Hobbs has suggested that the waters of the Housatonic may have been
ponded at a point near West Redding until they rose high enough to
overflow into the "fault gorge" below Still River Station, thus giving
the streams of the Danbury region an outlet to the Sound by this
route. This hypothesis calls for a glacial dam which has not been
found. It is true there are glacial deposits in the Umpog valley south
of Bethel. The Umpog flows as it does, however, not because of a
glacial "dam" but in spite of it. The river heads on rock beyond and
above the glacial deposits and picks its way through them (fig. 7).
Drift forms the divide at the western end of Still River valley beyond
Mill Plain, but the ponded water which it caused did not extend as far
as Danbury (see discussion of Still-Croton valley). The Sugar Hollow
pass is also filled with a heavy mantle of drift, but the valley is
both too high and too narrow at the col to have been the outlet of the
Housatonic.
It might be assumed that just previous to the advent of the ice sheet
Still River headed south of its present mouth and flowed southward. In
this case the Still, when reversed, should have overflowed at the
lowest point on the divide between it and the Housatonic. It should
have deepened its channel over the former divide, and the result would
have been a gorge if the divide were high, or at least some evidence
of river cutting even if the divide were low. On the contrary, Still
River joins the Housatonic in a low, broad, and poorly drained plain.
The existing relief is due to the uneven distribution of drift. The
river is now cutting a gorge at Lanesville, but the appearance of the
valley to the west indicates that glacial deposits forced the river
out of its former bed (fig. 6) and that no barrier lay between the
preglacial Still River valley and the Housatonic Valley.