[Ord. No. 19-2020, 6-8-2020]
Requiring structures and soil absorption fields to be set back
from the top of bluffs and ravines along Lake Michigan helps reduce
erosion hazards and related damages to structures and property. Compliance
with the regulations of this division does not guarantee or warrant
that development will be free from all erosion damage over the useful
life of a structure.
[Ord. No. 19-2020, 6-8-2020]
The minimum required bluff setback is based on the bluff recession
distance expected over a sixty-year period, plus the distance needed
to establish a stable slope, plus a minimum structure setback from
the edge of the computed stable slope, as follows:
(a)
The bluff recession distance for a sixty-year period must be
calculated using a minimum recession rate of one foot per year, unless
site-specific information justifying a greater distance is established
by the Community Development Director or Public Works Director. The
bluff recession distance must be measured from the toe of the bluff.
(b)
The distance required to achieve a stable slope must be based
on a ratio of one foot vertical distance to 2.5 feet horizontal distance.
The measurement must be made from the landward edge of the bluff recession
distance.
(c)
Soil absorption fields and structures, except those listed in the following Subsection (d), must be set back at least 100 feet from the landward edge of the stable slope distance.
(d)
Storage sheds, driveways, walkways, patios, and fences accessory
to a principal use are permitted within the bluff setback area.
[Ord. No. 19-2020, 6-8-2020]
All structures and soil absorption fields must be set back from
the top of a ravine. The required ravine setback is based on the distance
needed to establish a stable slope plus a minimum structure setback
from the edge of the computed stable slope, as follows:
(a)
For ravines having a depth of 10 feet or more, as measured from
the bottom of the ravine to the horizontal level of the land adjacent
to the ravine, the distance required to achieve a stable slope must
be based on a ratio of one foot vertical distance to 2.5 feet horizontal
distance. The measurement must be made from the center of the deepest
part of the ravine.
(b)
For ravines having a depth less than 10 feet, as measured from
the bottom of the ravine to the horizontal level of the land adjacent
to the ravine, the distance required to achieve a stable slope must
be based on a ratio of one foot vertical distance to three feet horizontal
distance. The measurement must be made from the center of the deepest
part of the ravine.
(d)
Storage sheds, driveways, walkways, patios, and fences accessory
to a principal use are permitted within the ravine setback area.
[Ord. No. 19-2020, 6-8-2020]
Modification of the minimum bluff and ravine setbacks may be
approved in accordance with the conditional use approval procedures
of this zoning chapter, upon submittal of a detailed report by a registered
professional engineer with demonstrated geotechnical expertise documenting
lower recession rates, more stable slope conditions, plans for structural
protection against wave attack, or plans for stabilization of the
bluff or shoreline. Engineering studies evaluating slope stability
must use the top of the lake sediments or 75% of the height of the
bluff, whichever is greater, as the groundwater surface. The required
100-foot setback from the top of bluffs and ravines must be provided
from the landward edge of the modified stable slope distance.
