Cowes Outer Harbour Project Harbour flow - post breakwater HW-1 At HW-1:! Cross harbour flow...
Transcript of Cowes Outer Harbour Project Harbour flow - post breakwater HW-1 At HW-1:! Cross harbour flow...
Cowes Outer Harbour Project
Bill Cooper and Gordon Osborn
19 May 2016
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Solent and Cowes tidal regime
Cowes water level
Solent tidal flows
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Solent and Cowes tidal regime
Cowes water level
Solent tidal flows
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Cowes tidal regime
Harbour area tidal flow
Cowes water level
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Cowes tidal regime
Harbour area tidal flow
Flow offshore of breakwater
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Harbour flow - post breakwater
HW-1
At HW-1:! Cross harbour flow
deflected and increased! Reduced cross harbour
flow in the lee of the breakwater
! Increased flow north and south along west Cowes
! Slight increase in flow rotation
Changes at other states of the tide more subtle
Improved wave protection
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Differences in predicted flows
HW-1
! Offshore flow increase! Cross harbour flow
increase! West Cowes flow slightly
increased! West entrance flow
reversal earlier! Majority of tide correctly
predicted
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Advantages offered by new model
! Bathymetry update! Coastal developments! Different periods in time! Improvements in
modelling technology, including flexible mesh structure
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Confidence of new modelling
! Hydrodynamic and Sediment transport models judged “fit for purpose” by HRW.
! Calibration proves good reproduction of measured tidal flows.
! Confidence in absolute levels of sedimentation, is not possible.
! Confidence in the model is high, particularly in predicting the relativeeffects of the development.
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Tidal Differences – Conclusions
Review has included:! Investigation of observed data; and! Testing of suggested causes including;
! Bathymetry changes! Location of observed data! Design and geographical extent of the old
model
Conclusions;! Lunar nodal cycle and resulting tidal phase
changes! Discrepancy in the originally observed data
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Harbour sedimentation
! Complex flow patterns and processes make sedimentation more difficult to predict than tidal flows
! Dynamic equilibrium of sediment exchange within the estuary and Solent
! Man made interventions disturb this equilibrium
! Dredging results in a natural increase in sedimentation rates
! Providing sheltered waters results in a natural increase in sedimentation rates
! Majority of sediment comes from Solent but there are other sources
! Storms and rainfall influence sedimentation rates
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Harbour sedimentation
! Variation in sediment rates over time! Observations show an increasing trend,
and higher since 2013! Model simulation does not include
! Vessel movements! Moored vessels! Marina structures
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Sedimentation - post breakwater
! Little change to the total harbour sedimentation! General trend:
! Some reductions in sedimentation in West Cowes! Some increase in sedimentation in East Cowes
Net change in sedimentation due to the breakwater
Breakwater – No Breakwater
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Consented scheme tidal differences
Breakwater only
Full Scheme
Influence of the dredging and Shrapeextension at HW-1:! Cross harbour flow
! Slight increase; and! Deflected further north
! Flow rotation offset to the left
Changes at other states of the tide:! Some changes near to Victoria Marina! More subtle changes elsewhere
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Consented scheme sediment differences
! Some increase to the total harbour sedimentation! Sedimentation in the dredged area of the new marina! General pattern of sedimentation in West Cowes similar to
the existing breakwater condition
Breakwater – No BreakwaterBreakwater – No Breakwater Full Scheme – No Breakwater
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Optimised scheme tidal differences
Breakwater only
Comparing flow with breakwater only configuration, at HW-1:! Cross harbour flow
! Similar flow speeds, but some reductions in main channel south
! Slight deflection further north to give a wider spread of flow
! Some reduction in flow rotation
Changes at other states of the tide:! Some changes near to Victoria Marina! More subtle changes elsewhereAmended
Scheme
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Optimised scheme sediment differences
! Some increase to the total harbour sedimentation! Sedimentation in the additional dredged areas! General pattern of sedimentation in West Cowes similar to
the Consented Scheme condition
Full Scheme – No Breakwater Optimised Scheme – No Breakwater
Thank you for your attention
Note
ABPmer Page 1 of 1
Ref: R/4238
Subject: Cowes Outer Breakwater – Public Consultation Meeting These slides have been prepared to inform the public meeting held on the 19 May 2016. The information provided should not be used or quoted out of context and may be subject to change at a later date. Please refer to the full published reports for more details of the modelling services undertaken as part of the Outer Harbour Project. Prepared by G. Osborn 19 May 2016