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NEW YORK STATE MUSEUM 



and on May 20tk the mean discharge at Rochester was 12,900 

 cubic feet per second. Flood discharges of these amounts are 

 sufficient to render farming operations impossible on a consider- 

 able portion of the flat area. On June 2, 1889, the discharge at 

 Rochester was about 20,000 cubic feet per second, and from per- 

 sonal observations on that day it is known that nearly the whole 

 flat area of the valley was flooded. The answer to the question as 

 to the value of the annual overflow is, therefore, that in the case 

 of the Genesee valley, the May overflow comes at such a time as to 

 do only injury, without any opportunity to realize what would be, 

 if the inundation came only in March or April, a great benefit. 



The cash value then of so regulating the flow of the river as to 

 do away with the May overflow can be estimated as an average of 

 80 square miles, at say $40 per acre, or the increased valuation of 

 the whole area would be about $2,050,000. 



Moreover, the flats above Rochester are a further benefit to the 

 lower river by reason of an immense storage of ground water 

 therein, which, as the flood level subsides, gradually runs out with 

 the result of greatly decreasing the period of extreme low water. 



Again, in case of excessively heavy rains, in the middle of the 

 summer, from the effect of which the river channel is temporarily, 

 partially or wholly filled, such an amount of water is stored in 

 these flats as to keep the river comparatively well up during the 

 fall. 



This actually happened in the season of 1893, when on August 

 29, 1893, there occurred a rainfall of nearly three inches over the 

 whole catchment area in a period of about 12 hours, which pro- 

 duced a flood-flow of 5800 cubic feet per second at Mount Morris 

 and 3800 cubic feet at Rochester, an amount of water sufficient 

 to partly fill the channel between these two places, but without 

 any overflow of the adjoining flats. Previous to this heavy rain- 

 fall the mean flow at Rochester had been for a month about 300 

 cubic feet per second. At Mount Morris it had not averaged, for 

 the same period, more than 125 cubic feet per second. The effect 

 of this rain on the ground water of the flats is strikingly shown by 

 comparing the flows at Mount Morris and Rochester, when it will 

 be found that on September 3 the flow at Mount Morris was again 

 down to 200 cubic feet per second, and remained below that figure. 



