[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.
(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 determined in accordance with Subsection (a) or (b), above.
(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.