COASTAL SUSTAINABILITY FOR UNCERTAIN FUTURES. A MEDITERRANEAN CASE FROM THE RISES-AM- PROJECT

A. SANCHEZ-ARCILLA, JP. SIERRA , V. GRACIA, M. GARCIALEON, JA. JIMENEZ, C. MOSSO & H. VALDEMORO

Year 1990 Year 2004 Year 2015 Year 2025 Year 2035 Year 2045

1) Coastal-scale climate change

2) Climate impact projection i. Deltaic beaches ii. Urban beaches

3) Coastal adaptation

4) Final remarks (3rd Catalan Rep. on Climate Change)

Contents

A

Climate Change Global sea level projections

(IPCC, 2013)

Likely range, 66%

Upper limit (95%, RCP8.5), 1.8m

AR-4

AR-5

o Increase in AR o Probabilistic characterization

Jevrejeva et al, 2014

• Change in wave conditions → studied with AR4 (AR5 waves in the “oven”) • Projections indicate

– Slight reduction of Hs & surges under future scenarios – Increase in MSL (smaller than for N Atlantic)

1970 1975 1980 1985 1990 1995 2000 2005 2010Year

14

15

16

17

18

19

20

Tem

pera

ture

ºC

Estartit Yearly Averaged Mean, Min and Max Temp.Yearly Averaged Mean TemperatureYearly Averaged Max TemperatureYearly Averaged Min Temperature

Lionello et al S.-Arcilla et al, data from J. Pascual

Ebro delta

Dam / barrages ~ 180

Regulated basin 82,300 km2 (96.4 %)

Climate Influence on CZ

Locally

Basin-wise

Impact projection (deltaic vulnerability hotspot) o Catchment basin analysis o Anthropic coastal disconnection (from river basin) o Increasing sediment starvation (risks)

Impact vs Natural Deltaic response(RSLR)

Feed-back: RSLR-vertical accretion

(marshes & full delta) Pulsing events (wave

storms/river floods) supply large sediment volumes naturally

(deltaic resilience to CC) Natural mechanisms

can be enhanced to reduce impact (controlled flooding…)

Natural resilience (present and future) → working with Natural processes (against) Reduced cost and risk (economic sustainability) Reduced impact (environmental and energetic sustainability) Favouring flexible adaptation (no rigid infrastructures)

Based on natural accretion

Novel interventions: o Promoting vertical

accretion o Flooding offsetting

subsidence

Courtesy MMA, Spain

Natural accretion

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 beach

Zmax = 1.5 m Z min = 0.7 m Z med= 1.14 m

tan β = 0.019

Ru time series o Storm events o With overwash (Ru > Zbeach) 81 storms (1.84 events/year) 44 years (Nguyen et al 2006 transport model)

0.0

0.0

0.0

0.1

1.0

10.0

100.0

Qow

(m3 /m

/sto

rm e

vent

)

Estimations for storm events (Ru > Zbeach) for evolving profiles

Zmin Zmed Zmax

STUDY SITE

Impact projection – Urban beaches (vulnerability hotspot)

TEST CASES

PRESENT CLIMATE CHANGE SCENARIOS

(0m) RCP 4.5 (0.47m)

RCP 8.5 (0.88m)

High End (1.88m)

Beach Normal Wave

incidence

Tr=1 yr • • • • Tr=5 yr • • • •

Tr=50 yr • • • •

time (hours)

Hs (m)

0 24

Erosion before – after storm (erosion depth in m)

Flooding at t=12.5 hours (water depth in m – minimum 0.1m )

Coastal impacts as a function of storm shape

PRESENT CONDITIONS

EROSION BARCELONETA BEACH Tr=50 YEARS (present PDF)

EROSION BARCELONETA BEACH Tr=50 YEARS HIGH END LIMIT

FLOODING BARCELONETA BEACH Tr=50 YEARS HIGH-END

GENERAL ADAPTATION OPTIONS 1- ↑ sediment supply (vertical/horizontal accretion) 2- ↑ natural accretion mechanisms 3- ↓ sediment losses (bio filters…) 4- ↓ sediment mobility (vegetation…) 5- ↑ raising defences (locally, geotextiles…) 6- ↑ water pumping 7- ↑ whole unit synergies

DRIVERS (D) 1- RSLR (+ subsidence) 2- Change of wave climate (South) 3- T (ºC) ↑ (water consumption) 4- Decrease of freshwater (Ql) 7- Decrease of sed supply (Qs)

PRESSURES (P) 1- Flooding 2- Erosion 3- Reshaping 4- Salinization

IMPACTS (I) 1- Rice yield 2- Agro-Tourism 3- Industry 4- Habitats 5- Connectivity

N ^

Adaptation options = f (D, P, I)

Ebro delta case study MED Vulnerability Hotspot

Efficient coastal responses under Climate Change should consider Multiple scale pressures: combined riverine/marine factors (ave. trends + extremes) Multiple scale responses: full catchment basin (avoiding short term “mortgages”)

RIVER

COAS

TAL

FRIN

GE

COAS

TAL

SEA

ideal management scale

usual management scales

Final Remarks 1. Scales

Efficient coastal responses under Climate Change should consider Cost at short to long term scales (initial + maintenance + impact) Ranking with risk (vulnerability) (deltaic, urban & small islands coasts) Rising grounds (high end conditions)

Final Remarks 2. Ranking as function of risk/cost

Maldives Is. SOTON 2014

Courtesy IRTA

Efficient coastal responses under Climate Change should consider Cost at short to long term scales (initial + maintenance + impact) Ranking with risk (vulnerability) (deltaic, urban & small islands coasts) Rising grounds (high end conditions)

Maldives Is. SOTON 2014

Courtesy IRTA

Final Remarks 2. Ranking as function of risk/cost