HYDROLOGY OF NEW YORK 



435 



heaviest rainfall. In case there happens to be gagings of the 

 stream, the maximum runoff may be obtained from the gagings, 

 but thus far there are gagings of comparatively few of the New 

 York streams, and probably the flood-flow will require to be com- 

 puted. As to just how this is accomplished is foreign to the 

 purpose of this report, but it may be simply stated that there is 

 no special difficulty, provided that the data of catchment and 

 rainfall, together with the steepness of slope, length of catchment, 

 etc. are known, in computing a flood-flow from which a bridge 

 opening may be ascertained that will be large enough to carry 

 the maximum flood. 



Lack of data a source of difficulty. One difficulty in design- 

 ing regulation works arises from lack of data and in order to 

 render data of this character accurate within 2 or 3 per cent 

 there should be a record about thirty years long. Such a record 

 should include rainfall, maximum, or flood-flows, and minimum, 

 or low-water flows. In this way only can accurate knowledge of 

 the regimen of streams be gained. 



River conservancy in England. Germany and France. In 

 England, largely due to the prevalence of the common law rule 

 that every riparian proprietor owns to the thread of the channel, 

 river conservancy has not made the progress which it should. The 

 taxpayers have generally insisted that all who are to be taxed 

 have a voice in determining the kind of regulation to be carried 

 out. The result is that many important works have not been 

 undertaken, and on many streams the work has been carried 

 out piecemeal, thus greatly increasing the expense, with ineffectual 

 results. 



In Germany the system is quite different. Here the State 

 assumes control of the main and navigable rivers, defraying the 

 expenses of their management out of tolls collected from those 

 using the streams for navigation, mill power and other purposes. 

 The State claims absolute ownership in the waters and prevents 

 any interference, even with tributary streams. In. some cases 

 the riparian owners may combine for purposes of draining lands 

 and flood protection. On application to the government they are 

 constituted a conservancy authority, armed with powers to compel 

 those who fail in their duty to construct the necessary protection 



