13.11.150 Shoreline stabilization | Bothell Municipal Code

13.11.150 Shoreline stabilization.

Shoreline stabilization includes actions taken to address erosion impacts to property and dwellings, businesses, or structures caused by natural processes, such as current, flood, wind, or wave action. These actions include structural and nonstructural methods. Nonstructural methods include shoreline buffers or setbacks, relocation of the structure to be protected, groundwater management, and planning and regulatory measures to avoid the need for structural stabilization. Structural methods include hard and soft structural stabilization. “Hard” structural stabilization measures refer to those with solid, hard surfaces, such as concrete or stacked boulder bulkheads, while “soft” structural measures utilize more natural arrangements of hard and soft materials, including boulders, cobble, gravels, large woody debris and vegetation. Soft shoreline stabilization is preferred because it protects development while minimizing impacts to ecological functions. Generally, the harder the construction measure, the greater the impact on shoreline processes, including sediment transport, geomorphology, and biological functions.

1. The feasibility of nonstructural or soft structural shoreline stabilization using natural materials, such as logs, root wads, plant materials, soil stabilization and other soft methods, shall be evaluated when new, enlarged or replacement hard structural shoreline stabilization measures are being considered. The appropriate documentation per subsection H of this section shall be submitted to demonstrate that nonstructural and soft structural alternatives have been thoroughly evaluated, and only the softest technique that will accomplish the necessary stabilization shall be approved.

2. A qualified professional (see Chapter 13.03 BMC for complete definition) with experience and education or training in the pertinent discipline, such as a fisheries biologist, hydrogeologist, geotechnical engineer, or landscape architect, shall prepare shoreline stabilization plans. The required geotechnical report must be prepared by a professional engineer or geologist who has professional expertise about the regional and local shoreline geology and processes.

3. When any structural shoreline stabilization measures are demonstrated to be necessary, the size of stabilization measures shall be limited to the minimum necessary.

4. Shoreline stabilization shall be designed so that no net loss of ecological functions occurs.

5. Publicly financed or subsidized shoreline erosion control measures shall not restrict appropriate public access to the shoreline except where such access is determined to be infeasible because of incompatible uses, safety, security, or harm to ecological functions. Where feasible, ecological restoration and public access improvements shall be incorporated into the project.

1. New development shall be located and designed to avoid the need for new or enlarged shoreline stabilization.

2. New development on erosion or landslide geologically hazardous areas, as defined and regulated in BMC 13.13.050, shall be designed to ensure that shoreline stabilization is unlikely to be necessary during the life of the structure, as demonstrated by a geotechnical analysis.

3. New shoreline stabilization which causes significant adverse impacts to adjacent or down-current properties and shoreline areas shall not be allowed.

4. Lots shall not be created by the subdivision process if such lots require shoreline stabilization in order to accommodate development.

5. New or enlarged structural stabilization measures shall be allowed in the following circumstances:

a. To protect an existing primary structure, including residences, when conclusive evidence, documented by a geotechnical report prepared by a qualified professional engineer or geologist, is provided that the structure is in danger from shoreline erosion caused by currents, boat wakes, or waves. 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 before considering shoreline stabilization.

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

(1) The erosion is not being caused by upland conditions inside or outside of shoreline jurisdiction, such as drainage or the loss of vegetation;

(2) 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 adverse erosion impact; and

(3) The need to protect primary structures from damage due to erosion is demonstrated through a geotechnical report prepared by a qualified professional engineer or geologist. The damage must be caused by conditions beyond the control of the applicant, such as natural processes, including currents or waves.

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

(1) The erosion is not being caused by upland conditions on the subject property, such as drainage, the presence of inadequate on-site surface water control, or the loss of vegetation. Upland conditions on the subject property that result in erosion should be addressed before approving new or enlarged shoreline stabilization;

(2) The erosion is being caused by upland conditions outside of shoreline jurisdiction or on adjacent properties outside of the applicant’s control, such as drainage, the presence of inadequate upstream surface water control, or the loss of vegetation;

(3) Nonstructural measures, such as planting vegetation, or installing on-site drainage improvements, are not feasible or not sufficient to adequately address erosion causes or adverse impacts; and

(4) The need to protect primary structures, including residences, from damage due to erosion is demonstrated through a geotechnical report prepared by a qualified professional engineer or geologist who has professional expertise about the regional and local shoreline geology and processes.

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 adverse impacts.

1. For purposes of this section, “replacement” means the construction of new shoreline stabilization to perform the shoreline stabilization function of an existing structure which can no longer adequately serve its purpose due to age, deterioration, or increased flood flow rates and volumes. Replacements that include additions to or increases in size of existing shoreline stabilization measures shall be considered new structures.

2. An existing structural stabilization structure may be replaced subject to the following provisions:

a. There is a demonstrated need to protect principal uses or structures from erosion caused by currents, tidal action, or waves.

b. Replacement hard structural shoreline stabilization measures protecting existing residences 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 is 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.

c. Shoreline stabilization measures may allow some fill waterward of the OHWM to provide enhancement of shoreline ecological functions through improvements in substrate condition or gradient.

3. When replacement is allowed pursuant to the provisions of subsection (C)(2) of this section, an existing structural stabilization structure shall be replaced with the softest stabilization measure that will provide the necessary level of stabilization consistent with the findings of the required submittal documents outlined in subsection H of this section.

1. For purposes of this section, “repair” means modifications or improvements to an existing shoreline stabilization structure that are designed to ensure the continued function of the structure by preventing failure of any part.

2. “Repair” shall not include:

a. Additions to or increases in size of existing shoreline stabilization structures. Such additions or increases shall be considered new or enlarged structures;

b. The placement of a new shoreline stabilization structure landward of a failing shoreline stabilization structure. Such placement shall be considered a new structure; and

c. Replacement of greater than 50 percent of the linear length of existing shoreline stabilization structure when an 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 replacement). Such activity must be designed and reviewed as a replacement structure.

1. Areas of temporary disturbance within the shoreline buffer shall be stabilized within seven days of project completion, and revegetated within 30 days using native plant species that will return the area to its preproject condition or a condition with improved ecological functions such as increased native tree or shrub cover, or shade of water bodies.

2. Soft shoreline stabilization structures shall be used to the maximum extent practicable for new, enlarged, and replacement of legally established shoreline stabilization structures, limiting hard shoreline stabilization structures to the portion or portions of those sites determined necessary to protect or support existing shoreline structures or trees, or where necessary to connect to existing hard structural shoreline stabilization structures on adjacent properties. Hard structural shoreline stabilization transition areas between the applicant’s otherwise soft shoreline structure and the adjacent hardened shoreline, when needed on the subject property to prevent destabilization of adjacent hardened shorelines, shall be minimized and extend into the applicant’s property from the property line no more than 10 feet and shall not extend onto the adjacent property.

3. For enlarged or replacement shoreline stabilization structures, the following location and design standards are preferred in descending order:

a. Conduct excavation and fill activities associated with the structural shoreline stabilization landward of the existing OHWM except as authorized above.

b. Where subsection (E)(3)(a) 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 adverse impacts of adjacent hard structural shoreline stabilization.

4. All shoreline stabilization activities shall minimize and mitigate any adverse impacts to ecological functions resulting from short-term construction. Impact minimization techniques may include compliance with appropriate timing restrictions, use of best management practices to prevent adverse water-quality impacts related to upland or in-water work, and stabilization of exposed soils following construction.

5. New and enlarged shoreline stabilization structures shall mitigate any adverse impacts to ecological functions by incorporating the following measures, at a minimum, if appropriate for local conditions:

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

b. Plant native riparian vegetation, as necessary, along at least 75 percent of the shoreline frontage affected by the new or enlarged stabilization. The vegetated portion of the shoreline buffer shall average 20 feet in depth from the OHWM, but may be a minimum of 10 feet wide to allow for variation in landscape bed shape and plant placement. Restoration of native vegetation shall consist of a mixture of trees, shrubs, and groundcover and be designed to improve habitat functions. At least three trees per 100 linear feet of shoreline must be included in the plan. Plant materials must be native to King or Snohomish County. An alternative planting plan or mitigation measure in lieu of meeting these requirements may be allowed if approved by other state and federal agencies.

6. The shoreline stabilization structure shall not interfere with normal surface and/or subsurface drainage into the water body.

7. The shoreline stabilization measure shall be designed so as not to constitute a hazard to navigation.

8. Stairs or other water-access measures may be incorporated into the shoreline stabilization structures (e.g., steps integrated into the bulkhead), but shall not extend waterward of the shoreline stabilization structure and the OHWM.

9. The shoreline stabilization structure shall be designed to ensure that it does not restrict appropriate public access to the shoreline. When a structural shoreline stabilization measure is required at a public access site, provisions for safe access to the water shall be incorporated into the shoreline stabilization structure design (e.g., steps integrated into the bulkhead). Access measures should not extend farther waterward than the face of the shoreline stabilization measure and the OHWM.

10. Shoreline stabilization structures shall not extend waterward of the OHWM, except for soft shoreline stabilization elements which enhance shoreline ecological functions or are allowed under subsection (C)(2)(b) of this section.

11. When repair or replacement shoreline stabilization structures intended to improve ecological functions shift the OHWM landward of the premodification location, any buffers from the OHWM or lot area for the purposes of calculating lot coverage shall be measured from the premodification location. The premodification OHWM shall be noted in a record of survey approved by the city of Bothell and recorded at the King or Snohomish County recorder’s office.

12. Repair or replacement shoreline stabilization measures which relocate the OHWM landward of the premodification location, and result in an expansion of the shoreline jurisdiction on any property other than the subject property, shall not be approved until the applicant submits a copy of a statement signed by the legal owners of all affected properties, on a form approved by the city of Bothell and recorded at the King or Snohomish County recorder’s office, consenting to the shoreline jurisdiction creation and/or increase on such property.

1. The soft structural shoreline stabilization design shall provide sufficient protection of adjacent properties by tying in with the existing contours of the adjoining properties to prevent erosion at the property line. Projects that include necessary use of hard structural shoreline stabilization measures only near property lines in order to tie in with adjacent properties shall be permitted as soft shoreline stabilization measures. The length of hard structural shoreline stabilization transition area to adjacent properties should be minimized to the maximum extent practicable, and extend into the subject property from adjacent properties no more than 10 feet. The hard structural shoreline stabilization transition area shall not extend waterward of the OHWM, except as necessary to make the connection to the adjoining stabilization, and shall not extend onto the adjacent property.

2. 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 and dissipates wave and current energy, without presenting extended linear faces to oncoming waves or currents.

3. 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 currents and waves;

b. Allow safe passage and migration of fish and wildlife; and

c. Minimize or eliminate juvenile salmon predator habitat.

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

a. Limiting the size of hard shoreline stabilization structures to the minimum necessary to protect existing upland development, including length, height, depth, and mass; and

b. Shifting the hard shoreline stabilization structures landward and/or sloping the hard shoreline stabilization structures landward to provide some dissipation of wave energy and increase the quality or quantity of habitat.

2. 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.

3. The following provisions apply when hard structural shoreline stabilization is approved on a site where hard structural shoreline stabilization is located on adjacent properties:

a. The proposed stabilization may tie in flush with existing stabilization measures on adjoining properties; provided, that:

(1) The new stabilization does not extend waterward of the OHWM, except as necessary to make the connection to the adjoining stabilization; and

(2) The new stabilization does not extend onto the adjacent property.

b. Where a portion of stabilization extends waterward of the OHWM per subsection (G)(3)(a)(1) of this section, the remaining portion of the stabilization shall be placed landward of the existing OHWM such that no net intrusion into the water body occurs nor does net creation of uplands occur.

4. Backfill behind hard structural shoreline stabilization intended to protect single-family residences 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 SMP pertaining to fill activities and the requirement for obtaining a shoreline substantial development permit or shoreline conditional use permit.

1. For all new, enlarged, or replacement structural shoreline stabilization structures (including soft shoreline stabilization structures), detailed construction plans, including, but not limited to, the following:

a. Plan and cross-section views of the existing and proposed shoreline configuration, showing accurate existing and proposed topography and ordinary high water lines; and

b. Detailed construction sequence and specifications for all materials, including gravels, cobbles, boulders, logs, and vegetation.

2. 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 the performance objectives of the plan are not met.

3. For new or enlarged hard or soft shoreline stabilization structures, a geotechnical report prepared by a qualified professional with an engineering license. The report shall include the following:

a. 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 shoreline stabilization structures shall not be authorized, except when a report confirms 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 shoreline stabilization structures, or where waiting until the need is immediate results in the loss of opportunity to use measures that would avoid adverse 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, the report may still be used to justify more immediate authorization to protect against erosion using soft structures.

b. An assessment of the cause of erosion, looking at processes occurring both waterward and landward of the ordinary high water mark.

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

(1) Placing the development farther from the ordinary high water mark.

(2) Correcting any on-site groundwater or drainage issues that may be causing shoreline erosion.

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

5. Design recommendations for minimum sizing of hard 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.

6. For replacements of existing hard shoreline stabilization structures with a similar hard structure, the applicant shall submit a written narrative providing a demonstration of need. The narrative must be prepared by a qualified professional and shall consist of the following:

a. 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.

b. 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.

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

(1) Relocating the development farther from the OHWM;

(2) Correcting any on-site groundwater or drainage issues that may be causing shoreline erosion; and

(3) An assessment of the feasibility of using soft shoreline stabilization measures in lieu of hard structural shoreline stabilization measures.

7. Soft structural shoreline stabilization may include the use of gravels, cobbles, boulders, and logs, as well as vegetation.

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

9. A demonstration of need may be waived when an existing hard shoreline stabilization structure is proposed to be repaired or replaced using soft shoreline stabilization structure that would result in significant restoration of shoreline ecological functions or processes. (Ord. 2112 § 3 (Exh. C), 2013).