Salmon Credit Calculation Rules and Equations

Salmon Credit Calculation
Rules and Equations

Introduction

The Salmon Credit Calculation Method was developed as part of the "Counting on the Environment" NRCS grant project managed by Willamette Partnership. It is intended to quantify the changes in ecosystem services that directly affect the health of salmon habitat. This document explains how the indicators collected in a field survey drive the various functions used to evaluate salmon habitat.

Overview of Biotic Support Groups
and Functions Used in Salmon Currency

Justification of Functions Used

Cover/RefugiaAnadromous Fish Biotic Support

Salmon need areas of cover/refugia that protect them from avian and aquatic predation while allowing escapement. Cover/refugia for salmon is assessed on a site level and is defined as spatially discrete habitat structures that provide protection for salmon. The structure may range from a piece of large wood that provides in-stream shelter for a single fish, or individual pools that provide cool water for several rearing juveniles during hot summer months.

ForagingAnadromous Fish Biotic Support

Foraging is a life cycle requirement for salmon. For salmon, foraging consists of the feeding activities of fry and smolts within freshwater habitats (excluding brackish or saltwater estuaries) prior to entering saltwater. Foraging of adult salmon does not typically occur in freshwater and is not considered here. Structural components that provide important forage locations and opportunities are considered.

Nesting/SpawningAnadromous Fish Biotic Support

Nesting/spawning is a life cycle requirement for salmon. Salmon require specific stream habitat types and structures to successfully spawn.

ConnectivityAnadromous Fish Biotic Support

Salmon require connectivity due to their anadromous nature. Salmon often ascend several miles of stream channel in their quest to spawn, the same channel that, as smolts, they descend in their out-migration to the sea. For salmon, connectivity refers to stream characteristics that promote fish movement within a stream channel. All man-made (anthropogenic) structures in or partially in a stream channel are considered to be constraints to connectivity.

Insect/Invertebrate Biotic Support

Salmon in multiple life stages rely heavily on insects and invertebratesas a food source.Cover/Refugia and Nesting functions for insect and invertebrates are included as measures of the system to provide.

Habitat Formation

Habitat formation supports the natural processes that promote channel diversification, energy dissipation, flow modulation, and depth in aquatic habitats. In addition, biotic processes that occur outside the immediate stream channel can indirectly affect streams and salmon. Therefore, we assess habitat formation within 300’ of the stream channel (riparian) as well as within the channel.

Temperature Regulation

Water temperature is one of the most critical aspects of salmon habitat. Preventing or reducing high summer water temperatures is important, as salmon become stressed at temperatures above 18º C. High water temperatures can limit fish production in some watersheds.

Spatial Separation

Spatial separation is a measure of habitat complexity. Spatial separation provides salmon with a diversity of separate and distinct micro-habitats within the stream environment. Micro-habitats are typically small areas used by fish or other organisms for feeding, resting, and protection from predators.

Variable Velocity

Salmon use a variety of stream channel characteristics during their life cycle. Promoting variable velocity promotes both erosion and deposition processes which are vital to stream health. Variable velocities provide both resting and foraging opportunities for salmon. Fish require little expenditure of energy to reside in pools and other slow water features, while easily foraging in the feeding lanes of faster waters nearby.

Channel Diversity

Channel diversity indicates the extent of potential fish habitat within a stream. Salmon utilize a variety of habitats promoted by different channel types. Variety and complexity are hallmarks of good salmon habitat.

Rules

Salmon credit is calculated for:

Any aquatic map unit that is part of a salmon-bearing stream.

The reach that the map unit is part of has been verified as salmon-bearing by authorized state agency.

A wetland map unit that is within 300’ of the near stream disturbance zone (OHW) of a salmon-bearing stream.

The reach that the map unit is part of has been verified as salmon-bearing by the authorized state agency.
A wetland map unit outside the OHW, but still within the 300’ constraint, will only receive scoring for the large wood recruitment indicator of the habitat formation function.

A map unit that is within 300’ of the OHW of a salmon-bearing stream.

The reach that the map unit is part of has been verified as salmon-bearing by the authorized state agency.
A map unit outside theOHW, but still within the 300’ constraint, will only receive scoring for the large wood recruitment indicator of the habitat formation function.

Nesting/Spawning is calculated only if the reach the map unit is part of has been identified as having spawnable substrate by authorized state agency.
The functional performance score for an intermittent stream map unit is reduced by 50%.
Salmon credit is reduced by 50% for the length of the stream segment above a partial constraint that meets fish passage criteria.

Fish passage criteria determined by authorized state agency.

Salmon credit is not calculated for the length of the stream segment above a partial constraint that does not meet fish passage criteria or above a full barrier to fish passage.

Fish passage criteria determined by authorized state agency.

Salmon Credit Determination

The actual determination of the salmon credit/debit generated by a project is determined through a multistep process. The methodology is applied and scored for three basic conditions, baseline (or existing conditions), design alternative, and as-built conditions. The baseline credit/debit score is determined by evaluating the functions based on how the site is currently performing. To determine the credit/debit score associated with a design alternative, new data is derived based upon projecting the information in the design plan out 20 years. The baseline credit/debit score is then subtracted from the 20-year projection of the design plan credit/debit score. This will result in the potential credit/debit generated from the design. If the value is positive, the design has resulted in a credit, and if the value is negative the result is a debit. In order to determine the final credit/debit score for a project, a similar credit/debit analysis must be done based on data collected after the on the ground design work has been completed. The as-built survey will collect the data for the site as it would appear in 20 years, the same as the process used for the design plan. The final credit/debit score for the project is derived by subtracting the baseline credit/debit score from the as-built credit/debit score. Again, if the value is positive, the design has resulted in a credit, and if the value is negative the result is a debit.

General Equations

See Figure 1.

Salmon Credit Calculation
Draft from Parametrix’s Method Library

Function: Cover/Refugia for Anadromous Fish Biotic Support

Definition

On a site scale, cover/refugia provide specific locations for resting and shelter or protection during times of danger or distress. Cover/refugia typically constitute high quality habitat. Refugia areas on a landscape scale can act as a temporary refuge or as a center from which dispersion may take place to re-colonize areas (Talabere and Jones 2002). Refugia can also provide a hedge against the difficulty in restoring extensive, degraded habitat and recovering imperiled populations in a timely manner (IMST 1999). Cover and refugia, as defined, are used interchangeably.

Triggering Conditions

Any map unit identified as a natural aquatic habitat type,man-made aquatic habitat type, or wetland habitat type,or that is adjacent to (i.e., shares a boundary with) an aquatic and/or wetland habitat type is eligible for anadromous fish cover/refugia scoring. For all aquatic habitat types, the anadromous fishcover/refugia scoring calculation is performed only if the map unit is part of a stream reach identified as salmon-bearing by the regulatory agency(ies). For all other habitat types, the anadromous fish cover/refugia calculation is performed only if the map unit is adjacent to or is within 300’ of a reach that has been identified as salmon bearing by the regulatory agency(ies).

Modifier

Man-made aquatic map units and intermittent streams cannot get full aquatic cover scores.Final aquatic cover scores for respective aquatic habitats aremultiplied by the percentages listed below.

Habitat / Percent of Final Aquatic Cover Score
Canal / 5%
Culvert / 5%
Ditch / 5%
Fish passage structure / 5%
Intermittent stream / 50%
FUNCTION: Cover/Refugia for Anadromous Fish Biotic Support
Aquatic and Man-made
Aquatic Habitat Types
Canal, culvert, ditch,
fish passage structure
INDICATORS:

Large Wood(Bisson et al. 1987)
Dominant Aquatic Features (Nickelson 1998)
Aquatic Conditions

Undercut Banks
(Moore et al. 2002)
Aquatic Substrate Composition
(Moore et al. 2002)
Total Aquatic Vegetation (Bleier et al. 2003)

Predominant Water Depth (Moore et al. 2002)

/ Wetland and
Man-made Aquatic
Habitat Types
Lake, reservoir, constructed pond, abandoned open pit
INDICATORS:

Down Wood
(Maser et al.1998)
Total Aquatic Vegetation (Bleier et al. 2003)

/ All Remaining
Habitat Types
Must meet
triggering conditions
INDICATORS:

Overhanging Vegetation (Moore et al. 1999)

References

Bisson, P.A., R.E. Bilby, M.D. Byrant, C.A. Dolloff, G.B. Grette, R.A. House, M.L. Murphy, K.V. Koski, and J.R. Sedell. 1987. Large woody debris in forested streams in the Pacific Northwest: past, present, and future. Pages 143-190. In: E.O. Salo and T.W. Cundy, editors. Streamside management and fishery interactions. Institute of Forest Resources, University of Washington. Seattle, Washington.

Bleier, C., Downie, S., Cannata, S., Henly, R., Walker, R., Keithley, C., Scruggs, M.; Custis, K., Clements, J. and R. Klamt. 2003. North Coast Watershed Assessment Program Methods Manual. California Resources Agency and California Environmental Protection Agency,Sacramento, California. 191 p.

Independent Multidisciplinary Science Team (IMST). 1999. Recovery of Wild Salmonids in Western Oregon Forests: Oregon Forest Practices Act Rules and the Measures in the Oregon Plan for Salmon and Watersheds. Technical Report 1999-1 to the Oregon Plan for Salmon and Watersheds, Governor's Natural Resources Office, Salem, Oregon.

Maser, Chris; Benner, Patricia A. From the Forest to the Sea: A Story of Fallen Trees. 1988. United States. Bureau of Land Management; Pacific Northwest Research Station, Portland, Or. (USA). Pacific Northwest Research Station, U.S. Dept. of Agriculture, Forest Service.

Moore, K., K. Jones, and J. Dambacher. 2002. Methods for stream habitat surveys: Aquatic Inventories Project, Natural Production Program: Oregon Department of Fish And Wildlife, Version 12.1. Oregon Department of Fish and Wildlife, Aquatic Inventories Project, Natural Production Program. Corvallis, Oregon.

Moore, Kelly, Kim Jones, Jeff Dambacher, Jennifer Burke, Charlie Stein, and STEP Biologists. 1999. Surveying Oregon's Streams, "A Snapshot In Time;” Aquatic Inventory Project Training Materials and Methods for Stream Habitat Surveys. Oregon Department of Fish and Wildlife. Portland, OR.

Nickelson, T. E. 1998. A Habitat-Based Assessment of Coho Salmon Production Potential and Spawner Escapement Needs for Oregon Coastal Streams. Oregon Department of Fish and Wildlife, Northwest Region Portland, Oregon. 15 p.

Talabere, Andrew G. and Kim K. Jones. 2002. Pacific Salmon Conservation: Designating Salmon Habitat and Diversity Watersheds, A Process to Set Priorities for Watershed Protection and Restoration. Oregon Department of Fish and Wildlife.

FUNCTION:Cover/Refugiafor Anadromous Fish Biotic Support
HABITAT TYPE:Aquatic and Man-Made Aquatic
(Canal, Culvert, Ditch, Fish Passage Structure)

Large Wood or Large Woody Debris (LWD)

Pieces of wood, either natural or cut, with some part of the piece within the active channel of the stream. The minimum size for counting a piece of large wood is 6 inches in diameter by 10 feet in length. The minimum length does not apply to root wads.

Data Collection

Number of pieces
Number of pieces with attached rootwads by length and diameter classes

Modifiers

Rootwads– Large wood volume is modified by the presence of rootwads. The large wood volume is increased by 10% per piece if a rootwad is attached. (Units/Increments for rootwads are included in the above table: “# with rootwad attached.”)
Wetted width (feet)– The boundaries of the wetted width are the points at which substrate particles are no longer surrounded by free water. The wetted width is the width (in feet) of the wetted stream during typical summer (base) flow conditions (Moore et al. 2002). Wetted width will modify large wood score relative to stream size: wetted widths <22’ (small streams), wetted widths between 22’ and 49’ (medium streams), and wetted widths >49’ (large streams).

Units/Increments

Diameter classes: <6”, 6”-12”, 12”-24”, 24”-36”, 36”-48”, >48”

Length classes: <10’, 10’-20’, 20’-30’, 30’-40’, 40’-50’, 50’-60’, >60’

Small Stream Large Wood Volume (ft³/ft²)Score

Not Present / 0.02-0.061 / 0.062-0.110 / 0.111-0.202 / 0.203-0.452 / >0.452
0 / 7 / 8 / 9 / 10 / 10

Medium Stream Large Wood Volume (ft³/ft²) Score

Not Present / 0.02-0.061 / 0.062-0.110 / 0.111-0.202 / 0.203-0.452 / >0.452
0 / 6 / 7 / 8 / 9 / 10

Large Stream Large Wood Volume (ft³/ft²) Score

Not Present / 0.02-0.061 / 0.062-0.110 / 0.111-0.202 / 0.203-0.452 / >0.452
0 / 5 / 6 / 7 / 8 / 9

Reference

FUNCTION:Cover/Refugiafor Anadromous Fish Biotic Support
HABITAT TYPE:Aquatic and Man-Made Aquatic
(Canal, Culvert, Ditch, Fish PassageStructure)

Dominant Aquatic Features (Percent of Map Unit)

Estimate of the percent area for each feature present within the map unit. The dominant feature is the feature that occupies the largest percent of the map unit. Where dominance is shared over multiple features, their scores are averaged.

Units/Increments

Alcove– A backwater along the shoreline; not scoured during typical high flows(Moore et al. 2002).
Backwater channel –Off-channel habitat located away from and along the main channel. May occur in secondary channels or as flood overflow channels (e.g., beaver run).
Intermittent– A course of water flowing along a bed in the earth for only part of the time, generally in response to periods of heavy runoff either from snowmelt or storms. Flow generally occurs for several weeks or months in response to seasonal precipitation, or due to groundwater discharge.
Log jam – An accumulation of fallen trees (large woody debris) that may impede or block a waterway.
Mud flat –A level area of fine silt and clay along a shore alternately covered or uncovered by the tide or covered by shallow water. May or may not contain detritus material.
Cascade– Series of small steps of alternating small waterfalls and small pools.
Backwater pool– Found along channel margins; created by eddies around obstructions such as boulders, root wads, or woody debris. Part of active channel at most flows; scoured at high flow. Substrate typically sand, gravel, and cobble (ODFW 2003).
Dammed pool– Water impounded upstream of channel blockage (debris jams, rock landslides), including beaver ponds (ODFW 2003).
Trench pool– Long, usually deep slot in a stable substrate (often bedrock) (ODFW 2003).
Lateral scour pool – Formed by flow impinging against one stream bank or partial obstruction (logs, rootwad, or bedrock). Asymmetrical cross section. Includes corner pools in meandering lowland or valley bottom streams (ODFW 2003).
Plunge pool– Formed by scour below a complete or nearly complete channel obstruction (logs, boulders, or bedrock). Substrate is highly variable. Frequently, but not always, shorter than the active channel width (ODFW 2003).
Rapid– Shallow reach of gradient >4% with high current velocity and considerable turbulence. (A reach of stream that is characterized by small falls and turbulent high velocity water – StreamNet 2007).
Low gradient riffle – Shallow reach of gradient <4% with moderate current velocity and moderate turbulence.
High gradient riffle – Shallow reach of gradient >4% with moderate current velocity and moderate turbulence. (A reach of stream that is characterized by shallow, fast moving water broken by the presence of rocks and boulders – StreamNet 2007).
Run/glide– Areas of swiftly flowing water, without surface agitation or waves, which approximates uniform flow and in which the slope of the water surface is roughly parallel to the overall gradient of the stream reach.
Sand/gravel bar – Areas of sand/gravel built up near the middle of a river/stream bed. Can also be used to identify point bars, or depositional points of sand/gravel on the insides of river/stream curves.
Waterfall –A sudden, nearly vertical drop in a stream, as it flows over rock.
Other– “Other” is chosen if a predefined type does not apply to the map unit.

Modifier

Channel type: Primary/Secondary

Units/Increments

Primary– The primary channel of a stream carries the majority of the stream flow. In many streams, it is the only wetted channel during the summer months. Some stream configurations, such as unconstrained braided streams, have no single primary channel.
Secondary –Secondary channels are all channels other than the main, or primary, channel of a stream.

Dominant Aquatic Structure Score
Dominant Aquatic Structure / Primary Channel / Secondary Channel
Alcove / 10 / 10
Backwater channel / 8 / 8
Backwater pool / 9 / 9
Intermittent / 7 / 7
Log jam / 9 / 8
Mud flat / 4 / 4
Cascade / 4 / 4
Dammed pool / 9 / 7
Lateral scour pool / 8 / 9
Plunge pool / 7 / 9
Trench pool / 8 / 9
Rapid / 5 / 5
High gradient Riffle / 5 / 5
Low gradient Riffle / 5 / 5
Run/glide / 7 / 7
Sand/gravel bar / 4 / 4
Waterfall / 0 / 0
Other / 0 / 0

References