HYDROLOGY OF NEW YORK 



433 



3) In order to protect the adjoining country from tidal inunda- 

 tion, it Avill be necessary to construct on either bank, dykes at 

 such distances that at ebb tide the force of the river will be 

 sufficient to carry out to sea the silt, etc., deposited during the 

 inflowing of the tide. 



The foregoing principles of river regulation are general in their 

 character, and apply in some degree to every river in the United 

 States. 1 



In regard to the definition of river conservancy as given on a 

 preceding page, it may be mentioned that the third head — the 

 culture and preservation of fish — has already been fully cared 

 for by the Forest, Fish and Game Commission of this State, and 

 in regard to the second head — the maintenance and regulation of 

 streams for navigation — this phase of the subject has been under- 

 taken by the Federal government and is therefore not specially 

 considered here. The first head — the preservation and improve- 

 ment of a stream for domestic, sanitary and industrial purposes 

 ■ — the fourth head — the effectual drainage of the district through 

 which the stream runs — and the fifth head — the abatement of 

 injury to lands by floods — are specially considered. The three 

 heads are interrelated and the discussion may proceed without 

 further special subdivision. 



Flood overftoics not necessarily injurious. Flood flows, when 

 occurring either late in the fall or early in the spring, are not 

 only not necessarily injurious, but may be a source of consider- 

 able benefit to agriculture. Streams carry, when in flood flow, 

 a large amount of silt which is valuable for manure, which 

 enriches land, and when the inundation is annual, it may be a 

 source of unending fertility. To cite one case, the river Nile 

 has maintained the fertility of its valley from time immemorial 

 from this source. The same thing is true on the Mohawk and Gen- 

 esee rivers, and many other streams of this State. 



It is also true that floods in the late spring or early summer, 

 after crops have been planted, may be a source of very serious 

 damage. During the summer of 1902 very serious floods occurred 

 in the month of July. Probably the damage from such floods in 



ir The Regulation of Rivers and Waterways, With a View to the Prevention 

 of Floods, by Gustav Ritter von Wex, Proc. Inst. C. E., Vol. LXIX. p. 323. 



