Coastal safety- case studies in Flanders
Transcript of Coastal safety- case studies in Flanders
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Coastal safety-
case studies in
Flanders
Duinkerke, June 12th 2018
MDK-Coastal Division
ir. Daphné Thoon
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Content
1. Introduction
2. Coastal Safety Masterplan - status
3. Management of the sandy coast
4. Case studie ‘Ostende- Mariakerke and Raversijde’
5. Case studie ‘seawall Middelkerke’
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1.Introduction
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A low-lying hinterland
5
Low lying hinterland
More than 85% of the polders beneath +5m TAW (average storm)
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Urban areas
Harbors
Dunes
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A ‘man-made’ coast line:
beaches and sea walls
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Harbor areas: quaywalls, locks &
weirs
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Non urban areas: beaches and
dunes
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Storm 1953
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2. Coastal Safety Masterplan
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Safety assessment and risk calculations:
2007-2008 Norm: No victims due to a 1000-year storm surge event: • Limited overtopping: 1l/m/s • No breaching of dunes and seawalls • No erosion that threatens protected buildings
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• Weak links (1000 year ARI): 1/3d coastline + harbors
• Mostly at locations with sea walls and quay walls
Safety Assessment 2007-2008
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2007: start voorbereiding Masterplan
Kustveiligheid
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Aim:
protect the Flemish coastline and the hinterland against the impact of a 1000 year ARI storm surge and prevent large scale floodings by taking into account climate changes till 2050
estimated sea level rise in 2050: 30cm
Coastal Safety Master Plan
Coastal Safety Master Plan
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Types of measures
‘Soft’ measures
‘Hard’ measures
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Soft measures
• Beach nourishments
• Dune nourishments
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Hard measures
Sea walls and quay walls: storm walls or elevation
Reinforcement of locks and weirs
Stilling wave basin
Storm surge barrier
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• study Master Plan started in 2007
• Master Plan and proposed measures approved by the Flemish government in 2011
• estimated cost: 300 millions €
• works started in 2011;
Coastal Safety Master Plan
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11/06/2018 │20
Anno 2011: measures to be executed
Beach
nourishment
Dune
nourishment
Storm wall/ storm
surge barrier
Stilling wave
basin
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11/06/2018 │21
Anno 2018: Measures to be exectuted
Beach
nourishment
Dune
noruishment
Storm wall/ storm
surge barrier
Stilling wave
basin
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3. Management of the sandy coast
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Coastal Safety Masterplan: Management
Sandy flood measures: management is required
• Dynamic environment: natural sand transport + maintenance is needed after heavy storm surges
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Coastal Safety Masterplan: Management
Sandy flood measures: • Topographic and bathymetric measurements: 2 times/year
• 6 yearly detailed safety assessment: 2015
• Safety assessments after every heavy storm surge
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Results safety assessment of 2015
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Safety assessment conclusions
• No breaching of dunes and seawalls • Weak zones remain ‘weaker’ but are much better • Nourished zones that don’t comply to the standard:
the norm is just exceeded, so maintenance is needed
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4. Case studie ‘Ostende – Mariakerke &
Raversijde’
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Ostende ‘Mariakerke & Raversijde’
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1. Reinforcement of the coastal defence 2. Reduce sand blowing on the sea wall and coastal road 3. Create added value to inhabitants and tourists
Design of flood measures: 3 goals
Cooperation of MDK en City of Oostende
Design is almost finished
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1.Beach nourishment and storm walls
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2.Reduce excessive eolian transport
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Dune creation for reducing eolian transport
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3. Added value
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5. Case studie ‘Seawall reinforcement of
Middelkerke’
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Middelkerke
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1. More ‘protection’ 2. More ‘experience’ 3. More ‘sun’ 4. More ‘green’
Design of flood measures: 4 goals
Cooperation of MDK en Town of Middelkerke
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1.More protection: combination of soft
and hard measures
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2.More experience
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3.More sun
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4.More green
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Questions