Coastal sustainability for uncertain futures

1. 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

2. 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

3. 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

4. • 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 2010
Year
14
15
16
17
18
19
20
TemperatureºC
Estartit Yearly Averaged Mean, Min and Max Temp.
Yearly Averaged Mean Temperature
Yearly Averaged Max Temperature
Yearly Averaged Min Temperature
Lionello et al
S.-Arcilla et al, data from J. Pascual

5. 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)

6. 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…)

7. 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

8. Natural accretion
0 100 200 300 400 500 600 700
cross-shore distance (m)
-6
-5
-4
-3
-2
-1
0
1
2
elevation(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/stormevent)
Estimations for storm events (Ru > Zbeach) for evolving profiles
Zmin Zmed Zmax

9. STUDY SITE
Impact projection – Urban beaches (vulnerability hotspot)

10. 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

11. PRESENT CONDITIONS
EROSION BARCELONETA BEACH Tr=50 YEARS
(present PDF)

12. EROSION BARCELONETA BEACH Tr=50 YEARS HIGH END LIMIT

13. FLOODING BARCELONETA BEACH Tr=50 YEARS HIGH-END

14. 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

15. 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
COASTAL
FRINGE
COASTAL
SEA
ideal management scale
usual management scales
Final Remarks
1. Scales

16. 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

17. 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