Show eat rivals J V tt wk ti 1 i t 7 hii sa 4 f YM fi Vy y aw p i ai f J byc Z z Z in t mr ate 4 a te N all 11 I 1 I 1 fen w hs 1 alx fw flood waters Matere raging in a mississippi levee prepared prepare b by the national Hit lonii geographic society t 7 washington sto D a played favorites to in apportioning N NATURE the great rivers of the world ot of the dozen larg est six are in asia and three to in africa leaving only three for the two continents of the new world word and among the twelve leaders europe and australia are wholly tile the longest single river Is tile the nile measuring some millis miles from head to mouth the nile ls Is further distinguished in that it tins has no tributaries tributa ries for or the last iasi 1500 miles of its course cours to the sea during this stretch its waters are reduced in volume by evaporation and irrigation so that 11 I 1 grows smaller instead of larger toward its mouth other african rivers among the length scoring twelve ore are tile the niger and the congo holli both fed by the tropical rains of hot regions near the equator in a general way hey more nearly resemble south americas representative the amazon than the great streams of the colder northern continents of asias six longest rivers four are in siberia the ob oad and lena flowing north into the arctic ocean and the amur emptying into an firm arm of the pacific the other two are the yangtze and hwang or Yellow river of china these twelve river basins represent tile the greatest variety of climate and civilization the amazon and the congo low flow through lush equatorial jungles inhabited by birds of brilliant plumage wild animals and savage tribes while the months of the and the lena are above the northern timber line and their valleys support the sparsest population the mississippi and tile the yangtze flow through established if divergent civilizations with rich cities along their banks like jewels on a string the nile Is one of tile the cradles of world history the mackenzie 1 Is 3 still a 0 frontier str stream etim fave of the dozen rivers flow to the north these are the nile mackenzie oh Te nisel nod lena tile the sippi and niger flow south the amur hwang and amazon run east eastward vard only the congo points toward the west difference in floods all these streams overflow their banks at it intervals but the results are strangely different in the case of the 1 mississippi and the yangtze Yang tze floods are national disasters bringing untold suffering to millions the ann annual I 1 overflow of the nile with resulting fertilization liza tion of the valley by the deposit of silt Is fit the source of the wealth of egypt tile the hwang or yellow river from its habit of overflowing its banks banka aad changing tta its entire course at in teals Is known as the scourge of uhlna china the amazon and the congo tie lie almost under the equator and the other r ten longest rivers are in the northern hemisphere four flow into the arctic ocean A reason Is not far to seek the greatest land masses are in the northern halt half of tile the world and without large land areas long rivers tire are impossible the smaller continents of australia and burc europe bifid are not represented in the dozen similarly the reason tor for the longest rivers flowing to tile north and east cast 1 Is that the longest continental slopes extend in those directions the yangtze and the mississippi are lined with wealthy cities largely because of their location in the temper jute ate zone sone the tropic amazon niger ond and co congo i ngo ore are too hot the mackenzie and the siberian rivers are too cold for or the favorable growth of towns the nile valley alley be yond calro cairo Is a mere inere strip of green from 10 15 to 30 miles wide between two burning des erts the hwang Is too variable in its habits to encourage navigation or river ports from tile the earliest times these long rivers have furnished high roads for th the e exploration of continental interiors nero sent tin an expedition to discover the he headwaters of the nile which failed to reach its objective object le lius sian penetration of siberia followed the great river beds the amazon and tile the congo are still highways of discovery head reaches of the yangtze are yelled veiled in asiatic obscurity ity the niger was the river of romance in ibe the great days of alm im bulau the histories of the worlds river basins have peon been the til story of tile the worlds empires A grea great t river Is both a roadway and a source of life menace of thi the mississippi although north america cork can claim only twi of the worlds dozen longest rivers it possesses in the mississippi BlIsso missouri url the longest of them all tills magnitude of the miss mississippi Is becoming more and more of a menace because each hood flood seems grea greater t er than the preceding one why this his t should be true tins lias been a problem aroble m to some laymen lawmen but one of tile the c chief alef factors Is plain enough it la Is the us usually ual Y hnud able effort ot of amei americans leans to develop and nd build up their country aside from the fact that several decades ca des ago there were fewer people living in slid and fewer dollars invested ln ested ln in the regions subject to overflow in the lower mississippi valley tile the flood stages were actually lower to in those duya days they were ere lower to consider one im fact for the very good reason that then less water was fed into the is tributaries tributa ries in a glien given space of time forests and woodlands that do not now exist held a large part of the rainfall and fed it slowly into brooks and creeks and ahers irregularities la ili the lie ile of the land formed puddles that later e v ap orated or sent seat rills in tortuous tortu oui p paths achs that slowed up the runoff in late years a constantly increasing population lifts has been busy changing these conditions every tree cut ev ery cry roof built every street paved ev ery dra drainage llinge ditch dug and every cut cul vert constructed la in the vast area drained dral by the mississippi appi river BS tern tem has fins done its bit toward pouring rainfall more quickly into tile the great river rh er not only has man helped to put more water into the mississippi ills his works have helped to confine it there when de soto and ills his followers first knew the mississippi it spread out at each flood season over a wide area sometimes in its lower reaches it was 20 0 30 rind and even 40 miles wide the fact act that tile the flood waters spilled away at numerous places into swamps and lowlands kept the flood crest down in ili the fill lower river in 1717 threefoot three foot levees protected new orleans now they rise 25 feet or more above the city even as late ns as 1882 the highest flood stage at new orleans was 10 feet in 1022 it was above 22 feet one reason at least for this Is that more efficient levee maintenance for many hundreds of miles allies niong along the river has herd herded edthe the flood waters past new orleans as is well ns as other lower river points la in the regular channel levees protect vast areas more moie intensive development of tile the lowlands has made this levee system tem necessary now some square miles are dependent on the levees tor for protection breaks still occur and when they do they drain off some of the flood waters and so relieve in some measure the he strain on the banks farther down stream hut but it Is not the innocuous affair that it was in the days dais of de soto now towns and plantations tat ions railways rind industrial plants lie ile in the lowlands arid and any relief that flint a levee break may occasion to down river points Is at a cost of many lives and much valuable property on the whole a considerable qu quan an city of water finds its way from the lower mississippi through ia lavee y ee br breaks eaks and bayous the most important natural safety valve calvit Is the atchafalaya Atchafala ya river or bayou babou which flows away front from tile the mississippi at the mouth of the red river and finds its way directly to tile the gulf of mexico some 50 miles nest of new orleans in flood times tills this out flowing stream takes from tho the swollen mississippi as much as cubic feet of water each second an amount equal to more than half the average flow of the mississippi it Is because of such losses as tills this coupled with the much greater depth of the channel iannel il in the tower lower river that the flood stape stage can be between bentiv een 60 and 00 feet lit at memphis and vicksburg and only a little more than 20 at new or leans the mississippi river system Is truly a continental feature draining a aji lion iton and n quarter of the three billiou odd square miles odthe of the united states thirty of the 43 48 states send a greater or less contribution of water to this great stream the ninin main mississippi river Is more mois titan than 2500 2 BOO miles long while tha mississippi sis sippi missouri Is miles to n length the longest river over system in the world the great scale on which the mississippi Is built becomes evident when one considers the elnie required tor for floods to pass p ss down its course about thirty days are ro required for or the surging flood crest to 10 pass from tile the mouth of tile the ohio to new nely orleans and from ten days to two weeks frota from greenville was to draw orleans |