Management Unit of the North Sea Mathematical Models MUMM | BMM | UGMM [1][1] Changes along the...
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Transcript of Management Unit of the North Sea Mathematical Models MUMM | BMM | UGMM [1][1] Changes along the...
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
[1]
Changes along the Belgian part of the North Sea
BelSPO-SSDStrategic Research Network
2007-2011
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[2]
Surface area: 3600 km²
N
Increasing human pressure
Maes et al., 2005
Marine AggregatesAverage 1.5 106 m³/yr
Coastal protection may demand
>10 106 m³
Disposal of dredged material
2006: 12 106 TDM
R. Janssens, 2009
In Quest4D compilation of distribution and intensity of human activity, incl. the extent of fisheries’ impact on the seabed
Quantitative analysis of fishing marks, based on multibeam backscatter dataExample Thornton Bank
?Cumulative impact?
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[3]
Main problems in impact studies No baseline information - No historic reference
points
Significance of impacts? Time-scale of change?
Cumulative impacts? – Far field influence?
Links between cause and effect?
Threshold of habitat change?
What is natural and what is anthropogenically-steered???
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[4]
Changes in bathymetry
Changes in sediments
Changes in macrobenthos
Partner: RBINS, Dep. Invertebrates / Ghent University, Marine Biology Section
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[5]
Long-term vs. short- to medium-term changes
Decifering natural vs anthropic change
– Natural change: Sediment volumes and bedform changes against hydro-
meteorological conditions Influence of storms on sediment transport
– Anthropic change: Analysis of short- to medium-term changes against
intensity data of anthropic activities (e.g. data on disposal of dredged material and aggregate extraction)
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[6]
Natural evolutionSediment volumes vs hydro-meteo from measuring piles (Flemish Authorities)
WindHigh- and low frequency wavesCurrentsWater levels
Natural vs anthropic Surveys 96099611961297029709971198029803maximum
change9609 0.05 0.03 0.09 0.01 0.05 0.05 0.04 0.09
9611 -0.02 0.03-0.04 0.00 0.00-0.01 -0.04
9612 0.05-0.02 0.02 0.02 0.01 0.05
9702 -0.08-0.03-0.03-0.04 -0.08
9709 0.04 0.04 0.03 0.04
9711 0.00-0.01 -0.01
9802 -0.01 -0.01
9803 0.00maximum
change0.00 0.05 0.03 0.09 -0.08 0.05 0.05 0.04
Baland Bank bathymetric surveys.Matrix of all the intersurvey volume differences per surface unit (m³/m²). The maximum differences are indicated in italic. Surveys are indicated as YYMM.
Varying sediment volumes over sandbank areas
Event–driven vs. yearly-averaged changes
Decifering threshods of ‘natural’
change
Van Lancker, in prep.
Findings along ‘undisturbed’ near coastal small sandbank:
(1) Enhanced SW conditions bring in sediment(2) Persistent NW and NE conditions evoque erosion(3) Overall shallowing of the area
Scenario’s will be used to predict sediment transport changes, due to climate change
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[7]
Anthropic change: case study on the disposal of dredged material
Stiff clay from maintenance dredging worksand increase of mud pebbles
Vibrocore
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[8]
Analysis of bathymetric data Analysis of corresponding data on the disposal of dredged
material
Activecooperatio
n end-users
1976-1979 1981-1985
Regional sedimentation beyond the disposal grounds, in the direction of navigation channels
Analysis of vibrocores:• top 25-50 cm highly dynamic• natural vs anthropic sedimentation patterns
1 2
3
Decifering thresholds of ‘anthropic’ change
Short-term impact
Medium-term impact
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[9]
Sediment change analysis
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[10]
Sand fraction is generally well-sortedPoorer sorting associated with gravel or shell hash areas
Period around 1900
Management Unit of the North Sea Mathematical ModelsMUMM | BMM | UGMM
http://www.mumm.ac.be/
Ocean Dynamics
[11]
Wide-spread worsening in sorting:esp. around harbours, near disposal and aggregate extraction sites
Present-day