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BEST AVAILABLE SCIENCE REVIEW FOR RIPARIAN AND WETLANDS AREAS IN DOUGLAS COUNTY PREPARED FOR: DOUGLAS COUNTY TRANSPORTATION AND LAND SERVICES 140 19TH STREET N.W. EAST WENATCHEE, WA 98802 PREPARED BY: GRETTE ASSOCIATESLLC

151 SOUTH WORTHEN, SUITE 101 WENATCHEE, WASHINGTON 98801 (509) 663-6300 SEPTEMBER 2018

Douglas County Shoreline Master Program i September 2018 BAS Review for Riparian and Wetlands Areas Grette AssociatesLLC

TABLE OF CONTENTS 1 INTRODUCTION .................................................................................................................. 1

2 SOURCES OF BEST AVAILABLE SCIENCE .................................................................... 3

3 FISH AND WILDLIFE HABITAT AND CONSERVATION AREAS ................................ 6

3.1 RIPARIAN HABITAT ........................................................................................................... 6

3.2 GENERAL CHARACTERISTICS OF DOUGLAS COUNTY RIPARIAN AREAS .............................. 8

3.3 RIPARIAN HABITAT FUNCTIONS ...................................................................................... 14

3.3.1 Fish and Wildlife Habitat ................................................................................... 14

3.3.2 Shade and Cover ................................................................................................ 15

3.3.3 Erosion Control .................................................................................................. 16

3.3.4 Water Quality ..................................................................................................... 17

3.3.5 Organic Input ..................................................................................................... 19

3.4 SPECIAL CONSIDERATION OF ANADROMOUS FISHERIES .................................................. 20

3.5 RECOMMENDATIONS ....................................................................................................... 22

3.5.1 Recommended Riparian Buffers ........................................................................ 22

4 WETLANDS......................................................................................................................... 23

5 SPECIFIC BEST AVAILABLE SCIENCE REVIEW QUESTIONS ................................. 25

6 REFERENCES ..................................................................................................................... 29

Douglas County Shoreline Master Program 1 September 2018 BAS Review for Riparian and Wetlands Areas Grette AssociatesLLC

1 INTRODUCTION

The Shoreline Management Act (SMA) of 1971 regulates development within 200 feet of Shorelines of the State and Shorelines of Statewide Significance, along with the lands within 200 feet of the ordinary high water mark (OHWM) of those waterways, floodplains up to 200 feet from the floodway edge, and associated wetlands. The goal of the SMA is “to prevent the inherent harm in an uncoordinated and piecemeal development of the state’s shorelines” (Revised Code of Washington 90.58.020; RCW).

The SMA requires counties to adopt a Shoreline Master Program (SMP), which contains goals, policies, regulations, and a use map. Following adoption of the SMP and pursuant to RCW 90.58.080(4), the SMA requires that jurisdictions review the science surrounding their SMP to ensure that the program complies with applicable laws and guidelines in effect and to assure consistency with local governments comprehensive plan and development regulations. As outlined in RCW 90.58.080(4)(b)(iii), Douglas County must complete this review on or before June 30, 2021. As part of this review, Douglas County is currently reviewing the structure and effectiveness of the SMP provisions relating to wetlands and fish and wildlife habitat conservation areas. The review will ensure that the County is meeting the resource protection goals of the SMA and assist with determining if revisions to these sections of the SMP are warranted.

Grette Associates has been contracted to conduct a review of Best Available Science (BAS) surrounding the Douglas County SMP. Specifically, Grette Associates will review Chapter 2 (Wetlands) and Chapter 3 (Fish and Wildlife Habitat Conservation Areas) of Appendix H of the SMP. The review of the existing critical areas code will occur to determine if the existing regulations and protections are consistent with the current knowledge and science available. The review of existing information regarding the protection of wetlands, riparian areas, and aquatic habitat will satisfy the requirement for a BAS review. The BAS review will specifically focus on the following six (6) issues:

1. Are the current wetland buffers, riparian area buffers and structural setbacks appropriately contributing to achieving the no net loss of ecological functions standards of WAC 173-26-201 (2)(c)?

2. Does the current BAS applicable to Douglas County support the current wetland buffers, riparian area buffers, and structural setbacks?

3. Is there best available science and/or compensatory mitigation applicable to Douglas County that could support modifications to default wetland and riparian buffers? If so, what modifications could be supported.

4. Do the provisions of the buffer width averaging (SMP 3.050(D)) and administrative buffer reduction (SMP 3.050 (E)) still provide a reasonable approach to balance resource protection goals and the circumstances of challenged properties?

5. Is the function and value of wetland buffers and riparian area buffers maintained by the SMP provisions and their application for private, single-family associated shoreline access trails?

6. Are mitigation ratios in the SMP and the structure of the five-year monitoring program and benchmarks appropriate? If not, what revisions are recommended.


The following is a review of the science of the functions of riparian and wetland buffers. The scope of this review is focused on residential development pressures along the Columbia River and other Douglas County Shorelines, particularly single-family residential development. This review does not primarily address uses such as agriculture or industrial.

This review utilizes related reviews of BAS previously conducted, including existing approved SMPs from other jurisdictions and their supporting BAS reviews, Washington Department of Ecology (Ecology) wetland buffer guidance, and Washington Department of Fish and Wildlife (WDFW) riparian and wildlife habitat recommendations. Primary sources are used, but to a limited degree.

Section 2 includes an overview of the functions of riparian buffers, as well as the best available science regarding buffer widths and characteristics necessary to provide those functions. A summary and recommendation is provided in Section 3. Section 4 addresses wetland buffers.


2 SOURCES OF BEST AVAILABLE SCIENCE

WAC 365-195-905 identifies eight sources of BAS: Research, Monitoring, Inventory, Survey, Modeling, Assessment, Synthesis, and Expert Opinion that are appropriate for use in updating Critical Areas Ordinances under the Growth Management Act. The table below (from WAC 365-195-905) presents text that describes the sources and characteristics of BAS. Information derived from one of the following sources may be considered scientific information if the source possesses the characteristics in Table 1.

Table 1. Characteristics of BAS sources

CHARACTERISTICS

SOURCES OF SCIENTIFIC INFORMATION

Pee

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Con

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Ref

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A. Research. Research data collected and analyzed as part of a controlled experiment (or other appropriate methodology) to test a specific hypothesis.

X X X X X X

B. Monitoring. Monitoring data collected periodically over time to determine a resource trend or evaluate a management program.

X X Y X X

C. Inventory. Inventory data collected from an entire population or population segment (e.g., individuals in a plant or animal species) or an entire ecosystem or ecosystem segment (e.g., the species in a particular wetland).

X X Y X X

D. Survey. Survey data collected from a statistical sample from a population or ecosystem.

X X Y X X

E. Modeling. Mathematical or symbolic simulation or representation of a natural system. Models generally are used to understand and explain occurrences that cannot be directly observed.

X X X X X X

F. Assessment. Inspection and evaluation of site-specific information by a qualified scientific expert. An assessment may or may not involve collection of new data.

X X X X

G. Synthesis. A comprehensive review and explanation of pertinent literature and other relevant existing knowledge by a qualified scientific expert.

X X X X X

H. Expert Opinion. Statement of a qualified scientific expert based on his or her best professional judgment and experience in the pertinent scientific discipline. The opinion may or may not be based on site-specific information.

X X X

X = characteristic must be present for information derived to be considered scientifically valid and reliable Y = presence of characteristic strengthens scientific validity and reliability of information derived, but is not essential to ensure scientific validity and reliability

Excerpt from WAC 365-195-905:

(a) Characteristics of a valid scientific process. In the context of critical areas protection, a valid scientific process is one that produces reliable information useful in understanding the consequences of a local government's regulatory decisions and in developing critical areas policies and development regulations that will be effective in protecting the functions and values of critical areas. To determine whether information received during the


public participation process is reliable scientific information, a county or city should determine whether the source of the information displays the characteristics of a valid scientific process. The characteristics generally to be expected in a valid scientific process are as follows:

1. Peer review. The information has been critically reviewed by other persons who are qualified scientific experts in that scientific discipline. The criticism of the peer reviewers has been addressed by the proponents of the information. Publication in a refereed scientific journal usually indicates that the information has been appropriately peer-reviewed.

2. Methods. The methods that were used to obtain the information are clearly stated and able to be replicated. The methods are standardized in the pertinent scientific discipline or, if not, the methods have been appropriately peer-reviewed to assure their reliability and validity.

3. Logical conclusions and reasonable inferences. The conclusions presented are based on reasonable assumptions supported by other studies and consistent with the general theory underlying the assumptions. The conclusions are logically and reasonably derived from the assumptions and supported by the data presented. Any gaps in information and inconsistencies with other pertinent scientific information are adequately explained.

4. Quantitative analysis. The data have been analyzed using appropriate statistical or quantitative methods.

5. Context. The information is placed in proper context. The assumptions, analytical techniques, data, and conclusions are appropriately framed with respect to the prevailing body of pertinent scientific knowledge.

6. References. The assumptions, analytical techniques, and conclusions are well referenced with citations to relevant, credible literature and other pertinent existing information. In addition, WAC 173-26-201(2)(a) provides counties with guidance on the process of preparing or amending their SMP. This section highlights the use of scientific and technical information to determine whether or not a proposed amendment demonstrates that it will result in no net loss of shoreline ecological functions. In order to do this, the County must first “identify and assemble the most current, accurate, and complete scientific and technical information available that is applicable to the issues of concern.” Secondly, “base master program provisions on analysis incorporating the most current, accurate, and complete scientific or technical information available.” “Where information collected by or provided to local governments conflicts or is inconsistent, the local government shall base master program provisions on a reasoned, objective evaluation of the relative merits of the conflicting data.”

Based on this guidance, this review of BAS relies heavily on information provided in a number of other documents relevant to the physical and biological environments present in Douglas County. Additionally, Larry Lehman and Glenn Grette provided Expert Opinion on buffer issues pertaining to wetlands and riparian areas of Douglas County. Grette Associates staff (led by Larry Lehman) has conducted approximately 200 assessments of the shorelines of the Columbia River reservoirs, ponds and streams pursuant to Douglas County’s Critical Areas Ordinance over the last fifteen years. This has included wetland ratings, wetland management mitigation plans that assess impacts to the wetland, and/or riparian area and association buffers. These assessments have been submitted to Douglas County planning staff in support of specific development permits and have been reviewed by Washington Department of Ecology (WDOE) and WDFW staff in accordance with their pertinent authorities.


These projects have provided extensive experience with the character and function of riparian vegetation in Douglas County. The firm’s experience with these assessments has been incorporated into the Expert Opinion supporting the recommendations in this report.

Mr. Lehman’s experience with Douglas County habitats is derived from the assessments he has prepared or directed along Douglas County shorelines as described above. Mr. Grette’s experience with riparian issues is based on previous research and publications he has contributed to on the interaction of riparian areas and salmon habitat in forested ecosystems, and over 30 years as a fisheries biologist working on salmon habitat issues in Washington State.


3 FISH AND WILDLIFE HABITAT AND CONSERVATION AREAS

3.1 RIPARIAN HABITAT

Recognizing that Douglas County must use BAS when updating riparian buffers (fish and Wildlife Habitat Conservation Areas Buffers), the County relies on the definitions of the National Research Council (NRC 2002). Because Douglas County’s riparian buffers will encompass riparian vegetation and upland vegetation as a means to provide effective buffers for its multiple purposes, clarity on the distinctions between the terms and the characteristics of these areas is important.

Douglas County’s riparian buffers need to serve two primary regulatory and ecological functions. They need to: 1) protect riparian vegetation that is a Fish/Wildlife Habitat Conservation Area (Appendix H) under the SMP; and 2) protect the physical and ecological functions in the adjacent aquatic environment. Protection of riparian vegetation is a relatively simple concept and entails determining the limits of such vegetation and applying appropriate measures to ensure no-net-loss of function. Protection of adjacent aquatic habitat is less clear cut. In arid environments the greatest influences on the adjacent aquatic habitat (e.g., shade, inputs of woody debris, filtration of turbid water) is provided by the lush riparian vegetation (see below) growing relatively close to the stream. The uplands located landward of this vegetation have much less influence on the aquatic habitat. Due to the multiple regulatory and ecological roles served by riparian buffers, the terms “riparian vegetation,” “riparian areas,” and “riparian buffers” are not synonymous and care is needed in their application to arid environments.

The NRC publication Riparian Areas: Functions and Strategies for Management uses the following definition for riparian areas:

Riparian areas are transitional between terrestrial and aquatic ecosystems and are distinguished by gradients in biophysical conditions, ecological processes, and biota. They are areas through which surface and subsurface hydrology connect water bodies with their adjacent uplands. They include those portions of terrestrial ecosystems that significantly influence exchanges of energy and matter with aquatic ecosystems (i.e., a zone of influence). Riparian areas are adjacent to perennial, intermittent, and ephemeral streams, lakes, and estuarine-marine shorelines (pg. 33).

The NRC has provided guidance on differentiating riparian areas from aquatic ecosystems based on hydrology, vegetation and soils; they state that

“riparian areas are normally dominated by woody plants (e.g., trees), grasses and emergent herbaceous plant cover, in contrast to aquatic ecosystems where these plant types are absent (pg. 40).” It is further concluded by the NRC that “the aquatic boundary of riparian areas could be established where permanent water begins (pg. 40).”

Based on this definition, the County uses the Ordinary High Water Mark (OHWM) as the boundary between aquatic habitats and riparian areas. The “landward” edge of riparian areas must also be defined. The NRC has defined riparian areas by their source of water in contrast to upland areas. This distinction is particularly important in arid areas such as Douglas County.


Unlike uplands that receive precipitation as their principal or only source of water, moisture in riparian areas may be supplied from both adjacent uplands and aquatic ecosystems. Water enters riparian areas from uplands in the form of groundwater discharge, shallow subsurface flow, and overland flow. From the aquatic side, water is supplied by over bank flow, infiltration through adjacent channel banks (Bank storage), and by hyporheic flow from alluvium upstream” (pg. 42). “…because riparian areas exist where depth to the water table is relatively shallow, specific assemblages of shrubs and trees withdraw water directly from the saturated area (Robinson, 1958), a phenomenon not generally possible in uplands. In low-elevation settings of arid landscapes, riparian areas may be the only place where cottonwoods and willows are present, and the only place where mesquite grows vigorously (Stromberg et al., 1996) (pg. 42-43).

Based on these considerations, the NRC concludes that riparian areas can be differentiated from uplands by their vegetation.

It is this complexity of vegetation types that contributes to the enormous richness of riparian areas in comparison to uplands, particularly in arid regions (Gregory et al., 1991; Brinson and Verhoeven, 1999). Thus, in the Great Plains and the arid and semiarid West, the contrast in species composition and physiognomic structure between riparian areas and uplands is large (pg. 91). Riparian forests persist in arid regions where there is insufficient precipitation to support upland forests (Brinson, 1990), thus creating a distinct boundary (pg. 43). In the lower elevations of the Great Basin, riparian forests are the only forests, and their structure varies substantially with latitude (Stine et al., 1984; Minshall, 1989). In the northwestern regions, riparian forests included black cottonwood, willow, hawthorn, water birch, chokecherry, and gray alder (pg. 95).

The NRC essentially defines “riparian areas” by the presence of “riparian vegetation” that is watered by rooting into groundwater rather than supported solely by direct rainfall. This definition of riparian areas is too limited for Douglas County’s use in developing its CAO. The NRC’s definition of riparian areas is appropriate to apply to the concept of “riparian vegetation” as used by Douglas County.

Therefore, the County’s “riparian buffer” encompasses the “riparian vegetation” (NRC’s “riparian areas”) and sufficient upland to ensure the ecological functions of the adjacent aquatic habitat are protected.

Based on the NRC’s definitions and Grette Associates’ experience in Douglas County riparian areas, we believe a clear delineation of the extent of the riparian vegetation can be made by examining the vegetation species present to determine where the influence of the river’s moisture regime ends and upland vegetation begins. The Critical Area that needs to be protected pursuant to the SMP is this typically narrow strip of riparian vegetation, the NRC’s “riparian area.” The Grette Proposal incorporates a riparian buffer, which extends beyond the riparian vegetation Critical Area up into the upland. Therefore, the approach extends the buffer beyond the limits of


the Critical Area, which is a conservative assumption relative to protecting the function of the riparian vegetation.

Further, according to WDFW’s definition, the riparian area is the area alongside a stream/river. The riparian area supports the riparian ecosystem, which is defined as:

The area alongside a river or stream that significantly influences exchanges of energy and matter with the aquatic ecosystem. It includes the active channel, the active floodplain and terraces, and portions of the adjacent uplands that contribute organic matter and energy to the active channel or floodplain. It is a zone of influence; a transitional ecotone between terrestrial and aquatic ecosystems that is distinguished by gradients in biophysical conditions, ecological processes, and biota. (Riparian Ecosystems 2018, p. xiii)

Riparian habitat provides numerous beneficial habitat functions. Prominent among these benefits are 1) fish and wildlife habitat, 2) shade and cover, 3) erosion control, 4) water quality, and 5) organic material input. The benefits of these functions are discussed in more detail below, along with a review of the best available science and a summary conclusion.

3.2 GENERAL CHARACTERISTICS OF DOUGLAS COUNTY RIPARIAN AREAS

Unlike the forested landscapes wherein most of the studies of buffer functions and effectiveness have been conducted, annual precipitation in Douglas County ranges from 6 to 12 inches, and potential evapotranspiration can exceed precipitation. Riparian habitat in Douglas County is limited by low precipitation and altered hydrology. Average annual precipitation in Waterville is 11.3 inches; along the Columbia River in southern Douglas County, annual precipitation averages as low as 8.75 inches (WRCC 2018). Thus, the native vegetation communities found throughout all but the highest-elevation portions of the County are dominated by shrubs and grasses adapted to arid or desert climates, and trees are rare. The composition of the vegetative community even along riparian areas in Douglas County is constrained by the local water table, and the position of the water table is primarily a function of riverbank slope. Therefore, the distribution of what has typically been considered “riparian vegetation” (i.e., lush growth of water-dependent species, especially trees such as black cottonwood [Populus trichocarpa]) along Douglas County waterways is variable, with expanses of shoreline vegetated only with arid grass and shrub communities interspersed with areas of distinctly lush vegetation (see Photographs 1 – 8 in Attachment 1). The distinction between these communities is that the lush vegetation is not supported by precipitation only and is a limited and valuable habitat type in this part of Washington. Further, it is this vegetation zone that influences adjacent aquatic habitat. The typical configuration for a riparian area is a narrow area of lush vegetation (often 0-50 ft in width), with an abrupt transition to arid upland habitat.

The Columbia River is the main water feature in Douglas County, with approximately 155 river miles within the county. Additionally, 26 lakes are under shoreline jurisdiction. Riparian habitat is typically limited to a narrow strip along watercourses. Columbia River riparian habitat in Douglas County is typically relatively narrow (less than 50 ft), depending on the slope of the riparian zone. Typically riparian habitat wider than 50 ft includes wetlands, which have their own buffers.


Photograph 1. Representative condition of the riparian habitat along the Columbia River adjacent to developed/disturbed properties; historic agricultural use.



Photograph 5. Representative condition of the riparian habitat along the Columbia River adjacent to undeveloped/undisturbed properties.



3.3 RIPARIAN HABITAT FUNCTIONS

Riparian habitats provide a transition between the upland areas and open water. The level of functions provided by riparian habitats is extremely variable and primarily dependent on existing vegetation, shoreline slopes, and adjacent land use. The functions provided by riparian habitat include:

Fish and wildlife habitat Shade and Cover Erosion Control Water Quality Organic Input

The functions, BAS review of these functions, and summary are provided below. 3.3.1 Fish and Wildlife Habitat

3.3.1.1 Function

Riparian areas provide vital habitat for fish and wildlife species, particularly in arid regions. It functions as a corridor for movement of animals within drainage (Gregory et al. 1991). It is estimated that, in the west, up to 70% of bird species are dependent on riparian habitat for survival and breeding (Ohmart 1996). Similarly, wildlife are either directly dependent on riparian habitat or utilize it more than other habitats (Thomas et al. 1979). Riparian habitat hosts the highest density and diversity of vegetation in the arid west region due to the moisture availability. Tree and shrub species can survive in riparian habitat that cannot survive in the arid upland. Increased moisture also allows for higher density of vegetation in the riparian zone than in adjoining uplands. Consequently, this higher diversity and density provides cover and forage for a greater density and diversity of wildlife species.

3.3.1.2 Best Available Science

In order to provide the habitat functions listed above, riparian habitat should be contiguous and intact to the extent possible. Fischer et al (2000) review literature regarding buffer widths necessary to support wildlife, including amphibians (30-165 m), mammals (>50 m), invertebrates (>30 m), fish (>30 m), and birds (40 m to 500 m). In 2013 Ecology reviewed the state of wetland buffer science to determine of updates to their guidance were warranted as the science progresses (Hruby 2013)1. This review also found that buffers are species-specific. Hruby (2013) cites one study that recommends buffers anywhere between 100 ft - 1,000 ft for wildlife (Environmental Law Institute 2008 in Hruby 2013), and one study from Wisconsin that recommends a minimum buffer of 400 ft and up to 900 ft along streams for sustaining the majority of wildlife species (Slawski 2010 in Hruby 2013). One study examining frog species in wetlands at varying distances from a highway noted lower abundances in wetlands within 250 m (820 ft) of the highway (Eigenbrod et al. 2009 in Hruby 2013).

As demonstrated by these studies, optimal buffer widths within which wildlife species are completely unaffected are both variable and infeasible. Further, many of these studies were

1 Though the review was focused on wetland buffers, the conclusions are generally true for riparian buffers as well.


conducted in forested buffer areas where wildlife habitat and appropriate vegetation was not limiting. In Douglas County, the width of riparian habitat is naturally limited by water availability and slope.

3.3.1.3 Summary

Different wildlife species habitat requirements vary widely, from 30 m up to 500 m in Fischer et al (2000). However, as mentioned above, riparian habitat width is limited by actual conditions in Douglas County, where the true riparian habitat is often less than 50 ft wide.

Based on recommendations in the literature, and as moderated by conditions in Douglas County, we recommend protecting the entire riparian habitat up to 75 ft. Typically, riparian habitat is much less than 75 ft due to steep slope, as riparian vegetation transitions to shrub-steppe upland habitat rapidly with elevation gain away from the river.

3.3.2 Shade and Cover

3.3.2.1 Function

Mature riparian vegetation provides shade and cover that serves both terrestrial and aquatic species. Shade is an important function provided by riparian vegetation and it influences other functions occurring within the riparian zone (e.g., thermal protection for wildlife) and in adjacent aquatic habitat (e.g., moderating temperature flux). However, significant shade will only be provided where vegetation is tall enough to cast a shadow on the adjacent habitat.

Unlike the forested watersheds of western Washington, in Douglas County riparian areas, only the lush vegetation is capable of providing shade to the adjacent water surface. Further only those areas with substantial canopy coverage by trees will provide substantial shade. Along much of the shoreline in Douglas County, the tallest vegetation layer is the shrub layer or a discontinuous single line of short trees and its influence on the main stem Columbia River water temperature is negligible. Along perennial and intermittent stream, the shade and cover functions are much greater; however, the extent of function is limited based on the narrow width of riparian vegetation present (typically limited to less than 25 feet). Particularly in the arid west, riparian habitat provides a thermally moderate habitat relative to surrounding arid (NRC 2002).


Temperature moderation varies with waterbodies; for example, the Wenatchee River temperature is less responsive to overwater shading than to hyporheic exchange (Scholz 2001 in NRC 2002). Riparian vegetation provides shade and cover for both terrestrial and aquatic species. Overhanging vegetation provides shade and cover for aquatic species. Shading reduces water temperature, particularly in critical summer months when temperature is of concern for fish species (Gregory et al. 1991). Many salmonid species rely on cooler water temperatures, and many fish species that prey on juvenile salmonids prefer warmer water (USFWS 2010). Shading reduces solar radiation to the water, minimizing water temperature fluctuation (Gregory et al. 1991; NRC 2002; Osborne and Kovacic 1993). Shading function on the water is provided by trees and shrubs immediately adjacent to the water, and thus does not require a substantial width of buffer. The entire riparian habitat provides cover, similar to fish and wildlife habitat above. Often, the limiting factor is the actual width of riparian habitat in the field. Trees typically do not


establish landward of the immediate riparian zone due to the limitation of water availability (Riparian Ecosystems V.1 2018).

3.3.2.3 Summary

Shading of the aquatic habitat provided by riparian vegetation can occur with a narrow band of riparian trees or shrubs. To protect cover function for birds and wildlife, as with fish and wildlife habitat discussed above, the entire riparian habitat area should be protected, with a maximum of 75 ft being sufficient to provide this function.

3.3.3 Erosion Control

3.3.3.1 Function

The riparian zone controls erosion by reducing input of sediment into the river from overland flow. The level of reduction depends on site-specific variables, such as slope, vegetation, and precipitation (Anchor QEA LLC 2013). The presence of vegetation increases retention of sediment, though studies have noted no significant difference in retention between type of vegetation (Barden et al. 2003 in Buffler et al. 2005). Vegetated buffer strips are highly effective at removing large particles (>40 micron), though smaller particles (<40 micro) were most effectively removed through the infiltration of the carrying flow (Gharabaghi et al. 2001 in Buffler et al. 2005).

A vegetated riparian zone also reduces erosion of streambanks by stream flow, as rooted vegetation retains soil on the bank. Vegetated stream banks are typically more stable than unvegetated (Hicken 1984 in NRC 2002).


Sediment is removed from the surface water as it passes through a buffer area with sufficient surface roughness (e.g., vegetation or other features that trap sediment). The literature indicates that a relatively narrow vegetated buffer effectively removes the majority of sediment from overland flows. A three to ten (10) meter-wide grass buffer is sufficient to remove most particulates from overland flow (Buffler et al. 2005). Robinson et al 1996 (in Buffler et al. 2005) found 85% sediment removal within 9.1 m. High flows were found to overwhelm vegetated buffers, regardless of vegetation type (Daniels and Gilliam 1996 in Buffler et al. 2005). However, it stands to reason that vegetation that remains erect in high flows provides more surface roughness to trap sediment.

The slope of the riparian zone affects the effectiveness of sediment trapping, but that up to 15% the relationship between slope and effectiveness is weak (Yuan et al. 2009). Hook (2003 in Buffler et al. 2005) found 94-99% removal of particulates in a 6 m (19.7 ft) buffer, regardless of vegetation type or slope (up to 20%).

Infiltration capacity of the buffer affects sediment removal as well. As the erosive flow infiltrates, the suspended sediment is deposited onto the riparian surface rather than flowing into the river. Saturated soils are less likely to perform this function (Buffler et al. 2005).


No studies were found that examined slopes in excess of 25%. Kleinschmidt Associates (1999) indicate that slopes greater than 25% or lacking surface roughness, or with little infiltration capacity, likely require increased buffer widths.

Riparian vegetation reduced streambank sediment loss to the river as the width and density of riparian vegetation increases (Patten 1998). Deep-rooted plants and fibrous root grasses are among the most effective at holding soil (Schultz et al 1994; Lyons et al. 2000 in Buffler et al. 2005). The root/soil matrix Exposed roots from riparian vegetation along the shore also increase channel roughness, which helps moderate flow and further reduce erosion (Griffin et al. 2005). Reduced flows may also encourage deposition, further stabilizing stream banks (Riparian Ecosystems v.1 2018).

3.3.3.3 Summary

Best available science indicates that a vegetated buffer that is 40-50 ft wide is able to achieve 90% sediment removal, and vegetation of any kind is effective up to 15% slopes. However, studies did not examine slopes as steep as are commonly found along shorelines in Douglas County, which can approach 100%. It should also be noted that in steep slope areas, much of the riparian zone in Douglas County along the Columbia River consists of soils classified as “Excessively Drained” or “Somewhat Excessively Drained” (NRCS 2018). Soils are frequently coarse sand and cobble, which facilitate rapid infiltration. This minimizes the role of a wide vegetated buffer to eliminate erosion, as the erosive water infiltrates rather than runs off into the river.

Considering the lack of data for extremely steep slopes, and considering the soil drainage capability in the steep slopes, a 50 ft buffer is likely sufficient

3.3.4 Water Quality

3.3.4.1 Function

Riparian habitat improves water quality by filtering out pollutants (Fennessey and Cronk 1997). Similar to erosion control, a vegetated buffer captures pollutants as a function of width and vegetative density. Common contaminants entering streams from the upland include phosphorus, nitrogen, and pesticides from crop applications, pathogens originating from livestock, and on-site septic systems.


Nutrients Generally, removal of nutrients by a buffer is correlated to buffer width and slope. However, recent studies indicate that the removal of both phosphorus and nitrogen is more complex than originally thought, and dependent on other factors such as soil type, subsurface water regime, and subsurface biochemistry (Mayer et al. 2007 in Hruby 2013). The processes by which nutrients are removed vary by nutrient type and by transport method (groundwater or surface water) (Hruby 2013). For the purpose of this review, surface water transport is the focus.

Phosphorus


Phosphorus is most commonly bound to particulates, and is readily adsorbed to minerals and organic soil particles (Uusi-Kamppa 1997; Zheng 2004 in Buffler et al. 2005). For this reason, sediment-bound phosphorus is predominantly filtered by riparian areas by the same mechanism as sediment (Uusi-Kamppa 1997; Zheng 2004 in Buffler et al. 2005). Chaubey et al 1994 (in Buffler et al. 2005) found that a 50-65 ft vegetated buffer removed 95-97% of phosphorus. However, when high levels of phosphorus are entering a buffer, the soil can become “saturated” with phosphorus as binding sites are used up; at this point the buffer does not filter out phosphorus (Hickey and Doran 2004; Ward et al. 2010 in Hruby 2013). Dissolved phosphorus is less readily removed, but many studies found a high percentage of removal within 9 m (30 ft) to 21 m (69 ft) (reviewed in Buffler et al. 2005).

Nitrogen Nitrogen enters the riparian zone in a dissolved form, and is removed through denitrification by soil microbes or through uptake by plants within the riparian zone (Gilliam et al. 1997, Burt et al. 1999, in Buffler et al. 2005). Generally, nitrogen removal increases with increasing buffer width, and under normal conditions a relatively narrow vegetated buffer can effectively attenuate nitrogen. A 3 m (10 ft) vegetated buffer attenuated 65%, of nitrogen, and a 21 m (69 ft) buffer attenuated 92% (Chaubey et al 1994 in Buffler et al. 2005). Fennessey and Cronk (1997) found 100% removal within 65 ft. However, various factors other than width affect nitrogen removal, including site-specific conditions that are difficult to predict (Mayer et al. 2007 in Hruby 2013). In some cases, a buffer less than 20 m (66 ft) is sufficient to remove nitrate, though this depends on the soil texture (Vidon and Hill 2006 in Hruby 2013). As with phosphorus, high levels of nitrogen entering a buffer can overwhelm its filtering ability (Sabater 2003 in Hruby 2013).

Pathogens Pathogens such as bacteria, viruses, protozoa, and parasitic worms can enter waterways from cattle use of riparian areas, and a vegetated buffer can trap such pathogens similarly to particulates. Lim et al (1998 in Buffler et al. 2005) found that 20 ft of grass buffer removed 100% of pathogens. Effective distance likely varies with concentration.

Pesticides Pesticides represent a range of chemicals, which often are adsorbed onto soil particles (Buffler et al. 2005). Buffer widths of 8 m (26 ft) to 20 m (66 ft) have been observed to remove up to 100% of pesticides (Patty et al. 1997; Verdilis et al. 2002 in Buffler et al. 2005).

3.3.4.3 Summary

Due to varying effectiveness of buffers as water quality filters based on site-specific factors and pollutant concentration, a single buffer width that would effectively remove pollutants for all land uses is not supported by science. However, residential uses are likely generating water quality impairments at lower levels than would overwhelm buffers’ ability to filter. Therefore, adjacent to residential uses, water quality impairment factors would be effectively filtered out by a 65-70 ft vegetated buffer. For land uses that generate higher levels of nutrients, pesticides, or pathogens (such as agriculture), BAS indicates a wider buffer may be necessary.


3.3.5 Organic Input

3.3.5.1 Function

Riparian habitat provides an input for organic material and nutrients into the river from overhanging vegetation. Overhanging trees provide input of organic material, including terrestrial invertebrate for fish species, leaves and twigs that decompose and provide nutrients, and eventually large woody debris (LWD) from large branches or fallen trees. Terrestrial macroinvertebrates are one of the primary food sources for bull trout.

LWD provides cover for juvenile salmonids, contributes to channel roughness, helps in complex in-stream habitat forming processes, and helps moderate flows (Riparian Ecosystems V.1 2018). It’s strength, size, and shape make it well-suited to redirect hydraulic forces. This effect on hydraulic forces creates a diversity of velocities that initiate multiple in-stream habitat forming process features such as pool formation, streambed scour, sediment deposition, and channel migration (Riparian Ecosystems V.1 2018). LWD input requires mature trees, which will not establish in many riparian areas along the Columbia River (Riparian Ecosystems V.1 2018).


Nutrient and invertebrate input occurs from a relatively narrow band of vegetation immediately adjacent to the river. Contribution of LWD depends on the height of tree and proximity to the river, but requires mature trees. Because of the low precipitation levels in Douglas County, mature trees do not establish in all riparian areas, and thus large wood recruitment cannot occur in all riparian areas (Riparian Ecosystems v.1 2018). Black cottonwood is the only true riparian large tree that establishes in Douglas County riparian areas. Quaking aspen (Populus tremuloides) is less common and typically a small tree in Douglas County. Most riparian areas are dominated by smaller woody species, including black hawthorn (Crataegus douglasii), water birch (Betula occidentalis), thinleaf alder (Alnus incana), red osier dogwood (Cornus sericea). Non-native Siberian elm (Ulmus pumila) and Russian olive (Elaeagnus angustifolia) are also common small to mid-size riparian trees.

WDFW recommends that the site potential tree height (SPTH) method be used to determine an appropriate riparian width to support organic input. This method accounts for the tallest potential tree that would establish in the riparian zone, thus ensuring that all trees that could potentially contribute LWD to the river would be protected. However, in our opinion, this method is not well-suited to estimating the potential zone of LWD contribution in Douglas County.

First, this assumes that maximum size trees are present in the entire width of the riparian zone. WDFW indicates that, in the dryland ecoregions such as Douglas County, trees only grow in moist streamside areas, and do not grow in the drier areas farther landward, even though these areas influence and are influenced by riparian habitat (Riparian Ecosystems v.1 2018). This is corroborated by our observations—black cottonwood only grows in the riparian area nearest to the river. Thus, assuming that cottonwood establish laterally from the stream up to their maximum potential height is erroneous for Douglas County2.

2 Cottonwood establish over this entire width only on areas with very low slope. Often these areas have developed wetlands, which are afforded separate protection.


Second, using the listed maximum height of black cottonwood would over-estimate their actual height in Douglas County. Black cottonwood have a listed maximum height of 30 m (98 ft) to 60 m (196 ft) (USDA NRCS 2003). However, they do not achieve maximum height in Eastern Washington (Riparian Ecosystems v.1 2018). Rather, they attain an average height of 70 ft at 150 years (Roe 1958 in Riparian Ecosystems v.1 2018), with maximum height and size usually reached in 60-75 years, and a maximum age of approximately 200 years (USDA NRCS 2003).

3.3.5.3 Summary

Riparian vegetation within Douglas County does not usually support large trees, with the exception of black cottonwood. Further, riparian trees grow only immediately adjacent to the river, unless the slope is very flat, and this is almost always associated with a wetland. Based on black cottonwood’s zone of establishment in riparian habitat in Douglas County, plus the expected maximum height (70 ft) of black cottonwood in Douglas County, a 75 ft buffer would incorporate any trees that could contribute organic material.

3.4 SPECIAL CONSIDERATION OF ANADROMOUS FISHERIES

In addition to the above functions, special consideration was taken to account for the presence of anadromous fish within the Columbia River. Specifically, this section will assess the ability of proposed riparian buffers to protect endangered species and associated critical habitat. Based on recent consultations with National Marine Fisheries Service (NMFS) and US Fish and Wildlife Service (USFWS) species and critical habitat present within Douglas County include:

Species Upper Columbia River spring-run chinook salmon

Upper Columbia River steelhead

Columbia River bull trout

Critical Habitat

Upper Columbia River steelhead critical habitat

Columbia River bull trout critical habitat One way to evaluate this question is to check the approach used to develop the recommendations above against the habitat perspectives that have been incorporated by the NMFS and USFWS into defining “Critical Habitat” for species listed under the Endangered Species Act. On September 2, 2005, NMFS designated critical habitat for numerous ESUs, including Upper Columbia River spring-run Chinook salmon and Upper Columbia River steelhead trout (NOAA 2005). USFWS recently expanded bull trout critical habitat to include the mainstem Columbia River (effective November 17, 2010; USFWS 2010). This listing extends up to Chief Joseph Dam.

This analysis evaluates the potential effects of the Project on Chinook salmon and steelhead trout critical habitat by means of the primary constituent elements (PCEs) of critical habitat presented in the Federal Register (NOAA 2005) describing the critical habitat designated by NMFS.


The protection of critical habitat for each of the species identified critical habitat types as Primary Constituent Elements or PCEs (i.e., physical and biological features), that are “essential for conservation of these ESUs”. These PCEs embody the concept of the importance of riparian vegetation and other upland vegetation in protecting and influencing designated critical habitat for salmonids. Specifically, the references to the protection of water quality and the need for woody debris as a component of instream cover are directly tied to functions provided by riparian vegetation and, to a much lesser extent, adjacent upland vegetation. The recommendations above incorporate the concept of the influence of both riparian vegetation and upland vegetation on aquatic habitat including that which has been designated as critical habitat. The approach protects the riparian vegetation, which has the greatest potential for influencing the structure and function of critical habitat while also protecting the additional upland habitat.

Another approach to evaluating the effectiveness of the buffers to protect salmonid habitat could be based on the logic used to establish buffers in forested ecosystems. In these cases the height of the trees that could grow at a site (the site potential tree height) has been used as a surrogate for an appropriate width buffer zone. The logic is that trees of that height (for example 200 feet in an old-growth forest) located 200 feet from the stream still influence the adjacent aquatic habitat based on input of leaf litter, shade, and falling into the stream to provide woody debris. Applying this logic to riparian buffers in Douglas County, they should extend only to the landward edge of the riparian vegetation because the vegetation beyond that point has very limited influences on the adjacent aquatic habitat due to its very low height. As stated earlier, based on the characteristics of Douglas County riparian areas, the buffers proposed will encompass and protect the riparian vegetation that directly influences salmonids habitat.

An additional function of riparian buffers is to protect aquatic habitats from contaminants such as pesticides applied on adjacent areas. The recommended buffers include a 65-70 foot buffer to protect water bodies from pesticides. The proposed buffers would provide sufficient water quality protection.


3.5 RECOMMENDATIONS

The Douglas County SMP regulations apply to the Columbia River, seven Rock Island lakes, and 19 interior lakes. Because of the Columbia River dams, riparian habitats adjacent to these water bodies perform similar functions. Thus, the recommendations below apply to all shorelines of Douglas County.

3.5.1 Recommended Riparian Buffers

Based on the best available science, and taking into consideration typical riparian conditions in Douglas County, we believe a 75 ft riparian buffer is adequate to support no net loss of riparian functions and values. This would, in almost all cases, preserve the entire riparian zone and provide for wildlife habitat and shade/cover functions to the extent that they exist on site. This would provide adequate erosion and water quality protection for residential uses, and would encompass sufficient area landward of the river to protect any potential LWD inputs. A 75 ft riparian buffer would also match the SMP riparian buffers of Grant County and provide consistent regulations along adjacent portions of the Columbia River.

In some cases, this width would be more than sufficient to protect functions and values. Much of Douglas County shoreline contains no appreciable riparian habitat due to steep slopes and mineral soils. Thus, it is also our recommendation that provision be made for a reduced buffer with the preparation of a habitat management and mitigation plan that proposes buffer enhancement, such that the enhanced buffer functions at a comparable or higher level than the full buffer. We propose an option for a 25% buffer reduction with the preparation of a Habitat Management and Mitigation Plan that demonstrates that the reduced width still results in no net loss of ecological functions. This plan should focus on the existing vegetation and slopes on the property.


4 WETLANDS

Wetlands within shoreline jurisdiction are managed by the SMP. The SMP prescribes that wetland delineations be conducted according to the Washington State Wetlands Identification and Delineation Manual (WDOE, March 1997, as amended), the U.S. Army Corps of Engineers’ Federal Manual for Identifying and Delineating Jurisdictional Wetlands (1987, as amended), and the US Army Corps of Engineers, (2006), Interim Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Arid West Region, Wetlands Regulatory Assistance Program, Environmental Lab ERDC/EL TRT-06-16, as amended. Currently, the State WDOE delineation manual is no longer in use, and Ecology requires using the 1987 U.S. Army Corps of Engineers Manual and the relevant Regional Supplement. Aside from the State manual, all of these references have been updated and this reference, “as amended,” is still current.

Wetlands are those areas that are inundated or saturated by surface water or ground water at a frequency and duration sufficient to support, and which under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. In order to determine appropriate buffer widths, it is important to identify what the specific functions of wetlands that need to be protected are, and which wetlands need additional protection because they have other important characteristics. Wetland buffers maintain existing functions by reducing the impacts of adjacent land uses. Wetland buffers are to be established based on the Washington State Wetland Rating System for Eastern Washington-Revised (WDOE 04-06-015, as amended). Since the implementation of the 2008 SMP, WA Department of Ecology (Ecology) has issued an updated wetland rating system (Hruby 2014) based on best available science. Thus, the SMP’s adoption of the WDOE wetland rating manual “as amended” ensures that the SMP uses best available science in wetland protection. The SMP requires set buffer widths depending on the wetland rating determined by the WDOE rating system. Ecology has more recent guidance regarding buffer widths, which recommend a range of buffer widths within each category (I through IV) depending on habitat score (Bunten et al. 2016). This is intended to provide greater sensitivity to the particular wetland’s characteristics and provide the wetland with appropriate protection. Recommended buffer widths range from 50 ft to 200 ft, or with the implementation of mitigation measures can be reduced to 40 ft to 150 ft. This approach has been implemented by some cities, notably the cities of Cashmere and Leavenworth.

Again, the function of a wetland buffer is to maintain the existing function of the wetland, not to replace the function of a wetland. For example, a wetland buffer is established to minimize the amount of input (nutrients, pollutants, etc) into the wetland, not to eliminate the input altogether, as a main function of wetlands is improvement of water quality. Buffers are established to ensure that the amount of input does not exceed the ability of the wetland to function properly. Biologically, wetlands provide refuge, rearing and breeding habitat for a wide variety of species.

However, it is our opinion that implementing Ecology’s most recently recommended variable buffer matrix system is not necessary to ensure proper wetland protection. The best available science for assessing wetlands is already incorporated in perpetuity into the SMP by the phrase “as amended,” ensuring the rating system that is used will be the most up-to-date version. Since the wetland rating system already attempts to incorporate best available science and reflect that


in the wetland category rating, a simple wetland buffer table as is currently used in the SMP is sufficient. Further, the current SMP wetland buffer widths are similar enough to Ecology’s proposed buffer width range as to represent a similar level of protection.

Therefore, it is our opinion that changes to the current wetland rating and buffer system are not required by best available science, and the current buffer protection is adequate and comparable with most recently proposed buffer widths.


5 SPECIFIC BEST AVAILABLE SCIENCE REVIEW QUESTIONS

1. Are the current wetland buffers, riparian area buffers and structural setbacks appropriately contributing to achieving the no net loss of ecological functions standards of WAC 173-26-201 (2)(c)?

Based on the review of BAS, the current wetland buffers are appropriately contributing to achieving the no net loss of ecological functions standards. The current wetland buffers are consistent with the current state of science on wetland buffer. Based on the review of BAS on riparian buffers, it appears that the current riparian buffers in Douglas County’s Shoreline Master Program (SMP) are wider than those required to achieve the no net loss of ecological functions standards.

There is little scientific support for a structural setback off of the buffer. It is understood that the setback’s purpose is to ensure that during construction of the structure no disturbance to the buffers occur and that the use of the entire buffer by wildlife species is protected. The structural setback would ensure that construction would not adversely impact the habitat functions and values within the buffers and no compensatory mitigation would be required. The structural setback accomplishes this goal for properties where the buffer consists of native vegetation. However, on properties where the buffer is already disturbed as part of the historic recreational/residential development or agricultural use of the properties, the structural setback is not providing any protective function. This is due to the fact that there is little habitat functions and values provided by this portion of the shoreline and there is little if any use by wildlife species. Thus no habitat functions would be disturbed. Typical disturbances include lawngrass, landscaped areas, recreation uses, previous agricultural use that are currently mowed and maintained upland grasses and weedy species which occurred prior to the establishment of the current riparian buffers. On disturbed properties, construction up to the edge of the buffer would not disturb any buffer habitat functions and values, since existing conditions are providing a low level of functions and values and those existing values would be restored immediately following the construction (no net loss of habitat functions and values). It appears that the current structural setbacks on disturbed properties are not required to protect the existing habitat functions and values of the buffers, as there would be no change in use or disturbances.

2. Does the current BAS applicable to Douglas County support the current wetland buffers, riparian area buffers, and structural setbacks?

As stated above, we believe the current BAS supports the current SMP wetland buffers; no modifications are proposed. As stated above, the current BAS warrants the reduction of the current riparian buffers, as the current riparian buffers are wider than required to provide a no net loss of habitat functions and values. This is based on the semi-arid climate within Douglas County and the minimal width of native riparian vegetation along the majority of the rivers, streams, and lakes. The minimal widths provide a lower level of habitat functions and values, thus require a narrower buffer width to protect those habitat functions and values. The proposed modification to the existing riparian buffers would be the elimination of a Zone 2 buffer. Rather, one buffer will be applied for all shoreline properties. Proposed riparian buffers are:


Environmental Designations Perennial and intermittent streams in all environmental designations

50 feet

High Intensity 50 feetRural Conservancy, Shoreline Residential, Urban Conservancy

75 feet

Natural 100 feet These proposed buffers would be for the low and moderate intensity residential and recreational uses of the shoreline properties and may not provide sufficient protection for higher-intensity uses. This is based on the fact that the quality of habitat varies significantly from property to property and the impacts to the habitat vary significantly with different high intensity uses. The proposed modification to the riparian buffers does include a provision that allows the County the ability to increase riparian buffers where a high-intensity use of the shoreline will result in a net loss of ecological functions and values. This would also include the conversion of undisturbed shoreline property to agricultural lands (pesticides and fertilizers require additional protection). This would be accomplished by requiring a Habitat Management and Mitigation Plan for high-intensity uses within the shoreline zone and if the report indicates that additional protection is required the buffer may be increased on a case by case basis.

The proposed modification to the structural setback would be to eliminate the setback on disturbed properties, specifically where the existing vegetation within the buffer is maintained. The structural setback would still apply to the properties where the vegetation is undisturbed to the landward edge of the buffer.

3. Is there best available science and/or compensatory mitigation applicable to Douglas County that could support modifications to default wetland and riparian buffers? If so, what modifications could be supported.

The current compensatory mitigation ratios for allowance of the modifications and development within wetland and riparian buffers are sufficient to protect the functions and values of the buffers and result in no net loss. Compensatory mitigation at a rate of 1:1 for disturbance of buffer (consisting of upland grasses and weedy species) and 2:1 for disturbance of native vegetation will ensure that the habitat functions and values are protected.

The one proposed modification to the existing compensatory mitigation would be an increased ratio for the removal of non-native trees and shrubs. Currently, the compensatory mitigation ratio for the removal/disturbance to non-native species is 1:1 ratio; however, it is recognized that these non-native trees and shrubs are providing habitat functions and values that are not adequately replaced by the installation of smaller species at a 1:1 ratio. A mitigation ratio of 2:1 for removal of trees and shrubs within the buffers would be required to ensure the no net loss of habitat functions and values. The increased ratio would account for the temporal loss of habitat while the installed mitigation matures to the level of the species removed. No changes to the current mitigation ratios for the removal/disturbance of grasses (native or non-native), weedy species, and/or ground cover are proposed as the 1:1 ratio ensures no net loss to functions and values regardless of native or non-native. In Douglas County, the installation of native vegetation


(riparian, upland, or shrub steppe) at the above ratios will enhance the functions and values provided by the buffers. This is based on the overall low level of native vegetation within the buffers and the ease at which the functions of the vegetation within the buffers are providing.

4. Do the provisions of the buffer width averaging (SMP 3.050(D)) and administrative buffer reduction (SMP 3.050 (E)) still provide a reasonable approach to balance resource protection goals and the circumstances of challenged properties?

The provisions of the buffer width averaging and administrative buffer reduction provide for reasonable use of challenged properties by replacing the habitat functions and values lost through the application of these tools. The application of these provisions typically requires the enhancement of a portion of the buffer equal to that reduced. The enhancement of the buffer (installation of native vegetation) results in a net increase in habitat functions and values of the remaining buffers. These provisions are still a reasonable approach to offer relief to challenged properties. The provisions limit their use to only what is necessary, subject to reasonable mitigation sequencing. Further, because the reduction standards reference percentage reductions rather than absolute reductions, they would still be applicable even if the reduced riparian buffer recommended herein is adopted.

5. Is the function and value of wetland buffers and riparian area buffers maintained by the SMP provisions and their application for private, single-family associated shoreline access trails?

The existing limitations on shoreline access trails (width, orientation, avoidance and minimization measures, mitigation measures) within the SMP are still providing protection for the functions and values of the wetland and riparian buffers. For many reasons, shoreline access trails are typically designed to avoid wetlands and wetland buffers. The placement of shoreline access trails typically impact riparian buffers and riparian areas. The avoidance and minimization requirement encourages trail design that avoids native vegetation (mature trees and shrubs) and directs access through areas with non-native species. Avoidance and minimization measures and the existing compensatory mitigation ratios support no net loss of habitat functions and values. As stated above, a proposed change would be to increase the compensatory mitigation ratio for removal of mature non-native trees and shrubs to 2:1. The mitigation ratio for disturbance of upland grasses and weedy species would remain 1:1.

6. Are mitigation ratios in the SMP and the structure of the five-year monitoring program and benchmarks appropriate? If not, what revisions are recommended.

The mitigation ratios set forth in the SMP are still valid as there is little research on the functions and values provided by differing mitigation ratios. The current mitigation ratios of 1:1 (for disturbance of buffer) and 2:1 ( disturbance of native vegetation) is sufficient with the requirement for no net loss of ecological functions and values. Existing mitigation ratios for disturbances to wetlands and wetland buffers are consistent with the recommendations in the Ecology guidance documents, which are the same as those ratios at the time of the approval of the current SMP. Existing mitigation ratios for the disturbance to riparian buffers are providing sufficient replacement of functions and values. The primary mechanism to verify the effectiveness of the mitigation ratios is the County’s ability to enforce the proper installation,


protection, and survival of mitigation plantings. The current ratios are consistent with the current BAS on mitigation ratios for riparian buffers. The existing mitigation ratio for impacts below the OHWM are sufficient as they are set by NMFS, USFWS, and Corps. The goal is to follow the federal guidance on mitigation for impacts below the OHWM as the mitigation ratios are driven by the Endangered Species Act. The existing buffers allow for the County to not be the driving factor on structures within ESA waters.

The five-year monitoring program and benchmarks are appropriate for verifying successful replacement of habitat functions and values. This monitoring period is consistent with the federal and state monitoring programs. As always, the five-year period and benchmarks are only effective when the County can ensure that the mitigation is installed per approval and that the monitoring reports are submitted. The primary concern is the enforcement of the monitoring program and ensuring that all projects that require mitigation establish sureties. For projects without a building permit, there is currently no mechanism to ensure that a surety is established. In addition to ensuring the reports are submitted, the County needs to establish criteria that allows for an increase in monitoring years if the majority of mitigation plantings are replaced prior to the five-year monitoring effort.

The only way to ensure that the mitigation plantings and monitoring program results in no net loss of habitat functions and values is to ensure that the plants are installed and the plants have survived for five years. Without verification of at least 3-5 years survival, there is no verification that the plantings will provide the required level of functions and values.


6 REFERENCES

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