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Safety on sea and biomass holding capacity from a high resolution wave model (SafeBioCapMod).

Knud Simonsen

Fróðskaparsetur Føroya (NVD)

Aðrir luttakarar:
Bárður A. Niclasen

Original: 1.1.2007-31.12.2008
Final: 1.1.2007 - 1.3.2009

Samlaður kostnaður:
1.158.116 kr.

Stuðul úr Granskingargrunninum:
642.116 kr.

Original description:
The Faroese economy is still entirely depended on marine activities. For safe operations, proper design or production optimalization information about the sea state is of vital importance. In order to develop a sea state prediction system, and to generate better understanding of sea state competence to analyse wave measurements and perform numerical wave modelling has been built up at the University of the Faroe Islands. The objective of this proposal is to continue to develop this competence, and further develop the model technology into practical application related to

• Ship traffic and safety on sea

• Design of sea farming cages and harbour constructions

• Estimation of biomass holding capacity of fjords

• Create a classification atlas for the fish farming sea cages in order to contribute to a economic and environmentally sustainable and safe aquaculture, and to prevent accidents, which may harm our natural resources and human lives.

Final report:
The project includes two main issues, and therefore two abstracts are written:

Seastate predictions and safety on sea.
Traditionally most metrorologica offices forecast height, direction and period of wind sea and swell based on pahsedaveraged wave models. In recent years, there has been speocial interest in whether it is possible to produce better forecasts, which include information about highrisk situations that are not resolved by traditional wave parameters.

A review of seastate parameters and safety warningindicies that have been suggested in recent years is conducted . Most accidents happens in abnormals waves, which can arise due to reasons, which still is not properly understood, or in waves different from the climate mean for the area. Another challenge is to combine local experience based warnings of dangerous sea states, which are not resolved in the models, with the results from the simulations. In the review it is concluded that an uniqe warning indices, which is applicable in all situations, is still to be found.

The projects conclude that it is technical possible to run an operative high resulution sea state warning system for the Faroe Shelf, provided neccesary upgrading of the computer facilities and hiring of properly educated personell. Another operatively less demanding, but less accurate, option is to presimulate a large number of possible situations, and then develop a webbased system, which based on single point measurements picks out the most likely sea state map for a given situation.

Wave induced resuspension in fish farming areas
Fish farming (netpen aquaculture) generates substantial amounts of waste, which will affect the local ecology and wellbeing of the caged fish, if not transported out of the production area. There is therefore a financial as well as an ecological incitement to investigate resuspension and waste transport mechanisms in fish farming areas. In the straits of the Faroe Islands the tidal current is generally strong enough to transport the waste out of the area. However many fish farming areas are located in closed fjords where the tidal current often is to weak to resuspend the settled waste. In such locations waves might be the key contributor to waste resuspension and subsequent flushing of the fjords.

In this investigation we looked at the role of wave generated resuspension in the fish farming areas of Suðuroy. The approach was as following: 1) Wave measurements measured offshore were transported into the fish farming areas by using idealised high resolution wave model runs, 2) linear wave theory was used to transform the modelled surface waves in the farming areas into water movement at the sea bed, 3) the modelled wave induced shear stress at the bottom was coupled to reported resuspension threshold values, 4) a time series of estimated wave induced resuspended material was calculated 5) time series converted into monthly averages of wave induced resuspension at two locations in each fish farming area.

The simulations show that waves can resuspend waste in the autumn, winter and spring, in all the investigated fish farming areas. The simulations also show that waste might accumulate in some of the more sheltered locations in the summer months if operating with maximum allowed quantity of fish in each cage. This investigation is only based on model results, theory and reported thresholds, and is not verified or tuned to any sedimentation/resuspension data. It is therefore encouraging to observe that the results seem to be quite compatible with reported conditions, and further investigations and measurements are recommended for establishing a biomass classification system for the fish farming area.


[1] Niclasen, B. A., and K. Simonsen, Validation of the ECMWF analysis wave data for the area around the Faroe Islands. Fróðskaparrit 55. bók, 2007, 126144.

[2] Niclasen, B. A., K. Simonsen, Note on wave parameters from moored buoys, Applied Ocean Research, 29, 4, 231238, 2007.

[3] Niclasen, B. A., K. Simonsen, and A. K. Magnusson, Wave forecasts and vessel safety: A review of possible operational warning parameters. Marine Structures, Subm.

Technical reports:
[5] Hans Pauli Joensen, Brandur K. Jacobsen, Khanh Duc Nguyen, Bárður A. Niclasen, Knud Simonsen & Dávur Sørensen, HighPower Computer Facilities at the Faculty of NaturalSciences, University of the Faroe Islands. NVDRit 2007:09, 2007.

[6] Niclasen, B. A. and K. Simonsen, Wave forecasts for the Faroe Shelf: What are our options? University of the Faroe Islands. NVDRit, 2009:04, 2009.

[7] Niclasen, B. A. and K. Simonsen, Wave induced resuspension in fish farming areas of Suðuroy: an introductory model based investigation, University of the Faroe Islands. NVDRit, 2009:03, 2009.

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