Bas van Maren Ana Colina Alonso Albert Oost
Towards a Mud Balance for the Trilateral Wadden Sea Area
19-03-2021
Where mud matters
N a a m
Where Mud Matters
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Foto: Catrinus van der Veen
Foto: Jan Spoelstra
Foto: Tobias Bruns Foto: Chrisph Bellin
4 million m3/year
1 million m3/year
10 million m3/year 20 million m3/year
10 million m3/year
Sedimentation of mud in ports and navigation
channels requires dredging ➔ costly and negatively impacting ecology
Total Wadden Sea: ~50 million m3/year
Where Mud Matters
3
Mud may also negatively impact ecology:
- reduction in visibility → limiting algae growth
Where Mud Matters
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Mud may also negatively impact ecology:
- reduction in visibility → limiting algae growth - anoxic conditions → fish mortality
Mud may also negatively impact ecology:
- reduction in visibility → limiting algae growth - anoxic conditions → fish mortality
- shift in benthic organisms species & mass
Where Mud Matters
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Compton et al., 2017
However, mud also has ecological benefits:
- productivity of intertidal flats - promotion of salt marsh growth
Where Mud Matters
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Foto: Klaus Dieter Meinen
… and a safety function, protecting the hinterland through accreting mudflats and saltmarshes
Where Mud Matters
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Where Mud Matters
8 Foto’s: Focko Gerdes
Mud is brought on land for various purposes
▪ disposal dredged material & soil improvement
Where Mud Matters
Foto: Hunze en Aa’s 9
Mud is brought on land for various purposes
▪ disposal dredged material & soil improvement
▪ harvesting mud as a resource (for e.g. dikes)
Where Mud Matters
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Mud is brought on land for various purposes
▪ disposal dredged material & soil improvement
▪ harvesting mud as a resource (for e.g. dikes)
▪ future: raising land to grow with SLR?
Land lower than the Wadden Sea bed level
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Understanding mud availability is crucial for sustainable sediment management of the trilateral Wadden Sea
▪ How much is supplied to the Wadden Sea?
▪ Where does it settle?
▪ How much is taken out?
Mud Matters
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Mud therefore matters. But:
- How much is supplied to the Wadden Sea?
- Where does it settle?
- How much is taken out?
Summary ‘Mud matters’
Marine supply: 10 – 15 million ton Fluvial supply: ~1.6 million ton Deposition: ~9 million ton Extraction: ~2 million ton
Nearly closed sediment balance ➔ sensitive to changes (SLR, extraction)
Mud Matters
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Mud therefore matters. But:
- How much is supplied to the Wadden Sea?
- Where does it settle?
- How much is taken out?
Major discussion points
▪ Mud supply is, or may become, limiting (especially in the eastern Wadden Sea)
▪ Questions to scientists:
▪ How can we further detail this mud budget?
▪ What is the impact of SLR?
▪ What is the large-scale impact of human interventions?
▪ Questions for policy makers:
▪ Is this a problem? (less mud ➔ less dredging & disposal)
▪ What are implications for human interventions?
▪ Need for large-scale (trilateral!) system understanding of the impacts of SLR & extraction on the mud balance
