8.0 TIDAL CHANNEL FORMATION AT THIRD BERTH PROJECT

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1 Coastal Geomorphology Study Appendix C November TIDAL CHANNEL FORMATION AT THIRD BERTH PROJECT This section of the report assesses the potential for tidal channel formation at the planned Third Berth Project. The assessment is based primarily on the experience and information that has been developed from the historical studies and field studies described previously. 8.1 PROJECT DESCRIPTION Figure C8-1 shows the general layout of the proposed Deltaport Third Berth Project. The main components relevant to the geotechnical investigations consist of (1) a wharf to accommodate the third berth, (2) a container storage yard constructed of dredge fill, (3) a tug basin and boat launch, and (3) an extension to the ship channel. The wharf is 427 m long and may consist of either a pile and deck structure or a caisson structure. The berth will be dredged to a depth of 16 m CD with the top of the deck at +8.0 m CD. Approximately 20 ha of new land will be constructed to provide the container storage yard. The land will be created through dredging and landfill operations. Revetment works along the north side of the fill will consist of rock riprap. The existing tug moorage area on the northeast corner of Deltaport will be re-located to the north corner of the Third berth. The tug moorage area will consist of a floating dock, walkway and dredged basin. The tug moorage area will be dredged to a depth of 6.5 m CD. Estimates of dredge cut and fill volumes are preliminary at this time and indicate 1.6 million m 3 of material will have to be excavated for the ship channel and an additional 2.0 million m 3 is required for constructing the Third berth and terminal area. It is estimated that up to 2.3 million m 3 of the total dredged volume will be unsuitable for site fill. Details of the dredge spoil disposal plan are not available at this time. 8.2 POTENTIAL FOR CHANNEL FORMATION Figure C8-2 shows two profiles through the proposed excavations for the Deltaport Third Berth Project. The main excavation involves deepening the approach channel to the wharf extension. This excavation occurs in deep water where the existing ground level is -12 m CD. Based

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4 Coastal Geomorphology Study Appendix C November 2004 on our understanding of past tidal channel formation on Roberts Bank, there should be no potential for headcutting to occur from this excavation. Furthermore, due to the large depths, the peak velocities generated by tidal currents in this area are very low-typically less than 0.2 m/s. Simulation of current patterns with the hydraulic model showed velocities will remain well below the threshold for significant sediment transport in this region after the Third Berth Project is implemented (Appendix B). Therefore, the risk of any significant new channel formation occurring from this excavation appears negligible. Preliminary plans show the tug basin extending into the existing crest protection. In this area the crest protection is at ground level and does not project above the tidal flats. Some modification to the structure is anticipated, although details of this feature are not finalized at this time. Excavation of the tug basin could involve cutting into portions of the tidal flats that are above LLW. Therefore, there is some theoretical potential for headcutting to be initiated in this area, particularly if the crest protection was eliminated. However, given the very limited extent of the excavation and its orientation with respect to the existing drainage patterns, the potential for headcutting is expected to be minor. Furthermore, this effect should be eliminated if the crest protection structure is modified to tie-in with the tug basin.

5 Coastal Geomorphology Study Appendix C November CONCLUSIONS There are two main factors that have triggered drainage channel development from previous port developments at Roberts Bank: 1. dredging into the tidal flats above the low tide line lowered the base level for water draining off the tidal flats and initiated shoreward headcutting; 2. expansion of eelgrass beds and resulting changes to flow resistance and water storage on the tidal flats affected runoff patterns and promoted channelization. The crest protection structure was constructed in 1981 to limit headcutting processes by artificially maintaining the original base level. The structure appears to have effectively limited the growth of at least two channels. However, the large channel near the centre of the intercauseway area has by-passed the structure by flowing along the inside of it. As a result, this channel is continuing to expand in both the seaward and landward directions. It is expected that the trunk channel will expand shoreward before eventually stabilizing. A small channel that developed near the Tsawwassen Ferry terminal was also observed to have by-passed a riprap control structure. This illustrates the difficulty of mitigating channel development using relatively localized structures that are not be tied-in to inerodible boundaries. The planned Deltaport Third Berth Project is not expected to initiate any new tidal channels on Roberts Bank. The preliminary plans indicate all of the excavation will take place in deep water, well below the low tide line. As a result, there will not be any base lowering or triggering of head-cutting. Furthermore, the main structures associated with the Deltaport Third Berth Project will not affect tidal current patterns or waves sufficiently to initiate scour or erosion.

6 Coastal Geomorphology Study Appendix C November REFERENCES Barrie, J.V., Recent geological evolution and human impact: Fraser Delta, Canada. In, Pye, K. and Allen, J.R.L (eds.). Coastal and Estuarine Environments: sedimentology, geomorphology and geoarchaeology. Geological Society of London, Special Publications, 175, Barrie, J.V. and Currie, R.G., Human impact on the sedimentary regime of the Fraser River Delta, Canada. Journal of Coastal Research, 16, Beak Hinton & Associates Ltd, National Harbours Board (Port of Vancouver), Environmental Impact Assessment of Roberts Bank Port Expansion, Vol. 2, Main Report. Report prepared for Beak Hinton Consultants Ltd., 201 pp. Christian, H.A., Mosher, D.C., Barrie, J.V., Hunter, J.A. and Luternauer, J.L., Seabed slope instability on the Fraser River delta. In, Geology and Natural Hazards of the Fraser River Delta, British Columbia, (ed.) J.J. Clague, J.L. Luternauer, and D.C. Mosher. Geologic Survey of Canada, Bulletin 525, pp Clague, J.J., Geologic setting of the Fraser River delta. In, Geology and Natural Hazards of the Fraser River Delta, British Columbia, (ed.) J.J. Clague, J.L. Luternauer, and D.C. Mosher. Geologic Survey of Canada, Bulletin 525, pp Duggan, D. and Luternauer, J.L., Development-induced tidal flat erosion, Fraser River Delta, British Columbia. In, Current Research, Part A, Geological Survey of Canada, Paper 85-1A, Engelund, F. and E. Hansen, A Monograph on Sediment Transport in Alluvial Streams, Teknisk Forlag, Copenhagen, Denmark. Fonesca, M.S., Zieman, J.C., and Thayer, G.W., Influence of the seagrass, Zostera marina L., on Current Flow. Estuarine, Coastal and Shelf Science, 15, Geo Sea Consulting Ltd., Sediment transport and its environmental implications in the Lower Fraser River and Fraser Delta. Report prepared for Environment Canada, Environmental Conservation Branch, DOE FRAP , 41 pp. Hawley, P.M., Erosional Stability of a Dredged Borrow Pit on Southern Roberts Bank, Fraser River Delta, British Columbia. B.A.Sc. Thesis, Department of Geological Engineering, University of British Columbia, 65 pp. Hay and Company, Erosion at Roberts Bank Geophysical Evaluation. Report to Vancouver Port Corporation, 23 pp.

7 Coastal Geomorphology Study Appendix C November 2004 Hemmera Envirotech Inc., History of Development at Roberts Bank An Overview (Draft). Report prepared for Vancouver Port Authority, 1900 Granville Square, 200 Granville Street, Vancouver, BC., 19 pp. Howard, A.D., Drainage analysis in geologic interpretation: a summation. American Association of Petroleum Geologists Bulletin, 51, Hutchinson, I., R. Patterson and R. Mathewes, Plant Macrofossil, pollen, Diatom and Foraminiferal Biofacies of the Fraser Delta. In, Geology and Natural Hazards of the Fraser River Delta, British Columbia, ed. J.J. Clague, Geological Survey of Canada, Bulletin 525, pp Johnson, J. W., Characteristics and Behaviour of Pacific Coast Tidal Inlets. Journal of the Waterways, Harbors and Coastal Engineering Division, ASCE. Vol 99, No. WW3, Kellerhals, P. and Murray, J.W., Tidal flats at Boundary Bay, Fraser River Delta, British Columbia. Bulletin of Canadian Petroleum Geology, 17(1), Koch, E.W., Beyond Light: Physical, Geological, and Geochemical Parameters as Possible Submersed Aquatic Vegetation Habitat Requirements. Estuaries, 24(1), Luternauer, J.L., Fraser Delta Sedimentation, Vancouver, British Columbia. In, Report of Activities Part A, Geological Survey of Canada, Paper 76-1A, Luternauer, J.L., and Murray, J.W., Sedimentation on the western delta-front of the Fraser River, British Columbia. Canadian Journal of Earth Sciences, 10, Luternauer, J.L., Mosher, D.C., Clague, J.J. and Atkins, R.J., Sedimentary environments of the Fraser River delta. In Geology and Natural Hazards of the Fraser River Delta, British Columbia, (ed.) J.J. Clague, J.L. Luternauer, and D.C. Mosher. Geologic Survey of Canada, Bulletin 525, pp Luternauer, J.L., Duggan, D. and Hendry, M Development-induced tidal flat erosion, Fraser River Delta, British Columbia. In, Current Research, Part A, Geological Survey of Canada, Paper 84-1A, Mason, C., Regime Equations and Tidal Inlets. Journal of the Waterways, Harbors and Coastal Engineering Division, American Society of Civil Engineers, Vol. 99, WW3, pg Mathews, W.H, Fyles, J.G. and Nasmith, H.W., Postglacial crustal movements in southwestern British Columbia and adjacent Washington State. Canadian Journal of Earth Sciences, 7,

8 Coastal Geomorphology Study Appendix C November 2004 Mathews, W.H., and Shepard, F.P, Sedimentation of the Fraser River Delta, British Columbia. Bulletin of the American Association of Petroleum Geologists, 46(8), McLaren, P. and Bowles, D., The effects of sediment transport on grain size distributions. Journal of Sedimentary Petrology, 55, NHC, Review of Fraser River Sediment Budget. Report to Dredge Management Advisory Committee, Fraser River Estuary Management Program, by Northwest Hydraulic Consultants Ltd. NHC, Sediment Budget of Lower Fraser River. Report to Dredge Management Advisory Committee, Fraser River Estuary Management Program, by Northwest Hydraulic Consultants Ltd. O Brien, M.P., Estuary Tidal Prisms Related to Entrance Areas. Civil Engineering, American Society of Civil Engineers. Vol. 1, No. 8, Precision ID, Cynthia Durance, Precision Identification, 3622 West 3 rd Vancouver B.C., V6R 1L9, precid@shaw.ca Avenue, Reinich, H.-E. and Singh, I.B., Depositional sedimentary environments : with reference to terrigenous clastics. Springer-Verlag, New York, 434 pp. Stevens, M. and C. Nordin, First Step Away from Lacey s Regime Equations. Journal of Hydraulic Engineering, American Society of Civil Engineers, Vol. 116, No. 11, pg Strahler, A.N Quantitative Analysis of Watershed Geomorphology. American Geophysical Union Transactions, Vol. 38, pg Tarbotton, M., Luternauer, J.L. and Mattila, M., Tidal flat response to development and mitigation work at Roberts Bank, Fraser River Delta, British Columbia. In, Proceedings of the 1993 Canadian Coastal Conference, May 4-7,1993, Vancouver, British Columbia. Published by the Canadian Coastal Science and Engineering Association, and Simon Fraser University, Triton Consultants Ltd., A Review of the Recent Physical and Biological Development of the Southern Roberts Bank Seagrass System, Report prepared for Roberts Bank Environmental Review Committee, June USACE, Coastal Inlet Stability Analysis Using Escoffier Method, Coastal Engineering Technical Note CETN IV-11, Waterways Experimental Station, US Army Corps of En gineers, Coastal and Hydraulics Laboratory, Vicksburg, Mississippi, 7 pp. van Rijn, L Sediment Transport by Currents and Waves. Delft Hydraulics Report H 461, June Delft Hydraulics.