Storm-induced coastal risks at the Tordera delta under different climate scenarios

José A. Jiménez, Marc Sanuy,Agustín Sánchez-ArcillaAgustín Sánchez-Arcilla

jose.jimenez@upc.edu

Laboratori d’Enginyeria Marítima. Universitat Politécnica de Catalunya · BarcelonaTechBarcelona, Spain

Introduction

Storm-induced inundation and erosion are two of the most frequent coastal hazards affecting worldwide coastlinesfrequent coastal hazards affecting worldwide coastlines.

Associated coastal risks are likely to increase in the future due to changes in climate forcing which should require a re-evaluation of coastal disaster risk reduction strategies.

To develop a methodology to assess the influence of SLRTo develop a methodology to assess the influence of SLR on storm-induced coastal flooding & erosion taking into account the SLR-induced coastal response.

CC-induced effects in the forcing

steady (no change in storminess)

∆R

Ocean

∆R

dc

R

Surge Level

QovRu

storm surge level

Barrier S

Mean Water Level

SMWLincreasing

(SLR)(SLR)

Static approach

(source: USGS)

but ….. Only valid if the coast is rigid/passive (e.g. revetment, rocky)

hpr

oach

mic

ap-d

ynam

2015

Qua

si-

m e

t al.

2Q

Bos

o

How relevant is? Accomodation space

Active vs non-active coaststo SLR

p

Erosion hazard

Magnitude of erosion hazard not affected.

Narrow beaches Larger/greater exposure Higher risk

2

4

6

2

4

6

-4

-2

0

elev

ació

n (m

)

-4

-2

0

elev

ació

n (m

)

10

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-6

10

-8

-6

50 75 100 125 150 175 200 225 250 275 300 325 350 375 400distancia (m)

-10

50 75 100 125 150 175 200 225 250 275 300 325 350 375 400distancia (m)

-10

Inundation hazard (I)Long time series (> 40 y) ofwave and water level time

8

Ru Total water level

time series

wave and water level timeseries

Stockdon’2006

7

time series

P O T

5

6P.O.T.

Select thesholde.g. quantile 0.995

4

R

2

3Ru

Total water levelextreme events

1 10 100

Return period (years)

ExtremeExtremeProb. Function fitting

GPD

Inundation hazard (II)Rc

Q

MWL

tanβTi,Hi,

OvertoppingHedges and Reis (1998)coefficients modified by Reis et al. (2008)y ( )Function of Ru (wave-induced forcing) and Rc (coastal characteristics)

Rc = 1.5 m

Rc = 2.0 m

Rc = 2.5 m

Inundation hazard (III)

Inundation

LISFLOOD-FP model (Bates & de Roo)( )

Inundation hazard (IV)

SLR – induced changes

No changes in forcing (waves and storm-surge) – steady Ru

Changes in overtopping due to decreasing freeboard due to Changes in overtopping due to decreasing freeboard due to changes in MWL . Beach profile adaptation to SLR

Ch i b h fil Changes in beach profile –Bruun rule + accommodationspace availability

Changes in floodwater

Changes in inundation

Study site

Change in overtopping hazard (WC)

RCP 8.5 (2050): +0.25 m

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479500 480000 480500 481000 4815004610400

479500 480000 480500 481000 4815004610400

479500 480000 480500 481000 4815004610400

479500 480000 480500 481000 4815004610400

Concluding Remarks

The use of traditional static approach to account changes in storm The use of traditional static approach to account changes in storm-induced inundability due to SLR overpredicts the induced effects and it must be considered as the worst case scenario.

Including the SLR-induced coastal response (quasi-dynamic approach) reduce the effects, specially in areas with a large accommodation space .

In developed coasts, this reduction is more detectable at shorter time horizons, when SLR-induced retreat is small in comparison with the , paccommodation space.

In relative terms the effects are more detectable for high probability stormsIn relative terms, the effects are more detectable for high probability storms (smaller Tr).

Erosion risk is affected by reducing the capacity of protection provided by Erosion risk is affected by reducing the capacity of protection provided by the beach.

Acknowledgements

Wave data Puertos del Estado(Spanish Ministry of Public Works)(Spanish Ministry of Public Works)

Topographic data Institut Cartogràfic i Geologic de Catalunya)

Funded by

EU FP7 Research projects

RISC-KIT (603458) http://www risckit eu/RISC KIT (603458)

RISES-AM (603396)

http://www.risckit.eu/http://www.risesam.eu/