Introduction to Introduction to River IceRiver Ice

Introduction to Introduction to River IceRiver IceKathleen D. White, PEKathleen D. White, PE

Research Hydraulic EngineerResearch Hydraulic EngineerIce Engineering Research DivisionIce Engineering Research Division

US Army Cold Regions Research and Engineering LaboratoryUS Army Cold Regions Research and Engineering Laboratory

NWS Hydromet 99-2NWS Hydromet 99-2Boulder, COBoulder, CO

Monday, June 28, 1999Monday, June 28, 1999

CRRELCRRELCRRELCRREL

ColdCold Problem Solvers for the NationProblem Solvers for the NationColdCold Problem Solvers for the NationProblem Solvers for the Nation

Ice Cover Crystal StructuresIce Cover Crystal Structures

• Fine grained iceFine grained ice– Frazil or snowFrazil or snow

– ““White” iceWhite” ice

– Resists solar penetrationResists solar penetration

• Columnar iceColumnar ice– Thermally grownThermally grown

– ““Black” iceBlack” ice

– Transparent, allows solar penetration,”candle Transparent, allows solar penetration,”candle ice”ice”

Frazil IceFrazil Ice• Frazil is the predominant type of ice found in most river Frazil is the predominant type of ice found in most river

and streamsand streams

• Formed only in areas of open waterFormed only in areas of open water

• Formed in turbulent waterFormed in turbulent water

Flow velocityFlow velocity

Wind mixingWind mixing

• Formed in supercooled waterFormed in supercooled water

-.01°C to -.02°C -.01°C to -.02°C

FRAZIL ICE IN RIVERSFRAZIL ICE IN RIVERS

Entrainment

Seed Crystals

Supercooled Water

Surface Growth and Surface FlocculationStable Ice Cover

Deposited Slush

Disks

BuoyantAnchor Ice

Disks

Anchor Ice Transported Frazil

Ice Crystals Nucleatedin Cold Air

Frazil Slush

Anchor Ice

Frazil Evolution: Ice FloesFrazil Evolution: Ice Floes

Frazil SlushFrazil Slush

Frazil SlushFrazil Slush Pancake IcePancake Ice Large FloesLarge Floes

““High Energy”High Energy” ““Low Energy”Low Energy”

Mountain StreamsMountain Streams Steep RiversSteep RiversLarge WavesLarge Waves

Rivers withRivers withMild SlopesMild Slopes

Ice Cover FormationIce Cover Formation

• Static Ice Cover FormationStatic Ice Cover Formation– Typical of ponds, small lakes, and slow flowing Typical of ponds, small lakes, and slow flowing

rivers rivers

– Dominated by thermal growth Dominated by thermal growth

AirAir

WaterWater

IceIce

Ice GrowthIce Growth

Heat transferHeat transfer

FDD

Ice Cover FormationIce Cover Formation

• Dynamic Ice Cover FormationDynamic Ice Cover Formation– Dominated largely by the interaction between Dominated largely by the interaction between

ice floes and the flowing waterice floes and the flowing water

– An ice cover may initially form dynamically and An ice cover may initially form dynamically and later thicken due to thermal growthlater thicken due to thermal growth

River Ice Cover BreakupRiver Ice Cover Breakup

• Thermal Breakup: Ice cover melts in placeThermal Breakup: Ice cover melts in place– Direct sunlight plays a large roleDirect sunlight plays a large role

– Surface color influences absorption of Surface color influences absorption of

sunlight: Dusting ice promotes meltingsunlight: Dusting ice promotes melting

– Water on ice decreases reflection, mayWater on ice decreases reflection, may

promote meltingpromote melting

– Open water areas absorb sunlightOpen water areas absorb sunlight

River Ice Cover BreakupRiver Ice Cover Breakup

• Mechanical Breakup: Hydrodynamic forces Mechanical Breakup: Hydrodynamic forces acting on cover exceed cover strengthacting on cover exceed cover strength

• Results from an increase in flowResults from an increase in flow– Precip. eventPrecip. event

– Snowmelt eventSnowmelt event

– Dam operationDam operation

Mechanical Ice Cover BreakupMechanical Ice Cover Breakup

• Increase in flow & stageIncrease in flow & stage

• Fractures in ice coversFractures in ice covers

• Ice cover freed from constraints of banks Ice cover freed from constraints of banks and transported downstreamand transported downstream– Stage rise 1.5 to 3 times ice thicknessStage rise 1.5 to 3 times ice thickness

• Ice floes broken into smaller floesIce floes broken into smaller floes

• Ice jam formation downstreamIce jam formation downstream

Ice Jam Formation Ice Jam Formation

• Jams occur at locations where the rivers Jams occur at locations where the rivers transport capacity is exceededtransport capacity is exceeded– Intact ice coverIntact ice cover

– Sharp bendsSharp bends

– Decreases in channel slopeDecreases in channel slope

– ConstrictionsConstrictions

– ConfluencesConfluences

• Abrupt flooding can occur upstream of jamAbrupt flooding can occur upstream of jam

What constitutes a Jam ?

IAHR Working Group onIAHR Working Group onRiver Ice Hydraulics DefinitionRiver Ice Hydraulics Definition

IAHR Working Group onIAHR Working Group onRiver Ice Hydraulics DefinitionRiver Ice Hydraulics Definition

An ice jam is a stationary accumulation of An ice jam is a stationary accumulation of fragmented ice or frazil that restricts flowfragmented ice or frazil that restricts flowAn ice jam is a stationary accumulation of An ice jam is a stationary accumulation of fragmented ice or frazil that restricts flowfragmented ice or frazil that restricts flow

Ice JamsIce Jams

• Cause floodingCause flooding• Promote bed and bank erosionPromote bed and bank erosion• Remove or damage bank vegetationRemove or damage bank vegetation• Suspend navigationSuspend navigation• Damage channel training worksDamage channel training works• Flood upland wetlandsFlood upland wetlands• May be important for maintaining near-May be important for maintaining near-

stream habitatstream habitat

Freezeup JamsFreezeup Jams

• Early to mid-winter formation• Early to mid-winter formation• Subfreezing air temperatures• Subfreezing air temperatures• Frazil and broken border ice• Frazil and broken border ice• Unlikely to release• Unlikely to release• Fairly steady water flow• Fairly steady water flow• May exhibit cohesion• May exhibit cohesion• Smooth to moderate surface roughness• Smooth to moderate surface roughness

Primary Flow AreaPrimary Flow AreaPrimary Flow AreaPrimary Flow Area

FrazilFrazilFrazilFrazil

Drained FrazilDrained FrazilDrained FrazilDrained FrazilRefrozen Refrozen Surface LayerSurface LayerRefrozen Refrozen Surface LayerSurface Layer

Border Ice PiecesBorder Ice PiecesBorder Ice PiecesBorder Ice Pieces

Cross Section of Freezeup JamCross Section of Freezeup JamCross Section of Freezeup JamCross Section of Freezeup Jam

Breakup JamsBreakup JamsBreakup JamsBreakup Jams

• Mid to late winter formationMid to late winter formation• Mid to late winter formationMid to late winter formation• Near-freezing air temperaturesNear-freezing air temperatures• Near-freezing air temperaturesNear-freezing air temperatures• Broken sheet and border iceBroken sheet and border ice• Broken sheet and border iceBroken sheet and border ice• Highly unstable, releasing suddenlyHighly unstable, releasing suddenly• Highly unstable, releasing suddenlyHighly unstable, releasing suddenly• Unsteady water flow (surges)Unsteady water flow (surges)• Unsteady water flow (surges)Unsteady water flow (surges)• Negligible cohesionNegligible cohesion• Negligible cohesionNegligible cohesion• Moderate to extreme surface roughnessModerate to extreme surface roughness• Moderate to extreme surface roughnessModerate to extreme surface roughness

Primary Flow AreaPrimary Flow AreaPrimary Flow AreaPrimary Flow Area

Cross Section of Breakup JamCross Section of Breakup JamCross Section of Breakup JamCross Section of Breakup Jam

Brash/slushBrash/slushBrash/slushBrash/slushIce BlocksIce BlocksIce BlocksIce Blocks Water LevelWater LevelWater LevelWater Level

Brash, frazil, and larger pieces

Mid-winter JamsMid-winter JamsMid-winter JamsMid-winter Jams

• Forms due to "mid-winter thaw"Forms due to "mid-winter thaw"• Forms due to "mid-winter thaw"Forms due to "mid-winter thaw"• Breakup jam characteristicsBreakup jam characteristics• Breakup jam characteristicsBreakup jam characteristics• Refreezes in place to form significant Refreezes in place to form significant blockageblockage• Refreezes in place to form significant Refreezes in place to form significant blockageblockage• May result in more jamming during May result in more jamming during subsequent spring breakupsubsequent spring breakup• May result in more jamming during May result in more jamming during subsequent spring breakupsubsequent spring breakup

Undercover Transport and DepositionUndercover Transport and DepositionUndercover Transport and DepositionUndercover Transport and Deposition

• Frazil (and small blocks) transported beneath a Frazil (and small blocks) transported beneath a cover come to rest at areas of low water velocitycover come to rest at areas of low water velocity• Frazil (and small blocks) transported beneath a Frazil (and small blocks) transported beneath a cover come to rest at areas of low water velocitycover come to rest at areas of low water velocity

• Accumulation builds up until critical velocity is Accumulation builds up until critical velocity is reached (0.5-1.0 m/sec)reached (0.5-1.0 m/sec)• Accumulation builds up until critical velocity is Accumulation builds up until critical velocity is reached (0.5-1.0 m/sec)reached (0.5-1.0 m/sec)

• Tends to fill in deep sections so that accumulation Tends to fill in deep sections so that accumulation follows bed topographyfollows bed topography• Tends to fill in deep sections so that accumulation Tends to fill in deep sections so that accumulation follows bed topographyfollows bed topography

• May deform ice surface due to buoyancyMay deform ice surface due to buoyancy• May deform ice surface due to buoyancyMay deform ice surface due to buoyancy

• Also referred to as "hanging dam"Also referred to as "hanging dam"• Also referred to as "hanging dam"Also referred to as "hanging dam"

Undercover Transport and DepositionUndercover Transport and DepositionUndercover Transport and DepositionUndercover Transport and Deposition

Frazil SlushFrazil SlushFrazil SlushFrazil Slush

Solid Ice CoverSolid Ice CoverSolid Ice CoverSolid Ice Cover

Pans or BlocksPans or BlocksPans or BlocksPans or Blocks Ice JamIce JamIce JamIce Jam

Submergence/Frontal ProgressionSubmergence/Frontal ProgressionSubmergence/Frontal ProgressionSubmergence/Frontal Progression

• Existing jam fails when downstream acting forces Existing jam fails when downstream acting forces rise above jam strengthrise above jam strength• Existing jam fails when downstream acting forces Existing jam fails when downstream acting forces rise above jam strengthrise above jam strength• Cover is transported downstream until resisting Cover is transported downstream until resisting force increasesforce increases• Cover is transported downstream until resisting Cover is transported downstream until resisting force increasesforce increases• Cover thickens as it comes to rest, thereby Cover thickens as it comes to rest, thereby increasing jam strengthincreasing jam strength• Cover thickens as it comes to rest, thereby Cover thickens as it comes to rest, thereby increasing jam strengthincreasing jam strength• Commonly occurs with breakup jamsCommonly occurs with breakup jams• Commonly occurs with breakup jamsCommonly occurs with breakup jams• Also referred to as "wide channel jam"Also referred to as "wide channel jam"• Also referred to as "wide channel jam"Also referred to as "wide channel jam"

Failure and ThickeningFailure and Thickening

Failure and thickeningFailure and thickeningFailure and thickeningFailure and thickening

Jam after failureJam after failure and thickeningand thickeningJam after failureJam after failure and thickeningand thickening Jam before failureJam before failureJam before failureJam before failure

Intact ice sheetIntact ice sheetIntact ice sheetIntact ice sheet

Modeling Ice-covered RiversModeling Ice-covered Rivers

• Steady Flow Steady Flow – HEC-2HEC-2

– HEC-RASHEC-RAS

• Unsteady Flow Unsteady Flow – UNETUNET

– Discrete Element ModelsDiscrete Element Models

• 2 Dimensional Flow2 Dimensional Flow– Currently in development Currently in development

HEC River Analysis System (RAS)

HEC River Analysis System (RAS)

• Water surface profiles for steady flowWater surface profiles for steady flow• Full networksFull networks• River geometry described by cross sectionsRiver geometry described by cross sections• 1-D energy eq. or momentum eq.1-D energy eq. or momentum eq.• Bridges, culverts,weirs, hydraulic Bridges, culverts,weirs, hydraulic

structures,etcstructures,etc• Multiple plans/profiles/bridge openingsMultiple plans/profiles/bridge openings• Graphical and tabular outputGraphical and tabular output

HEC-RAS with ice: HighlightsHEC-RAS with ice: Highlights

• View results graphically View results graphically • Profile PlotProfile Plot

HEC-RAS with ice: HighlightsHEC-RAS with ice: Highlights• View results graphically View results graphically

• X-Y-Z Perspective PlotX-Y-Z Perspective Plot

What about climate change?What about climate change?