BD Credit 1:  Preservation of Aquatic Resources

1 - 3 Points

    INTENT

To preserve continuity and function of waterways and wetlands.

    REQUIREMENTS

Construction on sites adjacent to streams is commonly evaluated by floodway requirements: i.e., whether the site is within the 100-year floodplain. The actual impact of development is a function of the extent to which the development impedes fluvial processes, which include meander migration and other changes that need to be anticipated during the planning stage. Similarly, wetland impacts are commonly judged by affected acreage, rather than overall effects to function.

Wetlands and Stream Channels:  The meander belt of a waterway is roughly outlined by the outside extent of the existing stream channel and includes associated wetlands. Development within this belt would be restricted, unless it can be established by professional evaluation that the channel is entrenched (i.e., that meander migration no longer occurs). Channel armoring is discouraged but may be permitted tangential to the outside of the meander belt, if it does not hinder downstream migration of meanders. Armoring must be consistent with natural material exposed in stream banks.

Development within jurisdictional wetlands on any given site shall be avoided in order to receive maximum points.  If any development occurs in wetlands, steps must be taken to enhance wetland continuity and function and only 1 point can be achieved. Constructed wetlands must not only meet acreage requirements but must be demonstrated by professional evaluation to be consistent in function with patterns of existing regional wetlands. Consistency of function may include continuity with existing wetlands, unless the regional pattern is small, isolated wetlands (e.g., glacial potholes).

(2 points for placing development outside any wetlands and the meander belt;

    OR

1 point for demonstrating that fluvial processes are not impeded by any development within these zones)

Aquatic Habitat:  Development should enhance patterns of shading, introduction of woody debris, and other off-channel impacts to streams. Constructed or reclaimed streams should mimic regional channel patterns for similar streams, including channel geometry, meander wavelength, riffle and pool sequencing, and gradient. An aquatic biologist should evaluate potential aquatic effects of any instream improvements.

Constructed water features, primarily referring to off-channel self-contained ponds and small waterways are generally discouraged in the Greater Yellowstone region.  If considered, they must enhance function and continuity of existing wetlands and maintain water and sediment delivery to adjacent streams. Instream dams on perennial streams must be demonstrated to preserve seasonal flow patterns and sediment delivery. Constructed channels should mimic similar natural channel patterns.