Abstract
Background
CH2M (formerly Halcrow Group Ltd.) was commissioned by Scottish Ministers to develop a ‘Hydrodynamic model of Scottish Shelf waters’. The contract was commissioned under the Scottish Government Framework Contract for the Provision of Strategic Environmental Assessment, Appropriate Assessment and Marine Planning Services and Advice to Support Sustainable Economic Development in Scottish Marine Waters (REF: 177895) – Call Off Number 11 - Provision of a Hydrodynamic Model of Scottish Shelf waters – 16 May 2012. The project is managed on behalf of the Scottish Ministers by Marine Scotland.
The Scottish Government is committed to the development of a successful marine renewable energy industry in Scotland, which is currently also the largest producer of farmed Atlantic salmon in the EU and third largest globally. To achieve the sustainable development of both the offshore renewable energy industry and the aquaculture sector, Marine Scotland has adopted a planning approach to identify potential developmental areas.
Both of these factors are drivers for the development of a regional hydrodynamic model of the Scottish Shelf Waters and four more localised models which will be used to inform their planning approach. Marine Scotland will take ownership of the hydrodynamic models at the end of the study enabling them and other community organisations they work with, to undertake simulations and further development to meet their planning and research needs.
One of the key aims of the integrated model is to use it in the development of connectivity indices between various fish farms. This will ensure a seamless flow of hydrodynamic modelling data from the high resolution local area models into the larger Scottish shelf model, thereby ensuring that the model covers the entire region of influence of each fish farm. The integrated model will therefore contribute to improved understanding of potential sea lice dispersal, to help inform management and mitigation measures.
Study Areas
The overall study area includes all of the Scottish shelf waters out to the 200m depth contour at the edge of the continental shelf. This model simulates the hydrodynamic conditions in three-dimensions, including meteorological and tidal forcing. The shelf model resolution varies from 10km offshore to 1km at the coast.
Within this region-wide shelf waters model, four local three-dimensional models have been setup providing higher resolution to resolve key bathymetry, coastline and physical processes over smaller more local areas. These four model areas have been defined as case studies and cover the following regions:-
Case Study 1: Pentland Firth and Orkney Waters (PFOW) Case Study
2: Wider Loch Linnhe System (WLLS) Case Study
3: East Coast of Lewis and Harris (ECLH) Case Study
4: Northwest Shetland mainland – St Magnus Bay area (SMB)
Aims and scope of numerical modelling works
The main aims of the project are to: 1) develop a validated three dimensional hydrodynamic model for the Scottish shelf waters; 2) develop a validated three dimensional hydrodynamic model for each of the four identified case studies, plus a validated wave model for the Pentland Firth and Orkney Waters (Case Study 1); and 3) integrate the case study sub-models into the wider domain shelf model.
The modelling is aimed at providing a quantitative description of marine currents and water properties for the whole of Scottish waters on a range of spatial scales. The outputs of this study will be a validated hydrodynamic model capable of predicting tidal and non-tidal currents for the whole of the Scottish shelf and inshore waters and include a more accurate assessment of the connectivity of different regions, and the available energy resources in those regions. It will also include description of methods for assessing the impact of extracting some of that energy upon the physical environment.
The modelling has been undertaken using an open-source threedimensional (3D) hydrodynamic model called FVCOM. One of the reasons behind the choice of this modelling software is that the models developed in this project will be freely available to others at the end of the Project. Marine Scotland have a vision that the models will be used and developed further by Marine Scotland staff and the marine modelling community as more data becomes available and/or other needs are identified.
This Report
This report documents the work carried out in developing the East Coast of Lewis and Harris (ECLH) model. This work includes: data collated and/or identified for the numerical modelling, setup and calibration of the flow model, and the longer term simulations required for this study. It is noted that the data section in this report is a summary of the overall Data Review report (Halcrow, 2012) that is relevant to the ECLH area. This report is Volume 1 of the ECLH model report. A companion volume (Volume 2 – Model Documentation Report for ECLH) contains additional details on model development (data preparation, mesh generation, preparation of model setup files, how to run the model, etc.) and lessons learnt.