coastal impact on barrier islands: application to praia de ... · this project has received funding...

This project has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demostration under Grant Agreement No. 603458. This presentation reflects the views only of the authors, and the European Union cannot be considered liable for any use that may be made of the information contained therein.

Coastal Impact on barrier Islands:

Application to Praia de Faro

RISCKIT Final Meeting

Theocharis Plomaritis, Oscar Ferreira and Susana Costas

Regional to Local: Hotspot Tool

• Transform offshore physical parameters into onshore hazard;

• Transform the hazard into impact for selected receptors;

• Surrogate the computationally expensive morphodynamic

simulations within an EWS using a BN

• Incorporate into the tool DRR measures so it can be used by coastal managers as a DSS.

RISCKIT Final Meeting 2017

Study Site – Praia de Faro

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Coastal lagoon system protected by a barrier-island, with sandy shores and dunes.

Storms Hs > 3m; up to 6-7m

Tidal range up to 3.5 m

Storm surge < 1 m

Reduced river input

Early Warning and Decision Support System (EWS/DSS) for use on hot spots.

1. Traditional EWS incorporated in Delft-FEWS that

includes Tides/Surges-Waves-Morphodynamics 2. Store results in Bayesian Network for immediate

evaluation of event impact. 3. Evaluation of Disaster Risk Reduction measures

(DRR)

EWS/DSS

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Model Train for EWS Do

mai

n 1

Dom

ain

2 Domain 3

Surrogated

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FEWS EWS

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• Regional and local

Hazards and relevant model selection (XBeach) Overwash

Coastal/Dune Erosion

Car-park 1996

Protection Works 1990

Camping 1991 C. Sector 1995

Road colapse 1990

Car-park 1990

Study Site – Praia de Faro

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• Historic events Date Duration

(hours)

Wave height (Dir)

Total Water elevation, MSL

(m)

Impact

15/02/1941 24 4.2(SW) 1.8 Inlet opening at Praia de Faro (Ancao Peninsula)

12/01/1969 15 4.3 (SW) 1.1 Major overwash of houses; opening of an inlet and shoreline retreat

11/2/1979 35 7.1 (SW) 1.3 Damages and house destruction at Praia de Faro

13-27/11/1989 40 7 (SW) 1.7

Destruction of houses and seawall

23/01/1996 49 6.5 (SW) 2.31 The entire seawall was damaged at Praia de Faro

02-08/02/1998 28 5.6 (SW) 1.7 Destruction of few houses at Praia de Faro 23-31/12/2009 50 5.8 (SW) 1.3/1.7 7 houses destroyed at Fuzeta

04/01/2010 12 4.7 (SW) 1.6 11 houses destroyed at Fuzeta 15/02/2010 45 4 (SW) 1.56 Strong overwash and breaching (downdrift)

02/03/2010 23 5.2 (SW) 2.15 3 houses destroyed at Praia de Faro

The BN training

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• Synthetic events Hs vs. Tp Hs vs. Surge Hs vs. Duration

Poelhekke et al., 2016 Coastal Engineering

Number of Events

Data Interval Surge (m) Hs (m) Tp (s)

Historic 10 0.31 -0.58 4.5 - 7.1 9.6 - 13.5

Synthetic 30 0.15 – 0.66 3.0 - 7.9 8.1 - 17.4

The BN training

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Synthetic Event Schematisation 1 Simulation for each tidal stage 3x30 =90

The BN training

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DRR measures Three DRR measures have been selected for the Praia de Faro case study (Considering end-users input from interviews): • Beach nourishment (T1) (hazard related, extra modelling)

• House removal (T2) (exposure related)

• Create and/or improve Communication Channels (T3)

(vulnerability related)

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DRR measures • Beach nourishment (T1) (extra modelling )

Nourishment specification were adopted from regional authorities protection plan for Praia de Faro

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DRR measures • House removal (T2)

Areas Selection:

• 4 areas based on exposure characteristics

Receptos Type

• Houses

• Infrastructure

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DRR measures • Channels of Communication (T3)

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Non-primary measures based on two primary measures: • Sandbags

• Constructions on Piles

Model Results Observed Hazard threshold

Hs vs Tp: Good separation of hazard/no hazard event

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Model Results Proxy selection for Praia de Faro:

• Overwash: Max water Flux (cross-shore)

• Erosion: Vertical Erosion in 3 areas

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Bayesian Network Boundary Conditions Hazard

Receptors

Impact Measures

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BN Results • For Hs> 7m and Tp> 14.5sec (Tr ≈ 50 years)

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BN Results : Current Conditions

18 3

79

PotentiallyDamagedDamaged

Safe

• Tr ≈ 50 years

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• Tr ≈ 50 years – Erosion

45

5

50

PotentiallyDamagedDamaged

Safe

BN Results : Current Conditions

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BN Results : Beach Nourishment • Tr ≈ 50 years - Overwash

18 3

79

PotentiallyDamaged

Damaged

Safe

8 0

92

PotentiallyDamaged

Damaged

Safe

Current Conditions Nourishment

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45

5

50

PotentiallyDamaged

Damaged

Safe

2 0

98

PotentiallyDamaged

Damaged

Safe

• Tr ≈ 50 years – Erosion Current Conditions Nourishment

BN Results : Beach Nourishment

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18 3

79

PotentiallyDamaged

Damaged

Safe

12 1

87

PotentiallyDamaged

Damaged

Safe

• Tr ≈ 50 years - Overwash Current Conditions House Removal

BN Results : House Removal

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45

5

50

PotentiallyDamaged

Damaged

Safe

28

2 70

PotentiallyDamaged

Damaged

Safe

• Tr ≈ 50 years – Erosion Current Conditions House Removal

BN Results : House Removal

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18 3

79

PotentiallyDamaged

Damaged

Safe

13 2

85

PotentiallyDamagedDamaged

Safe

• Tr ≈ 50 years - Overwash

BN Results : Channels of Communication

Current Conditions Channels of Communication

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45

5

50

PotentiallyDamaged

Damaged

Safe

41

5

54

PotentiallyDamaged

Damaged

Safe

• Tr ≈ 50 years – Erosion

BN Results : Channels of Communication

Current Conditions Channels of Communication

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18 3

79

PotentiallyDamaged

Damaged

Safe

3 0

97

PotentiallyDamaged

Damaged

Safe

• Tr ≈ 50 years - Overwash

BN Results : Nourishment + House Removal

Current Conditions Nourishment

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Sem SA4 Com SA4

45

5

50

PotentiallyDamaged

Damaged

Safe

1 0

99

PotentiallyDamaged

Damaged

Safe

• Tr ≈ 50 years – Erosion

BN Results : Nourishment + House Removal

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Concluding remarks • Nourishment is the most effective DRR in reducing the impact

on the houses.

• The use of a BN in EWS could result in significant reduction of the computational effort.

• The method requires a large number of simulation for the initial setup but can result in a very useful tool the event scale protection measures.

• The inclusion of DRR measures makes the proposed tool useful also for long-term decision making process.

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Any questions ?

Thank you

Consequences - Impact (C) From Hazard to Impact - Overwash

House Type 0 1 2 3 4 5 6 7 >7Wood-Framed:

UnanchoredPartial Collapse

Wood-Framed: AnchoredMasonry,

concrete and brick

No Collapse Partial Collapse (if v is also ≥ 2 m²/s)Total Collapse (if v is also ≥ 2 m²/s)

Depth-Velocity Product - vd (m²/s)

No Collapse Total Collapse

No Collapse Partial Collapse Total Collapse

From Hazard to Impact - Erosion Sr-A >= Tp Tp <= Sr-A <=Tpm Tpm <= Sr-A <= Tl Tl <= Sr-A

ErVI None

Low probability of asset collapse:

Disruption caused by preventive evacuation

before and during the event

Medium probability of asset collapse:

Disruption caused bypreventive evacuation as well

asduring and post event

checking/monitoring by civil protection and coastal

management institutions

High probability of collapse:

High disruption and total loss of asset

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