Chapter 14.110
EROSION HAZARD AREAS
Sections:
14.110.020 Erosion hazard area.
14.110.030 Erosion hazard area review procedures.
14.110.040 Erosion hazard area standards.
14.110.050 Buffer requirements.
14.110.010 Purpose.
The following statements describe the purpose of this chapter:
A. Protect human life and health;
B. Regulate uses of land in order to avoid damage to structures and property being developed and damage to neighboring land and structures;
C. Identify and map any erosion hazard area;
D. Minimize impacts on wetlands and critical fish and wildlife species and their associated habitat that can result from erosion;
E. Establish a permit requirement and review procedures for development proposals in areas with potential erosion hazards;
F. Strike a balance between the need to maintain natural shoreline erosion/regression processes and the need to protect existing and proposed development. (Ord. 17-513 § 3 (Exh. A)).
14.110.020 Erosion hazard area.
A. Erosion Hazard Area Indicators. Erosion hazard areas are areas potentially subject to land regression or retreat due to a combination of geologic, seismic, hydrologic, or manmade factors. Erosion hazard areas can be identified by indicators of active land retreat as a result of fluvial processes.
B. Erosion Hazard Area Categories.
1. Potential Erosion Hazard Areas. Potential erosion hazard areas, as depicted on the geologically hazardous areas map, are those areas where the suspected risk of erosion through either loss of soil, slope instability, or land regression is sufficient to require additional review to assess the potential for active erosion activity or apply additional standards. These potential erosion hazard areas are determined using the following criteria:
a. Shoreline Erosion Hazard Areas. Areas within 200 feet of a freshwater lake, pond, or shoreline. The distance shall be measured landward perpendicularly from the edge of the ordinary high water mark.
b. Riverine Erosion Hazard Areas. The rivers subject to regulation as a CMZ listed in EMC 14.80.040(B)(4).
c. Soil Erosion Hazard Areas. Areas identified as having slopes of 20 percent or greater and that are classified as having severe or very severe erosion potential by the Soil Conservation Service, United States Department of Agriculture (USDA).
2. Active Shoreline Erosion Hazard Areas. Land areas located directly adjacent to surface water bodies that, through the geological assessment process, are identified as regressing, retreating, or potentially unstable as a result of undercutting by wave action or bluff erosion. The limits of the active shoreline erosion hazard area shall extend landward to include that land area that is calculated, based on the rate of regression, to be subject to erosion processes within the next 10-year time period.
3. Riverine Erosion Hazard Areas or CMZs. Riverine erosion hazard areas are located within the lateral extent of likely watercourse channel movement due to bank destabilization and erosion, rapid incision, and shifts in location of watercourse channels. Rivers and streams subject to erosion are regulated as a CMZ.
4. Soil Erosion Hazard Areas. Soil erosion hazard areas are identified by the presence or absence of natural vegetative cover, soil texture condition, slope, and rainfall patterns, or man-induced changes to such characteristics that create site conditions which are vulnerable to erosion of the upper soil horizon. Soil erosion hazard areas include those areas with slopes of 20 percent or greater and that are classified as having severe or very severe erosion potential by the USDA Natural Resources Conservation Service. (Ord. 17-513 § 3 (Exh. A)).
14.110.030 Erosion hazard area review procedures.
A. General Requirements.
1. The city’s geologically hazardous areas map provides an indication of where potential erosion hazard areas are located. The actual presence or location of an erosion hazard area or additional potential erosion hazard area that has not been mapped, but may be present on or adjacent to a site, shall be determined using the procedures and criteria established in this chapter.
2. The department will complete a review of the geologically hazardous areas map, and any other source documents for any proposed regulated activity, to determine whether the site for the regulated activity is located within a potential erosion hazard area.
3. When the department’s maps, sources, or field investigations indicate that the site for a proposed regulated activity is located within a potential shoreline erosion hazard area, the department shall require a geological assessment as outlined in subsection (B) of this section.
4. When the department’s maps, sources, or field investigations indicate that the proposed project area for a regulated activity is located within a potential riverine erosion hazard area or CMZ, the department shall conduct a review pursuant to Chapter 14.80 EMC.
5. When the department’s maps, sources, or field investigations indicate that the proposed project area for a regulated activity is located within a potential soil erosion hazard area, the department shall require submittal of an erosion control plan pursuant to the requirements set forth in Chapter 13.05 EMC, Stormwater Manual – Site Development Regulations.
6. Applicants requesting to develop a bulkhead along a shoreline shall be required to submit a geotechnical report.
B. Geological Assessment. A geological assessment is a site investigation process to evaluate the on-site geology affecting a subject property and proposed development.
1. Geological assessments shall be submitted to the department for review and approval together with a shoreline erosion hazard area application.
2. The geological assessment shall include a field investigation and may also include review of public records and documentation, analysis of historical air photos, LiDAR mapping, published data and references, etc.
3. The geological assessment shall include the following information and analysis:
a. An analysis of the shoreline erosion processes on and in the vicinity of the site including an evaluation of erosion and shoreline retreat that has occurred over the past decade and an estimated probable rate of erosion based upon the historic rate of erosion that has occurred on the site.
b. A determination of which areas on the site meet the criteria for an active shoreline erosion hazard area.
c. A determination of the area on the site or in the vicinity of the site that will experience regression in the next 120 years given natural processes.
d. All of the information required per EMC 14.10.080(C).
4. Geological assessments shall be prepared, signed, and dated by a geotechnical professional and the format shall be pre-approved by the department.
5. A geotechnical professional shall complete a field investigation and geological assessment to determine whether or not an active shoreline erosion hazard area exists within 200 feet of the site.
a. The geological assessment shall be submitted in the form of a geotechnical letter when the geotechnical professional finds that no active shoreline erosion hazard area exists within 200 feet of the site.
b. The geological assessment shall be submitted in the form of geotechnical verification when the geotechnical professional finds that an active shoreline erosion hazard area exists but is located more than 200 feet away from the proposed project area.
c. The geological assessment shall be submitted in the form of a geotechnical report when the geotechnical professional finds that an active shoreline erosion hazard area exists within 200 feet of the proposed project area or when a geotechnical professional determines that mitigation measures, such as a bulkhead, are necessary in order to construct or develop within a potential shoreline erosion hazard area.
6. The department shall review the geological assessment and either:
a. Accept the geological assessment and approve the application; or
b. Reject the geological assessment and require revisions or additional information.
7. A geological assessment for a specific site may be valid for a period of up to five years when the proposed land use activity and surrounding site conditions are unchanged. However, if any environmental conditions associated with the site change during that five-year period, the applicant may be required to submit an amendment to the geological assessment.
C. Riverine Erosion Hazard Area (Channel Migration Zones) Review. Riverine erosion hazard areas shall be reviewed pursuant to the requirements set forth in Chapter 14.80 EMC.
D. Soil Erosion Hazard Area Review. Soil erosion hazard areas shall be reviewed pursuant to the requirements set forth in Chapter 13.05 EMC, Stormwater Manual – Site Development Regulations. (Ord. 24-660 §§ 15, 16 (Exh. B); Ord. 17-513 § 3 (Exh. A)).
14.110.040 Erosion hazard area standards.
A. Active Shoreline Erosion Hazard Areas. Any development, encroachment, clearing and grading, timber harvest, building structures, impervious surfaces, and vegetation removal shall be prohibited within active shoreline erosion hazard areas and associated buffers except as specified in the following standards:
1. Shoreline Erosion Protection Measures. Shoreline erosion protection measures located within or adjacent to freshwater or marine shorelines shall be allowed subject to the following:
a. The proposed shoreline protection measure shall comply with the standards set forth in Chapter 14.50 EMC, Critical Fish and Wildlife Habitat Areas.
b. A geological assessment geotechnical report that indicates that the shoreline is currently experiencing active erosion, i.e., land retreat or regression.
c. The use of the shoreline erosion protection measure will not cause a significant adverse impact on adjacent properties or critical fish and wildlife species and their associated habitat (i.e., increase erosion on adjacent properties).
d. The use of soft armoring techniques is the preferred method for shoreline protection.
e. Hard armoring shoreline erosion control measures shall be approved only when a geological assessment – shoreline erosion geotechnical report has been completed and indicates the following:
i. The regression has been monitored on a yearly interval for a period of at least five consecutive years prior to allowing a bulkhead to be constructed. This monitoring shall be conducted by field survey measurements of a licensed surveyor. The department may shorten or eliminate the monitoring period if there are indicators that the regression rate is rapid and an existing structure may be threatened prior to completion of the monitoring period;
ii. The use of beach nourishment alone or in combination with soft armoring techniques is not adequate to protect the property from shoreline erosion processes; and
iii. The property contains an existing structure(s) that will be threatened within the next 10 years or the buildability of an undeveloped site will be threatened within the next 10 years if a hard armoring method of shoreline erosion protection is not provided.
f. Hard armoring shoreline protection measures shall not be allowed when structures can be located landward of the 120-year rate of regression area.
2. Stormwater Conveyance. Surface drainage into an active shoreline erosion hazard area should be avoided. If there are no other alternatives for discharge, then drainage must be collected upland of the top of the active shoreline erosion hazard area and directed downhill in a high density polyethylene stormwater pipe with fuse welded joints that includes an energy dissipating device at the base of the active landslide hazard area. The pipe shall be located on the surface of the ground and be properly anchored so that it will continue to function in the event of an underlying slide. The number of these pipes should be minimized along the slope frontage.
3. Utility Lines. Utility lines will be permitted when no other conveyance alternative is available. The line shall be located above ground and properly anchored and/or designed so that it will continue to function in the event of an underlying slide.
4. Roads, Bridges, and Trails. Roads, bridges, and trails shall be allowed when all of the following conditions have been met:
a. Mitigation measures are provided that ensure the roadway prism and/or bridge structure will not be susceptible to damage from active erosion.
b. The road is not a sole access for a development.
B. Shoreline Erosion Hazard Management Area. All regulated activities such as but not limited to building structures, impervious surfaces, vegetation removal, timber harvest, or grading activities may be allowed in areas located within 200 feet of an active shoreline erosion hazard area subject to the following standards:
1. The department reviews and approves a geological assessment – shoreline erosion hazard geotechnical report and determines that the proposed project area is located outside an active shoreline hazard area and the required buffer.
2. The proposed recommendations and mitigation measures contained within the geotechnical report are adequate to reduce or mitigate risks to the natural environment, health, and safety.
3. Surface drainage from the proposed project area, including downspouts, landscape irrigation systems, and runoff from paved or unpaved surfaces upland of the shoreline, shall not be directed through an active shoreline erosion hazard area or its associated buffer unless it is conveyed in conformance with the provisions in subsection (A)(2) of this section.
4. Stormwater retention and detention systems, such as dry wells and infiltration systems utilizing buried pipe or French drains, shall not be permitted unless such systems are designed by a professional engineer and the geotechnical report indicates that such a system will not affect the stability of the shoreline.
5. Proposed developments, with the exception of shoreline erosion protection measures, shall be sited far enough from regressing shorelines to ensure 120 years of useful life for any proposed structures or infrastructure.
C. Riverine Erosion Hazard Area or CMZ Review. Riverine erosion hazard areas shall be reviewed pursuant to the requirements set forth in Chapter 14.80 EMC.
D. Soil Erosion Hazard Area Review. Soil erosion hazard areas shall be reviewed pursuant to the requirements set forth in Chapter 13.05 EMC, Stormwater Manual – Site Development Regulations. (Ord. 24-660 § 17 (Exh. B); Ord. 17-513 § 3 (Exh. A)).
14.110.050 Buffer requirements.
A. Determining Buffer Widths.
1. The buffer width shall be measured on a horizontal plane from a perpendicular line established at the edge of the active shoreline erosion hazard area limits.
2. An undisturbed buffer of existing vegetation shall be required for an active shoreline erosion hazard area. The required standard buffer width is either subsection (A)(2)(a) or (b) of this section, whichever is greater:
a. Fifty feet from all edges of the active shoreline erosion hazard area limits; or
b. A distance of one-third the height of the slope at the top of the slope and a distance of one-half the height at the bottom of the slope.
3. The buffer width may be reduced or eliminated upon the director’s approval of a geotechnical report that demonstrates that such a reduction would not result in an increased risk of erosion either on or off of the subject property.
B. Modification of Buffer Widths. The department may require a larger buffer width than the standard buffer distance, as determined in subsection (A) of this section, if any of the following are identified through the geological assessment process:
1. The adjacent land is susceptible to severe erosion and erosion control measures will not effectively prevent adverse impacts.
2. The area has a severe risk of slope failure or downslope stormwater drainage impacts. (Ord. 17-513 § 3 (Exh. A)).
14.110.060 Appendices.
A. Geological Assessment – Shoreline Erosion Hazard Geotechnical Letter.
B. Geological Assessment – Shoreline Erosion Hazard Geotechnical Verification.
C. Geological Assessment – Shoreline Erosion Hazard Geotechnical Report.
APPENDIX A
GEOLOGICAL ASSESSMENT – SHORELINE EROSION HAZARD GEOTECHNICAL LETTER
A. A geotechnical letter shall, at a minimum, include the following:
1. The general critical areas report requirements.
2. A summary of the findings of the site visit, a site plan, and a summary of the findings from the review of documents listed in EMC 14.110.030(B)(2). The appropriate professional preparing the geotechnical letter shall provide conclusions and recommendations as to shoreline stability for the proposed development.
B. The geotechnical professional who prepared the geotechnical letter shall stamp the letter with his or her seal.
C. Hold harmless clauses, disclaimers, and limitations are not allowed within a geotechnical letter.
APPENDIX B
GEOLOGICAL ASSESSMENT – SHORELINE EROSION HAZARD GEOTECHNICAL VERIFICATION
A. A geotechnical verification shall, at a minimum, include the following:
1. The general critical areas report requirements.
2. A summary of the results, conclusions, and recommendations resulting from the geological assessment, as set forth in EMC 14.110.030(B). The verification will also include a summary of the findings of the site visit, a site plan, and a summary of the findings from the review of the documents listed in EMC 14.110.030(B)(2).
3. An accurate site plan drawn at a scale of one inch equals 20 feet, one inch equals 30 feet, one inch equals 50 feet (or other scale deemed appropriate by the department) is required. The department may require that the site plan information listed below be based on a field survey by a licensed surveyor. The site plan shall include:
a. The limits and location of the active shoreline erosion hazard area(s).
b. The limits of the required shoreline erosion hazard buffer.
c. The limits and location of the shoreline erosion hazard management area.
d. The limits and location of the 120-year regression area.
e. The location of any existing structures, utilities, on-site septic systems, wells, and stormwater management facilities.
f. The location of any proposed structures, utilities, on-site septic systems, wells, and stormwater management facilities.
g. The full geographical limits of the proposed project area to be developed.
h. Dimension of the closest distance between the identified active shoreline hazard area boundary and the proposed project area.
i. Dimension of the closest distance between the 120-year regression line and the proposed project area.
j. Existing contours on the site at two-foot intervals.
k. Property lines for the site.
l. North arrow and scale.
B. The geotechnical professional who prepared the geotechnical verification shall stamp the verification with their seal.
C. Hold harmless clauses, disclaimers, and limitations are not allowed within a geotechnical verification.
APPENDIX C
GEOLOGICAL ASSESSMENT – SHORELINE EROSION HAZARD GEOTECHNICAL REPORT
A. A geotechnical report shall, at a minimum, include the following:
1. The general critical areas report requirements.
2. A summary of the results, conclusions, and recommendations resulting from the geological assessment. The report will also include a summary of the findings of the site visit, a site plan, and a summary of the findings from the review of documents listed in EMC 14.110.030(B)(2). The summary shall specifically address:
a. Whether it is possible given the physical constraints of the property (size, shape, building setbacks, utility requirements, etc.) to locate the proposed development outside of the 120-year area of regression based on natural shoreline processes.
b. If it is not possible to locate the development outside of the 120-year area of regression (based on natural processes), determine whether beach nourishment, soft armoring techniques, or both can be used to slow the rate of regression such that the proposed development is no longer within the 120-year regression area.
c. If it is not possible to locate the development outside of the 120-year area of regression, based on the use of beach nourishment or soft armoring techniques, outline the strategy to monitor the rate of regression on the site.
d. Determine whether any proposed shoreline erosion protection measures will cause an increase in the rate of regression on neighboring properties.
3. An accurate site plan drawn at a scale of one inch equals 20 feet, one inch equals 30 feet, one inch equals 50 feet (or other scale deemed appropriate by the department) is required. The department may require that the site plan information listed below be based on a field survey by a licensed surveyor. The site plan shall include:
a. The limits and location of the active shoreline erosion hazard area(s).
b. The limits of the required shoreline erosion hazard buffer based upon the requirements.
c. The limits and location of the shoreline erosion hazard management area.
d. The limits and location of the 120-year regression area based on natural shoreline processes and, if applicable, based upon proposed shoreline protection measures.
e. The location of any existing structures, utilities, on-site septic systems, wells, and stormwater management facilities.
f. The location of any proposed structures, utilities, on-site septic systems, wells, and stormwater management facilities.
g. The full geographical limits of the proposed project area to be developed.
h. Dimension of the closest distance between the identified active shoreline hazard area boundary and the proposed project area.
i. Dimension of the closest distance between the 120-year regression line and the proposed project area.
j. Existing contours on the site at two-foot intervals.
k. Property lines for the site.
l. North arrow and scale.
4. A discussion of any proposed shoreline protection measures including design and construction drawings is required.
5. A list of references utilized in preparation of the report.
B. The geotechnical professional(s) who performed the geological assessment shall stamp the report with their license stamp or seal. The report must be co-authored by a licensed professional engineer when engineering designs or interpretations are necessary to address the report requirements. The engineer must also stamp the report with their license stamp or seal.
C. The department may request a geotechnical professional to provide additional information in the geotechnical report based upon existing conditions, changed conditions, or unique circumstances occurring on a case-by-case basis.
D. Hold harmless clauses, disclaimers, and limitations are not allowed within a geotechnical report.
E. Geotechnical reports shall be in conformance with a format that is pre-approved by the department. (Ord. 17-513 § 3 (Exh. A)).