The Passaic Flood of 1903 | Page 2

the same time in different parts of the basin. For example, the gage-height records at Dundee dam show that the flood began to rise on October 8 at 6.30 a. m., and reached a maximum of 9-1/2 inches over the dam crest at 9 p. m. on October 10. Similarly, on Beattie's dam at Little Falls the flood began to rise at midnight on October 7, and reached its maximum at 2 p. m. on October 10, or about thirty-eight hours after the initial rise, the height of the water being 1.29 inches over the crest of the dam.
The flood rose on the highland tributaries as follows: On Ramapo River the flood crest passed Hillborn at about 10 a. m. on October 9 and reached Pompton, at the mouth of the river, shortly after noon of the same day.
The highest reading recorded on the Geological Survey gage at the feeder of Morris Canal, in Pompton Plains, was 14.3 feet, at about 6 o'clock on the morning of October 10. As this gage is read only once daily it is probable that this reading does not represent the height of the flood crest. Evidence shows that it passed this point on the previous day. Records of the Newark water department show that the flood on Pequanac River began to rise at Macopin dam on October 8 at noon, and rose rapidly to the maximum of 6,000 cubic feet per second at 4 p. m. on October 10.
No records are available with reference to the rise of flood on Wanaque River.
Observations made on Pompton Plains on the morning of the 11th show that Pompton River was well within its banks at that time; therefore the Ramapo, Wanaque, and Pequanac must have discharged their flood waters some time previous to this hour. The fact is important when considered in connection with the height of water in the main stream at that period. This observation was made only eighteen hours after the maximum height over Beattie's dam at Little Falls, and twelve hours after the flood crest passed Dundee dam. The conditions here outlined illustrate the rapidity with which flood waters are discharged from the Pompton drainage area, and the deterring effect of Great Piece Meadows upon the flood.
The rise of the flood on Rockaway River at Old Boonton was almost coincident with that on Pequanac River at Macopin dam. The maximum flow occurred fourteen hours later than the maximum on the Ramapo at Pompton.
The flood crest did not reach Chatham on upper Passaic River until the morning of October 11, or about twenty-four hours later than the flood heights in Pompton and Rockaway rivers, and about twelve hours later than the maximum over Dundee dam.
Adequate reasons for these differences in flood periods between neighboring points are abundant. They are apparent after a review of the physiographic conditions described in Water-Supply Paper No. 88.
The flood of 1903 was the immediate result of an enormous rainfall, and not, as is often the case in north temperate latitudes, the combined effect of rainfall and the rapid melting of accumulated snows. The records of weather-observation stations in northern New Jersey and New York fail to show, throughout their entire observation periods, as great an amount of precipitation in so short a period. The storm which was the immediate cause of the flood occurred principally between October 8 and 11. During that interval rain fell to an average depth of 11.74 inches over the Passaic Basin.
The Passaic Basin is fairly well supplied with storage facilities, which, under ordinary circumstances, would temper the severity of floods by holding back a large amount of water. In this case no such effect was produced, as the reservoirs, lakes, and ponds on the drainage area were filled, or practically so, at the beginning of the storm, and there was consequently no available space in which to hold back even an appreciable part of the run-off water. Over some of the dams in the highland region a comparatively small amount of water was being discharged at the beginning of the storm. Therefore, while these storage basins may have had a certain deterring effect upon the rate of flood accumulation, they could not, in the end, assist materially in preventing damages in the lower part of the drainage area.
PRECIPITATION.
The precipitation records for June, July, August, and September are given below:
Precipitation, in inches, in Passaic Valley and vicinity, June to September, 1903.
-----------------+--------------+--------------+--------------+------------ | June. | July. | August. | September. -----------------+--------------+--------------+--------------+------------ |Normal. |Normal. |Normal. |Normal. | Observed.| Observed.| Observed.| Observed. -----------------+--------------+--------------+--------------+------------ Highland region: | | | | | | | | Dover | 3.29 | 15.02 | 5.54 | 5.47 | 5.08 | 9.04 | 4.02 | 3.39 Chester | 3.48 | 12.80 | 6.42 | 7.59 | 5.16 | 9.35 | 4.60 | ...