Figure 1 - uploaded by Ronald M. Thom
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# Salmonid life cycle.

## Contexts in source publication

Context 1
... involves the placement of erosion resistant materials (e.g., large rocks and boulders, cement, pilings, and large woody debris) or the use of bioengineering techniques along shorelines, streambanks, or in other areas of high flow velocities and/or wave-tidal energy to reduce or eliminate erosion of natural shorelines and risk to human infrastructure. In general, it has been shown to be an effective method to control erosion and local scour along streams, particularly near bridges where structures induce additional turbulence that may stimulate erosion. Rock and/or debris structures may also be used in the form of groins or barbs to redirect the flow of rivers and tidal channels, or to modify the course of a waterway. Shoreline armoring is also used to reduce erosion from wave energy in the environment. Unfortunately, altering the physical conditions of the streambank or shoreline through armoring, or bank stabilization, can radically alter the local characteristics of natural habitats and may influence the habitat for some distance surrounding the structure. Bank stabilization also affects natural channel processes that are essential to habitat creation and maintenance (Bolton and Shellberg 2001). As a result, the ecological functions of the impacted area can be altered, including the use of these habitats by fish, macroinvertebrates, birds, and other organisms. Lost opportunity impacts (potential impacts that occur in response to what a channel is NOT allowed to do, including alteration of dynamic river processes and the reduction of the input of sediment and debris) are important for consideration as are their opposite, channel response impacts (impacts caused directly by a protection project). This report will focus on freshwater streambank armoring rather than armoring along marine shorelines. It emphasizes impacts to salmonids, but also impacts to habitat and habitat-forming processes. A thorough review of marine and estuarine shoreline modification issues related to habitat alteration can be found in Williams and Thom (2001). Salmon occupy habitats with very specific attributes that sustain incubation, residence and migration (Figure 1) . Many of these habitat attributes (e.g., substrate, current velocity) can be altered by artificial bank protection structures. Effects on fish can be direct, such as a change in velocity that results in different sizes and species of fish utilizing a specific bank area, or indirect, such as altering dynamic river processes and thereby reducing off-channel habitat (Cramer et al. 2002). Conditions under which bank stabilization significantly alters fish habitat are poorly understood (Carrasquero 2001). Similarly, mitigation measures that would reduce or eliminate negative impacts to biota and ecological processes along stabilized banks are poorly understood. A variety of methods has been used along inland streams to control general bank erosion. Until recently, fish and wildlife habitat considerations were not commonly addressed when projects were designed. Streambank stabilization techniques, while reducing streambank erosion, also impact aquatic ecosystems. Negative impacts may include loss of salmonid habitat. Current research indicates that conventional (hard) streambank armoring techniques may also result in a loss of instream habitat complexity and a reduction in juvenile salmonid abundance in the affected stream reach. There are, however, numerous data gaps in the understanding of how hard and soft streambank protection techniques impact aquatic ecosystems and the relative risks and uncertainties associated with each method. A recently completed Washington state report provides guidance on assessing streambank erosion, and selecting and designing appropriate corrective measures that consider wildlife in the solution to the problem (Cramer et al. 2002). The report emphasizes the need for an integrated approach that acknowledges the natural process of erosion and seeks to maintain fish and wildlife habitat functions while treating the cause of the erosion, rather than merely treating the symptoms. Though the physical processes affected by armoring have been studied in a variety of freshwater and marine ecosystems (Macdonald et al. 1994), almost no data exist on the biological impacts (Thom et al. 1994, Williams and Thom, 2001, Carrasquero 2001). The paucity of case studies highlighted by these authors emphasizes the critical need for development of a conceptual model that highlights conditions where additional research is needed to quantify impacts to salmon. Development and interpretation of the model would be followed by focused field monitoring and quantitative research regarding the potential impacts of shoreline modifications, particularly in relation to salmon species listed under the Endangered Species Act (ESA). As more shoreline and stream areas come under pressure for armor or other modifications, it is critical that management practices anticipate the effects of these changes. To date, a workshop on the ecological effects of armoring was conducted in November 2001. The results of the workshop provided WSDOT and the participants with a comprehensive bibliography and current state of knowledge and research activities related to shoreline armoring. The next step involves development of a conceptual model for freshwater systems to assess small- and large- scale effects of bank stabilization on system processes. The model is being developed from the extant literature and has the purpose of facilitating understanding of connections between the physical and biological conditions in freshwater systems, with special regard to listed species. Interpretation of the model will allow evaluation of potential effects of bank stabilization and help focus mitigation efforts on areas where they will be most beneficial. Anthropogenic disturbances, such as bank stabilization, may result in a significant modification of stream morphology, thereby potentially degrading fish habitat and fish populations. Long-term habitat alterations may result in changes to a stream’s physical, chemical, and biological processes and functions. Bank stabilization projects impact aquatic (riverine) and riparian (floodplain) habitat at both a small-scale site-specific level and at a large-scale reach level . Determining effects of bank stabilization on salmon at both scales is important for making permitting decisions, assessing impacts of habitat modification, making design recommendations, and/or deciding on appropriate mitigation. Site-level impacts are of particular concern to WSDOT because each bank stabilization project goes through a permitting process. Large-scale impacts may involve assessment of cumulative effects and a determination of whether or not the stream will retain its “opportunity”, or ability, to migrate within the channel and form fish habitat throughout an extensive reach and over time (Cramer et al. 2002). Examining the potential for the stream to migrate over time would allow decision-makers to evaluate the costs/benefits associated with moving a transportation system out of a stream’s path. small (site level) scales. The results are meant to (1) provide a comprehensive and technically defensible framework illustrating relationships between physical and biological conditions in freshwater systems subjected to stabilization, (2) highlight relationships that are most important and for which scientific data are lacking, not understood, or not agreed on, (3) assist resource managers in assessing potential effects of bank stabilization, and (4) help prioritize WSDOT research and mitigation projects related to bank stabilization in freshwater systems. Bank stabilization techniques that are evaluated in the model include in-stream flow redirection, structural bank protection, biotechnical bank protection, avulsion and chute cutoff prevention, and channel modification (Cramer et al. 2002). Particular emphasis is placed on the evaluation of effects on salmonid species and their essential habitat. The concerns about bank stabilization in freshwater systems center around a variety of salmon habitat needs associated with different life history stages, which include egg incubation, juvenile rearing, upstream migration by adults, and spawning (Figure 1) . Natural ecosystems comprise complex fish habitats, which provide salmon with the opportunity to occupy diverse habitats for a maximum amount of time. When humans alter the stream habitat through armoring, there is generally a simplification of the system for fish species and the organisms they prey upon. The basic purpose of bank stabilization is to interrupt the erosion process where it is deemed to conflict with social needs or ecological requirements (Fischenich 2001). The initial stabilization project results in alteration of the physical environment and in turn often interrupts or affects other ecological processes. Knowing the direct and ancillary effects of a stabilization technique could help engineers select designs that minimize adverse effects to the structure and function of the environment and to mitigate for unavoidable losses. In addition, it is important to remember that the nature and extent of impacts may be influenced ...
Context 2
... involves the placement of erosion resistant materials (e.g., large rocks and boulders, cement, pilings, and large woody debris) or the use of bioengineering techniques along shorelines, streambanks, or in other areas of high flow velocities and/or wave-tidal energy to reduce or eliminate erosion of natural shorelines and risk to human infrastructure. In general, it has been shown to be an effective method to control erosion and local scour along streams, particularly near bridges where structures induce additional turbulence that may stimulate erosion. Rock and/or debris structures may also be used in the form of groins or barbs to redirect the flow of rivers and tidal channels, or to modify the course of a waterway. Shoreline armoring is also used to reduce erosion from wave energy in the environment. Unfortunately, altering the physical conditions of the streambank or shoreline through armoring, or bank stabilization, can radically alter the local characteristics of natural habitats and may influence the habitat for some distance surrounding the structure. Bank stabilization also affects natural channel processes that are essential to habitat creation and maintenance (Bolton and Shellberg 2001). As a result, the ecological functions of the impacted area can be altered, including the use of these habitats by fish, macroinvertebrates, birds, and other organisms. Lost opportunity impacts (potential impacts that occur in response to what a channel is NOT allowed to do, including alteration of dynamic river processes and the reduction of the input of sediment and debris) are important for consideration as are their opposite, channel response impacts (impacts caused directly by a protection project). This report will focus on freshwater streambank armoring rather than armoring along marine shorelines. It emphasizes impacts to salmonids, but also impacts to habitat and habitat-forming processes. A thorough review of marine and estuarine shoreline modification issues related to habitat alteration can be found in Williams and Thom (2001). Salmon occupy habitats with very specific attributes that sustain incubation, residence and migration (Figure 1) . Many of these habitat attributes (e.g., substrate, current velocity) can be altered by artificial bank protection structures. Effects on fish can be direct, such as a change in velocity that results in different sizes and species of fish utilizing a specific bank area, or indirect, such as altering dynamic river processes and thereby reducing off-channel habitat (Cramer et al. 2002). Conditions under which bank stabilization significantly alters fish habitat are poorly understood (Carrasquero 2001). Similarly, mitigation measures that would reduce or eliminate negative impacts to biota and ecological processes along stabilized banks are poorly understood. A variety of methods has been used along inland streams to control general bank erosion. Until recently, fish and wildlife habitat considerations were not commonly addressed when projects were designed. Streambank stabilization techniques, while reducing streambank erosion, also impact aquatic ecosystems. Negative impacts may include loss of salmonid habitat. Current research indicates that conventional (hard) streambank armoring techniques may also result in a loss of instream habitat complexity and a reduction in juvenile salmonid abundance in the affected stream reach. There are, however, numerous data gaps in the understanding of how hard and soft streambank protection techniques impact aquatic ecosystems and the relative risks and uncertainties associated with each method. A recently completed Washington state report provides guidance on assessing streambank erosion, and selecting and designing appropriate corrective measures that consider wildlife in the solution to the problem (Cramer et al. 2002). The report emphasizes the need for an integrated approach that acknowledges the natural process of erosion and seeks to maintain fish and wildlife habitat functions while treating the cause of the erosion, rather than merely treating the symptoms. Though the physical processes affected by armoring have been studied in a variety of freshwater and marine ecosystems (Macdonald et al. 1994), almost no data exist on the biological impacts (Thom et al. 1994, Williams and Thom, 2001, Carrasquero 2001). The paucity of case studies highlighted by these authors emphasizes the critical need for development of a conceptual model that highlights conditions where additional research is needed to quantify impacts to salmon. Development and interpretation of the model would be followed by focused field monitoring and quantitative research regarding the potential impacts of shoreline modifications, particularly in relation to salmon species listed under the Endangered Species Act (ESA). As more shoreline and stream areas come under pressure for armor or other modifications, it is critical that management practices anticipate the effects of these changes. To date, a workshop on the ecological effects of armoring was conducted in November 2001. The results of the workshop provided WSDOT and the participants with a comprehensive bibliography and current state of knowledge and research activities related to shoreline armoring. The next step involves development of a conceptual model for freshwater systems to assess small- and large- scale effects of bank stabilization on system processes. The model is being developed from the extant literature and has the purpose of facilitating understanding of connections between the physical and biological conditions in freshwater systems, with special regard to listed species. Interpretation of the model will allow evaluation of potential effects of bank stabilization and help focus mitigation efforts on areas where they will be most beneficial. Anthropogenic disturbances, such as bank stabilization, may result in a significant modification of stream morphology, thereby potentially degrading fish habitat and fish populations. Long-term habitat alterations may result in changes to a stream’s physical, chemical, and biological processes and functions. Bank stabilization projects impact aquatic (riverine) and riparian (floodplain) habitat at both a small-scale site-specific level and at a large-scale reach level . Determining effects of bank stabilization on salmon at both scales is important for making permitting decisions, assessing impacts of habitat modification, making design recommendations, and/or deciding on appropriate mitigation. Site-level impacts are of particular concern to WSDOT because each bank stabilization project goes through a permitting process. Large-scale impacts may involve assessment of cumulative effects and a determination of whether or not the stream will retain its “opportunity”, or ability, to migrate within the channel and form fish habitat throughout an extensive reach and over time (Cramer et al. 2002). Examining the potential for the stream to migrate over time would allow decision-makers to evaluate the costs/benefits associated with moving a transportation system out of a stream’s path. small (site level) scales. The results are meant to (1) provide a comprehensive and technically defensible framework illustrating relationships between physical and biological conditions in freshwater systems subjected to stabilization, (2) highlight relationships that are most important and for which scientific data are lacking, not understood, or not agreed on, (3) assist resource managers in assessing potential effects of bank stabilization, and (4) help prioritize WSDOT research and mitigation projects related to bank stabilization in freshwater systems. Bank stabilization techniques that are evaluated in the model include in-stream flow redirection, structural bank protection, biotechnical bank protection, avulsion and chute cutoff prevention, and channel modification (Cramer et al. 2002). Particular emphasis is placed on the evaluation of effects on salmonid species and their essential habitat. The concerns about bank stabilization in freshwater systems center around a variety of salmon habitat needs associated with different life history stages, which include egg incubation, juvenile rearing, upstream migration by adults, and spawning (Figure 1) . Natural ecosystems comprise complex fish habitats, which provide salmon with the opportunity to occupy diverse habitats for a maximum amount of time. When humans alter the stream habitat through armoring, there is generally a simplification of the system for fish species and the organisms they prey upon. The basic purpose of bank stabilization is to interrupt the erosion process where it is deemed to conflict with social needs or ecological requirements (Fischenich 2001). The initial stabilization project results in alteration of the physical environment and in turn often interrupts or affects other ecological processes. Knowing the direct and ancillary effects of a stabilization technique could help engineers select designs that minimize adverse effects to the structure and function of the environment and to mitigate for unavoidable losses. In addition, it is important to remember that the nature and extent of impacts may be influenced ...

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