AVERAGE MONTHLY RUN-OFF (IN INCHES) OF THE GENESEE RIVER -(Continued). MONTH IN ORDER OF DRYNESS. 1896. 1897. 1898. 1904. 1905. TOTAL. Av. 11 YRS. Inches run-off. Inches run-off. Inches run-off. Inches run-off. Inches run-off. Inches run-off. Inches run-off. Sept., 0.16 Sept., 0.18 July, 0.45 Sept., 0.21 Sept., 0.25 0.31 4.75 0.432 0.44 Aug., 0.80 Dec., 0.54 Aug., 0.48 6.33 0.575 0.58 May, 0.49 7.25 0.659 0.60 Feb., 0.51 8.37 0.7€1 GENESEE STORAGE (FIRST STAGE). Increased power at present Genesee River Plants if Portage Reservoir be used solely for storage, and so regulated as to produce the most uniform rate of flow at Rochester. 800 cubic feet per second for entire year == 11.44 inches depth on watershed of 950 sq. miles. In this "First Stage" the discharge is supposed regulated wholly with a view to uniform flow and maximum power at Rochester--as might In the "Second Stage" the discharge of storage is supposed so regulated as to give best efficiency for a power station just below Portage- -T *The yield at Portage in an average year will be 1,030 c. f. s., against the mean dry year flow of 800 c. f. s. that could be drawn through sluices at a Note that whereas Mr. Rafter's report of 1896 proposed a uniform regulated flow at Rochester of 1,080 c. f. s. the above computation shows that GENESEE STORAGE (FIRST STAGE). Increased power at present Genesee River Plants if Portage Reservoir be used solely for storage. Average 6 mo. 264x74.782=19,738. The storage adds an average net 24-hour 7-day power of 19,738 h. p. for dryest 6 months, providing each of the above heads or falls is fully used. The above if used mostly in ordinary working hours or under a 40 % load factor would amount to nearly 50,000 horse power. Above is based on (min. flow in average year at Rochester of 1,900 c. f. s.), or 11.35 inches stored and released at Portage. (800 c. f. s. for entire year is equivalent 11.44" on watershed 950 sq. miles.) GENESEE RIVER STORAGE (SECOND STAGE), PORTAGE RESERVOIR. Increased power at present Genesee River Plants if constant flow of 700+100-800 c. f. s. be drawn from Portage Reservoir. Drainage area at Portage=950 sq. miles. 1-inch run-off per month from 950 sq. miles GENESEE RIVER STORAGE (SECOND STAGE) PORTAGE RESErvoir. Increased power on present Genesee River Plants if constant flow of 700+100=800 c. f. s. be drawn from Portage Reservoir. Or the storage adds an average net 24-hour, 7-day horse power for six dryest months of 8,752 H. P., if each of above falls be fully utilized. If concentrated in ordinary working hours, or under a 40 % load factor, this would amount to about 22,000 horse power added to the present resources of the stream over and above what is added at the new power site FLOOD CONTROL BY GENESEE STORAGE RESERVOIR. The chief purpose urged heretofore in proposing the construction of great storage reservoirs on the Genesee, first near Mt. Morris and later at the Portage site, has been the protection of the city of Rochester and the broad flat valley of the river lying between Mt. Morris and Rochester from the severe floods, which from time to time have inundated and endangered a large portion of the city, but in the report presented by Mr. Rafter, in the Report of the State Engineer for 1896 and as subsequently presented in the volume on the Hydrology of New York in 1905 and in sundry other publications, great stress has also been laid upon the increase of water power at sites within the city of Rochester, already developed and owned by private corporations, that would also result from the use of these reservoirs. The great floods from which Rochester has suffered most severely occurred on the dates named below on pages 196 and 197. The feature now of special interest is that these floods have occurred in spring, summer and autumn, in every month except August. So far as I can learn the estimates of cubic feet per second flowing given on this page and the next are very rough. Data From Report of Rochester Flood Commission of 1905. 1902, July 5th to 9th. From a heavy rainfall on ground saturated by previous heavy rains. Precipitation July 6th at Angelica 4.5 inches. Flood above Portage "heaviest ever known." Maximum rate of flow at Mt. Morris probably 40,000 cubic feet per second. Maximum rate of flow at Rochester only about 20,000 cubic feet per second. Great loss of growing crops in Genesee Valley due to flooding over flats. 1902, March 3rd. Mainly from melting snow. Total rainfall in 3 days previous about 1 inch. Less than maximum rate of flow at Rochester, about 38,000 to 40,000 cubic feet per second. Some cellars flooded and considerable overflow in various parts of city. 1896, April 4th. Maximum rate of flow at Rochester 35,000 to 36,000 cubic feet per second. Some cellars in Rochester flooded. Flats in valley from Rochester to above Mt. Morris covered. 1894, May 20th to 23rd. Maximum rate of flow at Mt. Morris 42,000 cubic feet per second. Maximum rate of flow at Rochester, 21,000 cubic feet per second. Flats between Mt. Morris and Rochester flooded. 1890, Sept. 10th to 13th. Maximum rate of flow at Mt. Morris 20,400 cubic feet per second. From 3 P. M. of 10th to 9 A. M. of 14th, no less than 3.5 billion cubic feet of water passed Mt. Morris. 1889, June 1st. Day following the Johnstown flood, water over the flats at Avon, Rush, etc. Maximum rate of flow at Rochester not above 20,000 cubic feet per second. Little or no damage done at Rochester. 1875, March 16th. Ice gorge at Clarissa street bridge, Rochester, setting water back in Erie canal and flooding certain districts. Maximum rate of flow at Rochester not above 25,000 cubic feet per second, except for an hour or two during passage of ice gorge, when it may have reached 35,000 cubic feet per second. Most serious flood ever known at Rochester. 1865, March 17th to 20th. Long continued cold weather and heavy snowfall followed by a sudden thaw accompanied by rain. Nearly the entire central portion of Rochester put under water and damages probably exceeded $1,000,000. Maximum rate of flow at Rochester estimated at 54,000 cubic feet per second. 1857, February 8th. Flood occurred which carried away piers of Main street bridge. 1835, October 23rd. Greatest flood ever known up to this time. Water on the Genesee flats 6 to 8 feet deep. Maximum rate of flow at Rochester estimated at 36,000 cubic feet per second. 1813, June 20th. Rained for three or four days about June 15th to 18th, and on June 19th, rain fell in torrents. "Seldom had such a storm been witnessed in the country." Colonel Rochester's sawmill carried away. "From 1865 to 1902, a period of thirty-seven years, no seriously destructive flood occurred at Rochester, although there were several at Mt. Morris " (p. 69, H. Com. Rept.). Immunity at Rochester was mainly due to storage over the flats above Rochester and lack of heavy rainfall at the critical time. The Rochester Flood Commission of 1905, concluded, p. 68, 66 Sometime there may be a flood of at least 60,000 cubic feet per second at Rochester." Conclusions Regarding Genesee River Floods. 1. Serious freshets caused by heavy rainfall may occur at Rochester and over the Genesee flats between Rochester and Mt. Morris at any time from March to October inclusive. 2. Twice in the past century, once in March, 1865, again in July, 1902, the rate of discharge at Rochester has been greater than existing river channel could safely convey and large areas within the city have been inundated, particularly in 1865. 3. The widespread inundation and great damage of 1865 were caused by a flood of much smaller volume than is likely to occur at some future time under a combination of the causes which have heretofore within the historic |