Agenda - Council - 05/22/1990 - Laserfiche WebLink

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I I I I I I I I I i I I I I I ! I I I The be~t solution to maintaining adequate wetland resources is to prevent disturbance to existin& natural basin~. When this is unavoidable, however, loss of nc'rural wetland basins can be at least partially offset or be compensated for b), construction of artificial basins. Based on our revie~ of recent literature on the subject, ~e recommend that the followin~ ~eneral design features be implemented, to the ex%eat possible, when constructing an artificial wetland basin' 1. The wetlan~ basin can be relatively small (0.5 acre), but, if at all possible, should be at leas: 1.0 acre in size. 2. A variable (rasher than an even-sided) shoreline should be constructed if at all possible since it ~ill increase the amoun~ of shoreline per unit area and. increase ~he waterfowl usage by providins isolated areas for feeding and loafing. 3. The bo=tom contour should be uneven and rolling, which ~ill produce a variable wa~er depth and allo~ for emergen~ vegetation growth on shallo~ areas ~hroughou[ basin. Water depth in shallo~ areas should be about 12-18 inches and about 3-& feet in the deepest areas. The shoreline area should have a gentle (10:l to 20:1) to provide for adequate vegetative grog:h, bu~ also can be variable :o provide small vegetative "fingers~ and open "bays' and thus more edge. Yegetation growin& in these shallower areas of ~he basin should produce vegetative islands and %hereby increase interspersion or edge habile:. A 50% open water and 50% vegetation coverage of the we:land (including the emergent vegetation around the shoreline) will provide the greatest species richness and diversity. A. The we=land should have a good clay sea! to prevent leakage. In addition, we recommend ~hat %opsoi! be placed on ~he bottom of ~he basin to provide a more suitable subs=rate for aquatic vegetation grot=h, which will quickly establish a detritus food chain and invertebrate abundance. We;land basins lined .only with clay no~-mally produce less vegetation, fewer invertebra;es and lower numbers of ~a%erfo~! ~nan ~hose lined ~i~h bo~n clay and topsoil. 5. On projects ~here existing we:tan~ are unavoidably impac~ed~ ~hen feasible, muck from existing wetlands should be placed in the bom:om of the newly-created basin. Tn. is would provide the basin ~ith a natural!y-occurring seed bank and other maueria! of high organic conten~. 6. lu may be desirable to construc~ one or nwo small earthen islands within some ne~!y-creaued wetland basins to increase diversity and provide an offshore nesting area for ~aterfo~! and other vii'~ 7. After construction, a layer of natural or domestic'hay should be placed on =be vet!and s~osura=e; this wi!! allow a de:titus food chain un become established more rapidly. $. Re-establishing and maintaining an upland vegetative buffer area around the perimeter of the newly-created wetland basin will provide nesting habitat and help to ensure optimum waterfowl produc=ion occurs on these areas, if mowing of the · vegetation around the ~euiand basin is necessa:?, iu should be deiaved "~ti! after Au~s= ~_ ~_~z =~ .... ~.~ possible to avoid disturbance to vaterfow!, uoiand, game birds and other ~i!d!ife, during ~he nesting season.