New modelling tools for coastal
problems related to climate change
Nils Drønen
Coastal and Estuarine Department, CED, DHI
Climate change and coastal
engineering
• Natural system
–
–
–
–
Beach and dune system
Coastal erosion
Coastline evolution
Time scales: Seasons, extreme events, decadal evolution
• Infrastructure
– Influence on environment (bypass harbours, breakwaters, revetments, …)
– Local damage (scour, erosion, sedimentation, …)
• Coastal erosion management
– Nourishment (soft solutions)
– Hard structure shore protection (detached breakwaters, groynes, revements, …)
• Coastal Flooding
– Dunes and dikes
– Threshold (critical wave height/water level) …affected by long term processes
– Catastrophic events affects long term development
New Tools
1m-10m
1-10 s
1-10 min
1-24 h
1-7 d
1-10 yr
10m-100m
100m-1km
1km-10 km
New Tools
1m-10m
1-10 s
Dune and
Dikes
Erosion
Profile
evolution
Nourishment
Run-up
Overtopping
Downrush
1-10 min
1-24 h
1-7 d
1-10 yr
10m-100m
M21BW+
Wave
model
100m-1km
1km-10 km
New Tools
1m-10m
1-10 s
Dune and
Dikes
Erosion
100m-1km
Profile
evolution
Nourishment
Run-up
Overtopping
Downrush
1-10 min
10m-100m
M21BW+
Wave
model
Hinterland
flooding
Prescribed
dike/dune
breach
Dynamic
flooding
1-24 h
MIKE21
Flooding
1-7 d
1-10 yr
1km-10 km
New Tools
1m-10m
1-10 s
Dune and
Dikes
Erosion
100m-1km
1km-10 km
Profile
evolution
Nourishment
Run-up
Overtopping
Downrush
1-10 min
10m-100m
M21BW+
Wave
model
Hinterland
flooding
Prescribed
dike/dune
breach
Dynamic
flooding
1-24 h
MIKE21
Flooding
Bypass
harbours
1-7 d
Hard
structure
shore
protection
Beach
nourishment
1-10 yr
”Hybrid
model”
New Tools
1m-10m
1-10 s
Dune and
Dikes
Erosion
100m-1km
1km-10 km
Profile
evolution
Nourishment
Run-up
Overtopping
Downrush
1-10 min
10m-100m
M21BW+
Wave
model
Hinterland
flooding
Prescribed
dike/dune
breach
Dynamic
flooding
1-24 h
MIKE21
Flooding
•
•
•
•
1-10 yr •
•
1-7 d
Climate scenario
Consequence analysis
Hazard and risk assessment
Mitigation measures
Dynamic decision making
Newest knowledge => best
boundary conditions
Bypass
harbours
Hard
structure
shore
protection
Beach
nourishment
”Hybrid
model”
New Tools
1m-10m
1-10 s
Dune and
Dikes
Erosion
Profile
evolution
Nourishment
Run-up
Overtopping
Downrush
1-10 min
1-24 h
1-7 d
1-10 yr
10m-100m
M21BW+
Wave
model
100m-1km
1km-10 km
Breaching and flooding
MIKE21 BW+
MIKE21 FM, HD/SW
Run-up formula
MIKE21 FM, HD
Overtopping formula
MIKE21 BW run-up
MIKE21BW overtopping
Breaching of dikes (and dunes)
Initation and development:
• Wave overtopping
• General flow
MIKE21 BW Backside erosion - wave
induced (soft barrier)
Dike strength?
MIKE21 BW – shear erosion, dikes
𝜏𝑐,𝑐𝑙𝑎𝑦 > 𝜏𝑐,𝑠𝑎𝑛𝑑
Dike strength?
Overtopping simulator?
van der Meer et al. 2009
Dune erosion
MIKE21 BW – Dune erosion
Dune erosion tests
MIKE21 BW – Dune erosion, model versus lab tests
Dune erosion – profile evolution
Detailed modelling - conclusions
New/revised M21BW tool represents an interesting alternative to empirical models
The tool has a better resolution than present available tools (Xbeach)
The tool can potentially be used to estimate hydrodynamic parameteres
The tool can potentially be used to estimate erosion and profile evolution
New Tools
1m-10m
1-10 s
Dune and
Dikes
Erosion
100m-1km
Profile
evolution
Nourishment
Run-up
Overtopping
Downrush
1-10 min
10m-100m
M21BW+
Wave
model
Hinterland
flooding
Prescribed
dike/dune
breach
Dynamic
flooding
1-24 h
MIKE21
Flooding
1-7 d
1-10 yr
1km-10 km
Hinterland indundation
MIKE21 FM, HD
1. Prescribed breach in dike/dune
2. Hydraulic resistance formulation for overflow
3. Line structure approach
Hinterland indundation
MIKE21 FM, HD – Development of breach
Hinterland indundation: New feature
MIKE21 FM, HD - Prescribed breach
Dike represented by a line => less computational cells
Breach develops in time according to prescribed evolution
Added hydraulic resistance over line structure
Test example
Video: Hinterland_ex
Hinterland flooding model conclusions
Strong tool for risk modelling flooding consequences for hinterland
Breach location, size and temporal evolution is prescribed
New Tools
1m-10m
1-10 s
Dune and
Dikes
Erosion
100m-1km
1km-10 km
Profile
evolution
Nourishment
Run-up
Overtopping
Downrush
1-10 min
10m-100m
M21BW+
Wave
model
Hinterland
flooding
Prescribed
dike/dune
breach
Dynamic
flooding
1-24 h
MIKE21
Flooding
Bypass
harbours
1-7 d
Hard
structure
shore
protection
1-10 yr
Beach
nourishment
LITLINE+
(M21
extension)
New Long Term Morphology Model
Model type
PROS
CONS
Area modeling Detailed representaion Long CPU time.
(MIKE21)
of physics:
Morphological
Wave/Bathymetry non- simulations tend to
uniformity, current
drift /degenerate
intertia, circulation, ...
coastal profile for
long term sims
1-line
modeling
(LITLINE)
Short CPU time.
Coastal profile is not
degenerated.
Assuming
alongshore
uniformity.
Profile is not
evolving.
New Long term morphological model
Combination of two model types
1) Morphological area modeling
2) 1-line shoreline evolution model
’Hybrid’ model:
Area modeling of waves, currents and sediment
transport
+
1-line shoreline evolution for morphology
Example: Offshore breakwater
Survey
Shoreline model
Status model development and
release
MIKE21 BW is still ‘work in progress’ (inhouse version)
MIKE21 HD dike lines with prescribed dike breaching will be released (2013)
MIKE21/LITLINE Hybrid one-line model will be implemented in MIKE21 FM
Thank you for your attention!