15.14.440 Shoreline stabilization | South Prairie Municipal Code

15.14.440 Shoreline stabilization.

Shoreline stabilization includes actions taken to address erosion impacts to property and dwellings, businesses, or structures caused by natural processes, such as flooding. These actions include structural and nonstructural methods. Nonstructural methods include shoreline buffers or setbacks, relocation of the structure to be protected, ground water management, planning and regulatory measures to avoid the need for structural stabilization. Structural measures include the use of bulkheads, riprap, concrete, or other rigid means to address erosion impacts.

1. Shoreline stabilization should be located, designed, and maintained to protect, restore and maintain shoreline ecological functions, ongoing shoreline processes, and the integrity of shoreline features. Ongoing stream processes and the probable effects of proposed shoreline stabilization on other properties and shoreline features should be considered.

2. Shoreline stabilization should not be developed for the purpose of filling shorelines.

3. When stabilization is necessary, mitigation for the loss of ecological function will be required.

4. Alternative methods (such as “log jams”) that can provide stabilization as well as fish habitat should be included in project alternatives.

5. Structural shoreline stabilization measures should only be used when more natural, flexible, nonstructural methods such as placing the development farther from the OHWM, planting vegetation, or installing on-site drainage improvements have been determined infeasible. Alternatives for shoreline stabilization should be based on the following hierarchy of preference:

a. No action (allow the shoreline to retreat naturally), increase buffers, and relocate structures;

b. Nonstructural methods such as drainage control, vegetative plantings, or relocation of structures;

c. Flexible defense works constructed of natural materials including soft shore protection, bioengineering, including protective berms, flood fencing or vegetative stabilization;

d. Rigid works constructed of artificial materials such as riprap or concrete.

6. Structures should be located and designed to avoid the need for future shoreline stabilization where feasible. Land subdivisions should be designed to assure that future development of the created lots will not require shore stabilization for reasonable development to occur.

7. New or expanded structural shoreline stabilization should only be permitted where demonstrated to be necessary to protect an existing primary structure, including residences, that is in danger of loss or substantial damage, and where mitigation of impacts would not cause a net loss of shoreline ecological functions and processes.

8. New or expanded structural shoreline stabilization for enhancement, restoration, or hazardous substance remediation projects should only be allowed when nonstructural measures, vegetation planting, or on-site drainage improvements would be insufficient to achieve enhancement, restoration or remediation objectives.

9. Shoreline stabilization should not be permitted when it interferes with public access to shorelines of the state, nor with other appropriate shoreline uses including, but not limited to, private recreation.

10. Shoreline stabilization should be developed in a coordinated manner among affected property owners and public agencies, particularly those that cross jurisdictional boundaries, to address ecological and geo-hydraulic processes and sediment conveyance issues. Where erosion threatens existing development, a comprehensive program for shoreline management should be established by the multiple affected property owners.

11. Provisions for multiple use, restoration, and/or public shore access should be incorporated into the location, design and maintenance of shore stabilization for public or quasi-public developments whenever safely compatible with the primary purpose. Shore stabilization on publicly owned shorelines should not be allowed to decrease long-term public use of the shoreline.

12. Materials used for construction of shoreline stabilization should be selected for long-term durability, ease of maintenance, compatibility with local shoreline features including aesthetic values, ability to provide fish and wildlife habitat, and flexibility for future uses.

13. New development that would require shoreline stabilization which causes significant impacts to adjacent or down-current properties and shoreline areas should not be allowed.

1. General. The purpose of this section is to provide standards and guidelines for the location and design of structural and nonstructural shoreline stabilization measures that have the potential to adversely impact the shoreline natural environment. New development, however, shall be located and designed to avoid the need for future shoreline stabilization to the extent feasible. In all cases, the feasibility of nonstructural measures shall be evaluated first, and then soft structural shoreline stabilization shall be evaluated prior to hard structural stabilization. Shoreline stabilization shall be designed so that net loss of ecological functions does not occur.

2. Sequencing. Structural shoreline stabilization measures shall only be used when more natural, flexible, nonstructural methods such as placing the development farther from the OHWM, planting vegetation, or installing on-site drainage improvements have been determined infeasible. Alternatives for shoreline stabilization shall be based on the following hierarchy of preference:

a. No action (allow the shoreline to retreat naturally), increase buffers, and relocate structures;

b. Flexible defense works constructed of natural materials including soft shore protection, bioengineering, including protective berms, flood fencing or vegetative stabilization;

c. Rigid works constructed of artificial materials such as riprap or concrete.

Applicants shall submit demonstration of stabilization sequencing in a form acceptable to the shoreline administrator.

3. New or Enlarged Structural Shoreline Stabilization. New structural shoreline stabilization measures, including both hard and soft structural shoreline stabilization measures, shall include measures installed to address erosion impacts. Enlargement of an existing structural shoreline stabilization shall include additions to or increases in size (such as height, width, length, or depth) to existing shoreline stabilization measures and these enlargements shall be considered new structures. New or enlarged structural stabilization measures shall not be allowed, except as follows:

a. To protect an existing primary structure, including residences, when conclusive evidence, documented by a geotechnical analysis, is provided that the structure is in danger from shoreline erosion. Normal sloughing or shoreline erosion itself, without a scientific or geotechnical analysis, is not demonstration of need. The geotechnical analysis should evaluate on-site drainage issues and address drainage problems away from the shoreline edge before considering hard or soft structural shoreline stabilization;

b. In support of new nonwater-dependent development, including single-family residences, when all of the conditions below apply:

i. The erosion is not being caused by upland conditions, such as drainage and the loss of vegetation,

ii. Nonstructural measures, such as placing the development farther from the shoreline, planting vegetation, or installing on-site drainage improvements, are not feasible or not sufficient to adequately address erosion impacts,

iii. The need to protect primary structures from damage due to erosion is demonstrated through a geotechnical report. Erosion must be caused by natural processes; or

c. In support of water-dependent development when all of the conditions below apply:

i. The erosion is not being caused by upland conditions, such as drainage and the loss of vegetation,

ii. Nonstructural measures, such as planting vegetation, or installing on-site drainage improvements, are not feasible over time or not sufficient to adequately address erosion causes or impacts,

iii. The need to protect primary structures, including residences, from damage due to erosion is demonstrated through a geotechnical report; or

d. To protect projects for the restoration of ecological functions or for hazardous substance remediation projects pursuant to Chapter 70.105D RCW when nonstructural measures, planting vegetation, or installing on-site drainage improvements are not feasible or not sufficient to adequately address erosion causes or impacts.

4. Repair of Existing Shoreline Stabilization Measures. This section allows repair and maintenance of existing shoreline stabilization measures, subject to all of the following standards: (Note: repair and replacement of shoreline stabilization structures may meet the criteria for exemption from a shoreline substantial development permit, but they are not exempt from the policies and regulations of this section or the SMP.)

a. Maintenance and repair shall include modifications or improvements to an existing shoreline stabilization measure that are designed to ensure the continued function of the stabilization measure by preventing failure of any part of the stabilization measure;

b. Modifications or improvements that include additions to or increases in size of existing shoreline stabilization measures shall be considered new structures and are not a repair;

c. Replacement of greater than 50 percent or 35 feet, whichever is smaller, of linear length of existing shoreline stabilization on a waterfront parcel is not considered a repair for purposes of these regulations and must be designed and reviewed as a replacement subject to the provisions contained in subsection (B)(5)(b) of this section. For shoreline stabilization projects, “replacement” occurs when the existing structure, including its footing or bottom course of rock, is removed prior to placement of new shoreline stabilization materials. Repairs that involve only removal of material above the footing or bottom course of rock are not considered replacements. Replacement of existing shoreline stabilization may still qualify for an exemption from a Shoreline Substantial Development Permit as listed in subsection (B)(3) of this section;

d. Areas of temporary disturbance within the shoreline buffer shall be expeditiously restored to their pre-project condition or better;

e. The placement of a new shoreline stabilization structure landward of a failing shoreline stabilization structure shall be considered a new structure and is not maintenance or repair.

5. Replacement. The following standards apply to replacement of existing hard and soft structural shoreline stabilization measures:

a. For purposes of this section, “replacement” means the construction of a new structure to perform a shoreline stabilization function of an existing structure that can no longer adequately serve its purpose. Additions to or increases in size of existing shoreline stabilization measures shall also be considered new structures;

b. Replacement shall be treated as a new shoreline stabilization measure subject to the restrictions of subsection (B)(3) of this section, as well as the submittal requirements of subsection (B)(9) of this section, except for the requirement to prepare a geotechnical analysis. A geotechnical analysis is not required for replacements of existing hard or soft structural shoreline stabilization with a similar or softer measure if the applicant demonstrates a need to protect principal uses or structures from erosion caused by natural processes operating at or waterward of the OHWM;

c. Replacement of hard structural shoreline stabilization measures shall not encroach waterward of the OHWM or waterward of the existing shoreline stabilization measure unless the residence was occupied prior to January 1, 1992, and there are overriding safety or environmental concerns. In such cases, the replacement structure shall abut the existing shoreline stabilization structure. All other replacement hard structural shoreline stabilization measures shall be located at or landward of the existing shoreline stabilization structure;

d. Hard shoreline stabilization measures may allow some accessory fill (cobble, gravel, or small material only) waterward of the OHWM to provide enhancement of shoreline ecological functions. In such cases, a study is required to ensure the flood storage and conveyance capacity shall not decrease;

e. Soft shoreline stabilization measures that provide restoration of shoreline ecological functions may be permitted waterward of the OHWM.

6. General Design Standards. When a hard or soft structural shoreline stabilization measure is demonstrated to be necessary, the following design standards shall be incorporated into the stabilization design:

a. Soft structural shoreline stabilization measures shall be used to the maximum extent practicable for new, enlarged, or replacement shoreline stabilization measures, limiting hard structural shoreline stabilization measures to the portion or portions of the site where necessary to protect or support existing shoreline structures or trees, or where necessary to connect to existing shoreline stabilization measures on adjacent properties. Hard structural shoreline stabilization transition areas between the applicant’s otherwise soft shoreline measure and the adjacent hardened shoreline, when needed on the subject property to prevent destabilization of adjacent hardened shorelines, should be minimized and extend into the subject property from the property line no more than 10 feet;

b. For enlarged or replacement soft and hard structural shoreline stabilization measures, the following location and design standards are preferred in descending order:

i. Conduct excavation and fill activities associated with the soft or hard structural shoreline stabilization landward of the existing OHWM to the maximum extent practicable,

ii. Where subsection (B)(6)(b)(i) of this section is not practicable because of overriding safety or environmental concerns, conduct necessary excavation and fill activities waterward of the existing OHWM as needed to implement a soft structural shoreline stabilization technique or to mitigate the impacts of hard structural shoreline stabilization;

c. All approved new, enlarged, repair, or replacement shoreline stabilization measures must minimize and mitigate any adverse impacts to ecological functions resulting from short-term construction activities, consistent with SPMC 15.14.290 (Ecological Protection and Critical Areas) and Appendix B (Critical Areas Regulations). Impact minimization techniques may include compliance with appropriate timing restrictions, use of best management practices to prevent water quality impacts related to upland or in-water work, and stabilization of exposed soils following construction;

d. All new, enlarged, or replacement hard structural shoreline stabilization measures should minimize any long-term adverse impacts to ecological functions by incorporating the following measures into the design:

i. Limiting the size of hard structural shoreline stabilization measures to the minimum necessary, including height, depth, and mass,

ii. Shifting the hard structural shoreline stabilization landward and/or sloping the hard structural shoreline stabilization landward to provide some dissipation of wave energy and increase the quality or quantity of nearshore shallow-water habitat,

iii. Fish habitat components;

e. Approved new and enlarged shoreline stabilization measures shall mitigate any adverse impacts to ecological functions by incorporating the following measures at a minimum into the design if appropriate for local conditions:

i. Restoration of appropriate substrate conditions waterward of the OHWM, to include substrate composition and gradient. The material should be sized and placed to remain stable during a two-year flood event,

ii. Plant native riparian vegetation, a minimum 10 feet in width, along the shoreline frontage affected by the new or enlarged stabilization, along the water’s edge. The vegetated portion of the shoreline buffer shall be approved by the shoreline administrator,

iii. Additional mitigation measures may be required by the town, depending on the level of impact;

f. The shoreline stabilization measure shall be designed to not significantly interfere with normal surface and/or subsurface drainage into the adjacent waterbody;

g. The shoreline stabilization measure shall be designed to ensure that it does not restrict appropriate public access to the shoreline. Access measures should not extend farther waterward than the face of the shoreline stabilization measure and the OHWM;

h. Shoreline stabilization measures shall not extend waterward more than the minimum amount necessary to achieve effective stabilization, except for those elements that enhance shoreline ecological functions and minimize impacts;

i. If repair or replacement of shoreline stabilization measures intended to improve ecological functions shift the OHWM landward of the pre-modification location and result in expansion of the shoreline jurisdiction on any property other than the subject property, the plan shall not be approved until the applicant submits a copy of a statement signed by the property owners of all affected properties, in a form approved by the town and recorded with Pierce County, consenting to the shoreline jurisdiction creation and/or increase on such property.

7. Specific Hard Structural Shoreline Stabilization Design Standards. In those limited instances when hard structural shoreline stabilization measures, such as concrete or riprap, are demonstrated to be necessary as outlined in subsection (B)(9)(a) of this section, the following standards shall be incorporated into the design:

a. In those limited cases when hard structural shoreline stabilization is approved on a site where hard structural shoreline stabilization is not located on adjacent properties, the construction of hard structural shoreline stabilization shall tie in with the existing contours of the adjoining properties, as feasible, such that the proposed stabilization would not cause erosion of the adjoining properties;

b. When hard structural shoreline stabilization measures are proved to be necessary, the stabilization structure shall:

i. Tie into existing contours of the adjacent parcel, or

ii. Tie into the existing adjacent stabilization structures.

At no time shall the above options permit the placement of fill below the ordinary high-water mark or create new uplands;

c. Fill behind hard structural shoreline stabilization shall be limited to one cubic yard per running foot of stabilization. Any filling in excess of this amount shall be considered a regulated activity subject to the regulations in this chapter pertaining to fill activities and the requirement for obtaining a shoreline substantial development permit or shoreline conditional use permit;

d. All structures should include fish habitat elements.

8. Specific Soft Structural Shoreline Stabilization Design Standards. In addition to applicable general design standards and hard structural shoreline stabilization standards above, the following standards shall be incorporated into the design:

a. The soft shoreline stabilization design shall provide sufficient protection of adjacent properties by:

i. Tying into the existing contours of the adjacent parcel, or

ii. Tying into the existing adjacent stabilization structures.

At no time shall the above options permit the placement of fill below the ordinary high-water mark or create new uplands. A maximum of 10 feet of hard structural measures may be utilized to tie into adjacent structures;

b. The soft shoreline stabilization design shall size and arrange any gravels, cobbles, logs, and boulders so that the project remains stable during a two-year flood event.

9. Submittal Requirements. In addition to submitting an application for the appropriate shoreline permit, the applicant shall submit the following as part of a request to construct a new, enlarged, or replacement shoreline stabilization measure:

a. For a new or enlarged hard or soft structural shoreline stabilization measure, a geotechnical report prepared by a qualified professional with an engineering degree (see subsection (B)(9)(b) of this section for replacement structures). The report shall include the following:

i. An assessment of the necessity for structural shoreline stabilization by estimating time frames and rates of erosion and reporting on the urgency associated with the specific situation. New hard structural shoreline stabilization measures shall not be authorized, except when a report confirms that that there is a significant possibility that an existing structure will be damaged within three years as a result of shoreline erosion in the absence of such hard structural shoreline stabilization measures, or where waiting until the need is immediate results in the loss of opportunity to use measures that would avoid impacts on ecological functions. Where the geotechnical report confirms a need to prevent potential damage to a primary structure, but the need is not as immediate as three years, that report may still be used to justify more immediate authorization to protect against erosion using soft measures;

ii. An assessment of the cause of erosion, looking at processes occurring both waterward and landward of the OHWM;

iii. An assessment of alternative measures to shoreline stabilization, including:

(a) Placing the development farther from the OHWM,

(b) Correcting any on-site ground water or drainage issues that may be causing shoreline erosion,

iv. Where structural shoreline stabilization is determined to be necessary, the assessment must evaluate the feasibility of using soft shoreline stabilization measures in lieu of hard structural shoreline stabilization measures. Soft shoreline stabilization may include the use of gravels, cobbles, boulders, and logs, as well as vegetation;

v. Design recommendations for minimum sizing of hard structural or soft structural shoreline stabilization materials, including gravel and cobble beach substrates necessary to dissipate wave energy, eliminate scour, and provide long-term shoreline stability.

b. For replacements of existing hard structural shoreline stabilization measures with a similar measure, the applicant shall submit a written narrative providing a demonstration of need. The narrative must be prepared by a qualified professional. The demonstration of need shall consist of the following:

i. An assessment of the necessity for continued structural shoreline stabilization, considering site-specific conditions such as water depth, orientation of the shoreline, wave fetch or flow velocities, and location of the nearest primary structure;

ii. An assessment of erosion potential resulting from the action of waves or other natural processes operating at or waterward of the OHWM in the absence of the hard structural shoreline stabilization;

iii. An assessment of alternative measures to shoreline stabilization, including:

(a) Relocating the development farther from the OHWM,

(b) Correcting any on-site ground water or drainage issues that may be causing shoreline erosion;

iv. An assessment of the feasibility of using soft shoreline stabilization measures in lieu of hard structural shoreline stabilization measures. Soft structural shoreline stabilization may include the use of gravels, cobbles, boulders, and logs, as well as vegetation;

v. Design recommendations for minimizing impacts of any necessary hard structural shoreline stabilization.

c. A demonstration of need may be waived when an existing hard structural shoreline stabilization measure is proposed to be repaired or replaced using soft structural shoreline stabilization measures, resulting in significant restoration of shoreline ecological functions or processes.

d. For all structural shoreline stabilization measures, including soft structural shoreline stabilization, detailed construction plans, including, but not limited to, the following:

i. Plan and cross-section views of the existing and proposed shoreline configuration, showing accurate existing and proposed topography and OHWMs;

ii. Detailed construction sequence and specifications for all materials, including gravels, cobbles, boulders, logs, and vegetation. The sizing and placement of all materials shall be selected to accomplish the following objectives:

(a) Protect the primary structures from erosion and other damage over the long term, and accommodate the normal amount of alteration from erosion,

(b) Allow safe passage and migration of fish and wildlife, and

iii. For projects that include native vegetation, a detailed five-year vegetation maintenance and monitoring program to include the following:

(a) Goals and objectives of the shoreline stabilization plan,

(b) Success criteria by which the implemented plan will be assessed,

(c) A five-year maintenance and monitoring plan, consisting of at least one site visit per year by a qualified professional, with annual progress reports submitted to the shoreline administrator and all other agencies with jurisdiction, and

(d) A contingency plan in case of failure. [Ord. 580 Att. A § 5.10, 2019.]