Faculty of Geosciences Faculty of Geosciences Beach-dune interaction for dynamic coastal management Gerben Ruessink
Faculty of Geosciences
Faculty of Geosciences
Beach-dune interaction for dynamic coastal management
Gerben Ruessink
Faculty of Geosciences
Beach-dune interaction
Urgency:• nature restoration• long-term coastal safety
No sand sharing: (1) loss in geomorphological dynamics(2) loss in biodiversity(3) no vertical growth with sea-level rise
Dune erosion Dune growth
Faculty of Geosciences
Building with Nature: Sand Engine
5 July 2011 10 January 2012
1 October 2013 1 oktober 20134 May 2015
Faculty of Geosciences
Building with Nature: Sand Engine
Beach-dune interaction:
• Short gradients (new embryo dunes)
• Foredune growth ~ 15 m3/m/year
• No dune erosion
Faculty of Geosciences
Building for Nature: NWNKern
Faculty of Geosciences
Building for Nature: NWNKern
Trenches:V- to U-shape
Construction After 2 years
Foredunescarping
Sedimentationlobes
Faculty of Geosciences
Combination: HPZ
Faculty of Geosciences
Questions
• How much sand is actually blown toward the dunes?
• Which factors affect this amount?
• What to expect from dune remobilization?
• Are present-day large-scale measures effective?
• Can nourishments and dune remobilization be combined?
• …
Faculty of Geosciences
Needs
• Experiments: Learning by doing
• Long-term (years) monitoring with high resolution (seasons)
• Close co-operation between stakeholders and scientists
• Models with different complexity
• …
Faculty of Geosciences
Beach-dune interaction: models
Keysers et al. (2014)Plos ONE
Poseidon Aeolus
Faculty of Geosciences
My projectBeach-dune interaction: models
Need
Accurate predictive
model of aeolian sand
supply
Challenges
Supply limitation
1. How wet?
2. When?
3. How much?
4. Upscaling
Faculty of Geosciences
Timing of aeolian events
Potential transport
• Events (4 hrs > 8 m/s)
• Hsu (1974)
Observed transport
• Sand-strip activity
Faculty of Geosciences
Timing of aeolian events
Mismatch between potential and actual events:
• Moderate wind speeds: considerable aeolian activity
• Large speeds are large: no aeolian activity
Faculty of Geosciences
Considerable aeolian activity under moderate, shore-oblique/parallel winds
Timing of aeolian events
Faculty of Geosciences
Timing of aeolian events
No aeolian activity under strong shore-normal / oblique winds because of surge
Faculty of Geosciences
Summary
• From preventing dune-erosion to beach-dune interaction
• Building with and for Nature
• Practice-inspired questions and scientific ideas
• Pilot experiments: ‘Learning by doing’ with long-term
monitoring to eventually predictively understand
Only then ready for the challenges of the decades to come
Faculty of Geosciences
Faculty of Geosciences
Surface moisture content
saturated
Reflection (dB)
Mo
istu
re c
on
ten
t (%
)
dry
Faculty of Geosciences
Surface moisture content
Faculty of Geosciences
Mismatch between potential and actual events:
• Moderate wind speeds: considerable aeolian activity
• Large speeds are large: no aeolian activity
Timing of aeolian events
Faculty of Geosciences
Transport magnitude
Faculty of Geosciences
Results (Xaver)
-80 -70 -60 -50 -40 -300
5
10
15
20E
lev
atio
n (
m M
SL
)
-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
Distance (m)
beforeafter
I. Destruction of new foredune and embryo dunes-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
-80 -70 -60 -50 -40 -300
5
10
15
20E
lev
atio
n (
m M
SL
)
Distance (m)-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
Distance (m)
II. Failure of dune front with successive rotational slides
beforeafter
Faculty of Geosciences
-80 -70 -60 -50 -40 -300
5
10
15
20E
lev
atio
n (
m M
SL
)
-80 -70 -60 -50 -40 -300
5
10
15
20
Ele
vat
ion
(m
MS
L)
Distance (m)
beforeafter storm
recovery
Results (post-Xaver)