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

1. 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 · BarcelonaTech
Barcelona, Spain

2. 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.

3. 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
S
MWLincreasing
(SLR)(SLR)

4. Static approach
(source: USGS)
but ….. Only valid if the coast is rigid/passive (e.g. revetment, rocky)

5. hproachmicap-dynam
2015
Quasi-
metal.2
Q
Boso

6. How relevant is?
Accomodation space
Active vs non-active coasts
to SLR
p

7. Erosion hazard
Magnitude of erosion hazard not affected.
Narrow beaches  Larger/greater exposure  Higher risk
2
4
6
2
4
6
-4
-2
0
elevación(m)
-4
-2
0
elevación(m)
10
-8
-6
10
-8
-6
50 75 100 125 150 175 200 225 250 275 300 325 350 375 400
distancia (m)
-10
50 75 100 125 150 175 200 225 250 275 300 325 350 375 400
distancia (m)
-10

8. Inundation hazard (I)
Long time series (> 40 y) of
wave and water level time
8
Ru
Total water level
time series
wave and water level time
series
Stockdon’2006
7
time series
PO T
5
6
P.O.T.
Select theshold
e.g. quantile 0.995
4
R
2
3
Ru
Total water level
extreme events
1 10 100
Return period (years)
ExtremeExtreme
Prob. Function fitting
GPD

9. Inundation hazard (II)
Rc
Q
MWL
tanβ Ti,Hi,
Overtopping
Hedges 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

10. Inundation hazard (III)
Inundation
LISFLOOD-FP model (Bates & de Roo)( )

11. 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 + accommodation
space availability
 Changes in floodwater
 Changes in inundation

12. Study site

13. Change in overtopping hazard (WC)
RCP 8.5 (2050): +0.25 m

14. 4612200
4612400
4612200
4612400
4612200
4612400
4612200
4612400
4611800
4612000
4611800
4612000
4611800
4612000
4611800
4612000
4611400
4611600
4611400
4611600
4611400
4611600
4611400
4611600
4611000
4611200
4611000
4611200
4611000
4611200
4611000
4611200
4610600
4610800
4610600
4610800
4610600
4610800
4610600
4610800
479500 480000 480500 481000 481500
4610400
479500 480000 480500 481000 481500
4610400
479500 480000 480500 481000 481500
4610400
479500 480000 480500 481000 481500
4610400

15. 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, p
accommodation 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.

16. 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/