EstProc 12092004

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EstProc 12/09/2004

• HYDRODYNAMICS
• POL D PRANDLE , A LANE , J WOLF
• HRW R SOULSBY
• ABP
• U CAM

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COMPONENT STUDIES IN HYDRODYNAMICS

• 1 CREEKS 2 SALTMARSH 3
  WAVE MODELS
• 4 Estuary 5 Cross-section 6
  EXTREME EVENTS
• assessment stability
  morphology theories
• 
  
  

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HYDRODYNAMICS

• A WAVES IN ESTUARIES
• Wave Models - Wave Current Stress - W C
  Estuary Model
• 
  MODEL DEVELOPMENT
• B IMPACTS OF SET-BACK / FLOOD DEFENCES
• Generic (model) Tool for examining
  Cross-Sectional Stability
• UNDERPINNING
  TOOLS KNOWLEDGE
• C EXTREME EVENTS - CLIMATE CHANGE
• Analytical Theories of Estuarine Morphology
• 
  INNOVATIVE FUNDAMENTAL RD
• 
  EstProc Deliverables

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Extent of Liverpool Bay Wave Model

Figure 1 Liverpool Bay SWAN model depths at
mid-tide.
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PEAK PERIODS IN SECS - 15 m/s wind
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WAVE HEIGHTS (m) 15m/s wind
PARAMETRIC MODEL
SWAN
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ASSESSMENT OF WAVE INFLUENCE ON SEDIMENTS IN
ESTUARIES

• SOULSBY SCHEMATIC OF WAVES CURRENTS

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ASSESSMENT OF WAVE INFLUENCE ON SEDIMENTS IN
ESTUARIES

• SOULSBY SCHEMATIC OF WAVES CURRENTS

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STRESS DUE TO COMBINED WAVES AND CURRENT
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(No Transcript)
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CROSS_SECTIONAL STABILITY

• GENERAL _PURPOSE MODEL
• TO INVESTIGATE
• CROSS-SECTIONAL EVOLUTION
• IMPACTS OF SET-BACK/FLOOD DEFENCES
• SENSITIVITIES TO CLIMATE CHANGE

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CROSS-SECTIONAL STABILITY
HW
1m
MSL
LW
Set-back Flood-protection
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2-D y-z cross-sectional model

• Morphology evolution (Langrangian)
• Depth 10 m, tidal amplitude 3 m, ws 10-3 m s-1

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EXTREME EVENTS CLIMATE CHANGE

• Estuary Research Programme
• 1995
• Scoping Study
• EMPHASYS
• EstProc
• 
  FD2107,FD2116,2117
• 2005
• 
  Estuarine Management System
• --------------------------------------------------
  -------------------
• WHAT DETERMINES EXISTING MORPHOLOGY?

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Estuarine shape and length
Integrating gives estuarine
shape estuarine length First
dynamically-derived estimate of estuarine
length, L No calibration coefficients
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SHADED AREA ESTUARY MORPHOLOGYTO ACCOMMODATE
SALINE MIXING
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Estuarine depth
For observed range of cross-section side slopes
0.95 Q0.4 lt D lt 2.4  Q0.4 First
dynamically-derived estimate of estuarine depth
D as f (Q) Range of Q shown incorporates 99
of all estuaries
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MORPHOLOGY DETERMINANTS ?

• PRECEDING THEORY INDICATES MORPHOLOGY DETERMINED
  BY TIDES AND RIVER FLOW
• (some influence of surficial sediments via
  bed roughness)
• HOW DOES THE SEDIMENT REGIME RESPOND TO THIS
  MORPHOLOGY ?

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How is stability maintained?
CONCENTRATION
Erosion
Deposition
Vertical profile
TRANSPORT
M4
Z0
Salinity
River flow
M2 tide
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Sensitivity of stability
EXPLAINS SORTING TRAPPING Turbidity Maximum
Half life in suspension (hours)
50
t
Half-life, (hours)
MOUTH
HEAD
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Settling velocity, Ws in mm s-1
Stable estuarine bathymetry requires 0.5lt Ws lt2
mm/s SEE FLOCCULATION RESULTS !
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IMPACTS OF EXTREME EVENTS CLIMATE CHANGE

SCENARIOS FOR CHANGE
IN TIDES MSL STORMINESS RIVER FLOW
SEDIMENT SUPPLY
EXPLICIT ALGORITHMS FOR IMPACT ON
ESTUARINE DEPTH LENGTH SALINE INTRUSION
FLUSHING TIME IN-FILL TIME
ASSESS WHETHER SPECIFIC ESTUARIES ARE IN
PRESENT-DAY OR HISTORIC EQUILIBRIUM
INDICATION OF LIKELY IMPACTS
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SUMMARY

• TECHNICAL DEVELOPMENTS IN
• MODELLING WAVES
• DETERMINING RESULTANT BED-STRESS
• MODELLING ESTUARY-WIDE IMPACT ON
  SEDIMENTS
• (Not presented, representation of
  creeks and saltmarsh)
• INSIGHT INTO IMPACTS OF
• EXTREME EVENTS
• GLOBAL CLIMATE CHANGE
• TOOLS FOR
  DETERMIMING
• EXAMINING INTERVENTION
  MANAGEMENT OPTIONS

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WAYS FORWARD

• Translate tools technologies into ensemble
  forecasts of likely changes in UK estuaries (FD
  2107,2116,2117)
• Assess results against existing ( recent and
  Holocene) morphological histories
• Identify future monitoring strategies

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HYDRODYNAMICS

• A WAVES IN ESTUARIES
• Wave Influence ltlt Tidal Influence
• B IMPACTS OF SET-BACK / FLOOD DEFENCES
• Slow Morphological Adjustments
• except for injudicious intervention
• C EXTREME EVENTS - CLIMATE CHANGE
• To 2050 , major impacts limited to (few)
  sensitive estuaries
• -------------------------------------------------
  ----------------------------------------
• Assuming little change to sediment supply or
  vegetation/biota
• SOUND SCIENTIFIC RESULTS

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