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of materials,and septic systems are typically BLUFFS AND STEEP SLOPES local ordinances apply specifically to wetlands
<br /> prohibited or restricted within buffer areas. The steeper the slopes around a stream orwa- independent of their shoreland status.
<br /> Roads and stream crossings,stormwater or ter body,the greater the potential for erosion As with other types of buffers,greater
<br /> drainage ditch outfalls,and utility structures and,in extreme cases,slope failure.A number width increases effectiveness.While much of
<br /> may also be regulated to manage erosion and of state regulations apply to steep slopes,typi- the sediment and nutrients are removed within
<br /> reduce runoff, cally defined as greater than 20 to 25 percent, the first 15 to 30 feet of the buffer,a width of
<br /> Where some state regulations and local within the defined shoretand area.Maine's 30 to loo feet is recommended for more con-
<br /> ordinances primarily restrict clearing,others in- shoreland management standards specify that sistent removal of pollutants.The narrower the
<br /> clude site-specific mitigation requirements.For in areas with slopes of 20 percent or more,the buffer,the.more likely it is to become saturated
<br /> example,Georgia requires mitigation as part setback for roads and other impervious sur- with sediment and nutrients overtime,reduc-
<br /> of a streambank buffer variance approval.The faces must be increased 10 feet for every five ing its effectiveness(McEtfish eta[.2008).
<br /> state's Department of Natural Resources'buffer percent increase in slope above 20 percent. According to a detailed study of wetland
<br /> mitigation guidance states:"A buffer extending Wisconsin's shoretand standards prohibit and stream buffers by Boulder,Colorado,the
<br /> out from a stream serves three main functions: construction on slopes steeper than 20 percent optimal width for a wetland buffer will depend
<br /> hydrologic,water quality,and aquatic/buffer over a 5o-foot horizontal distance.Minnesota on its desired function and local condition.
<br /> habitat protection"(Georgia Department of defines"bluffs"in shoretand areas as slopes Research points to recommended widths that
<br /> Natural Resources 2010).And there are sepa- rising at least 25 feet from the shoreline with a range from 50 feet to reduce sediment loading
<br /> rate mitigation requirements for each function. grade of 30 percent or more over the lowest 25 to as much as 300 feet for wildlife habitat.For
<br /> Applicants must address hydrologic func- feet.Buildings must be set back at least 30 feet practical purposes,however,it often makes
<br /> tions by meeting minimum stormwater man- from the top of a bluff,and no structures other more sense to establish a"zoned"system:an
<br /> agement standards that reduce downstream than staircases and landings are allowed on inner buffer with a fixed or average width and
<br /> bank and channel erosion and capture runoff the face of the bluff or within 20 feet of the top. a second or third zone outside it with progres-
<br /> from the first 1.2 inches of rainfall to ensure A simpler approach is to specify that sively less restrictive requirements.
<br /> an 8o percent reduction in total suspended slopes over 25 percent do not count toward the Boulder's current overlay district stan-
<br /> solids(TSS).They must address water quality required width of a buffer(Wenger and Fowler dards are based on an evaluation and classifi-
<br /> functions by implementing on-site best man- 2000). cation of wetlands and other water bodies as
<br /> agement practices that address common post- "high-functioning"or"low-functioning,"with
<br /> construction pollutants other than TSS.And WETLAND BUFFERS different standards for each(§9-3-9).A 5o-foot
<br /> applicants must address aquatic habitat func- Wetlands are a distinct class of water bodies buffer divided into 25-foot inner and outer
<br /> tions by meeting the requirements of a U.S. with many different water regimens,depend- zones is required for high-functioning water
<br /> Army Corps of Engineers Section qoq Permit, ing on whether they are flooded or saturated bodies,while low-functioning water bodies
<br /> or,if that permit is not required,by purchasing year-round,seasonally,or periodically.They (constructed stormwater ponds,for example)
<br /> mitigation credits, provide many benefits,from flood control to require only a 25-foot outer buffer zone.Veg-
<br /> groundwater recharge to wildlife habitat,and etation removal and most land-disturbing ac-
<br /> STRUCTURE SETBACKS AND these benefits can only be sustained when tivities are strictly limited within the inner zone.
<br /> IMPERVIOUS COVERAGE wetlands are surrounded by protective upland Plymouth,Minnesota,a large community
<br /> Most buffer regulations do not allow primary buffers.According to McElfish eta[.,"Relying in the Twin Cities metropolitan area,uses a
<br /> structures within the buffer zone closest to on regulations and conservation measures that similar approach.After inventorying all its wet-
<br /> the water,although small accessory structures deal only with the wetland is like trying to oper- lands,the city adopted an ordinance that ctas-
<br /> such as gazebos,decks,and boathouses may ate a municipal swimming pool without any sifies them by resource value,from"low"to
<br /> be allowed.Greater setbacks for primary struc- attention to the pipes,the deck,the lifeguard "exceptional,"and establishes variable buffers
<br /> tures are often required, stations,and the condition of areas draining around them(§21670).Buffers range from an
<br /> For example,Wisconsin requires a set- into the water"(zoos). average of 25 feet and a minimum of to feet for
<br /> back of 75 feet from the shoreline,although an Some state shoreland programs and the lowest quality to an average of 75 feet and
<br /> average of existing setbacks with a minimum of local ordinances address wetlands that are a minimum Of 50 feet for the highest quality
<br /> 35 feet may be used in developed areas.New hydrologically connected to lakes,streams, wetlands.Structures must be set back at least
<br /> Hampshire requires a minimum of 5o feet,ex- or tidal waters,but do not apply to isolated 15 feet from the outer edge of all buffer strips.
<br /> cept in certain urban areas,and Maine requires wetlands.For example,under Wisconsin's Plymouth's ordinance specifies that veg-
<br /> from 75 to 100 feet, shoretand program,communities must adopt etation within the buffer strip,where accept-
<br /> Impervious coverage is also regulated Shoreland-Wetland Zoning Districts that ap- able in quality,must be retained.Acceptable
<br /> within the broader shoretand zone.Most of ply to all wetlands of five acres or more within vegetation includes either a continuous,dense
<br /> the regulations surveyed specify a maximum the designated shoreland zone(Administra- layer of perennial grasses or an overstory of
<br /> Of 15 to 20 percent impervious coverage,ex- tive Code NR§117.05).Uses within the overlay trees or shrubs with at least 8o percent canopy
<br /> cept in highly developed areas or in conjunc- may include farming or forestry,but must not closure;both must have been unbroken or un-
<br /> tion with an approved stormwater manage- include"filling,flooding,draining,dredging, cultivated for at least five years.Invasive plant
<br /> ment plan. ditching,tiling or excavating."In other cases, species such as reed canary grass or purple
<br /> ZONINGPRACTICE 9.16
<br /> AMERICAN PLANNING ASSOCIATION Ipage5
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