EXECUTIVE SUMMARY

A Workshop titled: "Petitcodiac River and estuary technical workshop: modelling of hydrology and sediment in support of an environmental impact assessment" was held at the Hotel Beauséjour in Moncton, New Brunswick, from March 3 to 5, 2002. The Workshop was organized by Environment Canada and Fisheries and Oceans Canada with the assistance of the New Brunswick Department of Transportation and the New Brunswick Department of the Environment and Local Government and was attended by more than 65 people, including estuarine scientists from Canada, United States, Britain, Belgium and Denmark, as well as government scientists and other observers (see Appendix E).

The purpose of the workshop was to identify technically feasible and cost-effective modelling approaches that could be used to evaluate movement of water and sediment in the Petitcodiac River and estuary under existing conditions and under a range of openings in the Petitcodiac River dam/causeway. Results of the workshop as well as the Workshop Organizing Committee Recommendations (see Appendix A) were prepared for consideration during development of the environmental impact assessment project guidelines and terms of reference.

Although all expected outcomes as identified in the workshop terms of reference were not fully attained, some common areas of agreement did arise out of the workshop (see Appendix A) as follows:

• An enormous deficiency in very basic information exists, including information on tides, currents, salinity, sediment properties (grain size and shear stress plus other chemical and biophysical properties), the ice regime, and erosion processes.
• The combination of very large tides, the cold environment and the high concentration of sediments present unique challenges to understanding and potentially modelling the physical processes.
• Physical processes and conditions during the winter months, primarily the effect of ice on channel morphology, are poorly understood, but must be considered in the environmental assessment of a proposed project.
• To understand both far-field and localized effects, it may be necessary to consider the entire estuarine/riverine system and oceanographic processes in the Bay of Fundy/ Gulf of Maine.
• An inter-disciplinary team consisting of engineering and scientific experts would be needed to effectively understand the unique Petitcodiac River/Estuary system.
• Simple approaches should be used to develop a basic understanding of the estuary system before considering more complex analyses or methodologies.
• The knowledge base about macrotidal estuarine systems should be increased by the publication of data and study results.
  

The Workshop Organizing Committee has also formulated and unanimously agreed to numerous conclusions (see Appendix A). Major conclusions were the following:

• An understanding of the physical processes throughout the year is critical to the assessment of environmental conditions that presently exist or would exist if changes were made to the causeway and/or its gates.
• The link between hydrodynamics and sediment in fluid mud regions is not well understood.
• Additional data collection is essential to compensate for serious deficiencies and gaps in the information presently available on tides, currents, and sediment properties, the ice regime, and characteristics of the water column. Regardless of the type and scope of any future modelling efforts, additional data collection would be necessary to adequately assess the potential environmental implications of any proposed changes at the Petitcodiac causeway,
• Since existing data related to physical processes may be relevant to the development of a better understanding of estuarial processes, it should be synthesized and reviewed in order to improve the level of understanding of the Petitcodiac estuary system. New data should be incorporated into the knowledge base as it is collected.
• As a first step, the development of conceptual models for different processes would provide useful guidance when planning and carrying-out data collection and numerical modelling.
• Numerical modelling would be a useful tool in environmental impact assessment for the Petitcodiac River and estuary, but would require additional data and an understanding of the interactions between the hydrodynamics and sediments in highly turbid environments.
• If based upon scientifically valid objectives and test criteria, experimental openings of the existing gates in the dam/causeway could provide opportunities for acquisition of additional data for modelling purposes. The experiments should only be carried out if adequate arrangements for data collection have been established.
• Any proposed or implemented changes at the Petitcodiac Causeway would require ongoing monitoring, modelling, and evaluation.

Based on the common areas of agreement and the conclusions the Workshop Organizing Committee put forward eleven recommendations (see Appendix A) as follows:

1. A strategic plan describing the overall study approach should be prepared and adopted, including a gradual and incremental data collection and modelling approach. A step-wise approach involving data collection and modelling, such that data can be used to modify and improve subsequent modelling efforts, should be done.
2. Expertise and resources should be dedicated to synthesize existing information in order to begin the process of the development of conceptual models of the estuary. (See Appendix A - Table 1)
3. Baseline data collection of water elevations and river channel cross sections should continue.
4. Preliminary information gathering and testing of data collection equipment and approaches (see Appendix A - Table 2) should be done prior to the finalization of the terms of reference for detailed assessment involving modelling work.
5. A major data acquisition program should be launched to understand the basic characteristics of the tides, currents, sediments and their properties, the ice regime, and standard physical, chemical and biological characteristics of the water column and benthic layer of the estuary and river during all seasons of the year. This should be done in accordance with the strategic plan.
6. Different models with appropriate levels of complexity should be used depending on the questions to be answered. Modelling approaches should progress from simple to more complex models as required. An incremental approach involving data collection and interpretation to modify and improve subsequent modelling efforts should be considered.
7. Boundary conditions should be well defined and will likely be different for models developed to address specific issues.
8. As a first step, a mass balance type approach (conceptual models) should be considered followed by a one-dimensional hydrodynamic model. This should be implemented before any more detailed hydrodynamic, sediment or water quality modelling is considered.
9. A one-dimensional hydrodynamic model extending seaward from Salisbury to Hopewell Cape should be considered before any more detailed hydrodynamic, sediment or water quality modelling.
10. The proponent of the environmental assessment process should consider different modelling approaches with suggestions identified in Appendix A - Table 3, remembering that further data collection is essential for modelling and that modelling is an important tool in interpreting data for future scenarios.
11. A central warehouse for the sharing of data and information should be established. This would be an important component for the environmental assessment process as well as the ongoing scientific inquiries within the Petitcodiac River/estuary.