The purpose of this chapter is to protect human life and safety, prevent damage to structures and property, and minimize impacts to water quality and fish and wildlife caused by geologic hazards.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
1.
Designation. Lands classified as landslide, erosion (including channel migration zones), alluvial fan, seismic, and mine hazard areas, are hereby designated as geologically hazardous areas.
2.
Classification.
a.
Potential landslide hazard areas. Landslide hazard areas shall include areas potentially subject to landslides based on a combination of geologic, topographic, and hydrologic factors. They include any areas susceptible because of any combination of bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or other factors. Potential landslide hazard areas include, but are not limited to, the following areas:
i.
Areas of historic failures;
ii.
Areas designated as quaternary slumps, earth-flows, mudflows, or landslides on maps published by the U.S. Geological Survey or Washington State Department of Natural Resources;
iv.
Areas that have shown movement and/or are underlain or covered by mass wastage debris;
v.
Slopes that are parallel or sub-parallel to planes of weakness (which may include, but not be limited to, bedding planes, soft clay layers, joint systems, and fault planes) in subsurface materials;
vi.
Slopes having gradients steeper than 80% subject to rock fall during seismic shaking;
vii.
Areas that show evidence of, or are at risk from snow avalanches; and
viii.
Any area with a slope of 40% or steeper and with a vertical relief of 10 or more feet except areas composed of competent bedrock. A slope is delineated by establishing its toe and top and measured by averaging the inclination over at least 10 feet of vertical relief;
ix.
Potentially unstable slopes resulting from river erosion or undercutting;
x.
Areas that show past sloughing or calving of sediment or rocks resulting in a steep slope that is poorly vegetated;
xi.
Deep-seated landslide areas characterized by one or more of the following features: scalloped ridge crests at the top of the slope, crescent shaped depressions, head scarps, side scarps, ponds or sag areas on mid slopes, benches and scarps on mid slope areas, hummocky ground, linear fractures in the ground. These features may be evident in aerial images, topographic maps, LiDAR imagery or on the ground;
xii.
Areas below unstable slopes or that have been identified as landslide hazard areas that could be impacted by landslide run out; and
xiii.
Areas above or adjacent to unstable slopes that could be impacted if the landslide area expands.
b.
Potential erosion hazard areas. Erosion hazard areas shall include areas containing soils that may experience significant erosion, including:
i.
Soil areas identified by the Natural Resources Conservation Service as having "severe" or "very severe" erosion hazard.
ii.
Slopes 40% or steeper with a vertical relief of 10 or more feet, except areas composed of consolidated rock.
iii.
Concave slope forms equal to or greater than 15% with a vertical relief of 10 or more feet, except areas composed of consolidated rock.
iv.
Channel migration zones, which are defined as the areas along a river or stream within which the channel(s) can be reasonably predicted to migrate over time as a result of natural and normally occurring hydrological and related processes when considered with the characteristics of the river and its surroundings.
c.
Alluvial fan hazard areas. Alluvial fan hazard areas shall include those areas on alluvial fans where debris flows, debris floods, or clear water floods have the potential to significantly damage or harm the health or welfare of the community. They include the area generally corresponding to the path of potential flooding, channel changes, sediment and debris deposition, or debris flow paths as determined by analysis of watershed hydrology and slope conditions, topography, valley bottom and channel conditions, potential for channel changes, and surface and subsurface geology.
i.
If the approval authority determines that a proposed use along a Type S or F stream is within a historic channel migration zone, based on field conditions, historic information, LIDAR imagery or aerial photography, and the 100-year channel migration hazard area has not been mapped, the approval authority shall require the applicant to determine if a 100-year channel migration hazard area is present on the site and, if so, delineate its location and extent.
ii.
The determination as to whether the 100-year channel migration hazard area affects the subject property shall be based on the findings of a qualified professional proficient in fluvial geomorphology using a reliable methodology to determine channel migration accepted by the department (e.g., as described in the Washington Department of Natural Resources' Forest Practices Board Manual, Standard Methods for identifying Channel Migration Zones and Bankfull Channel Features, dated 8/2001, as amended; or in "A Framework for Delineating Channel Migration Zones," Washington Department of Ecology, 2003, as amended). Maps delineating the 100-year channel migration hazard area shall be of a scale and format specified by the department.
d.
Seismic hazard areas. Seismic hazard areas shall include 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.
e.
Volcanic hazard areas. Volcanic hazard areas shall include areas subject to pyroclastic flows, lava flows, debris avalanche, inundation by debris flows, mudflows, or related flooding resulting from volcanic activity. There are no active or dormant volcanoes located within Kittitas County; however, Mount Rainer and Mount St. Helens are relatively near. Hazards to Kittitas County residents from these volcanoes are likely limited to ash deposition.
f.
Mine hazard areas. Mine hazard areas shall include areas underlain by abandoned mine shafts, secondary passages between shaft tunnels, or air vents. Mine hazards include subsidence, which is the uneven downward movement of the ground surface caused by underground workings caving in; contamination to ground and surface water from tailings and underground workings; concentrations of lethal or noxious gases; and underground fires.
3.
Mapping. The approximate location and extent of geologically hazardous areas are shown on maps maintained by the County. These maps are useful as a guide for project applicants and/or property owners but do not provide a conclusive or definitive indication of geologically hazardous area presence or extent. Other geologically hazardous areas may exist that do not appear on the maps, and some geologically hazardous areas that appear on the maps may not meet the geologically hazardous areas designation criteria. The County shall update the maps periodically as new information becomes available and may require additional studies during the development review process to supplement and/or confirm the mapping. Historic maps showing the locations of known coal mines within the County are available from the Washington Department of Natural Resources.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
1.
Generally. New developments shall be located and/or engineered and constructed to minimize risk to health and safety, protect the building and occupants from the hazard, and not increase the risk of landslides or erosion that could impact either other properties, public resources, or other critical areas such as wetlands and fish and wildlife habitat conservation areas. If impacts to other properties, public resources or other critical areas cannot be avoided these impacts should be mitigated for. The Director may impose conditions on alterations and development in a geologically hazardous area as needed to:
a.
Protect slope stability and minimize erosion, seismic, and/or landslide hazard risks;
b.
Maintain natural sediment and erosion processes that are integral to the health and sustainability of freshwater ecosystems as well as minimizing impacts to stream and river processes such as channel infill, channel migration or flooding;
c.
Minimize the potential for property damage related to seismic events, erosion and/or landslides;
d.
Minimize the need for stream or river bank stabilization in the future;
e.
Protect human health and safety; and
f.
Reduce public liabilities for damages associated with seismic events, erosion and/or landslides.
2.
Impact avoidance. Impact avoidance measures shall include, but not be limited to, locating the use/ development outside of the hazard area, reducing the number, size or scale of buildings, driveways and other features; altering the configuration or layout of the proposed development; using environmentally favorable construction materials; implementing special engineering methods for construction, drainage, runoff management etc.; foregoing construction of accessory structures; preserving native vegetation; and other reasonable measures.
3.
Location of alterations. New development shall be directed toward portions of a parcel or parcels under contiguous ownership that are not subject to, or at risk from, geological hazards and/or are outside any setback or buffer established by this chapter.
4.
Critical facilities prohibited. Critical facilities shall not be sited within landslide, erosion, alluvial fan, or mine hazard areas unless there is no other practical alternative.
5.
Review by qualified professional. A qualified geologist or engineering geologist, or professional engineer licensed in the state of Washington, shall review development projects that occur in potentially geologically hazardous areas to determine the risk. If development takes place within an identified geologically hazardous area requiring design or structural elements to mitigate the hazard, a report describing the geologically hazardous area and conditions shall be prepared as described in KCC § 17A.06.100, and the design shall be approved by an qualified engineering geologist, or professional engineer licensed in state of Washington with expertise in geologically hazard mitigation.
6.
Life of structure. Proposed developments shall be sited far enough from erosion and landslide hazard areas to ensure at least 100 years of useful life for the proposed structure(s) or infrastructure. The location should be determined by a qualified geologist or engineering geologist, licensed in the state of Washington and be should be based on-site specific evaluation of the landslide and/or erosion hazard.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
1.
Generally. Alterations and development may be allowed adjacent to landslide hazard areas, provided that all responsible measures have been taken to minimize risks and other adverse effects, and the amount and degree of the alteration are limited to minimum needed to accomplish the project purpose. Prior to approving a new alteration or development in or adjacent to a landslide hazard area the Director shall determine that all the following standards are met:
a.
A minimum setback equal to the height of the slope or 40 feet, whichever is greater or as recommended in an approved geotechnical report;
b.
The alteration or development includes all appropriate measures to eliminate, reduce, or otherwise mitigate risks to health and safety;
c.
The alteration or development is located outside of a landslide hazard area and any required setback, as determined by a qualified engineer, engineering geologist, or geologist, licensed in the state of Washington;
d.
The alteration or development will not decrease slope stability on adjacent properties;
e.
The alteration or development shall not increase the risk or frequency of landslide occurrences;
f.
The removal and disturbance of vegetation, clearing, or grading shall be limited to the area of the approved alteration or development;
g.
The alteration or development will not increase surface water discharge or sedimentation to adjacent properties beyond predevelopment conditions;
h.
The proposed alterations will not adversely impact other critical areas; and
i.
Structures and improvements including drainage and vegetation management are designed to have no impact on the slope stability; and
j.
If development takes place within an identified geologically hazardous area, the development must be designed to fully mitigate the risk to the structure(s) and not increase the risk to the public, other properties or public infrastructure or resources.
2.
Permitted alterations and development. The following alterations and development may be allowed in landslide hazard areas when all reasonable measures have been taken to minimize risks and other adverse effects associated with landslide hazards, and when the amount and degree of alteration is limited to the minimum needed to accomplish the alteration or development:
a.
Above-ground utility lines and pipes. Utility lines and pipes that are above-ground, properly anchored and/or designed so that they will not increase the risk or consequences of static or seismic slope instability or result in an increased risk of mass wasting. Such utility lines may be permitted only when the applicant demonstrates that no other feasible alternative is available to serve the affected population. For pipelines, automatic shut off valves should be located as close as practical to the landslide area so that the release from the pipe upon breakage is minimized.
b.
Access roads and trails. Access roads and trails that are engineered and built to standards that avoid the need for major repair or reconstruction beyond that which would be required in non-hazard areas. Access roads and trails may be permitted only if the applicant demonstrates that no other feasible alternative route exists. Standards to minimize impacts may be specified by the Director.
c.
Stormwater conveyance. Stormwater conveyance through a properly designed stormwater pipe when no other stormwater conveyance alternative is available. The pipe shall be located above-ground and be properly anchored and/or designed so that it will continue to function in the event of a slope failure or movement of the underlying materials and will not increase the risk or consequences of static or seismic slope instability or result in increased risk of mass wasting activity.
3.
Setbacks. The Director shall require setbacks from the edges of any landslide hazard area in accordance with the following:
a.
The size of the setbacks shall be based on the findings of a qualified engineering geologist or geologist, licensed in the state of Washington, and shall protect critical areas and minimize the risk of property damage, death, or injury resulting from landslides caused in whole or part by the alteration or development and shall be sized to provide protection for a period of at least 100 years based on the assessment of the geologic processes within the landslide hazard area;
b.
The setback above the landslide hazard area shall include consideration of hydrologic contribution to the landslide area and/or the area subject to the potential for mass movement, and the setback down slope from the landslide hazard area shall include consideration of landslide run out; and
c.
The Director shall have the authority to require appropriate management of vegetation or land use within the setback area to minimize the risk of increasing the risk of landslides.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
1.
Generally. Alterations or development may be allowed within erosion hazard areas, provided that all responsible measures have been taken to minimize risks and other adverse effects with erosion hazards, and the amount and degree of the alteration are limited to minimum needed to accomplish the project purpose. Prior to approving a development or alteration in or adjacent to an erosion hazard area, a report will be prepared as defined in KCC § 17A.06.100. Based on this information, the Director shall determine whether all the following standards are met.
a.
The alteration or development includes all appropriate measures to eliminate or otherwise mitigate risks to health and safety;
b.
The alteration or development includes best management practices to prevent, control and minimize erosion;
c.
The alteration or development will not increase erosion potential;
d.
The removal and disturbance of vegetation, clearing, or grading shall be limited to the area of the approved alteration or development;
e.
The alteration or development will not increase surface water discharge or sedimentation to adjacent properties beyond predevelopment conditions, as documented in a geologically hazardous area risk assessment and/or geotechnical report;
f.
The proposed alterations will not adversely impact other critical areas; and
g.
Structures and improvements are designed to minimize alterations to the erosive soils and slopes.
2.
Channel migration zones. If County maps or consultation by the Director with qualified professionals or agencies with expertise indicate that a potential channel migration zone hazard exists on or adjacent to a proposed development site, the applicant shall either:
a.
Locate the proposed development outside of an already defined channel migration hazard area as indicated on the map; or
b.
Submit a Channel Migration Zone Report, as described in KCC § 17A.06.100 prepared by a qualified geologist, or engineering geologist, or professional engineer, licensed in the state of Washington with experience in analyzing channel response in the fluvial systems of the Pacific Northwest.
3.
Permitted alterations and development in channel migration zones. The following alterations and development shall be allowed as specified below and previous sections:
a.
Surface water discharge. Discharge of surface water, provided there are no other alternatives for discharge. The pipe shall be located on the surface of the ground and be properly anchored so that it will continue to function under erosion conditions and not create or contribute to adverse effects on downstream critical areas.
b.
Utility lines. Utility lines, when no feasible location is available. Above-ground lines shall be anchored and/or designed so that it will not preclude or interfere with channel migration. Below ground lines shall be of sufficient depth as to not be affected by future channel migration.
c.
Public roads, bridges, and trails. Public roads, bridges, and trails when no feasible alternative alignment is available. Facilities shall be designed such that the roadway prism and/or bridge structure will not be susceptible to damage from active erosion.
d.
Stream bank stabilization. Stream bank stabilization may be permitted subject to all of the standards listed in KCC § 17A.04.050.
4.
CMZ buffers or setbacks. Based upon the results of the channel migration zone assessment, the Director shall prohibit or limit use or development within a channel migration zone and may require a setback or a buffer of undisturbed natural vegetation from the edge of the channel migration zone in accordance with the following:
a.
The size of the setback or buffer shall be based on the findings of a qualified engineer, engineering geologist, or geologist, licensed in the state of Washington, and shall protect critical areas and processes and minimize the risk of property damage, death, or injury resulting from channel migration;
b.
The buffer shall include the area subject to bank failure as a result of erosion; and
c.
If the designated buffer lacks adequate woody vegetation, the Director shall have the authority to require vegetation enhancement or other measures to improve natural channel processes and large wood recruitment.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
1.
Permitted alteration and development. Alluvial fan hazards will be determined by County maps, LIDAR, and aerial photography. The following alterations and development may be allowed in alluvial fan hazard areas, after accounting for restrictions defined by other critical area regulations, when all reasonable measures have been taken to minimize risks and other adverse effects associated with alluvial fan hazards, and when the amount and degree of alteration are limited to the minimum needed to accomplish the alteration or development:
a.
Roads, utilities, bridges, and other infrastructure. Roads, utilities, bridges, and other infrastructure when located and designed to prevent adverse impacts on critical areas and avoid the need for channel dredging or diking or other maintenance activities that have the potential to substantially degrade river and stream functions.
b.
Residential and commercial developments. Permanent residential structures and commercial developments shall be allowed in alluvial fan hazard areas only if the alluvial fan has undergone a County-approved study to assess potential hazards, determine risks, and identify mitigation measures and is deemed suitable for development. The Director shall make this determination based on a detailed assessment by a qualified engineer, engineering geologist, or geologist, licensed in the state of Washington, that identifies the risks associated with a 500-year return period debris flow or the maximum credible event that could impact the alluvial fan.
c.
Accessory structures. Accessory structures not involving human occupancy shall be allowed.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
Permitted alterations and development. Alterations and development within seismic hazard areas shall follow the provisions of the Kittitas County-adopted version of the Uniform Building Code. Alterations and development within seismic hazard areas shall not require the submission of a geologically hazardous area risk assessment or geotechnical report.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
Permitted alterations and development. Because volcanic hazards in Kittitas County are limited to ash deposition, alterations and development located only within volcanic hazard areas, and not other geologically hazardous areas, shall not require the submission of a geologically hazardous area risk assessment or geotechnical report.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
Alteration. There are no additional protection standards for mine hazard areas; the standards of KCC § 17A.06.030 shall apply.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)
1.
Geologically hazardous area risk assessment. If a proposed development is located within or adjacent to a known or suspected landslide, mine, alluvial fan, or erosion hazard area, the applicant shall submit a Geologically Hazardous Area Risk Assessment prepared by a qualified professional geologist or engineering geologist. No further analysis shall be required if the Geologically Hazardous Area Risk Assessment concludes that the alteration or development is not at risk from potential geologic hazards, and that there is no geologic hazard present on or adjacent to the site.
If the Geologically Hazardous Area Risk Assessment and/or the Director concludes that a geologically hazardous area is located on or adjacent to the alteration or development and/or the alteration or development is at risk from potential geologic hazards, the applicant shall submit a Geotechnical Report consistent with the provisions of KCC § 17A.02.370, and prepared by a qualified engineer or engineering geologist.
2.
Geologically hazardous area risk assessment contents. When required by this chapter, Geologically Hazardous Area Risk Assessments shall include the general critical areas report requirements of KCC § 17A.01.080 in addition to the following:
a.
A description of the geology of the site and the proposed development;
b.
An assessment of the potential impact the project may have on the geologic hazard;
c.
An assessment of what potential impact the geologic hazard may have on the project;
d.
Appropriate mitigation measures, if any;
e.
A conclusion as to whether further analysis is necessary; and
f.
The signature and stamp of the engineering geologist, or geologist that prepared the assessment.
3.
Geotechnical report contents. When required by this Title, the Geotechnical Report shall include the general critical areas report requirements of KCC § 17A.01.080 in addition to the following:
a.
A detailed description of the geology and soil conditions of the site;
b.
Evaluation of the geologic conditions giving rise to the geologic hazard;
c.
An evaluation of the safety of the proposed project;
d.
Conclusion and recommendations regarding the effect of geologic conditions on the proposed development;
e.
Conclusions and recommendations on the suitability of the site to be developed;
f.
A statement regarding the risk of damage from the project, both on-and off-site; and whether or not the project will materially increase the risk of occurrence of the hazard;
g.
Recommendations concerning drainage practices, vegetation retention and other mitigation and monitoring measures which may be needed to ensure slope stability;
h.
Recommended erosion and sediment control measures;
i.
A bibliography of scientific citations;
j.
Any other specific measures which must be incorporated into the design and operational plan of the project to eliminate or reduce the risk of damage due to the hazard. This shall include a recommendation on the required buffer or setback distance that must be maintained between the proposed development and the hazard to ensure the safety of the development; and the signature and stamp of the engineer or engineering geologist who prepared the Geotechnical Report.
4.
Channel migration zones studies contents. When required by this chapter, Channel Migration Zone Studies shall include the general critical areas report requirements of KCC § 17A.01.080, and shall demonstrate the following:
a.
The parcel on which the development is proposed is effectively protected (disconnected) from channel movement due to the existence of permanent levees that are actively maintained by public agencies or infrastructure such as roads and bridges constructed and maintained by public agencies (not all roads and levees will be considered disconnection points); or
b.
The proposed development site has minimal risk of channel migration during the next 100 years as indicated by the existing channel type, land cover (and low likelihood of future alterations in land cover), presence of adjacent toe slope landslide hazard areas, surficial geology, low soil erosion potential, lack of evidence of likely avulsion pathways (including areas upstream of, but proximate to, the site), and/or low inundation frequency(ies). The assessment shall include a review of available data regarding historical channel locations at the site; identification of the site within a broader geomorphic reach of the river system and the general characteristics of that reach; description of existing channel type, existing channel alteration and likelihood of future alterations with changes in land cover; surficial geology, soils and erosion potential; and geotechnical setbacks relating to erosion at the toe of adjacent slope(s). The approach to assessing location shall be generally equivalent to the methods detailed in "A Framework for Delineating Channel Migration Zones" (Ecology Publication # 03-06-027), or similar method approved or sanctioned by Ecology.
(Ord. 2021-016, 2021; Ord. 2025-006, 7/1/2025)