Shoreline development projects above shoreline bluffs around the State of Washington have generally adopted the same county or city code guidance language:
"Minimum setback from top of shoreline bank is as follows: The standard setback for residential structures, including common appurtenant structures such as garages and workshops, shall be thirty (30) feet or one (1) foot for each foot of bank height, whichever is greater. This setback shall be measured from the bank's edge when the bank's height exceeds 10 feet. When the bank's height is less than 10 feet, the setback shall be measured from the ordinary high water mark."
Based on this language, the setback from the top edge of a 90-foot high bluff will be 90 feet from the edge of the bluff. If the bluff is 40 feet high, the setback will be 40 feet. If the bluff is a low bank of perhaps 8 feet, the home can be built within 30 feet of the ordinary high water mark, that is closer to the top edge of the shoreline bluff; if the water line is 15 feet out from the edge of the bluff, the home could be built within 15 feet of of the top edge of the bluff.
I am not a fan of this language as it is fails to take into a variety of variables and fails some simple logic tests.
For example a bluff with an average slope of 45 degrees covered with large straight mature trees and a well built up beach with very low erosion rates is treated the same as a vertical slope with rapid active erosion. Further, if wave action is equal on a 10-foot bluff and a 100-foot bluff, the bluff retreat rate of the 10-foot bluff will be much greater than the bluff retreat rate of a 100-foot bluff simply due to the shear volume of sediment that has to be eroded from the 100-foot bluff relative to the 10-foot bluff. The language fails to reflect variability in the geology.
And think about the low bluff scenario. A low bank will allow the home to be built even closer to edge of the bluff because one can measure from the water line mark. A low bluff will erode much faster than a high bluff everything else being equal if the low bluff is being eroded.
The above said, these setbacks based on general guidance language and can be altered. Typically, or at least hopefully, there is some language in the code either in the shoreline regulations or the critical areas ordinance for geologic hazardous areas that allows for or requires other considerations.
But the language sets up false expectations and a default setback established by the local government that may or may not be protective.
Hence, I am of the view this sort of default language should be scrubbed from hazard codes.
"Minimum setback from top of shoreline bank is as follows: The standard setback for residential structures, including common appurtenant structures such as garages and workshops, shall be thirty (30) feet or one (1) foot for each foot of bank height, whichever is greater. This setback shall be measured from the bank's edge when the bank's height exceeds 10 feet. When the bank's height is less than 10 feet, the setback shall be measured from the ordinary high water mark."
Based on this language, the setback from the top edge of a 90-foot high bluff will be 90 feet from the edge of the bluff. If the bluff is 40 feet high, the setback will be 40 feet. If the bluff is a low bank of perhaps 8 feet, the home can be built within 30 feet of the ordinary high water mark, that is closer to the top edge of the shoreline bluff; if the water line is 15 feet out from the edge of the bluff, the home could be built within 15 feet of of the top edge of the bluff.
I am not a fan of this language as it is fails to take into a variety of variables and fails some simple logic tests.
For example a bluff with an average slope of 45 degrees covered with large straight mature trees and a well built up beach with very low erosion rates is treated the same as a vertical slope with rapid active erosion. Further, if wave action is equal on a 10-foot bluff and a 100-foot bluff, the bluff retreat rate of the 10-foot bluff will be much greater than the bluff retreat rate of a 100-foot bluff simply due to the shear volume of sediment that has to be eroded from the 100-foot bluff relative to the 10-foot bluff. The language fails to reflect variability in the geology.
And think about the low bluff scenario. A low bank will allow the home to be built even closer to edge of the bluff because one can measure from the water line mark. A low bluff will erode much faster than a high bluff everything else being equal if the low bluff is being eroded.
The above said, these setbacks based on general guidance language and can be altered. Typically, or at least hopefully, there is some language in the code either in the shoreline regulations or the critical areas ordinance for geologic hazardous areas that allows for or requires other considerations.
But the language sets up false expectations and a default setback established by the local government that may or may not be protective.
Hence, I am of the view this sort of default language should be scrubbed from hazard codes.
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