[email protected] José A. Jiménez 2008 The Ebro delta

[email protected]é A. Jiménez 2008

The Ebro delta coastal response during 2001-2004:a proxy of the potential effectsof an increase in storminess?

José A. Jiménez, Vicenç Gracia & Herminia I. Valdemoro

Universitat Politècnica de CatalunyaBarcelona, Spain

[email protected]


Motivation & objective

Under a climatic scenario of increase in storminess

Which should be …

the most likely coastal response?

the implications?

Usually

model-based approach

Here

data-based approach



Low-lying coast (~ 50 % with z ≤ + 0.50 m).

Exposed sandy coast without obstacles.

Highly dynamic coastline.

High natural values (geo- & bio- diversity).

Strategic zone in Catalonia (land-planning).


Max erosion (Cap Tortosa)retreat > 1750 m in 43 yrs (1957-2000)

5 km

19571989


5 km

La Marquesabeach

Cap Tortosa

Illa de Buda

Trabucador

Riumar

La Banya

Fangar

Sensitive areas to storm impacts


5 km

La Marquesabeach

Cap Tortosa

Illa de Buda

Trabucador

Riumar

La Banya

Fangar

La Marquesadune/beach erosionoverwashhinterland inundation



5 km

La Marquesabeach

Cap Tortosa

Illa de Buda

Trabucador

Riumar

La Banya

Fangar

Illa de BudaBreachingInundation


breaches

1 kmEb

ro ri

ver m

outh

Els Calaixos


5 km

La Marquesabeach

Cap Tortosa

Illa de Buda

Trabucador

Riumar

La Banya

Fangar

TrabucadorBarrier breaching



IB-T M-IB

-T

M-IB-T

M-TTM-T


storm Hs (m) Tp (s) θ t (hours) Tr (years)§ Oct-1990-1 4.51 10 73 18 9§ Oct-1990-2 3.57 10 78 28 2

Oct-1997 4.91 12.5 76 39.5 15§ Nov-2001-1 5.62 13.3 78 63 71§ Nov-2001-2 5.95 11.1 81 38 117§ Apr-2002-1 3.25 8.3 90 43 1§ Apr-2002-2 3.17 8.3 87 48 < 1§ Apr-2002-3 3.05 10.5 68 20 < 1

May-2002 4.52 9.1 82 65 9Feb-2003 2.90 9 98 51 < 1Oct-2003 4.20 8.6 76 94 6Mar-2004 4.65 9.1 79 63 11Apr-2004 4.12 9.1 80 37 5


09/11/01 11/11/01 13/11/01 15/11/01 17/11/01Time (dd/mm/yy)

1

2

3

4

5

6

Hso

(m)

4

8

12

Tp (s

)Tp

Hs


-20 -10 0 10rate of displacement (m/yr)

0

5

10

15

20

25

30

35

40

45

50

55

60

co

ntro

l pro

files

dist

ance

(*10

0 m

)

1957/73

1973

/90

1990

/00

4 km

La Marquesa

El Fangarbay

El Fangarspit

2004

/07

-20 -10 0 10rate of displacement (m/yr)

0

5

10

15

20

25

30

35

40

45

50

55

60

co

ntro

l pro

files

dist

ance

(*10

0 m

)

2000/04

4 km

La Marquesa

El Fangarbay

El Fangarspit

Av increase: 330 %



2 km

-80 -60 -40 -20 0 20rate of displacement (m/yr)

0

5

10

15

20

25

30

35

40

45

50

55

co

ntro

l pro

files

dist

ance

(* 1

00 m

)

1957/73

1973

/90

1990

/00

Illa deBuda

Migjorn

CapTortosa

2004

/07

2 km

-80 -60 -40 -20 0 20rate of displacement (m/yr)

0

5

10

15

20

25

30

35

40

45

50

55

co

ntro

l pro

files

dist

ance

(* 1

00 m

)

2000/04

Illa deBuda

Migjorn

CapTortosa

Av increase: 240 %


Alfacs bay

La Banya spit

4 km

-30 -20 -10 0 10rate of displacement (m/yr)

0

5

10

15

20

25

30

35

40

45

50

55

cont

rol p

rofil

es

1957

/73

1973

/90

1990

/00

2004

/07Alfacs bay

La Banya spit

4 km

-30 -20 -10 0 10rate of displacement (m/yr)

0

5

10

15

20

25

30

35

40

45

50

55

cont

rol p

rofil

es

2000/04

Av increase: 800 %


Year

ly m

axim

um w

ave

even

ts

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005TIME (years)

0

2

4

6

8

Hs

max

(m)

2

4

6

8

10S

torm

dur

atio

n (d

ays)

45

90

135

180

225

Wav

e di

rect

ion

(o)


Ano

mal

ies

of y

early

max

imum

val

ues

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005TIME (years)

-20

-10

0

10

20

Inun

d. In

dex

Ano

mal

y (H

L 0)1/

2

-1.0

-0.5

0.0

0.5

1.0

Ero

. Ind

ex A

nom

aly

(D-D

eq)1/

20

200

400

600

Wav

e P

ower

Ano

mal

y (H

2 T)


Ano

mal

ies

of y

early

inte

grat

ed v

alue

s

0.94 0.74 1 1.68

0.86 0.70 1 1.24

0.98 0.70 1 3.60

Numbers : yearly av. value period / value 1990/20001955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

TIME (years)

-2000

0

2000

4000

Inun

d. In

dex

Ano

mal

y (H

L 0)1/

2

-200.0

0.0

200.0

Ero

. Ind

ex A

nom

aly

(D-D

eq)1/

20

20000

40000

60000

Wav

e P

ower

Ano

mal

y (H

2 T)


swas

h

collis

ion

overw

ash

inundation

Coastal Change Hazard Scale for low-lying coasts

Conceptual model of coastal response to storm impacts (Sallenger, 2000).

Basic parameters: Coast – Z (beach/dune height)Storm – Ru (runup / water level)

Ru / Z


0 100 200 300 400 500 600 700cross-shore distance (m)

-6

-5

-4

-3

-2

-1

0

1

2

elev

atio

n (m

)

La Marquesa (P33)La Marquesa

Zmax = 1.5 mZ min = 0.7 mZ mean= 1.14 m

tan β = 0.019

5 km

La Marquesabeach

Cap Tortosa

Illa de Buda

Trabucador

Riumar

La Banya

Fangar


La Marquesa

Estimated change in coastal inundation due morphodynamic variability

(year per year basis – observed variability)

1960 1970 1980 1990 2000Time (years)

0.80

1.20

1.60

2.00

2.40

Ru

2% (m

)

Zmax = 1.5 m

1960 1970 1980 1990 2000Time (years)

0.80

1.20

1.60

2.00

2.40

Ru

2% (m

)

Z mean= 1.14 m


La Marquesa F(Ru) = 1 – exp(-((Ru-0.971)/0.189)0.75)

1 10 100Tr (years)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Ru

(m)


Summary & Conclusions (I)Driving terms

Energetic period with the largest recorded storm (~ 100 y).No detected change in storminess.Largest values inund. & transp. potential (↑68% & ↑360 %).

Coastal Response

Largest erosion rates (↑250% & ↑800 %).Large overwash deposits (~ 17 Ha).Concentrated in narrow (≤ 150 m), lowlying & erosive areas


Summary & Conclusions (II)

Implications

Cumulative effects.

Snapshot of a period of accelerated coastal retreat.

Useful to better define a buffer area.

Need to be considered for long-term land-planning.

Documents

[email protected] José A. Jiménez 2008 The Ebro delta