APPENDIX G WEATHER DATA SELECTED EXTRACTS FROM ENVIRONMENTAL DATA FOR BCFS VESSEL REPLACEMENT PROGRAM DRAFT REPORT Prepared for: B.C. Ferries Services Inc. Prepared by: George Roddan, P.Eng. Roddan Engineering 12657-24-th Ave Surrey, B.C. V4A-2E7 Sept 2003
Introduction In order to accurately assess the environmental variables which affect the operation of the BC ferries transit on the various routes, it is instructive to first review the factors controlling weather patterns on the coast. Wind and Wave Climatology Two atmospheric pressure systems control the climate of the B.C. West Coast, the Pacific High and the Aleutian Low. In winter, the Aleutian low (centered near 50 deg N and 180 deg. W) is strongest. In summer, the Pacific high (centered near 30 deg N 130 deg W) is strongest. At their peaks, each system tends to dominate winds and weather patterns over the West Coast. Winter Winds In winter, storms originating in the eastern Pacific move rapidly northeastward and are then slowed by the coastal mountain ranges where the features of local terrain influence the wind patterns. The orientation of the coastal range forces a general northwestsoutheast behaviour of the major wind directions. The large-scale pressure gradient is northwest-southeast resulting in extreme winds in the southeast direction. The land/water thermal mass interaction also influences local wind conditions. In winter, the land mass is colder than the water, cold air drawn seaward through the inlets and fjords causes local wind to prevail in the direction of the orientation of the inlets. Summer Winds The Pacific High has its greatest intensity in mid-summer, with offshore prevailing winds in a northwesterly direction. Closer to land, the winds are constrained to move in channels governed by the land masses. Also during this time of year, local winds will be domininated by the heating land mass where sea- land breezes are a result. Autumn and Spring are a combination of the Winter and Summer extremes of weather in most parts of the coast. Waves The factors governing the wave environment over the BC west coast are many and complex. Offshore, the highest waves are correlated with maximum wind conditions. Closer to land, and in sheltered waters, the influences of fetch, duration, water depth, complex geography and currents affect the local wave climate. The fact that wind/wave/current environment is influenced by many variables necessitates measurement of these environmental parameters locally. A system of weather stations and weather buoys has been set up along the BC coast and has resulted in increased accuracy of predictions and statistical forecasting. The Transport Development Centre has compiled historical wind and wave data from these buoys for the West Coast for deep water and offshore locations. Presentation of the data is
comprehensive and includes Rose plots, exceedance diagrams, directional tables and wave spectra. The data is available online and is accessible at: (http://www.meds-sdmm.dfo-mpo.gc.ca/alphapro/wave/tdcatlas/tdcproducts.htm) Another organization, The Marine Environmental Data Service (MEDS) is a branch of the Department of Fisheries and Oceans (DFO) which has been set up to acquire, coordinate and analyze marine environmental data. MEDS provides this data to the marine community. MEDS has set up a site for access of historical and real-time wind/wave and current data along the coast, which can provide data for many of the BCFS routes. Below is a diagram showing some of the weather buoys accessible on the MEDS site: (http://www.meds-sdmm.dfo-mpo.gc.ca/meds/databases/wave/wave_e.htm): Figure 1. Map showing the locations of surface (ODAS) buoys in the west coast meteorological network. Coastal buoys (diamonds) have 3 meter discus hulls, and are in water ranging from 20 to 3000 m deep. Offshore buoys (squares) have 4 by 6 m NOMAD hulls and are in water 3100 to 3600 m deep. Optical instruments have so far only been installed on buoys at Halibut Bank (46146) and in Saanich Inlet (46134). Currents Currents also have an effect on the local wave climate and can effect operation of vessels. An example of this is steep standing wave conditions that can be found at the entrances to many of the passes along the coast when high winds and opposing currents jointly exist, (the eastern entrance of Active Pass is a good example of this). Currents also have an effect on docking of the BCFS vessels.
Current meter data and their ancillary time series observations observed at fixed locations or by acoustic doppler profiling instrumentation (ADCM) are managed by a distributed system of archive centres within DFO. In particular, the Institute of Ocean Sciences (IOS) in Sidney provides current information for some of the areas relevant to BCFS routes. This database can be accessed through the DFO site: http://www.pac.dfompo.gc.ca/sci/osap/data/searchtools/searchmoorings_e.asp. IOS staff provide data retrieval services and relevant current information on BCFS routes and is reported below. Current data available in the Canadian Tide and Current Tables (ref 11.) was also used for parts of this report, and wherever possible, checked against the data available through IOS. In general, a good correlation was found between the data in ref 11 and the maximum current velocities derived from the field data. In addition, it should be noted that trend analysis work is be done to identify any significant trends in environmental data that may be a result of El Nino and other global warming effects, ref 10. From this initial report, trends in wind speed are about 0.1 to 0.5 m/sec per decade, and in wave ht, 0.1 to 0.4m per decade in open water. Should the study of these data show any trends relevant to BCFS operational requirements, they should be taken into account. Environmental Conditions at Terminals Terminal Feasibility Studies and other reports provide additional information on environmental conditions relevant to BCFS vessel operation in the near-shore environment. A number of these past studies have been accessed through archives in the BCFS library and relevant information noted. A number of these reports are listed in the references below. Numerical Methods Increasingly, advanced numerical methods are being used to predict operational environments at terminals and other coastal locations. In the past, wave estimation methods such as the significant wave method, first developed by Sverdrup and Munk (1947) and refined by Bretschneider (1959) and termed the S-M-B method have been used as a first approximation to estimate significant wave heights and periods given inputs of wind speed, fetch length and wind duration for deep water. Recently, coastal engineers have developed more sophisticated wave estimation and hindcasting models which have the potential for accurately defining environmental wind/wave/current conditions for many complex systems, and include effects due to shallow water, including wave refraction, diffraction and shoaling. Should this be necessary to BCFC, a number of coastal engineering firms familiar with these methods have been listed in Appendix. Conclusion The environmental data presented below represent the best available information relevant to BCFS routes at the time of writing. The information contained herein should be reviewed and calibrated with detailed local knowledge and experience for each route. As
new monitoring systems are put into operation, the accuracy of environmental variables and resulting predictive value will increase. By accurate definition of the operating environment, new vessels can be designed and built which will be safer and will ensure the economic and efficient delivery of ferry services. Roddan Engineering
Route 10 Inside Passage (Port Hardy/Bella Bella/Prince Rupert) 274 N.MI. 15:00 hr. On this route, there is open water travel between Port Hardy and Bella Bella. The rest of the passage is largely sheltered, with maximum wind speeds in 30 knot range, with very little fetch for a sea to develop. Inside the largest sea is about 0.50 meter significant with estimated maximum of 0.925 meter, except where there is some exposure to more open waters. The maximum conditions are in the open water transit of Queen Charlotte Sound. Wave and Wind data have been obtained from The Wind and Wave Atlas Volume IV - The West Coast of Canada and from MEDS buoy C46204 data. These data are presented below for Queen Charlotte Sound:
Below are some processed data from the Buoy C46204 in Queen Charlotte Sound: Significant Wave Hts for all months: Wind Speed for all months:
Route 11 Queen Charlotte Islands (Prince Rupert)-(Skidegate) 93 n.mi. 8:00 hr. On this route, there is open water travel in Hecate Strait between Prince Rupert on the mainland and Skidegate on Queen Charlotte Island. Prince Rupert is somewhat sheltered compared to the open water transit. Note that the Hecate Strait transit has the ferry taking the largest seas on the bow and stern quarters. Wave and Wind data have been obtained from The Wind and Wave Atlas Volume iv The West Coast of Canada and from MEDS buoy C46183 data. These data are presented below for Queen Charlotte Sound:
Below are some processed data from the Buoy C46183 in Hecate Strait: Significant Wave Hts for all Months: Wind Speed for all months:
Route 40 Port Hardy Mid Coast, distance and times vary On this route, there is open water travel between Port Hardy and Bella Bella. The rest of the passage is largely sheltered with stops at Shearwater, Klemtu, Ocean Falls and Bella Coola. Inside the largest sea is about 0.50 meter significant with estimated maximum of 0.925 meter, except where there is some exposure to more open waters. The maximum conditions are in the open water transit of Queen Charlotte Sound. Wave and Wind data have been obtained from The Wind and Wave Atlas Volume IV - The West Coast of Canada and from MEDS buoy C46204 data. These data are presented above for Route 10, Queen Charlotte Sound. Roddan Engineering
Appendix II Wave and Wind Rose Key