Show r M SS 0 w SS tf its Z 4 K ma K 4 K S Z MK j 1 gg iw 1 l H aih ayt aa cf is A g S flood waters water raging through a break in 41 levee prep Proc areil aby by the th nations Xii donai geoco ahto S society 1 Y washl VV ath D C played favorites ju in apportioning anthe NT the great rent rivers of 0 the wo ild of the dozen largest sf x tire are in asia and three in airl africa cal leaving only three for the two continents of the new world and among the twelve lenders europe and australia are B wholly holly the T he longest single river Is the nile measuring some miles from head to mouth the nile Is further distin in that it has haa no tributaries tributa ries for or the last 1500 miles of its course to the sea during this stretch its waters are considerably reduced in volume by evaporation and irrigation so that it grows grow instead of larger toward its mouth other african rivers amons the length scoring twelve are the niger and the con bonso conso 0 o both fod fed by the lie tropical rains of hot regions near the initiator equator in a general way they more nearly clearly 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 nad add lena flowing north into the arctic ocean and the amur emptying into an arm of the pacific the other two are the yangtze and hwang or Yellow river of china these twelve river basins represent the greatest variety of climate and civilization the amazon and the gongo flow through lush equatorial jungles inhabited by bv birds of brilliant plumage wild animals and savage tribes while the mouths months of the ye elsel and the lena are above the northern timber line and their valleys support the sparsest population the mississippi and 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 Is still a frontier stream five of the dozen rivers flow to the north these are the nile mackenzie ob and lena tile the mississippi rind and niger flow south the amur yangtze Yang tze hwang and amazon run rua eastward only the congo points toward the west difference in floods all these streams overflow their banks fit at intervals but the results are strangely different in the ense case of the mississippi and the yangtze Yang te tze floods are national disasters bringing untold suffering to millions the annual overflow of the nile with resulting fertilization liza tion of the valley by the deposit of fit silt I 1 the source of the wealth of agypt the hwang or yellow river from its habit of overflowing its banks aid changing its entire course at in la Is known as the scourge of alna the amazon and the congo lie ile al most under the equator and the oth er ten longest rivers are in the northern hemisphere four flow into the arctic ocean A reason Is not far to seek the greatest land mashes are in the northern half of the world and without large land arena areas long are impossible the smaller continents of australia and r europe drope are not represented in the dozen similarly the reason for the longest rivers alws flowing to the north and east la Is that the longest continental slopes extend in those direct directions long the yangtze and the mississippi are lined with wealthy cities far largely gely because of their location in the temperate zone one the tropic amazon niger and coh congo a fire are too hot the mackenzie and the siberian rivers are too cold for the favorable growth of towns the nile valley beyond cairo Is a mere strip of green from 15 to 30 miles wide between two burning des erts the Is too variable in its halls to encourage navigation or river ports from the earliest times these long rivers have furnished high roads for the explore exploration tion of continental ingerl ors nero sent seat nn expedition to dig cover tile the headwaters of the nile which failed to reach its ita objective russian penetration of siberia followed afie great firc at river bd the amazon amaon and tile congo tire are still hl highways h of 0 discovery fiend alend reaches of the yangtze are veiled in asiatic obscurity ity the niger was wai the river alvar of romance in the great days daya of tim im bi balita lita tho the histories of tile the river baglai have bern the that history of tile the worlds I 1 empl empires res A great river la Is bolli a roadway and a source of life monaco of cf th thi mississippi Alth north america enn can claim only tw two of tho the worlds dozen longest rivers it possesses in the mississippi missouri the longest of them all tills this magnitude ot of the mississippi la is becoming inure ditore and more of a menace because each good flood seems greater than the preceding one why this should be true lias has been a problem to some laymen but one of the chief factors Is plain enough it Is the usually laudable effort of 0 americans to develop and ad build up their country aside from the tact fact that several decades ago there were fewer people ity ins ing and fewer dollars invested in the re regions subject to overflow to in the lower mississippi valley the flood stages were actually lower in those days they were lower to consider one important fact tor for the very good guo dreason reason that then less water was fed into the is tributaries tributa ries in it a given space pace of time forests andi and I 1 woodlands that do not now exist held a large part of the rainfall and red fed it slowly into brooks and creeks and rivers irregularities in the lie ile or of the land formed puddles that later evaporated e I 1 it or sent rills in tortuous p paths achs that slowed up the in late years a constantly increasing population has been busy changing these conditions every tree cut every roof built every street paved every drainage ditch duz dug and every culvert constructed in the vast area drained by the ulissis mississippi appi river system has done its bit toward pouring rainfall more quickly into the great river vot not only has maa helped to put more water into the mississippi his works have helped to confine it there when de soto and Ms his followers follone rs first knew the mississippi it spread out 0 ut at each flood season over a wide area sometimes in a its lower deac reaches lies it was 1 20 0 30 and even 40 miles wide the fact that the flood waters spilled away at numerous places into swamps and lowlands kept the flood crest down to in the lower river in 1717 11 17 threefoot three foot levees protected new orleans now they rise 25 feet or more above the city even as late as 1882 the highest flood stage at new orleans was 10 16 feel in 1922 it was above 22 feet one reason at least for this Is that more efficient levee maintenance for many hundreds of miles along the river has herd herded edthe the flood waters past new orleans as well as other tower lower river points in the regular channel levees protect vast areas area store more intensive development of 0 the lowlands has made this levee system necessary now some 1 square miles are dependent on the levees for protection breaks still occur and when they do they drain off some me of the flood waters and so relieve in some mea measure sture tin strata strain on the banks farther down stream but it Is not the innocuous affair that it was in the days of de soto now towns and plantations tat ions railways and industrial plants lie he in the lowlands and any tellef relief that a levee break may occasion to down river points Is at a cost of many lives and much valuable property on the whole a consid considerable emble quantity of water finds its way front from the lower mississippi through lavee laree breaks and bayous the most important natural safety valvil valve la Is the arch atchafalaya Atchafala afalava ya river or which flows away front from the mississippi at the mouth of the red river and finds its way directly to the gulf of some 50 miles west of new orleans in flood times this out flowing flowen stream takes from the swollen mississippi as much as cubic feet of water each second an amount equal to more halt half the average flow of the mississippi it Is because of such losses as this coupled with the much greater depth of the channel in the lower river that the flood stage can be between 50 and 60 6 feet nt at memphis and vicksburg and only a little more than 20 1 0 at new orleans the mississippi river system Is truly a continental feature draining a md flon 1100 and a quarter uart er of the three odd add square miles of the united states thirty of the 43 48 states send a greater or less contribution of water to this great stream the main mississippi river Is mote moia than 2500 nilles allies long iong while the missouri Is 4 miles in length the longest river system in the world the great scale on which the mississippi Is built becomes evident ibert oce ace com considers iders the time required for floods to pass down its course about thirty days art are required tor for the surging flood crest to pass from the lie mouth of the ohio to new orleans and from ten days to two weeks from was to orleans |