Abstract
On the bed of the North Sea sand waves are present, which grow up to 25% of the water depth and migrate with a speed of tens of meters per year. These sand waves can pose a hazard to offshore constructions, navigation, pipelines and telecommunication cables.
The bed of the North Sea is also covered by a great number of organisms, living in and on the bed of the sea, which are known to have significant influence on the stability of the bed. This paper proposes a parameterization of these bio-geomorphological interactions, in order to model the inherent dynamics in offshore seabed patterns.
Three species are included in the parameterization, which influence the stability of the bed in opposite modes. First, the bivalve Tellina fabula is known for its destabilizing effect on the bed during its burrowing and feeding activities. On the other hand, the tube building worm Lanice conchilega reduces the near-bottom flow around and across the tube fields. Finally, the sea urchin Echinocardium cordatum influences the
vertical sediment distribution by filtering the finer particles from the sediment surface to the deeper sediment.
T. fabula is found to be responsible for a reduction of the critical bed shear stress up to a factor 0.6, while L. conchilega reduces the ripple height with a factor 0.5, due to the deceleration of the near bottom flow. These ripples are present on top of the sand waves, and are the main origin of the bottom roughness. Finally, E. cordatum is able to increase the medium grain size at the bed-water interface with a factor 2. Given the
measured biomass of T. fabula, L. conchilega and E. cordatum on the Dutch Continental Shelf, the predicted occurrence of sand waves, in which the parameterization is included, shows significantly better results, compared to the prediction for the default case. This means that inclusion of biological activity is important to predict the occurrence of sand waves.
The bed of the North Sea is also covered by a great number of organisms, living in and on the bed of the sea, which are known to have significant influence on the stability of the bed. This paper proposes a parameterization of these bio-geomorphological interactions, in order to model the inherent dynamics in offshore seabed patterns.
Three species are included in the parameterization, which influence the stability of the bed in opposite modes. First, the bivalve Tellina fabula is known for its destabilizing effect on the bed during its burrowing and feeding activities. On the other hand, the tube building worm Lanice conchilega reduces the near-bottom flow around and across the tube fields. Finally, the sea urchin Echinocardium cordatum influences the
vertical sediment distribution by filtering the finer particles from the sediment surface to the deeper sediment.
T. fabula is found to be responsible for a reduction of the critical bed shear stress up to a factor 0.6, while L. conchilega reduces the ripple height with a factor 0.5, due to the deceleration of the near bottom flow. These ripples are present on top of the sand waves, and are the main origin of the bottom roughness. Finally, E. cordatum is able to increase the medium grain size at the bed-water interface with a factor 2. Given the
measured biomass of T. fabula, L. conchilega and E. cordatum on the Dutch Continental Shelf, the predicted occurrence of sand waves, in which the parameterization is included, shows significantly better results, compared to the prediction for the default case. This means that inclusion of biological activity is important to predict the occurrence of sand waves.
| Original language | English |
|---|---|
| Title of host publication | PECS 2008: Physics of Estuaries and Coastal Seas, 25–29th August, Liverpool |
| Subtitle of host publication | Process studies in the pre-operational era: Program and Abstracts |
| Editors | A.J. Souza, A. Lane |
| Pages | 19-22 |
| Publication status | Published - 25 Aug 2008 |
| Event | 14th Physics of Estuaries and Coastal Seas Conference, PECS 2008 - Liverpool, United Kingdom Duration: 25 Aug 2008 → 29 Aug 2008 Conference number: 14 http://2008.pecs-conferences.org/ |
Conference
| Conference | 14th Physics of Estuaries and Coastal Seas Conference, PECS 2008 |
|---|---|
| Abbreviated title | PECS |
| Country/Territory | United Kingdom |
| City | Liverpool |
| Period | 25/08/08 → 29/08/08 |
| Internet address |