The SH Wattenmeerstrategie 2100
ecosystem-based adaptation to stronger sea level rise from a nature conservation and safety perspective
Jacobus Hofstede
The challenge
The SH strategy
1. If no effective climate mitigation and adaptation measures are implemented, the
Wadden Sea will change
fundamentally
– in the second half of this century at the latest.
2. The Wadden Sea should be preserved
in its functionalities for nature conservation and coastal risk management and – as much as possible – in its present size.3. Common engagement is necessary
to preserve the Wadden Sea. Further actions arising from the strategy will be conducted in partnership by coastal risk management and nature conservation with active local involvement.Key Messages
The process
Steering group
6 members: MELUR and LKN
Project group
13 members: LKN, MELUR, WWF, IHKo, Schutzstation Wattenmeer
Project board
Steering group, 13 external institutions
Scientific workshop
Project group, 10 external experts from 7 scientific institutions
Task groups
Project group members Team work
Terms of reference
• Definition of a common vision and development goals
• Establishment of a common geo- scientific basis (structures and functions)
• Definition of scenarios (climate, hydrology, morphology, biology)
• Assessment of the consequences of the scenarios in relation to vision and goals
• Establishment of sustainable adaptation options
• Definition of next steps (outlook)
Climate (5)
Hydrology (6)
Morphology (8)
Biology (3)
It is all about sediment
Sediment is the problem, the challenge and, maybe, the answer!
Problems: - SLR may exceed 0.5 cm/y in the second half of this century - not enough natural sediment input to balance this SLR - long-term hazard of drowning flats / eroding marshes - no significant landward retreat possible, nor appropriate
Challenges: - how to maintain ecological integrity and functionality (World Heritage Site) - how to maintain CFD+P-significance of flats and marshes (energy dissipation)
Answers: - improve sediment input (natural / artificial), when necessary / appropriate
- do not increase sediment deficits by artificial measures!
Research project SH-TREND
Simulation of the morphological development in two tidal systems in Schleswig-Holstein for defined hydrological scenarios
Research cooperation with IOW Warnemünde (Prof. Hans Burchard) 01.04.2012 - 30.06.2015
Lister Tief
Meldorf Bight
GETM
Validation
Morphology
:• processes plausible
• Morphological development plausible
• Not able to reproduce pattern of erosion and sedimentation (i.e., topography 2010 could not be reproduced)
Hydrological scenarios (2010 - 2050 and 2050 - 2100)
COASTDAT2 data base (wind and water levels HZG) Time slice: 2000 - 2009
1. Reference scenario: no changes in sea level
2. Moderate scenario: moderate mean SLR in two phases (2010–2050: 2.5 mm/y; 2050–2100: 7.0 mm/y; absolute mean SLR 2010–2100: 0.45 m)
3. High scenario: strong mean SLR in two phases (2010–2050: 6.0 mm/y; 2050–2100: 17.0 mm/y; absolute mean SLR 2010–2100: 1.08 m).
For 2. and 3.: increase in MTR of 1.0 mm/y (2010–2050) and of 2.0 mm/y (2050–2100) Two wind scenarios: no change, +5% increase
Results Lister Tief
Moderate scenario Raised scenario
Missing coastal retreat!
Waves (storm surges)
not correctly considered
Results Lister Tief
Decrease in tidal flats 2010 – 2100
• MSLR: -26 km2 (-14%)
• HSLR: -87 km2 (-44%)
Results
Lister Tief tidal basin Meldorf Bight tidal basin 6
3-15
0
1546
-13
033 0
-14
-44
Tidal flats
Conclusions SH-Trend
• A positive correlation seems to exist among MTR and the capacity of Wadden Sea tidal basins to balance SLR.
• Hence, with respect to MTR, the tidal systems in the inner German Bight may have the highest resilience against accelerated SLR.
• Wadden Sea intertidal flats are effective sediment sinks and seem quite resilient against (higher rates of) SLR.
• Subtidal gullies may constitute a significant sediment source for accumulation on intertidal flats in Wadden Sea tidal basins in response to SLR.
• A positive correlation exists among SLR and accumulation on tidal flats (for the investigated scenarios and time periods)
• In general, Wadden Sea tidal systems seem relatively robust against higher rates of SLR due to effective internal and external sediment redistribution processes.
• However, under RCP8.5, SLR will outbalance accumulation on tidal flats (sooner or later)
Implementing the Strategy
• No need for extra adaptation measures in the first half of this century!
• Public measures may not further sediment deficits in the Wadden Sea
• i.e., sand needed for strengthening of sea embankments and dwelling mounds should come from the North Sea or the mainland
• i.e., if dredging becomes necessary, the material is redeposited in the system
• Optimization of hydro-morphological monitoring program with respect to early detection of climate change impacts
• Establishment of a hydro-morphodynamical model for future investigations
• Exploration or potential sediment sources in the North Sea
• Pilot projects: looking for win-win-situations (e.g., stabilizing the barrier islands by sand
nourishment may also support stabilization of tidal basins by resulting sediment input
into the basins; BASEWAD)
Some words about mud in the SH Wadden Sea
Some words about mud in the SH Wadden Sea
Some words about mud in the SH Wadden Sea
Hofstede, Stock (2018): Climate change adaptation in the Schleswig-Holstein sector of the Wadden Sea: an integrated state governmental strategy. Journal of Coastal Conservation 22:199–207; doi 10.1007/s11852-016-0433-0.
Hofstede, Becherer, Burchard (2018): Are Wadden Sea tidal systems with a higher tidal range more resilient against sea level rise?
Journal of Coastal Conservation 22, 71–78; doi 10.1007/s11852-016-0469-1.
Becherer, Hofstede, Gräwe, Purkiani, Schulz, Burchard (2018): The Wadden Sea in transition - consequences of sea level rise.
Ocean Dynamics 68, 131–151; doi.org/10.1007/s10236-017-1117-5.
