Upload
eamon
View
28
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Large-Scale Coastal Maintenance using Sand Experiences and Experiments in The Netherlands. MODEG meeting, March, 11, 2011 Ad van der Spek. Content. Introduction Coastal system of The Netherlands Coastal maintenance using sand fighting structural erosion ! Results coastal maintenance - PowerPoint PPT Presentation
Citation preview
Large-Scale Coastal Maintenance using SandExperiences and Experiments in The Netherlands
MODEG meeting, March, 11, 2011
Ad van der Spek
Content
1. Introduction
2. Coastal system of The Netherlands
3. Coastal maintenance using sand
fighting structural erosion !
4. Results coastal maintenance
5. Future developments
6. Lessons learned, experiments
data needs
7. Concluding remarks
March 11, 2011Coastal Maintenance in The Netherlands 2
March 11, 2011Coastal Maintenance in The Netherlands 3
Introduction: sand budget
March 11, 2011Coastal Maintenance in The Netherlands 4
Introduction: coastal cells
March 11, 2011Coastal Maintenance in The Netherlands 5
Introduction: coastal profile in dynamic equilibrium
Active coastal zone
March 11, 2011Coastal Maintenance in The Netherlands 6
The Netherlands: sandy coast
350 km
• Amsterdam
Young dunes
Old dunes
Young dunes
Old dunes
Netherlands• The Hague
March 11, 2011Coastal Maintenance in The Netherlands
How were The Netherlands built?
7
March 11, 2011Coastal Maintenance in The Netherlands
Long-term coastal evolution
supply > demand :
regression
Demand tidal basin
vs.
Supply coast
supply < demand :
transgression
8
March 11, 2011Coastal Maintenance in The Netherlands
Paleo-geography of The Netherlands
5000 BP
demand > supply
2600 BP
demand < supply
9
March 11, 2011Coastal Maintenance in The Netherlands
Holocene sediment budget
1.
2.
2.
3.
4.
sources & sinks
10
March 11, 2011Coastal Maintenance in The Netherlands 11
Total volume Holocene coastal deposits
( in billion m3 )
lithology volume percentage
----------------------------------------------------------------------------------
sand 151 - 157 67 -70 %
mud 59 - 65 26 - 29 %
peat 11 5 %
----------------------------------------------------------------------------------
Total 226 100 %
March 11, 2011Coastal Maintenance in The Netherlands
Holocene sediment budget - Infilling with time
period perc. volume vol. / yr
(billion m3) (million m3)
----------------------------------------------------------------------------------------
8000-5000 BP 60 % 136 41
5000-3000 BP 30 % 67 27
Since 3000 BP 10 % 23 7
----------------------------------------------------------------------------------------
12
“The Hague, we have a problem !”
March 11, 2011Coastal Maintenance in The Netherlands 13
Sediment balance Dutch coast
Western Scheldt
Coastal
Foundation
Wadden Sea
March 11, 2011Coastal Maintenance in The Netherlands
Solution: we do it ourselves !!
Keeping up by nourishing sand
14
March 11, 2011Coastal Maintenance in The Netherlands 15
What to do ?
Coastal Maintenance Programme
Yearly monitoring of coastline: jarkus
Bring sand where you need it
Yearly nourishment budget: 12 Mm3 sand
Why nourishing sand?1. Compensating sand deficit
2. Feeding sediment fluxes
3. Building sand buffer
March 11, 2011Coastal Maintenance in The Netherlands 16
Soft sea defence
Hard defence
Soft defence
Hard defence
Soft defence
350 km
• Amsterdam
March 11, 2011Coastal Maintenance in The Netherlands 17
Why nourishing?
1. Fighting structural erosion• Sand balance Dutch coast negative• 1965-1990: -6,5 Mm3 / yr• Dynamic Maintenance (preferably sand …)
2. Reinforcing the coast• upfront compensation SLR• upscaling: mega-nourishments, Sand Engine
3. Land reclamation• near future ?
March 11, 2011Coastal Maintenance in The Netherlands 18
How to nourish ?
1. Beach
2. Shoreface
3. Channel
4. Combinations
Future: directing natural processes ?
March 11, 2011Coastal Maintenance in The Netherlands
Nourishment policy since 1990
1990 – 2000:
6 Mm3/year
2001 - :
12 Mm3/year
1990 – 2000:
6 Mm3/year
2001 - :
12 Mm3/year
19
March 11, 2011Coastal Maintenance in The Netherlands
0
5
10
15
20
jaar
Su
pp
letie
ho
ev
ee
lhe
de
n (
10
6 m
3)
0
10
20
30
40
BK
L-o
ve
rsc
hri
jdin
ge
n (
%)Onderwaters uppleties
Strands uppletiesBKL-overs chrijdingen
refe
rence
coas
t lin
e pro
ble
ms
(%)
1991
2006
0
5
10
15
20
jaar
Su
pp
letie
ho
ev
ee
lhe
de
n (
10
6 m
3)
0
10
20
30
40
BK
L-o
ve
rsc
hri
jdin
ge
n (
%)Onderwaters uppleties
Strands uppletiesBKL-overs chrijdingen
refe
rence
coas
t lin
e pro
ble
ms
(%)
1991
2006
Result 1: coast line position maintained
20
March 11, 2011Coastal Maintenance in The Netherlands 21
Result 2: outbuilding of coastal dunes !!
Wassenaar
Katwijk aan Zee
Noordwijk aan Zee
March 11, 2011Coastal Maintenance in The Netherlands
dune growth 1998 - 2007pro-active
nourishment approach is succesfull
from: Arens, 2010
22
March 11, 2011Coastal Maintenance in The Netherlands
today 1990
Prograding dune at Bergen aan Zee
23
March 11, 2011Coastal Maintenance in The Netherlands 24
Safety against flooding
residual strengthdays / meters
MSL
- 20mdunes
beach
shore face
dunes
Am sterdam
The Hague
Rotterdam
March 11, 2011Coastal Maintenance in The Netherlands 25
basal coast line
coastal foundation
years / km
decades – centuries / 10’s – 100’s km
MSL
- 20m
days / metersdunes
coast line
coastal foundation
SustainableSafety against flooding
residual strength
pro-active
nourishment policy
Conclusion:
• The balance concept works
sea-level rise ≠ coastal erosion !• Outbuilding: we can tip the balance• Future: maintaining coast with sand
• Strict monitoring:• Coastline position: decision on nourishing• Development shoreface nourishments: learning• Coastal foundation: yes, but how ??
March 11, 2011Coastal Maintenance in The Netherlands 26
March 11, 2011Coastal Maintenance in The Netherlands 27
Coastal Foundation
Western Scheldt
Coastal
Foundation
Wadden Sea
active sand sharing coastal system
March 11, 2011Coastal Maintenance in The Netherlands 28
Challenge: explore feasible ways of upscaling
12 Mm3/year
20 Mm3/year
85 Mm3/year
March 11, 2011Coastal Maintenance in The Netherlands 29
Building a sand buffer …
March 11, 2011Coastal Maintenance in The Netherlands 30
Kijkduin 2
March 11, 2011Coastal Maintenance in The Netherlands 31
The new Delfland coast
March 11, 2011Coastal Maintenance in The Netherlands 32
Pilot Sand Engine
• Surplus of sand, distributed by tide/waves/wind• 20 mln m3• Initial design: Ca 100-150 ha,
1000 m seaward• Total budget 70 Meuro• Realisation planned 2010-2011
Artist impressionwww.kustvisiezuidholland.nl/zandmotor
Holland Coast
Sand Engine
March 11, 2011Coastal Maintenance in The Netherlands 33
• Joint initiative:• Province• National government• Water Board• Local authorities• NGO’s
Pilot Sand Engine
ambition agreement
Co-financing:• 17 %• 83 %
Sand Engine objectives
Long-term: guarantee coastal safety by promoting dune development
Medium-term: knowledge development, innovation
Short-term: create space for nature and/or recreation
March 11, 2011Coastal Maintenance in The Netherlands 34
March 11, 2011Coastal Maintenance in The Netherlands 35
Sand Engine design
• Dynamic design ( not a well defined end result )
• Dynamic optimization of different functions
• Balance between long term benefits (safety against flooding) and short term benefits (nature and recreation)
• Challenge: management of expectations with different stakeholders
(zeetorenhvh)
March 11, 2011Coastal Maintenance in The Netherlands 36
Monitoring and evaluation
monitoring morphology hydrology ecology
tourism management risks
(zeetorenhvh)
evaluation 5 years: 2015 10 years: 2020 20 years: 2030
Lessons learned (1): data needs
• System analysis• Reconstruction coastal evolution• Sediment balance
• Volume nearshore sand resources
Information enables design maintenance strategy
• Monitoring
• Relative sea-level rise• Coastal state (yearly)• Frequent monitoring large nourishments
(learning by doing)
March 11, 2011Coastal Maintenance in The Netherlands 37
Lessons learned (2): sand as a resource
• Sufficient nearshore sand resources only on certain stable broad shelves
• In other cases sand resources insufficient or sufficient only for nourishing coastal hot spots
• For most shelves sand resources have not yet been investigated
March 11, 2011Coastal Maintenance in The Netherlands 38
March 11, 2011Coastal Maintenance in The Netherlands 39
Sea-level low-stand river deposits
Sand deposits can be unexploitable:
• too far from the coast
• at too deep water
• buried under non-sandy sediments
March 11, 2011Coastal Maintenance in The Netherlands 40
Global nearshore sand resources
Sand resource > 1 km3 / 100 km
Sand resource between 0,1 and 1 km3 / 100 km
Lessons learned (3)
Learning by doing:• Step by step• Co-operation with other countries
• EU-programmes:> NOURTEC: shoreface nourishing> COAST3D: nearshore processes> SANDPIT: effects of sand extraction> SAFECOAST, EUROSION, CONSCIENCE etc.
• Data availability• Central storage?• Flexible formats?
> Fitting in relevant, extra information• Monitoring programmes or project-related acquisition?
March 11, 2011Coastal Maintenance in The Netherlands 41
March 11, 2011Coastal Maintenance in The Netherlands 42
Concluding remarks: What is nourishing ?
Compensation of sand deficits
Feeding of sediment fluxes
Building a sand buffer
• Flexible• Tailor-made• Relatively cheap• Swift reaction to unexpected changes
March 11, 2011Coastal Maintenance in The Netherlands 43
Concluding remarks
Analysis sediment balance crucial
Available resources?
Sand volume?
potential resources? > sand captured in reservoirs> restoring sediment supply
Sand Engine experiment
case study for european coastal community?
March 11, 2011Coastal Maintenance in The Netherlands 44
Thank you for your attention !