Fish Passage and Sediment Control

Washington Department of Forestry, Stream Habitat Restoration Guidelines, 2004

Ryan Johnson

OverviewFish passage restoration

Spawning gravel cleaning and placement

Instream Sediment Detention Basins

Washington Fish SpeciesAnadromous

o Steelheado Coho, Chinook, Pink, Chum, and Sockeye Salmono Cutthroat Trouto Pacific and River Lampreyo Green and White Sturgeono American Shado Dolly Varden/Bull Trouto Longfin Smelto Eulachon

Washington Fish SpeciesFreshwater

o Juveille Coho, Chinook, and Steelheado Kokaneeo Rainbow and Cutthroat Trouto Brown and Brook Trouto Bull Trout/Dolly Vardeno Olympic Mudminnowo Sticklebacko Sculpino Pygmy and Mountain Whitefisho Cyprinidso Catostomidso Sturgeono Western Brook Lamprey

Fish PassageAll listed fish require unimpeded access

up and downstreamoSafe, effective passage between reproduction, feeding, and refuge habitats

Passage timing, frequency, and duration varies with each species

Passage not limited to mainstreamoLateral movement

Blockage of Passage2,256 road crossings of fish bearing

streamso1,036 identified as barriersoPotential for >33,000 salmonid blockages

Coincides with blockage of downstream transport of habitat elementsoSediment, water, wood

Fish Passage RestorationPotential for greatest return on valueoAs simple as retrofitting a culvert

Can restore fish population, and habitats downstream

Best used in vertically and laterally stable streamsoPassage structures can become buried

Risk & UncertaintyRisk to resident fish

o Can create competition with established species

o Can introduce species historically not ever present

Structures can fill with sedimento If not maintained, possible catastrophic failure

of road fill

With relevant data and proper analysis, uncertainty is minimal

Spawning Gravel Cleaning and Placement

Salmonid Spawning HabitatControlling factorsoSize, permeability, and compaction of substrate

oVelocity, depth, direction, and dissolved oxygen content of flow

oProximity to cover and rearing habitat

Excessive Fine SedimentBuries spawning gravelReduces availability of dissolved oxygen

to eggsReduces removal rate of metabolic wastes

from the reddDisplaces aquatic invertebrates from

gravel pore spacesoPrimary source of food for juvenile

salmonids

Gravel CleaningMechanized removal of fine materialoOccasionally hydraulic removal

Temporary if source of fines not tended to

Should only be used where excessive fines are the limiting factor for salmonids

Gravel PlacementSpawning gravel added to replace identified loss

of gravelConstruction of discrete spawning pads

o Typically created by channel constriction or streambed control structures

Must be careful with placemento High flows can wash away eggs

Appropriate if stream’s capacity to retain gravel is restored

May be used in fines-dominated stream if there is no continuing source of fines

Sediment SizeOptimal sediment size for most salmonid specieso80% of 10-50 mm gravelo20% up to 100 mm graveloTrace coarse sand (2-5 mm)

No angular or crushed gravel

Risk & UncertaintyRelatively low risk for both methods

oTemporary destabilization of habitatoTargeting benefits toward one species

may hurt other speciesoPlacing gravel may cause aggradation in

unwanted placesSignificant uncertainty

oStream-specific and species-specificoObservation and evaluation important

Data and AssessmentMust understand requirements of involved species

and habitatGravel cleaning questions (lots of fines):

o Single event or chronic source of sediment?o Fines increased by land use?

o If yes, watershed and riparian restoration viable?

Gravel placement questions (no gravel):o Gravel recruitment problem?o Limits by transport conditions?o Anthropogenic or natural?

o If natural, should the habitat be altered?o If human, can the source be addressed?

VariationVariation in redd creation from different

specieso Substrate size, water depth, and water velocity

CostCan be costly and vary from project to

project, depending on specific needs

MaintenanceGravel cleaning should require no maintenance

Gravel placement should be monitored regularlyoGravel moves slowly downstreamoPeriodic replenishment

Instream Sediment Detention Basins

Gravel TrapsPools built to capture and store sediment

for removalUseful for curbing excessive aggradation

in a pinchoTreats only the symptom, not the source

Should only be used after developing a full understanding of sediment source(s) and patterns of depositionoMust allow appropriate types of

sediment to continue

ConsiderationsBuilding structures of this nature

disrupt the habitat on a local scaleCauses discontinuity in sediment

and debris flowsCan interfere with organism survival

requirements

All-in-all, very invasive

GoalShort-term solution for removal of excess sediment

Used before long-term measures can be implemented or before they become effective

Most effective for gravels, cobbles, and boulders

Risks & UncertaintyImpedance of fish passage up and downstreamMay strand fish during low or no-flow periodsCleanout requires fish relocation

o High stress, injury, or deathIf unmonitored, lateral channel migration can

occurCan increase flood levels

High natural variability causes high uncertainty in efficacy of trap and size of particle trapped

PlanningMake sure there is no alternativeIs mitigation necessary? Is the obligation

worth it?Starvation of downstream spawning

habitats of gravel?Downstream incision or scour?How often will inspection, maintenance,

and cleanout be necessary?Where will the sediment be dumped?How will the trap be decommissioned?

LocationShould be placed at a natural grade break or constrictionoLow velocityoIncrease natural tendency for sediment to accumulate

ConstructionTwo major componentsoExcavation of the basinoConstruction of the flow control structures

Off-site assembly reduces time stream is impacted

Flow Control StructuresWeirs

oControlled by shape, elevation, and length of weir crest

oFlow passes over weir crestSlots

oConfigured in vertical orientationoFlow passes through slot

Flashboard risers and gatesoAllows isolation of active working area

Slot & Weir

Sediment RemovalBasin design should include bypass ditch or pipeoDiverts stream flow while removal occurs

Cost and MaintenanceIncludes excavation and hauling, and

construction of structures, includingoFlow control devices and bypass

channelsMaintenance costs for sediment removal

Frequent monitoring importantoSediment removal can be initiated near

operating capacityoShould be checked after each flood

DecommissioningShort-term projectShould be as simple as removing the flow control devices

SummaryFish passage restoration

o Simple and cost-effectiveo Must consider needs of different species

Gravel cleaningo Removal of fines, which can negatively impact

salmon spawningGravel placement

o Creation of spawning pads where gravel deposition is minimal

Gravel trapso Short-term solution to excessive sediment

transportation