| title: | Impact of ship waves on the resuspension of bottom sediments and underwater light climate |
|---|---|
| reg no: | ETF5595 |
| project type: | Estonian Science Foundation research grant |
| subject: |
1.10-1.16. Bio-Geo Sciences 2.3. Mechanics |
| status: | completed |
| institution: | TTU Marine Systems Institute |
| head of project: | Ants Erm |
| duration: | 01.01.2003 - 31.12.2004 |
| description: | We intend to quantify the influence of ship-wave-induced changes of underwater light intensity on the environmental situation, sediment resuspension and transport, primary production and bottom plants in the coastal areas of the Tallinn Bay. The intensity of natural wave loads in the coastal areas of Estonia is extremely variable owing to particularly complex and anisotropic wind regime. As a result, in many semi-enclosed areas adjacent to ship lanes with heavy traffic (Tallinn Bay, Muuga Bay, Pärnu Bay) tha natural wave intensity is relatively low. The bottom sediments in these areas are fine and (at least, at certain depths) may be easily resuspended by long-period ship waves (in particular, by waves that are caused by superfast ferries). Within the lase decade, the intensiti of ship traffic has increased drastically, and direct measurements have shown that wake wash of superfast ferries indeed causes extensive resuspension of fine sediments at certain depths and areas. This process is accompanied by essential increase of water turbidity at the distance of at least 3 m from the bottom.To the day, studies into dynamical properties of ship waves and their possible role in beach destruction have already started. However, these studies do not consider wave-induced changes of optical properties (except recording a few turbidity time series) or influence of possible major changes of the underwater light regime on the underwater and bottom ecosystem (the existence of the latter is partillay limited by the available light).We plan to analyse the main properties of the natural wave field and its influence on the optical properties of the water on the one hand, and separately loads caused by ship waves and the resulting specific changes of the underwater light field. To achieve this goal, we first intend to model the wave climate of the Tallinn Bay on the basis of contemporary spectral wave model, measure wave properties and estimate natural variability of the underwater light field in the PAR region (400-700 nm) on the basis direct measurements in typical wave conditions. The specific influence of ship waves on the underwater light field (as well as on the primary production or on the conditions for the bottom plants) will be analysed on the basis analogous measurements performed in calm situations (that occur regularly in the area in question) during the navigational season. The field data and results of wave climate modelling will serve as a basis for modelling of the influence of ship traffic on the resuspension of bottom sediments and underwater light regime.The planned interdisciplinary studie combines elements from bio-geosciences (influence of the underwater ligth regime on the bottom ecosystem), mechanics (dynamics of ship wash and climate of wind waves) and physics (measurement and modelling of underwater light regime). An important applicational consists in constructing an express method for estimating the (ship) wave influence on bottom sediments. |
| project group | ||||
|---|---|---|---|---|
| no | name | institution | position | |
| 1. | Helgi Arst | MSI | senior scientist | |
| 2. | Ants Erm | TTU Marine Systems Institute | senior scientist | |
| 3. | Ove Pärn | MSI | engineer | |
| 4. | Tarmo Soomere | MSI | senior scientist | |