The airline distance from the bend in Rocky River at Sherman to its
mouth at the Housatonic is 2-3/4 miles, but the course of the river
between these two points is 15 miles, or 5.4 times the airline
distance. This is a more extraordinary digression than that of
Tennessee River, which deserts its ancestral course to the Gulf and
flows northwest into the Ohio, multiplying the length of its course
3-1/3 times. The fall of Rocky River between Sherman and its mouth is
240 feet or 16 feet to the mile, and were the river able to take a
direct course the fall would be 87 feet to the mile. The possibility
of capture would seem to be imminent from these figures, but in
reality there is no chance of it, for an unbroken mountain ridge of
resistant rock lies between the two forks of the river. This barrier
is not likely to be crossed by any stream until the whole region has
been reduced to a peneplain.
Measured from the head of its longest branch, Rocky River is about 19
miles long and falls 950 feet. Of this fall, 710 feet occurs in the
first 4 miles and 173 feet in the last 2-1/2 miles of its course. For
the remaining distance of 12-1/2 miles, in which the river after
flowing south doubles back on itself, the fall is 67 feet, or slightly
less than 5-1/2 feet to the mile (fig. 3, A).
[Illustration: ~Fig. 3.~ Profiles of present and preglacial Rocky River.
Elevations at a, b, c and i are from U. S. G. S. map.
Elevation at d is estimated from R. E. Dakin's records.
Elevations at e, f, g and h are from R. E. Dakin's records.
The U. S. G. S. figures for the same are enclosed in parenthesis.]
In tabular form the figures, taken from the Danbury and
New Milford atlas sheets and from reports of R. E. Dakin, are
as follows:
Miles Fall in feet per mile
Source to Sherman 4 177.5
Sherman to Wood Creek 8 6.25
Wood Creek to Jerusalem 4.5 3.8
Jerusalem to mouth 2.5 69.2
Near Jerusalem, where Rocky River makes its sudden change
in grade, there is an abrupt change in the form of the valley
from broad and flat-bottomed to narrow and V-shaped. The
profile of Rocky River is thus seen to be sharply contrasted with
that of a normal stream, which is characterised throughout its
course by a decreasing slope.