Revised SMP Appendix E

Santa Clara Valley Water District

1.0      OVERVIEW

Bank protection involves any action by the District to repair stream banks that are eroding as well as to prevent bank erosion. The District may implement stream bank repair when the continuing stream degradation: (1) causes or could cause significant damage to a property or adjacent property, (2) is a public safety concern, (3) adversely affects transportation or recreational use, (4) adversely impacts beneficial uses of surface water, or (5) adversely affects riparian habitat. Bank protection also includes preventive maintenance to ensure that banks do not erode in the future. Such erosion protection reduces sedimentation and improves water quality.

The District uses a wide range of bank protection techniques. Repairs can take several forms, ranging from the use of soft structures (i.e., willow brush mattresses, log crib walls, pole plantings) to the installation of hard structures (i.e., rock blanket, concrete, sack concrete, gabions) or combination of hard and soft structures.

Riparian corridors in Santa Clara County provide a remarkable range of biological functions. These functions range from fish and other aquatic habitat in the streams themselves to foraging and nesting habitat for birds in the woodland canopy above to movement corridors for numerous terrestrial species. Bank protection activities may alter the biological resource values of the stream environment by changing the conditions in the stream itself or by changing the vegetation surrounding the stream.

The Stream Maintenance Program (SMP) provides for routine bank protection activities throughout the District's jurisdiction. The SMP proposes to incorporates a programmatic impact assessment and mitigation for routine bank protection activities that is intended to meet the majority of concerns for the function of aquatic and riparian habitats in the streams. This programmatic assessment will be supplemented by other DEIR sections that describe specific potential impacts to water quality, listed species, etc., from bank protection and other SMP components and provide the numerous (BMPs) that address those impacts.

2.0      BANK PROTECTION WORK

Based on 1513-year historical records, the District estimates that an average of roughly one linear mile of stream banks may be repaired annually. Many repair sites are small and are not easily predicted. The quantity and location of bank protection activities varies greatly from year to year, based on watershed conditions (heavy rains often lead to more work in the following year), degree of safety hazard, work load, budget, and quantity of other priority work to be done in a given year. The description of historical bank protection in the SMP shows that a greater concentration of bank protection occurs in cities and semi-rural foothills of the Santa Clara Valley. Actual future bank protection work could potentially be done anywhere it is needed within District jurisdiction.

Many areas receiving bank protection are void of native riparian vegetation as a consequence of erosion. Nevertheless, over the 10-year 20-year life of this proposed program permit, some 10 20 miles of the approximately 1650 miles of bank under District jurisdiction can be expected to be modified, and some increment of existing riparian vegetation can be expected to be lost. Soft erosion control methods are not always adequate to protect life and property. Therefore, some portion of that 10 20 miles will be protected with hardscape methods, and riparian vegetation may be precluded from reestablishing. Under the Stream Maintenance Program, the District has committed to installing no more than 50% of the bank protection work using impervious hardscape designs.

The general design criteria and cross-section for each of the bank protection methods used by the District are included in this appendix Appendix A. In addition to those criteria, design of a particular bank protection project includes evaluation of other site specific characteristics, such as location (for example, the inside of or outside of a curve), soil type, shear stress, features of the channel adjacent to the site and available right of way. Figure E-1 is a flow diagram of the bank protection alternatives selection process.

3.0      CLASSIFICATION OF RESOURCES, TECHNIQUES, IMPACTS, AND REVEGETATION POTENTIAL

This programmatic impact assessment and the accompanying mitigation rely on several simple classifications of the biological species, and stream functions and biotic resources impacted, the bank protection techniques utilized, and the potential for site revegetation. Obviously conditions vary widely from stream to stream and even over short distances within a stream. The intent in these classifications is to represent the typical conditions and to allow site assessment to verify the actual conditions and the suitability of the measures to be applied.

3.1   Species

As described in the Environmental Setting section, healthy riparian habitat is critical to maintaining biological diversity in areas such as Santa Clara County, where upland habitat has been intensively modified for agricultural and urban uses. Biological species potentially impacted include strictly aquatic species, such as fish, strictly terrestrial (upland) species, such as songbirds, and numerous species that move between the aquatic and adjacent upland habitat, such as frogs. Qualitatively, the aquatic species of greatest concern is the federally listed steelhead. Other aquatic species of concern include land-locked rainbow trout, chinook salmon, and other native fish. The terrestrial species of particular concern include birds, especially neotropical migrants and raptors. Impacts to the semi-aquatic reptiles and amphibians, such as California red-legged frogs and western pond turtles, are of potential concern in both aquatic and terrestrial habitat.

3.2   Stream Functions

Stream functions potentially affected by bank protection are classified as either in-stream functions primarily affecting the aquatic environment or stream side functions primarily affecting the riparian environment, but also affecting the aquatic environment. Note that other in-stream functions generally not impacted by bank protection, such as steelhead spawning habitat, are also addressed in the DEIR. For in-stream functions, conditions beneficial for native fish are of paramount importance. The following discussion oversimplifies the aquatic species habitat relationship, but is a reasonable guide for application of programmatic mitigation.

3.2.1   In-stream

In-stream functions provided in or immediately adjacent to the normal flow channel directly serve aquatic and semi-aquatic species. For the programmatic mitigation, the channel is defined to be the area below Ordinary High Water. Functions include:

1. In stream Escape Cover: provided by undercut banks, large boulders, tree roots, downed trees, and other structural elements (including deteriorating bank protection projects)
2. Hydraulic Complexity: resulting from the interaction of current with the same structural elements providing instream escape cover
3. Velocity Refuge: also provided by structural elements
4. Shading and water temperature moderation: provided by mature riparian shrubs and trees
5. Overhanging escape cover: provided by shrubs and grasses near the stream edge

3.2.2 Stream-side

The stream-side environment includes the functions of riparian vegetation. This upland vegetation benefits terrestrial species, as well as semi-aquatic amphibians and reptiles and fish. Functions include:

1. Sediment stabilization: provided by riparian trees, shrubs and grasses

2. Shading and water temperature moderation: provided by mature riparian shrubs and trees
3. Overhanging escape cover: provided by shrubs and grasses near the stream edge

4. Bird breeding and foraging habitat: provided by mature native riparian species, such as cottonwoods and willows, oaks, other trees, shrubs, forbs, grasses, and the streambank itself
5. Foraging, refugia, estivation, and breeding habitat for semi-aquatic amphibian and reptile species: provided by low vegetation, rocks, downed materials, and the streambanks itself
6. 6.Foraging, breeding, hibernacula, and dispersal habitat for mammals: provided by the riparian vegetation and the streambanks, substrate

3.3 Bank Protection Techniques

Bank protection methods are classified here by their impact on (1) in-stream habitat and (2) stream-side habitat. For each habitat type, there are three categories of effects: those that (1) enhance biotic resources, (2) provide limited biotic resource, or (3) reduce or eliminate biotic potential. The Bank Protection Impact Assessment Matrix allow evaluation of the direct and potential impacts of bank protection. This appendix includes the descriptions and drawings for approximately 30 methods of bank protection and an evaluation of the impact for in-stream and stream-side habitat. The appendix will be updated as new methods or criteria are added to the program.

Bank protection measures that create extensive inflexible, impervious channel banks with essentially no revegetation are termed "hard," and the product is called "hard scape." Measures that retain natural earth banks and have higher capacity to support vegetation are termed "soft," and the product is called "softscape." The methods listed here are defined and illustrated in the Appendix A.

3.3.1   Bank Protection Techniques That Tend To Limit Biotic Potential

These techniques may include but are not limited to:

• Gabions
• Rock blanket (includes larger rip-rap with small rock fill)
• Sacked concrete
• Articulated concrete mat
• Synthetic cellular confinement

3.3.2   Bank Protection Techniques That Tend To Retain Biotic Potential

These techniques may include but are not limited to:

• Large boulder revetment
• Root wads and boulders
• Log crib walls
• Concrete crib walls
• Organic surface matting

4.0   IMPACT AND MITIGATION

The District proposes to implement a bank protection program that avoids potential impacts to the greatest extent possible and incorporates mitigation to balance impacts that can not be avoided. The impact of bank protection depends on the intensitytype the work done and the sensitivity of the environment where thework is done. This work type/environment relationship is reflected in an Impact/Mitigation the Impact Assessment matrix which follows section 4.3 of this appendix for in-stream and stream-side resource functions. The matricesx identifyies project effects as "Neutral", "Impact", or "Benefit", and in some cases, "Not in covered by SMP".

Neutral.   A project effect is said to be neutral when the environmental effect of a bank protection measure results in neither an adverse impact nor a significant net benefit to the existing environment.

Impact.   A project effect is said to be an impact when the environmental effect of a bank protection measure results in an adverse impact to the existing environment.

Benefit.   A project effect is said to be a benefit when the environmental effect of a bank protection measure results in a significant net benefit to the existing environment. This benefit can be used to offset or mitigate adverse impacts elsewhere.

Not Covered by the SMP. In some cases, the environment is judged to have a high environmental sensitivity and certain bank protection techniques would have a significant irreversible and cumulative effect that cannot be effectively mitigated by enhancing conditions elsewhere. Such projects are deemed to be outside of the scope of the routine maintenance in the SMP. Also excluded is emergency work.

4.1     In-stream Impacts

In-stream environmental quality is primarily determined by fisheries present. Other mitigation is proposed elsewhere for impacts on other protected aquatic species such as red-legged frog. The primary Work Measure is lineal extent of stream channel. Most District streams have been categorized by fisheries present.

High <QualitySensitivity Fisheries. Cold water fishery with trout or steelhead, warm water fishery with trout potential (DEIR fish habitat categories 5, 6, and 7).

Medium Quality Sensitivity Fisheries. Warm water native fishery, salmon present (DEIR fish habitat categories 3 and 4) or any reach used for steelhead migration.

Low QualitySensitivity Fisheries. Warm water fishery, mostly introduced species, fish limited or no value (DEIR fish habitat categories 1, 2 and 80,1 and 2), but only where the reach is not used for steelhead migration).

In-stream Impact and Mitigation Matrix

Environmental Sensitivity		Bank Protection Techniques Effect
Fisheries Present on Reach	In-Stream Functions	Methods That Tend to Retain Biotic Potential (e.g., Large Boulder Revetment, Crib Walls)	Methods that Tend to Limit Biotic Potential (e.g., Small Rock Rip-Rap, Gabions, Sacked Concrete)
High Quality	Present	Neutral	Not Covered by SMP
	Absent	Benefit	Not Covered by SMP
Medium Quality	Present	Neutral	Impact
	Absent	Benefit	Neutral
Low Quality	Present	Neutral	Neutral
	Absent	Benefit	Neutral
Work Measure is lineal extent of stream channel. Impact = Net adverse impact; must be mitigated 1:1. Neutral = No effect; no mitigation required. Benefit = Net improvement; provides mitigation credit 1:1.

4.2   Stream-side Impacts

Simply, the impact of bank protection on stream-side functions can be evaluated based upon the quality of the riparian habitat impacted and the potential for the site to be revegetated, based on the bank protection work being done. Although the primary Work Measure is lineal extent of stream channel (lineal feet), riparian value will also need to take into account the area affected (square feet) and the number of stems for large vegetation. See BMP 2.8, Replace Trees. Because area at each site is limited, direct (1:1) revegetation is sufficient (i.e., for 100 linear feet of impact, 100 linear feet of revegetation a minimum of 6 feet wide), but Large trees lost will need to be replaced at a higher ratio, such as 3:1 for all stems over 6 inch diameter at breast height (DBH), and 4:1 for trees greater than 18 inches DBH to account for mortality and the smaller size of replacement trees. Protocol for revegetation is currently being developed which includes location of revegetation sites, planting guidelines, maintenance and monitoring and reporting of the sites.

4.2.1   Riparian Habitat Quality

The riparian quality can be classified as:

High Quality Riparian Habitat. Sites with native overstory with continuous understory or occurring in dense thickets; dense native overstory with sparse, non-native or no understory; and native willow thickets. Site may provide overhanging escape cover and shading.

ModerateMedium Quality Riparian Habitat. Sites with sparse native overstory with sparse, non-native or no understory; non-native overstory with native understory; and dense nonnative overstory with sparse, non-native or no understory. Site may provide some overhanging escape cover and shading.

Low Quality Riparian Habitat. Sites with no or only sparse non-native overstory with sparse, non-native, or no understory. Site may provide some overhanging escape cover for fish.

4.2.2   Riparian Restoration Potential

Ideally, all bank protection projects would be revegetated to restore full natural potential values. There are practical limitations, however. First, creeks are often in a highly disturbed state with much of the natural system already absent. Second, the need to stabilize over-steepened banks or to withstand very high water velocities may preclude reliance on revegetation alone for bank protection. Third, the banks may be so steep and incised that they do not provide space for riparian vegetation. Fourth, the engineered bank itself may involve impervious surface or such heavily compacted earth that some normal stream side vegetation cannot become established and thrive. Rather than specify impact according to the type of bank protection technique, stream-side impacts are characterized by the potential for restoration, taking in to account the technique and the site limitations.

High Riparian Restoration Potential. Sites where dense native overstory and dense native understory, including willow thickets where appropriate, can be readily established. Overhanging escape cover and shading can be incorporated.

Moderate Riparian Restoration Potential. Sites where sparse native overstory with moderate to dense native understory can be established. Overhanging escape cover and shading may potentially be incorporated.

Low Riparian Restoration Potential. Sites where no or only sparse native overstory and no or only sparse native understory can be established.

Stream-side Impact and Mitigation Matrix

Existing Riparian Habitat Quality	Bank Protection Project Restoration Potential
	High Potential	Medium Potential	Low Potential
High Quality	Neutral	Impact	Not Covered by SMP
Medium Quality	Benefit	Neutral	Impact
Low Quality	Benefit	Benefit	Neutral
Work Measure is lineal extent of stream channel, also taking into account total area affected and number of tree stems removed. Impact = Net adverse impact; must be mitigated 1:1 in linear feet, a minimum of 6 feet wide; 3:1 in tree stems over 6 inch DBH. Neutral = No effect; no mitigation required. Overhanging escape cover and/or shading must be incorporated if present in pre project conditions. Benefit = Net improvement; provides mitigation credit 1:1 in linear feet, a minimum of 6feet wide. Overhanging escape cover and/or shading must be incorporated if present in pre project conditions.

4.3   Mitigation for Bank Protection

Using the bank protection impact assessment matrix to evaluate the environmental impact of bank protection, the District proposes a mitigation ratio of 1:1 by area for impacts or credit according to the assessment in the matrix. In-stream and stream-side impacts are evaluated separately and mitigation or credit are applied to each category. To further reduce the adverse effects of bank protection, the District will mitigate for all impacts for impervious hardscape and for unvegetated rock bank protection at a ratio of 3:1 and for all vegetated rock at a ratio of 1:1 regardless of the determination of the impact assessment matrix. This will account for all direct, potential and cumulative impacts from the bank protection program. All impacts and credits will be measured by area and the ongoing totals will be reported in the annual report. Mitigation for both in-stream and stream-side impacts will consist of revegetation consistent with the Protocol for Revegetation Associated with Use of Impervious Materials for Bank Protection in this appendix.