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NEW YORK STATE MUSEUM 



of level country, invariably, if the banks consist of deposits of 

 earth or gravel, attacks them, the lighter particles being carried 

 away, the heavier being deposited in the bed of the stream, so 

 that in course of time its width increases while its depth de- 

 creases, and at the same time islands, sandbanks, bends, creeks 

 and by-channels are formed. 



In rivers thus left to nature, the fall, mean velocity and 

 force of the current are continually decreasing while the river- 

 bed is rising; this naturally raises the general water-level 

 relatively to the adjoining country, and exposes it to frequent 

 inundation, the effects of which are disastrous floods and the 

 formation of innumerable branches and by-channels which inter- 

 sect the whole country, flooding and swamping it at every rise 

 of the river, and rendering it in time unfit for habitation by 

 either man or beast. Instances of this kind are at the present 

 time to be met with in many parts of the world, notably in Asia, 

 Africa and America. 



In order to deal effectually with such cases, namely, to abate 

 the floods, and to prevent disasters accompanying them, as well 

 as the ultimate formation of trackless swamps, the following 

 procedure is recommended : 



1) A new channel following the course of the valley should 

 be carefully laid down by the superintending engineer, either in 

 a direct line or with easy bends, and when excavated, the entire 

 body of water should be admitted into this new channel, the old 

 bed and all by-channels being filled up. 



2) Having carefully determined — 



a) The discharge per second at low, mean high water level 

 of a cross-section of the river, either immediately above or imme- 

 diately below the portion to be regulated, and 



b) The increased fall which the new channel will afford; 

 then the sectional area of the new bed must be fixed, according 

 to approved hydraulic formulas, so as to allow of the passage of 

 either an ordinary or an extraordinary volume of wafer. 



3) The water having been admitted, the next thing is to 

 protect the banks by random rubble or by stone pitching in order 

 to prevent the action of the current injuring them, or forming 

 bends or creeks. 



4) After the completion of the above, the old river bed and 

 by-channels should be filled up, the land thus reclaimed should 

 by degrees be brought under cultivation ; in the same manner the 

 marshy tracts exposed hitherto to inundation, and fertilized by 

 the deposit therefrom, should be raised by a coating of rich soil. 



5) If exceptionally high floods still overflow the banks and 

 inflict loss and damage to the freshly cultivated valley, dykes at 



