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NEW YORK STATE MUSEUM 



A record of floods has also been kept on a number of other 

 important French rivers, as the Garonne, of which special studies 

 were made over forty years ago, the Loire and the Rhone, all of 

 which are the subject of special extended memoirs. 



A number of rivers of Germany and Austria have been studied 

 carefully for from 50 to 100 years, but in the United States sub- 

 stantially nothing had been done until about twenty years ago, 

 from whence it results that river conservancy is a new subject 

 here, many persons supposing that nothing has ever been done 

 anywhere. 



Definition of river regulation or conservancy. The term river 

 regulation or conservancy may be considered as comprising the 

 following objects: 



1) The preservation and improvement of a stream for domes- 

 tic, sanitary and industrial purposes. 



2) In the case of navigable streams, their maintenance and 

 regulation for navigation. 



3) The culture and preservation of fish. 



4) The effectual drainage of the district through which a 

 stream runs. 



5) The abatement of injury to lands by floods. 



The cause of floods is, broadly, excessive and irregular rain- 

 fall, although very heavy rainfalls may occur without causing 

 a flood. General statements of why this is so have been made 

 in the preceding paragraph regarding the river Seine. Indeed, 

 an investigation into rainfall shows that the intensity of floods 

 is due only very remotely to the amount of rainfall. On the 

 contrary, floods are very closely related to hight of ground 

 water. On Genesee river, in August, 1893, when as the result of 

 a, serious summer drought ground water was very low, a rainfall 

 of several inches only produced a slight flood of about 4000 cubic 

 feet per second, whereas in July, 1902, preceded by rain enough 

 to fill the ground with water, about the same amount of sud- 

 den rainfall produced a devastating flood of from 20,000 to 

 30,000 cubic feet per second. 1 Many other examples could be 



i Floods on Genesee river vary greatly in Intensity. A flood of from 

 30,000 to 40,000 cubic feet per second at Mount Morris is not likely to pro- 

 duce, owing to temporary storage on the flats, a flood of more than 20,000 

 cubic feet per second at Rochester. The preceding statement considers the 

 flood as measured at Mount Morris. 



