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NEW YORK STATE MUSEUM 



Had the same precipitation which occur red in Allegany county oc- 

 curred on the northern portion of the catchment area with reason- 

 ably high water from the southern district, the flood wave would 

 not have been elongated as it was by its flow through the alluvial 

 valley north of Mount Morris, and as a result the wave would 

 have been shorter but with a higher maximum discharge. 



This liood of July is unique in the matter of the date of its 

 occurrence. The other great Hoods have occurred in March or 

 April, with minor severe floods occurring later. Occurring, as 

 this did, in July, with the crops well advanced toward maturity, 

 the resulting damage was greatly in excess of what would have 

 occurred under similar conditions in the early spring. The 

 destruction of crops was in itself serious. But it was a greater 

 disaster to agricultural interests that the season was then too far- 

 advanced to permit of replanting. 1 



The effect on floods of Genesee river flats. Considering Genesee 

 river as a whole, the following conditions govern : Between Roch- 

 ester and Mount Morris and between Mount Morris and Dans- 

 ville. in the broad valley of the Canaseraga creek, there are ex- 

 tensive flats, amounting for the whole to from 60 to 80 square 

 miles. The effective catchment area at Rochester is 23G5 square 

 miles, as against 1070 square miles at Mount Morris. The por- 

 tion of the catchment area below M'ount Morris also contains 

 Honeoye, Canndice. Hemlock and Conesus lakes, which altogether- 

 provide a large volume of surface storage, while above Mount 

 Morris there are few flats and only one small lake (Silver lake). 



There arc extensive flat areas in the catchment of Black and 

 Oatka creeks, which are tributary below Mount Morris. 



The preceding discussion shows that the upper section of the Gen- 

 esee river has a rapid runoff and is subject to sudden and excessive 

 flood-flows. These flood-flows are received in the extensive flats 

 below M'ount Morris, where they are partially retained and grad- 

 ually delivered to the extreme lower river. The flood-flows at 

 M'ount Morris are greater than at Rochester, although the dry- 

 weather flow at Rochester is, proportionately to catchment area, 

 usually greater than at Mount Morris, The flats then act to de- 

 crease the flood-flow at Rochester and to increase the dry-weather 

 flow there. At Mount .Morris we may expect flood-flows of from 



5 Abstract from the Report of the Water Storage Commission. 



