A. Erosion Hazard Areas. Erosion hazard areas are prone to soil erosion. Specifically these areas include any area where the soil type is predominantly (greater than 50 percent) comprised of sand, clay, silt, and/or organic matter and slope is greater than 30 percent.

B. Landslide Hazard Areas. Landslide hazard areas may be prone to landslides and/or subsidence that could include slow to rapid movement of soil, fill materials, rock and other geologic strata resulting in risk of injury or damage to the public and environment. Landslides could result from any combination of soil, slope, topography, underlying geologic structure, hydrology, freeze-thaw, earthquake and other geologic influences. Specific landslide hazard areas include slopes with an incline that is equal to or greater than 40 percent grade (22 degrees) with a vertical elevation change of at least 10 feet. Slope shall be calculated by identifying slopes that have at least 10 feet of vertical elevation change within a horizontal distance of 25 feet or less.

Slope shall not include those lands that have 10 feet of vertical change by virtue of a legally established retaining wall(s), foundation wall, stairways or similar vertical structure or those land areas where public infrastructure and its supporting elements have been developed.

C. Seismic Hazard Areas. Seismic hazard areas are areas subject to severe risk of damage as a result of earthquake induced ground shaking, slope failure, settlement, soil liquefaction, lateral spreading, or surface faulting. Specific areas of very high response to seismic shaking include areas depicted as “fill” and “alluvial deposits” within Whatcom County’s Map Folio of Geologic Hazards, 1995.

D. Mine Hazard Areas. Mine hazard areas are those areas underlain by or affected by mine workings such as adits, gangways, tunnels, drifts, or airshafts, and those areas of probable sink holes, gas releases, or subsidence due to mine workings. Specific areas of known and suspected historical mining activity and hazards include: