urs 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.| Obs