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Spectral Wave Modelingin Coastal Areasfor Wave Climate Studies: 

Spectral Wave Modeling in Coastal Areas for Wave Climate Studies

Slide2: 

SWAN MODEL IMPLEMENTATION Belgian coast 39 km 126 km

SPECTRAL WAVE MODELS: 

SPECTRAL WAVE MODELS The action density N is conserved in water with slowly varying depth h and current U Source terms described explicitly

JONSWAP experiment: 

JONSWAP experiment

Slide7: 

The WAMC4 Model

wind input: 

wind input WAM Cycle 3

whitecap dissipation: 

whitecap dissipation WAM Cycle 3

Slide10: 

quadruplet interactions DIA- approach

bottom friction: 

bottom friction JONSWAP model

~1990-~20..: 

~1990-~20.. shallow water spectral wave modeling

Slide13: 

(after Battjes, 1994)

Slide14: 

increased complexity ! source terms shallow water coupling data assimilation …

wind input: 

wind input and what with wind input on swell waves ?

whitecap dissipation: 

whitecap dissipation whitecap dissipation in the presence of swell waves ?

quadruplets: 

quadruplets DIA and what with quadruplets in shallow water ?

bottom friction: 

bottom friction JONSWAP model Madsen’s model Collins’ model Weber’s model

non-linear interactionstriads: 

non-linear interactions triads main problem : harmonics created but not released

depth induced breaking: 

depth induced breaking two tuning parameters: br : some tuning constant (~1) Hmax =  h distribrution over frequency space ?

shoaling + refraction: 

shoaling + refraction well known from theoretical considerations high directional resolution needed BUT ...

Slide22: 

stability in time of bottom topography

coupling with tide/surge model: 

coupling with tide/surge model

Slide28: 

The WAMC4 Model

Slide29: 

The Tide/Surge Model

Slide30: 

Grid Set-up - North Sea Experiment

influence of currents on waves: 

influence of currents on waves

Summary: 

Summary many variables become important and are present simultaneously: tidal elevation, wave characteristics, currents, .. our knowledge of the physical processes is limited

Wave Climate in Coastal Areas: 

Wave Climate in Coastal Areas extreme waves depends on water level (joint probability of waves, tide and surge) single wave will depend on spectral composition and local bathymetry average wave climate for coastal erosion models; joint probability with water level

Need for statistics: 

Need for statistics what do we do with the measurement and the model data in order to get design values ? what is the uncertainty including model uncertainty ?

Climate change: 

Climate change sea level rise ? change in storm patterns? …

Slide36: 

SWAN MODEL IMPLEMENTATION Belgian coast 39 km 126 km

and we still want to do more with spectral wave models: 

and we still want to do more with spectral wave models

Slide39: 

Forecasts and Statistics of Rogue Waves Investigation of Accidents due to Rogue Waves EU Project MaxWave http://w3g.gkss.de/projects/maxwave/

LOCATIONS: 

LOCATIONS Zeebrugge Measurement Site: WaveRider I WaveRider II Two additional buoys: A2B and BVH (limited no. of parameters stored)

EXTREME WAVES:: 

Assumption for extreme waves: all waves exceeding twice the significant wave height (Ochi, 1995). ~1 wave on 7000 satisfy: EXTREME WAVES:

Slide42: 

D15: Cumulative Ocean maps for the risk of freak waves encounter Ship Density Ship Accident Risk Ship Tonnage Seasonal Distribution of Accidents Ocean Currents Sea-State As single parameter As combination of parameters Thematic Maps

Slide43: 

Shipping Accidents due to Bad Weather Analysis of the Related Sea-States Comparison with Wave Climate

Ship Accidents Database: 

Ship Accidents Database Shipping accidents reported as being due to bad weather by the Lloyd’s Marine Information Service (period 1995-1999). The database includes: Time Only the day Location Only 270 cases have known latitude and longitude Ship type Ship age Accident type

Sea-State Parameters: 

Sea-State Parameters Sea-state parameters are from ERA-40 archive ECMWF Re-Analysis provides the global analysis of the state of the atmosphere, land, and sea conditions in the period from mid-1957 to 2001 The wave model resolution is 1.5°X1.5°. The model is intended for deep water The ECMWF ERA-40 archive provides 4 data sets per day (0, 6, 12, 18 UTC). Therefore three days were investigated for each case, to avoid the time lag. Wave parameters used for the analysis:

Ship Accidents vs. Sea-States: 

Ship Accidents vs. Sea-States Significant wave height Mean directions spread vs. Hm0 Steepness vs. Hm0

Wave Climate and Accidents: 

Wave Climate and Accidents Significant Wave Height

Wave Climate and Accidents: 

Wave Climate and Accidents Wave Period

Wave Climate and Accidents: 

Wave Climate and Accidents Wave Steepness