HYDROLOGY OF NEW YORK 



489 



channel is characterized by breadth and shallowness, with abrupt 

 changes of width and depth. This condition has been brought 

 about by the fact that the river approaches Elmira with a high 

 velocity, due to rapid descent for some miles above. It therefore 

 reaches the city loaded with sediment and moving large amounts 

 of detritus along its bed, but on reaching the flatter grades the 

 velocity is checked and the stream is no longer able to move this 

 material, which is left in the channel, gradually accumulating 

 with each successive flood. The shoaling of the channel, due to 

 such accumulation of material, encourages the erosion of banks, 

 with the result that the channel increases in width and becomes 

 shallower. During the flood of 1889 the river rose to a hight of 

 14 feet above low water mark, and a number of floods since that 

 time have approached this in severity. In March, 1902, about 

 thirteen hundred acres within the business and residence portions 

 of the city were inundated and the flood damage in that year has 

 been estimated at $155,000. 



Mr Collingwood prepared five alternative plans for flood pre- 

 vention, differing in the extent of protection to be secured and 

 the permanence and character of the improvement. The first of 

 these is estimated to cost $700,000; the second, $640,000; the 

 third, $376,000; the fourth, $336,000, while in the fifth scheme 

 an immediate expenditure of $133,000 is suggested, with moder- 

 ate annual expenditure until the desired result is finally reached. 



In this connection, Mr Collingwood suggests that the city 

 should buy its own dredging plant. The total cost of a suitable 

 plant would be about $25,000. In order to prevent the gradual 

 filling up of streams, raising them more and more with each 

 flood, Mr Collingwood suggests that the material should be taken 

 from the bed of the streams. 



Without knowing the condition fully, the writer doubts 

 whether any scheme of partial dyking on Chemung river can be 

 permanently effective. The whole river should be considered be- 

 fore any actual work of construction is undertaken. 1 



^he facts in regard to floods at Elmira Lave been obtained from the 

 Report on the Protection of the City of Elmira, N. Y.. against Floods, by 

 Francis Collingwood. dated February 12. 1890. The balance of the infor- 

 mation in regard to floods on Chemung river is from the Report of the 

 Water Storage Commission. 



