Physiography and Topography
The Pequannock Watershed is located in the New Jersey Highlands, a subdivision of the Reading Prong in the New England physiographic province. A layer of folded sedimentary rocks of Paleozoic age forms a series of ridges and valleys in a prominent northeast-southwest alignment. Altitudes within the Watershed range from 1491 feet above sea level north of Canistear Reservoir to about 200 feet above sea level in lower areas.
The flat-topped ridges are studded with bedrock outcrops and the narrow valleys are filled with a variety of unconsolidated deposits giving evidence that the whole area was subject to glaciation. Several of the ponds, swamps and lakes in the Watershed were formed by glacial activity, including Echo Lake, Hanks Pond and Cedar Pond.
Topography is an important factor in determining the location of areas for conservation and development because unwise use of steeper slopes promotes increased runoff of water and erosion. Both of these may have adverse impacts on water supply systems and the general ecology. An analysis of slopes within the Pequannock Watershed shows a complete range of conditions from flat (0-3%) slopes, associated with swamps, floodplains and fields, to steep (25% +) slopes in areas such as Bearfort Mountain. Normally, slopes in excess of 25% are categorized by the private sector as difficult to develop. For the Pequannock Watershed Plan an extra measure of safety has been adopted. No slopes in excess of 15% will be developed.
Geology
A knowledge of the geology of the Pequannock Watershed indicates where ground water for wells may be expected to exist, where the heaviest structures can be supported by bedrock, and also contributes to an understanding of the way water moves through the Watershed.
Bedrock in the Watershed is primarily pre-Cambrian and gneiss with a band of sandstone and shale through the middle of the site running from the northeast to the southwest. Although there are some variations within the Watershed, the granite and gneiss found there are not ordinarily good aquifers (do not hold or transmit ground water well). The band of sandstone and shale running through the site however has had several wells with sustained high yields. This area may offer some opportunities to tap limited amounts of ground water for use within the Watershed where appropriate.
Deposits from glaciation range from boulders to rocks and gravel mixed with sand and clay and are associated chiefly with the rolling topography characteristic of the sandstone and shale band. Some of this is difficult to distinguish from alluvial deposits (those brought by the rivers) preceding the glaciation, for instance, along the Pequannock River. Recent alluvium is composed of fine silt and sand and is not more than 20 feet deep. The depth of bedrock generally varies from zero to 25 feet although the average is three to five feet deep.
As noted above, the bedrock underlying most of the Watershed has a variable but has generally limited ability to hold and transmit water. In addition, the soils there do not allow much percolation downward through them. Therefore, it is unlikely that any area within the Watershed constitutes a major aquifer recharge area or that development within the Watershed will have any affect on the water supply systems in nearby communities.
All the bedrock in the Watershed has the capacity to bear magnificent structures envisioned. The most important aspect of the Watersheds geology which must be taken into account in planning and development is the fact that water moving underground toward the reservoirs and streams runs along the top surface of the bedrock and that this flow should not be interfered with.
There are several old faults running east and west across the Watershed. These are no longer active and only restrict development to the degree that they have altered drainage patterns and offset valleys in the past. Some are visible from Route 23.