basin in the past twelve j-ears due to deforestation, no records or 
 other evidence are presented' that there is not as much forest area in 
 this basin as there was twelve A-ears ago; or that, if there is a decrease, 
 it would be sufficient to account for such a large increase in flood 
 intensity. 
 
 But— and here is the most important matter in the consideration 
 of ilr. Leighton's conclusions — no matter how complete the data 
 may be, or how fundamentally sound and fair its collation and group- 
 ing, the comparison, the one with the other, of such short periods as 
 those measured by only twelve years, can not give results with regard 
 to changes in climate and floods that will permit the most skilled mete- 
 orologist or engineer to draw fundamental conclusions that can have 
 any value. Precisely the same amount of rain falling in the two 
 periods and no change whatever in forest or cultivated area might 
 produce largely differing results on floods, depending on the sequence 
 with which it fell over the different tributaries and how it was con- 
 centrated or scattered, and on many other complicated conditions 
 of run-off, such as the coinciding of the flood volume from one tribu- 
 tary with that of another, instead of each passing down the main 
 stream at different times. 
 
 There is also the difficulty of securing accurate precipitation data. 
 Whenever the height of the gage is altered or other change made 
 in its environment that disturbs the flow of the air currents the read- 
 ings of one period may not fairly be compared the one with the other. 
 These defects vitiate the precipitation data of many stations of the 
 Weather Bureau, especially those in large and growing cities, and 
 can only be remedied by the Government controlling for a long period 
 of years an area at each station so large that it can determine the 
 exposure and keep it constant. 
 
 Another tray oj comparing the precipitation and the river stages of 
 the Tennessee hitsivs. — I give in the following table tho rainfall at 
 Clii'.ttanooga and Knoxvillc scparatclj' for the months December to 
 Mav, inclusive, U>\' Oiich of the twenty-four years considered in 
 ^Va't(■r-'-^l^)])l_v ]*:ipor No. 234; also the total number of days of river 
 sta;;('.s of 20 feel, inul above on tho Cliiittanooga gage. The rainfall 
 so tal)u!:iti'(| inrludof? only the heavy rains, and tho arrangement 
 a('i,;/|iii" til iutensitv is precisely th(! same as that followed in Wator- 
 
 Sui.j.ly I'alHT .\. 
 
 >o. 
 
THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 29 
 
 Eeavij rains at Chattanooga and Knoxville, Tenn., during six months of each year 
 (December, 1883, to May, 1907). 
 
 
 1 to l.S Inches. 
 
 1.5 to 2 inches. 
 
 2 to 2.5 Inches. 
 
 2.5 to 3 Inches. 
 
 December-May, 1883-1907. 
 
 Num- 
 ber of 
 rains. 
 
 Total 
 amount. 
 
 Num- 
 ber of 
 rains. 
 
 Total 
 amount. 
 
 INum- 
 
 1 bcr of 
 
 rains. 
 
 Total 
 amount. 
 
 Num- 
 ber of 
 rains. 
 
 Total 
 amount. 
 
 First half: 
 
 Chattanooga 
 
 57 
 44 
 
 68.65 
 51.01 
 
 16 
 26 
 
 27.54 
 45.59 
 
 8 
 13 
 
 17.83 
 29.44 
 
 13 
 4 
 
 I 
 
 35.67 
 
 Knoxville 
 
 11.04 
 
 
 
 Total 
 
 101 
 
 119.66 
 
 42 
 
 73. 13 
 
 21 
 
 47.27 
 
 17 
 
 46.71 
 
 Mean 
 
 
 
 
 
 ".■;■■:: " w . ".:/ i 
 
 
 
 Second half: 
 
 Chattanooga 
 
 52 
 48 
 
 62.48 
 55.87 
 
 11 
 
 21 
 
 i 
 18.18 i 
 35.47 
 
 12 
 10 
 
 26.28 9 
 22. 19 10 
 
 24.13 
 
 KnoxTiUe 
 
 27.48 
 
 
 
 Total 
 
 100 
 
 118.35 
 
 32 
 
 53.65 i 
 
 22 
 
 48.47 
 
 19 
 
 51.61 
 
 Mean 
 
 
 1 i 1 ! 1 
 
 
 
 December-May, 
 1883-1907. 
 
 3 to 3.5 Inches. 
 
 3.5 to 4 inches. 
 
 4 to 4.5 Inches. 
 
 4.5 + Inches. 
 
 
 ?™; Total 
 
 Num- 
 ber of 
 rains. 
 
 Total Jf™: 
 amount. ^Y„?' 
 
 Total 
 amount. 
 
 Num- 
 ber of 
 rains. 
 
 Total 
 amount. 
 
 Grand 
 total. 
 
 First half: 
 
 Chattanooga 
 
 4 
 4 
 
 13.45 
 12.70 
 
 4 
 
 1 
 
 15.07 
 3.78 
 
 2 
 2 
 
 8.58 
 8.79 
 
 6 
 4 
 
 33.43 
 22.04 
 
 220.22 
 184.39 
 
 Enozville 
 
 
 Total 
 
 8 
 
 26.15 
 
 5 
 
 18.85 4 
 
 17.37 
 
 10 
 
 55.47 
 
 404.61 
 202.30 
 
 Mean 
 
 Second half: 
 
 Chattanooga 
 
 4 
 5 
 
 13.41 
 16.17 
 
 2 
 2 
 
 7.71 
 7.46 
 
 2 
 
 8.38 
 
 4 
 
 23.27 
 
 183.84 
 164.64 
 
 KnoxTiUe 
 
 Total 
 
 9 
 
 29.58 
 
 4 
 
 15.17 
 
 2 
 
 8.38 
 
 4 
 
 23.27 
 
 
 Mean 
 
 348.48 
 174.24 
 
 
 
 
 
 
 
 
 
 
 
 The data of the above table have been divided into two periods of 
 twelve years each, with the following results: 
 
 First period. 
 
 Total number of heavy rains at Chattanooga XXO 
 
 Total number of heavy rains at Knoxville ..!.!!!.].!!!!!!! 100 
 
 Total : ^ 210 
 
 Total amount of the above heavy rains as per table, 404.61 inches. 
 Dividinc this total by two, to get the approximate average of the heavy rains for 
 the ■watershed, we get 202.30 inches. 
 
 Total number of days with stages of 20 feet or more at Chattanooga 166 
 
 Dividing the amount of the heavy rains in the watershed by the number of days 
 
 with a river stage of 20 feet or over, we get -??^--?°=1.220 inches as the amount of rain- 
 
 ibb 
 fall that probably produced one day of a stage of water in the river of 20 feet or more. 
 
30 THE INFLUENCE OF FOEESTS OK CLIMATE AND ON FLOODS. 
 
 Second period . 
 
 Total nunil)cr of heavy rains at Chattanooga ^° 
 
 Total number of heavy rains at Knoxvillc ^ 
 
 Total 1^2 
 
 Total amount of the above heavy rains, 348.48 inches. , , , 
 
 Dividing this total aa before, we get as an approximate average of the hea'.\- rains 
 in the watershed 174.24 inches. 
 
 Total number of days with stages of 20 feet or over in the river 141 
 
 Dividing as before, we get as the probable amount of rainfall in the second period 
 required to produce a day of 20 feet or over in the river, 1.236 inches, as against IMt) 
 inches in the first period. 
 
 The diflference between the line of reasoning employed in getting 
 the above results and those given in Water-Supply Paper Ac. 2.34 is 
 that the author of the latter attempts to difFerentiate between the 
 stages produced by rains of varying intensity and to assign to such 
 rains a given number of so-called "flood days," while in this paper the 
 assertion is made that in the first period there were a given number 
 of days with a stage of 20 feet and over in the river, and that during 
 that tune the heavy or flood-produaiiig rains amounted to so much. 
 Dividing, then, the total of the flood-producing rains by the corre- 
 sponding number of days with a st^ of 20 feet or over, the results 
 given above are reached, viz, that for the first period it took 1.22 
 mches of rainfall to produce a day with a 20-foot sta^e in the river. 
 These figures contradict the contention that an equal depth of rain 
 in the last period as compared with the first produced more sevure 
 floods in the river. I onfy present them to snow how ea^' it is to 
 arrange data so as to prove both sides to a question. While this 
 line of inquiry is open to less objection than that followed by Leigh- 
 ton, it does conform to the plan of the latter in so far as it uses the 
 number of days that the river stood at or above 20 feet, instead of 
 taking into consideration the actual height of the water. The most 
 that can be said is that this form of inquiry shows no increase in 
 flood intensity. 
 
 Rainfall arid run-off of the Ohio Basin. — We now come to a different 
 and more reliable form of investigating this question of the relation 
 of precipitation to run-off. 
 
 We have no direct method of measuring the run-off, but we can 
 reach a fair approximation to it by a comparison of the rainfall and 
 river data for any given watershed. If, for example, the surtaco 
 conditions over any considerable part of a watershed have been 
 materially changed by deforestation or other means, and if, as 
 claimed, such change operates to increase the run-off, then the flow of 
 water in the streams after the change has been brought about should 
 be greater for equal depth of precipitation. This method is a rough 
 one, to be sure, but it appears to be the only one permitted by the 
 records as they exist. 
 
 Cincinnati, Ohio, has been chosen as the point whoso river observa- 
 tions are best adapted to our purpose, although some olijcction to 
 that place lies in the constriction or the natural river channel c:i'i-:i\l 
 by the encroachment on the banks of the stream by various artiiirial 
 structures. The station at Pittsburg, Pa., is bettor situatcii for 
 comparative purposes, but the low-water stages at that place of 
 
THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 31 
 
 lato yoars have boon vitiatocl by the construction of the Davis 
 Ishind (Uiin. The constriictit)n of dams at several places in other 
 rivers has hnverod the value of low river gauge readings for comparative 
 purposes. 
 
 In the tables whicli follow I have given the actual mean monthly 
 stage of the Ohio at Cincinnati for every month of the period 1S71 
 to 1908. Tlie average of these monthly means has been computed 
 for the first period of nineteen years; these averages have been 
 suramod up for the twelve months of the year, and that sum has 
 been divided by twelve in order to get the annual mean. The number 
 so obtained, 17.3 feet, is therefore the average stage of the river for 
 the entire nineteen years, as computed from all of the daily stages 
 for that period. In like manner the average stage of the river for 
 the second period of years has been computed and is given in the 
 following table : 
 
 Mean monthly and annual river stages in the Ohio River at Cincinnati, Ohio, for the 
 
 period 1871-1908. 
 
 [In fe«t and tenths.] 
 
 Year. 
 
 Jan. 
 
 Feb. 
 
 Mar. 
 
 Apr. 
 
 May. 
 
 June. 
 
 July. 
 
 Aug. 
 
 Sept. 
 
 Dot. 
 
 Nov. 
 
 Dec. 
 
 Annual. 
 
 1S71 
 
 14.6 
 14.0 
 22.6 
 29.7 
 18.3 
 31.4 
 2.S. 1 
 20.0 
 23.2 
 29.2 
 20.7 
 42.0 
 18.1 
 24.5 
 2.5.6 
 24.7 
 20.4 
 20.2 
 2.i.2 
 3.3.0 
 31.8 
 23. 8 
 12.7 
 17.3 
 2S.3 
 14.1 
 14.4 
 3j.3 
 31.8 
 18.7 
 1.5.8 
 10.9 
 23.1 
 19.4 
 14.9 
 2l',. -S 
 4.-,. 7 
 2J. 
 
 23. 8 
 
 2.3.1 
 14.1 
 29.4 
 27.9 
 16.7 
 a3.9 
 18.4 
 24.2 
 26.6 
 28.3 
 3.3.1 
 44.0 
 48.6 
 54.4 
 15.6 
 2(1. 
 48.4 
 20.1 
 24.1 
 37. 9 
 46. 8 
 24.5 
 41.1 
 27.2 
 1.3.9 
 23.6 
 30. 3 
 25.0 
 2.5.9 
 24.5 
 13 8 
 
 25.3 
 13.3 
 21.4 
 23.7 
 34.4 
 2.5.6 
 28.0 
 24.2 
 32. S 
 35.2 
 27.2 
 34.2 
 20.3 
 36.5 
 17.1 
 20.6 
 29.4 
 2.3.0 
 20.9 
 40.0 
 37.2 
 2.5.4 
 25.8 
 22.6 
 27.4 
 22.5 
 40.3 
 31.3 
 40.1 
 2S.9 
 
 16.5 
 25.8 
 29.2 
 31. r. 
 23.9 
 25.4 
 23.1 
 14.5 
 22.9 
 24.6 
 29.4 
 18.2 
 30.0 
 24.5 
 26.5 
 37.4 
 24.0 
 2,3.8 
 19.0 
 31.7 
 30,0 
 31.5 
 26.8 
 19.1 
 24.4 
 26.1 
 26.3 
 27.1 
 26.7 
 17.8 
 39.5 
 26.7 
 32.9 
 26.6 
 19.7 
 30.3 
 23.9 
 35.8 
 
 25.1 
 27.6 
 26.3 
 
 21.8 
 11.8 
 25.6 
 20.7 
 14.7 
 18.2 
 17.4 
 22.0 
 11.4 
 15.8 
 16.1 
 30.6 
 49.0 
 17.5 
 15.0 
 22.0 
 20.6 
 13.8 
 16. 
 32.5 
 9.8 
 2.3.2 
 36.1 
 16.9 
 12.3 
 12.3 
 23.1 
 23.7 
 17.4 
 11.2 
 2.5.5 
 13.6 
 12.0 
 20.1 
 25.2 
 14.3 
 22.5 
 30.8 
 
 20.0 
 20.2 
 20.1 
 
 8.2 
 10.9 
 
 9.2 
 
 7.8 
 11.8 
 10.1 
 12.1 
 12.5 
 
 7.1 
 14.0 
 16.5 
 26.5 
 61.5 
 11.3 
 14.7 
 15.5 
 14.8 
 10.4 
 25.2 
 19.8 
 18.9 
 23.1 
 14.9 
 12.3 
 
 6. .5 
 11.7 
 12.8 
 11.7 
 13.6 
 10.8 
 28.1 
 11.0 
 13.5 
 16.2 
 16.3 
 12.5 
 27.2 
 12.9 
 
 1.5.8 
 1.5.5 
 15.6 
 
 7.1 
 
 11.9 
 
 13.3 
 
 6.1 
 
 25.0 
 
 11.8 
 
 11.3 
 
 9.0 
 
 5.6 
 
 9.4 
 
 7.8 
 
 16.9 
 
 12.9 
 
 8.5 
 
 6.8 
 
 1.3.8 
 
 5.7 
 
 14.6 
 
 18.5 
 
 10.8 
 
 1.3.0 
 
 11.6 
 
 8.3 
 
 5.6 
 
 7.5 
 
 22.1 
 
 13.9 
 
 8.6 
 
 8.4 
 
 9.5 
 
 13.1 
 
 19.4 
 
 12.7 
 
 13. 5 
 
 15.8 
 
 10.1 
 
 18.3 
 
 10.0 
 
 11.4 
 12.2 
 11.8 
 
 S.l 
 
 8.4 
 
 10.0 
 
 9.0 
 
 26.7 
 
 10.6 
 
 6.5 
 
 10.6 
 
 9.9 
 
 8.4 
 
 4.9 
 
 13.7 
 
 8.7 
 
 6.5 
 
 12.5 
 
 10.0 
 
 4.9 
 
 12.1 
 
 12.2 
 
 9.7 
 
 11.2 
 
 7.7 
 
 4.8 
 
 4.3 
 
 6.1 
 
 20.1 
 
 10.3 
 
 20.2 
 
 8.0 
 
 7.9 
 
 9.6 
 
 9.9 
 
 6.7 
 
 6.3 
 
 12.9 
 
 14.4 
 
 13.5 
 
 8.6 
 
 10.0 
 10.1 
 10.0 
 
 5.4 
 5.1 
 6.6 
 4.2 
 S.l 
 
 16.8 
 6.2 
 
 13.7 
 6.9 
 7.0 
 3.6 
 
 13.9 
 4.4 
 3.6 
 
 11.0 
 5.4 
 3.3 
 
 16.4 
 6.7 
 
 20.8 
 9.7 
 5.7 
 7.2 
 4.8 
 4.9 
 6.7 
 4.8 
 7.7 
 5.1 
 5.0 
 
 10.9 
 4.4 
 8.2 
 5.0 
 
 10.2 
 
 10.1 
 
 12.1 
 4.4 
 
 7.6 
 7.8 
 7.7 
 
 3.2 
 4.2 
 7.3 
 5.4 
 7.4 
 
 10.7 
 5.1 
 6.0 
 3.2 
 4.6 
 4.4 
 9.0 
 7.9 
 3.9 
 8.5 
 5.2 
 3.3 
 
 17.9 
 8.0 
 
 21.2 
 4.9 
 4.3 
 
 10.5 
 4.6 
 3.0 
 
 14.8 
 3.5 
 
 10.1 
 3.9 
 4.3 
 6.4 
 7.6 
 6.6 
 3.8 
 
 10.8 
 
 13.3 
 
 10.6 
 3.6 
 
 6.6 
 7.8 
 7.2 
 
 6.5 
 
 10.0 
 
 15.6 
 
 4.6 
 
 15.9 
 
 11.7 
 
 12.1 
 
 '14.8 
 
 5.4 
 
 10.4 
 
 14.8 
 
 8.7 
 
 38.0 
 
 4.4 
 
 15.5 
 
 12.2 
 
 3.6 
 
 27.4 
 
 24.6 
 
 24.2 
 
 9.6 
 
 6.4 
 
 9.5 
 
 6.6 
 
 3.4 
 
 13.8 
 
 8.0 
 
 17.1 
 
 6.4 
 
 10.3 
 
 5.6 
 
 0.3 
 
 7.3 
 
 4.2 
 
 12.0 
 
 15.8 
 
 17.0 
 
 4.8 
 
 13.5 
 9.9 
 11 7 
 
 7.3 
 10.5 
 28.6 
 13.4 
 24.3 
 12.1 
 15.1 
 29.1 
 19.2 
 18.1 
 25.0 
 12.7 
 32.2 
 12.2 
 18.1 
 19.4 
 
 6.1 
 10.2 
 23.9 
 17.3 
 18.9 
 11.1 
 16.5 
 12.0 
 
 9.4 
 19.7 
 17.8 
 18.7 
 13.4 
 19.2 
 20.6 
 20.9 
 
 9.6 
 
 4.6 
 23.6 
 23.3 
 19.4 
 
 6.2 
 
 18.1 
 16.3 
 17.2 
 
 
 1,S7.' 
 
 
 1873 
 
 
 1S74 
 
 
 1S7:. 
 
 
 1S7C 
 
 
 1S77 
 
 
 1S7^ 
 
 
 1N7V 
 
 
 1.S<|| 
 
 
 ls,s; 
 
 
 IS'-:' 
 
 
 1SS-, 
 
 
 InM 
 
 
 K^■ 
 
 
 1>-J 
 
 
 l^.'-T 
 
 
 ISn^ 
 
 
 ISVI 
 
 
 lv>, 
 
 
 I'-'M 
 
 
 1-^'c 
 
 
 l-'i.-; 
 
 
 IS'.M 
 
 
 l^V 
 
 
 IWO 
 
 
 1897 
 
 
 l,S9,s 
 
 
 ISM 
 
 
 1900 
 
 
 19fjl .. .. 
 
 
 \v-i 
 
 19. 2 .37 2 
 
 
 IC»i3 
 
 .39.7 
 20.3 
 21.4 
 13.9 
 22.0 
 32.2 
 
 20.3 
 
 211.8 
 28.1 
 
 42.5 
 34.6 
 33.3 
 2ii.3 
 40.1 
 41.9 
 
 20.1 
 .32. 9 
 29.5 
 
 
 13'U. . . 
 
 
 I!ii|.'. 
 
 
 I'll',, 
 
 
 1'<(I7 
 
 
 l',i,v 
 
 
 ll.-L.ri: 
 
 l'^71-1'-s'l 
 
 IVKJ-lM-l. ... 
 
 '.h7l-l:,ii'< 
 
 17.3 
 17.6 
 17.4 
 
 T!, 
 
 .■|,VC|-;l''( 
 
 ,T, 
 
 0,M;tlUcil. ()l 
 pi('ci|>)!.-i,l irjji 
 rci uri! , ill 1:;|'_' 
 
 ' precipitation for tlic watorsliod has not been so easily^ 
 liy in ix'-cptioriul cu-rs arc (.■ontinuous mpusuremenl.'^ of 
 .•i'v;»il;i,blc for coinp.-irativc studios. Tlie ^^'ovornnitMit 
 V cities arc of neci'.^^ity made from gauges whose iiume- 
 
32 THE IJTFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 
 
 diate environment has been changed repeatedly in the course of a long 
 series of years, and it was for this reason that the rain-gauge records 
 from Cincinnati and Pittsburg were ignored. The points selected — • 
 viz, North Lewisburg and Portsmouth, Ohio, and Confluence and 
 Franklin, Pa.— -are the best and practically the only long-period rec- 
 ords available in this watershed. A better distribution tnroughout 
 the watershed woidd have been preferred, but it is not possible to 
 obtain it. The precipitation, like the river stages, has been computed 
 in periods of nineteen years each. The tables follow: 
 
 Annual precipitation in the Ohio watershed for the period 1S71 to 1908, inclvMve. 
 
 [In Inches and tenths.! 
 
 Year. 
 
 North Lew- 
 isburg, 
 Ohio. 
 
 Ports- 
 mouth, 
 Ohio. 
 
 Confluence, 
 Pa. 
 
 Franklin, 
 Pa. 
 
 For the 
 watershed. 
 
 1871 
 
 28.6 
 37.2 
 340 
 43.2 
 42.0 
 37.3 
 440 
 4&4 
 46.4 
 440 
 45.8 
 48.9 
 343 
 3&8 
 4a6 
 35.0 
 47.6 
 30.8 
 45.2 
 442 
 40.2 
 49.1 
 39.6 
 29.0 
 48.3 
 43.5 
 52L2 
 34.0 
 32.5 
 29.6 
 36.6 
 28.7 
 35.4 
 «35.1 
 «I33.7 
 <«37.6 
 
 aai 
 
 39.8 
 
 3ai 
 
 39.0 
 
 30.7 
 3L1 
 46.2 
 3&3 
 45.7 
 41.2 
 35.0 
 29.9 
 35.6 
 49.0 
 40.8 
 56.2 
 4&5 
 42.3 
 37.3 
 45.3 
 40.7 
 48.3 
 39.3 
 57.6 
 42.8 
 441 
 37.9 
 36.2 
 31.2 
 39.9 
 49.1 
 481 
 42.9 
 346 
 39 7 
 37.2 
 37.3 
 29.2 
 43.3 
 444 
 42.3 
 40.0 
 
 41.1 
 40.9 
 41.0 
 
 a27.7 
 "SLO 
 <>41.4 
 1 39. 4 
 39.1 
 46.1 
 45.0 
 41.1 
 3a 8 
 49.2 
 41.4 
 55.1 
 49.8 
 42.1 
 39.3 
 441 
 >31.2 
 6 47.3 
 400 
 60.1 
 57.5 
 3&4 
 43.4 
 42.1 
 35.1 
 50.2 
 45.8 
 53.2 
 48.9 
 440 
 41.2 
 45.9 
 3&3 
 31.4 
 61.1 
 48.7 
 55.8 
 42.1 
 
 41.5 
 46.0 
 418 
 
 347 
 
 41.6 
 
 649 
 
 47.4 
 
 45.8 
 
 46.9 
 
 43.5 
 
 40.1 
 
 37.7 
 
 340 
 
 39.1 
 
 45.8 
 
 41.3 
 
 42.0 
 
 446 
 
 38.8 
 
 40.8 
 
 49.2 
 
 43.8 
 
 68.5 
 
 <:51.4 
 
 '!47.6 
 
 C4a7 
 
 «43.3 
 
 <:33.5 
 
 «41.2 
 
 39 6 
 
 391 
 
 32.8 
 
 31.7 
 
 42.2 
 
 39.1 
 
 45.6 
 
 40.8 
 
 45.1 
 
 «40.2 
 
 «42.3 
 
 «41.1 
 
 42.7 
 42.3 
 42.5 
 
 
 1872 
 
 
 1873 
 
 
 1874 
 
 
 1875 
 
 
 1876 
 
 
 1877 
 
 
 1878 
 
 
 1879 
 
 
 1880 
 
 
 1881 
 
 
 1882 
 
 
 1883 
 
 
 1884 
 
 
 1885 
 
 
 1886 
 
 
 1887 
 
 
 1888 
 
 
 1889 
 
 
 1890 
 
 
 1891 
 
 
 1892 
 
 
 1893 
 
 
 1894 
 
 
 1895 
 
 
 1896 
 
 
 1897 
 
 
 1898 
 
 
 1899 
 
 
 1900 
 
 
 1901 
 
 
 1902 
 
 
 1903 
 
 
 1904 
 
 
 1905 
 
 
 1906 
 
 
 1907 
 
 
 1908 
 
 
 Uean: 
 
 41.3 
 
 1890-1908 
 
 41.8 
 
 
 41.6 
 
 
 
 o Record of Pittsburg, Pa. 
 
 * Record of Lock No. 4, Pennsylvania. 
 
 e Record of Warren, Pa. 
 
 d Record of Columbus, Ohio. 
 ' Record of Parkers, Fa. 
 
 Summarizing the above, we have: 
 
 Average stare of the Ohio River at Cincinnati, Ohio: Feet. 
 
 1S71 tols^ti 17.3 
 
 lS90tol90S 17-5 
 
 AverriKP, prpcititation in the Ohio watershed, as detenninod from the stations above named: Inches. 
 
 1871lol^vi jJ-3 
 
 ISOOtol'Ab ^1'8 
 
THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 33 
 
 I consider that the results secured from the discussion of the 
 
 firecipitation and the gauge readings in the Oliio basin, as given in the 
 oregoing tables, form one of the most important contributions made 
 by this paper. Here we have avoided the using of indefinite and 
 meaningless data, and have taken the longest period of time for 
 which accurate records can be secured on a watershed that is suitable 
 for this line of inquiry. We have not simply counted the number of 
 days that the river stood above some arbitrarily selected stage with- 
 out taking into consideration the exact height of the river. Neither 
 have we divided the gauge readings by some arbitrarily selected 
 portion of precipitation data. On the contrary, we have endeavored 
 to profit by the errors of previous investigations, and to lay the 
 foundation of an inquiry that would mean something when we reached 
 the end of our computations. For this reason we have selected a 
 typical station on the main stream that drains the Ohio Basin and 
 have discussed rainfall data that are the most accurate of any in the 
 region, having been subject to less errors due to varying environ- 
 ments. Any deductions made from an inquiry founded with less 
 care, or from data of a less degree of accuracy, must bring results 
 from which it would be unsafe to form definite conclusions. 
 
 Now let us see what is the result. The average stage of the river 
 for the first nineteen years is 17.3 feet, and for the last nineteen 
 years 17.5 feet, showing that there is practically no change in the 
 run-off of the Ohio Basin between the first period and the last. 
 When we examine the average precipitation over the watershed that 
 is drained by this-rirver we find that for the first nineteen years it was 
 41,3 inches, and for the last nineteen-year period it was 41.8 inches, 
 a sUght increase in precipitation for the latter period that agrees 
 precisely with the slightly greater average flow of water. There is a 
 perfect agreement here oetween the precipitation and the flow of 
 the stream. I do not know what has been, the area deforested in 
 this valley during the thirty-eight years under discussion, but whatever 
 it is it seems to be apparent that such altering of the relation of forest 
 area to cultivated area has had no appreciable «ffect on the flow of the 
 Ohio River. I am aware of the fact that by the studying of short 
 periods of data on small tributary streams, and especially by the 
 grouping of data dissimilar from what is employed in this discussion, 
 all manner of results may be shown. 
 
 I believe that the reader vnU acknowledge that I have shown in the 
 several preceding paragraphs that the average discharge of the Ohio 
 River, where I presume deforestation has heen as great as in any other 
 part of the country during recent time, has not changed for a period oj 
 thirty-eight years, except as caused hy precipitation. It will now he inter- 
 esting to Tcnow how the two periods compare with regard to extremely high 
 water and extremely low water, and this wiU he discussed in the coming 
 pages. 
 
 High water and low water on the rivers of the Ohio hasin. — I had Prof. 
 H. C. Frankenfield, Chief of the River and Flood Division of the 
 Weather Bureau, compile the data from one station on the Cumber- 
 land, three on tlie Tennessee, and five on the Ohio, and establish the 
 average high water for the four wet months, January to April, and the 
 average low water for the four dry months, July to October. He thcu 
 
 26320—10 3 
 
34 TllK INFLUE^■CE OF FOKESTS ON CLIMATE AND ON FLOODS. 
 
 took the departure from the normal, both for tlic precipitation and for 
 the height of the rivers, and found that tlie average high water was no 
 higher and the average low water was no lower for the last half of the 
 period than for the first half. The difFonmcos were so sHght as to he 
 inappreciable, but what cnanges occurred were in favor of the low 
 water being slightly higher and the flood waters slightly less. There 
 were variations in the periods and intensities of Hoods that bear a 
 direct and proper relation to the precipitation. In making his 
 report, Professor Frankenfield points to the fact that the low-water 
 stages at Pittsburg, Pa., and Nashville, Tenn., are not fairly com- 
 parable with those of the other stations on account of permanent 
 pool stages caused bj dams operated during the low-water season 
 tor purposes of navigation. The first dam below Pittsburg was 
 placed m operation in 1885, and that at Nashville in 1904. The 
 effect of these dams is to furnish higher low-water stages than would 
 result without them. The effect upon the normal low-water stage 
 at Nashville was not marked, but at Pittsburg it was perceptible. 
 However, in his conclusions he did not make allowance for the 
 slightly higher low-water stages at Pittsburg on account of the dam, 
 but when included with the other stages of the river this defect 
 probably is not apparent. 
 
 According to our line of reasoning, which we believe to be fair and 
 conservative, it is shown that the average discharge of the Ohio 
 River is not greater as the result of deforestation during the last 
 nineteen years than during the preceding like period, and that the 
 average high water in the rivers of the entire basin, which includes 
 the Tennessee, the Cumberland, and the Ohio, is not higher and the 
 low water is not lower. 
 
 Are real flood stages more numerous than formerly? — The next line 
 of inquiry will be for the purpose of determining whether or not 
 there has been in recent time an increase in the number of days 
 that these rivers were at or above the flood stage, and in making this 
 inquin'' exact flood stages will be used, not simply gauge readings less 
 than flood. Again I called on Professor Frankenfield to prepare the 
 necessary data. As the data was not complete with regard to flood 
 stages for the first ten years of the period that we have been dis- 
 cussing, he took a period of ten years less in length, beginning with 
 1879, and as the result of his computations we have tne following 
 table 
 
36 THE INFLTjEXCE OF FOEESIS OK CLIMATE AND ON FLOODS. 
 
 the forepart of the first fourtcen-ycar period, especially that which 
 caused the famous 1SS2 flood, places such a jirepondcrance of flood 
 days in the first period that it would be unfair to claim that there has 
 been anv such permanent decrease in flood intensity as is shown by 
 this table. It is jriren for what it is worth, and furtner to emphasize 
 the fact that conchisions on which fundamental theories or policies 
 are based should not be founded upon short-period data. Whilel 
 am strongly of the opinion that there is no permanent increase in the 
 number of flood davs for the rivers of the United States as a whole, 
 between the last fifty years and the preceding fifty years, I should 
 not rely upon such short-jseriod data as is contained in this table 
 to sustain mj- belief. But if these data of twenty-eight years, which 
 shows such a marked decrease in flood intensity of the rivers of the 
 Ohio Valley, and which are founded upon unquestionably accurate 
 data, are not sufficient evidence for a scientific man to claim statistical 
 proof of the decrease of floods, what shall one say of the statements 
 made by Messrs. Hall and Maxwell, of the Forest Service, in volume 
 2, Senate Document No. 676, in a paper on "Surface conditions and 
 stream flow," which begins at page 112, as follows: 
 
 THE TEXDEXCY IS TOWARD IXCREASED FLOODS. 
 
 On the Potomac River, for which measurements are given for eighteen years, the 
 number of floods during the first half of the period was 19; during the second half, 26; 
 while the number of days of flood in the first half was 33, and in the second half, 57. 
 
 On the Monongahela River measurements are given for twenty-two years. During 
 the firet half of the period there were 30 floods; during the second half, 52. The num- 
 ber of days of flood during the first half of the period was 55; during the second half, 100. 
 
 On the Ohio River measurements are given for twenty-six years. During the first 
 half of the period there were 46 floods; during the second half, 59. The number of 
 days of flood during the first LrJf was 143; during the second half, 188. 
 
 On the Cumberland River measurements were given for eighteen years. During 
 the first half of the period there were 32 floods; during the second half, 43. The num- 
 ber of days of flood during the nr-t half was 89; during the second half, 102. 
 
 On the Wateree Rivermeasurements have gone on for ei-^teen years. In the first 
 half of the period the number of floods was 46; in the second half, 70. The number of 
 davs of flood in the first half of the period was 147 , in the last half, 187. 
 
 On the Savannah River measurements have continued for eighteen years. During 
 the first half of the period the number of floods was 47; during the second half, 58. 
 The number of davs of flood durin-r the first period was 116 ; during the second half, 170. 
 
 On the Allojrhenv River me^.-=urement3 arc given for thirty-four years. During the 
 first half of the period there were 39 floods; during the second half, 53. The number 
 of days of flood during the first half was 92; during the second half, 131. 
 
 On the Tennessee River measurements have been taken for thirty-four yeare. Dur- 
 ing the first half of the period there were 32 floods; during the second half, 33. ine 
 number of days of flood durini' the first half was 173; during the second half (in this 
 case there was a falling-off;, 137. 
 
 The conclusions arrived at by the authors are, in my judgment, 
 
 faulty, because: , , ,. , ^, • •*„ 
 
 First. The shortness of the period of observations at the majority 
 
 of the stations discussed. n i ^ r <. •„ u„;„u+c, 
 
 Second. The arbitrarv assumption as flood stages of certam heights 
 of water much below that necessary to cause a flood. 
 
 As to the period of observations: Those ol us who are accustomed 
 to he crirapitation of normals or "lean values have always realized 
 how Mtrln v-iliie thev p'-^^-ss unless obtainod from data covering a 
 how httlG ^'^1 'e t '^> P.J-J • ^ „i' teiiiperature normals, which 
 lone; period ot M; - / .-^a IIow mu.h more must it bo true 
 S^'^ed^iluri^n'S Vlv^i-^ige data, with their wide extremes and 
 
THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 37 
 
 irregular fluctuations? As a matter of fact any average of river con- 
 ditions, or any mean annual precipitation determined from ten or 
 fifteen years' observations, would be of little or no value in a discus- 
 sion of this character, and when two of these short-period normals 
 are compared with each other the actual errors would probably be 
 multiplied. 
 
 Second, opinions may differ, of course, as to what constitutes a 
 flood, but the Weather Bureau (and engineers generally) have uni- 
 formly defined a river to be in flood when it reached a stage above 
 which damage would be caused, practically the bank-full stage. This 
 being so, it would appear reasonable and proper that this definition 
 of the term should be accepted and data discussed accordingly. If 
 the flood stage at a given point is 18 feet, an assumption of a lower 
 or a higher figure for purposes of investigating the frequency of floods 
 must necessarily be misleading. 
 
 I will now ta!ke up the rivers in the order named in the quotation 
 and give the net result of Professor Frankenfield's inquiry as to the 
 number of real floods: 
 
 Potomac. — On the Potomac River the number of floods has not 
 increased, but there were more days of a 12-foot stage in the last 
 period than in the first. The explanation of this increase is found in 
 the precipitation. 
 
 MonongaTiela. — On the Monongahela River, using data for Lock 
 No. 4, Pennsylvania, 40 miles above Pittsburg, there were two more 
 floods in the second period as compared with the first, the figures 
 being 13 and 11, respectively. Two of the days of flood occurred in 
 March, 1907, as a result of abnormal weather conditions over the 
 watershed. 
 
 Ohio at Wheeling. — There was an increase in the number of floods 
 at Wheeling, but said increase is not shown farther down the river 
 than Parkersburg. It (the increase) disappeared below the mouth 
 of the Great Kanawha, as indicated by the Cincinnati records. The 
 reason ascribed for this increase in flood frequency is an increase in 
 short-period heavy rains. The same conditions appear to have 
 obtained in the Allegheny at Freeport. 
 
 Cumberland. — There has been no increase in flood conditions in the 
 Cumberland. 
 
 Wateree.— There was a marked increase in the number of flood days 
 on this river during the second period. On the other hand, the pre- 
 cipitation in the watershed shows a like marked increase. 
 
 Savannah. — The record for the Savannah River at Augusta shows 
 a marked decrease in the second period as compared with the first. 
 Allegheny at Freeport. — See Wheeling. 
 
 Tennessee. — See detailed discussion on this river in another part of 
 this paper. 
 
 COXCLUSIONS. 
 
 (1) Any marked climatic changes that may have taken place are 
 of wide extent and not local, arc appreciable only when measured m 
 eeoio'ac periods, and evidence is strong that tlic cuttmg away of tlie 
 Wst" Iiiis had notbin;,' to do ^vith the crcatmg or the augmentmg of 
 drou'Jits in anv piirt of the world. , .• u v,,^ „. 
 
 (2) PrcciTiitution ('Oiitrols lorestation, but forestation has little or 
 no elfcct u])i>ii j)rocipitatiou. 
 
38 THE INFLUENCE OF FORESTS ON CLIMATE AND ON FLOODS. 
 
 (3) Any local modificatiou of temperature and humirlitv caused by 
 the presence or absence of forest covering, the buiidinirs of villages 
 and cities, etc., could not extend upward more than a "few hundred 
 feet, and in this stratum of air saturation rarely occurs, even durino' 
 ramfall, whereas precipitation is the result of conditions that exist at 
 such altitudes as not to be controlled or affected by the small thermal 
 irregularities of the surface air. 
 
 (4) During the period of accurate observations, the amount of 
 precipitation has not increased or decreased to an extent worthy of 
 consideration. 
 
 (5) Floods are caused by excessive precipitation, and the source of 
 the precipitation over the central and eastern portions of the United 
 States is the vapor borne by the warm southerly winds from the Gulf 
 of Mexico and the adjacent ocean into the interior of the country, 
 but little from the Pacific Ocean crossing the Eocky Mountains. 
 
 (6) Compared with the total area of a given watershed, that of the 
 headwaters is usually small and, except locally in mountain streams, 
 their run-off would not be sufficient to cause floods, even if deforesta- 
 tion allowed a greater and quicker run-off. Granting for the sake of 
 argument that deforestation might be responsible for general floods 
 over a watershed, it would be necessary, in order to prevent them, to 
 reforest the lower levels with their vastly greater areas, an impossi- 
 bility xinless valuable agricultural lands are to be abandoned as food- 
 producing areas. 
 
 (7) The run-off of our rivers is not materially affected by any other 
 factor than the precipitation. 
 
 (8) The high waters are not higher, and the low waters are not 
 lower than formerly. In fact, there appears to be a tendency in late 
 years toward a slightly better low-water flow in summer. 
 
 (9) Floods are not of greater frequency and longer duration than 
 formerly.