Beavers

Continued from Riparian Community
Bates (1963) studied the impact of beaver on stream flow in Red Butte Canyon. The vegetative cover was affected for approximately 91 m (298 ft) on either side of the portion of the stream in which the beaver were active, and sediment deposited behind the beaver dams in the canyon varied from 0.6 to 2.4 m (2 to 8 ft) in depth. He also noted that the small alluvial plains formed by the sediment made it apparent that during periods of high runoff, and perhaps during normal flow, the dams allowed the retention of quantities of suspended materials. Scheffer (1938), in a report on beaver as upstream engineers, ascertained that two beaver dams retained 4468 m3 (157,786 ft3) of silt. It is not known whether an actual count of the number of beaver dams in Red Butte Canyon was ever made; but the environmental change effected by their ultimate displacement during the 1983 flooding of what had to have been enormous quantities of sediment has been significant. The removal of all inactive beaver dams has inevitably led to the elimination of or significant reduction in the density of some 55 species of typically wetland plants from once marshy areas within Red Butte Canyon. For example, in 1990 it was noted that in an area which once supported a
nearly pure stand of closely spaced cattails (Typha latifolia) covering approximately 0.25 hectare (0.62 acre), only a few scattered clumps remained. According to Frest Service personnel, these losses would not have been as severe had the beaver dams been active during flooding. Species in teh following genera are among those undoubtedly affected: Eleocharis, Scirpus, Juncus, Agrostis, Catabrosa, Deschampsia, Betula, Cicuta, Heracleum, Rudbeckia, Solidago, Babarea, Cardamine, Nasturtium, Rorippa, Lonicera, Cornus, Trifolium, Mentha, Nepeta, Lemna, Epilobium, Habenaria, Polemonium, Polygonum, Rumex, Aconitum, Ranunculus, Geum, Ribes, Salix, Mimulus, Veronica, and Urtica.

The U.S. Forest Service, Salt Lake Ranger District, requested the Utah Division of Wildlife Resources to reintroduce the beaver during the summer of 1991. It is hoped that with time the plant diversity typically associated with beaver dams will be reestablished.