The Passaic Flood of 1903 | Page 6

and hours are given, while the figures for the 1902 flood represent flow determinations at six-hour intervals, beginning with the initial rise of that flood.
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U. S. GEOLOGICAL SURVEY WATER-SUPPLY PAPER NO. 92 PL. I
[Illustration: A. BEATTIE'S DAM, LITTLE FALLS, N. J., IN FLOOD.]
[Illustration: B. FLOOD-WATER LINES IN RESIDENCE DISTRICT, PATERSON, N. J.]
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Flood flow over Beattie's dam during floods of 1902 and 1903.
-----------------+------------+------------+ Date and hour. | 1903. | 1902.[A] | -----------------+------------+------------+ | Sec.-feet. | Sec.-feet. | Oct. 8. 12 p.m | 1,645 | 490 | 9. 6 a.m. | 4,235 | 700 | 12 m. | 8,560 | 1,350 | 6 p.m. | 15,755 | 2,120 | 12 p.m. | 23,927 | 3,540 | 10. 6 a.m. | 28,370 | 4,250 | 12 m. | 31,305 | 4,600 | 6 p.m. | 31,675 | 5,000 | 12 p.m. | 30,770 | 6,500 | 11. 6 a.m. | 29,840 | 7,600 | 12 m. | 28,950 | 8,250 | 6 p.m. | 26,960 | 9,000 | 12 p.m. | 25,530 | 10,200 | 12. 6 a.m. | 24,435 | 11,450 | 12 m. | 22,625 | 14,700 | 6 p.m. | 20,810 | 18,150 | 12 p.m. | 18,655 | 20,650 | 13. 6 a.m. | 17,930 | 22,200 | 12 m. | 16,190 | 22,700 | 6 p.m. | 14,900 | 23,400 | 12 p.m. | 13,615 | 23,300 | 14. 6 a.m. | 12,340 | 22,950 | 12 m. | 11,740 | 22,650 | 6 p.m. | 10,975 | 22,350 | 12 p.m. | 9,820 | 22,100 | 15. 6 a.m. | 9,180 | 21,150 | 12 m. | 8,330 | 19,900 | 6 p.m. | 7,700 | 18,900 | 12 p.m. | 7,005 | 17,350 | 16. 6 a.m. | 6,695 | 15,750 | 12 m. | 5,920 | 13,900 | 6 p.m. | 5,620 | 13,300 | 12 p.m. | 5,360 | 11,800 | 17. 6 a.m. | 4,855 | 10,650 | Below full bank | 8,900 | Do. | 8,500 | Do. | 8,100 | Do. | 8,200 | Do. | 7,000 | Do. | 6,250 | Do. | 5,900 | Do. | 5,300 | Do. | 5,200 | Do. | 4,900 | -----------------+------------+------------+ [Footnote A: At six-hour intervals.]
FLOOD FLOW OVER DUNDEE DAM.
The flood, as indicated by gage heights at Dundee dam, lasted from about 6.30 p. m. October 8 to about midnight October 18. Although the maximum recorded gage height was 19 inches higher than during the flood of 1902, the actual time during which the river was out of its banks was forty-five hours less than at the earlier flood. Examination of fig. 1 shows that the flood of 1903 was decidedly more intense than that of 1902, the maximum height being reached in 1903 in about sixty hours, while in 1902 the maximum was not reached until the expiration of about one hundred and twenty hours.
At Dundee dam the familiar break in the progress of the flood took place about thirty-five hours after the initial rise. It occurred before the time of the maximum gage height at the mouth of Pompton River, and there is nothing to indicate that it was caused, as has been claimed, by slack water from the Pompton flood being forced back into Great Piece Meadows. There is no doubt that a part of the Pompton flood was so diverted, but there was maintained throughout at Little Falls a steady pressure, which constantly increased to maximum. This flood check, at Dundee dam was observed in 1902, but it could not be shown to arise from the frequently mentioned phenomena at the mouth of Pompton River. It is important to prove or disprove this hypothesis. If it were found to be true, it could be advantageously taken into consideration in connection with measures for the prevention of flood damages. As the Pompton had no such effect upon the flood flow at Dundee dam in two consecutive historic floods, the writer is inclined to believe that the idea is entirely erroneous.
[Illustration: FIG. 1.--Comparative flood run-off at Dundee dam, March, 1902, and October, 1903.]
Since the flow curves in fig. 1 were drawn it has been found by careful observation that the depressions which occur in the rise of every flood over Dundee dam are probably due to the carrying away of the flashboards which are placed upon the dam crest in times of low water. A review of the gage heights recorded by floods for several years past shows that the break occurs when the height of water over the dam crest reaches from 40 to 60 inches. The flashboards used upon this dam are usually 18 inches wide, and as they are supported by iron rods, which are of approximately the same strength