Agenda - 10-07-1991 - Laserfiche WebLink

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cific example of how a healthy riparium neu- tralizes pollution. They discovered that ripar- ian substrates quickly remove ammonium from springwater. They suggested that micro- bial activity, rather than adsorption, was the more likely cause of ammonium uptake. This example underscores why feedlots should be separated from streams by a riparian buffer strip. Factors that affect the efficiency of riparia to neutralize pollution in run -off include pol- lutant load, width of the buffer, slope, resis- tance to flow, infiltration capacity, vegetation species, and ability of the "soil to hold moisture (Peterson et a1. 1987, Phillips 1989a). 3 From a cost - benefit point of view, healthy riparia pay for themselves. In Sweden, the monetary value of nutrient retention by riparia equals the cost of building a water treatment plant, the cost in agricultural produce, or the going rate for land as farmland (Peterson et al. 1987). In summary, riparia are ecologically im- portant because they reduce riverbank erosion, enhance fish habitat, contribute nutrients and energy to the stream, serve as wildlife refuges, provide dispersal corridors, promote fertility of the floodplain, and safeguard the water quality of the River's mainstream. And yet these valu- able ecosystems need help. Riparia Under Siege In the early 1900's, Appalachia's riparia were being raped, causing streams to be un- dercut and to fill with silt (Glenn 1911). Large - scale changes of native riparian vegetation were largely complete by the 1930's (Petersen et al. 1987). Of America's 123 million riparian acres within the 100 -year floodplain, only about 23 million remain now in semi- natural con- dition (Hunt 1988). Compared to other rivers in the mid -At- lantic region, the Cacapon's riparia are in fair shape, but they could still use more protection and rehabilitation. Local threats include all - terrain vehicles, logging, land development, and cattle herds. Ideal Riparia Riparia should be wide enough to filter and ameliorate run -off, as I described above. Rec- ommended widths vary from 25 to 250 feet (Jones and Battaglia 1986, Kundt 1988, Wehnes 1989, Phillips 1989, Gore and Bryant undated). Considering this variation (mean = 104 ft., range = 25 -250 feet), and the Cacapon's soil and slope characteristics, I recommend 100 feet as a general width for initial consideration, to be adjusted according to local circumstances. I am currently counseling .two land developers along the Cacapon to meet this goal. In addition to having a minimum width, a riparium should contain no buildings, mini- mal bank erosion, no failing banks, and a natural riparian plant community that in- cludes trees, shrubs, and thick leaf litter (Jones and Battaglia 1986, Wehnes 1989). Aerial view of a rlparium that is too thin for optimal river protection.... but better than nothing. a �•s: y�w1 14. v%, : -- .`err `fir PIZ