FRIENDS OF EDGEWOOD NATURAL PRESERVE
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FRIENDS OF EDGEWOOD NATURAL PRESERVE
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EDGEWOOD'S FROG POND By Susan Sommers The Frog Pond, one of the most popular places on the Serpentine Loop, is a dynamic area. It is a vernal pool with wetland plants, damsel flies, Pacific Treefrogs, meadowlarks, rabbits, and foxes. Deer often refresh themselves with its cool water. The pool exists year after year due to the influence of combined geologic features: rock, soil, slope, and seismic activity. The serpentine rock formation, not far below the pool, is associated with fault zones and tectonic activity. Soils from the surrounding hills, including the greenstone from the central ridge, are noted for their low drainage quality. A small fault courses eastward from the San Andreas Fault system through Edgewood between the southern hill and the central ridge. As the water drains from the uphill regions of Edgewood, it flows via this fault and greatly slows as the slope flattens. Here water collects since drainage is reduced to the low percolation rates of the soils and the presence of the serpentine rock formation not far beneath them. The basin of the pool may have been increased by the development of the old "Service Road" (now part of the Serpentine Loop Trail) since portions of the road were elevated above the floor of the riparian corridor through which the road cut. During the 1980’s the County Parks Department installed a culvert to improve the road by the pool. The culvert has affected the pool; its basin has decreased in breadth and depth. By providing drainage under the road, the culvert has reduced the severity of erosion and lowered the drainage level so that less water collects for shorter periods of time before flowing on into the Crystal Springs Reservoir. Be that as it may, road or no road, culvert or no culvert, Edgewood’s Pacific Treefrogs will move from their shrubs and upper grasslands to the vernal pool in the serpentine meadows to sing their chorus in the pageant of spring. |
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