APPENDIX C: Wind and Wave Modelling

Transcription

1 APPENDIX C: Wind and Wave Modelling

2 Wind data collected by Environment Canada was obtained and reviewed for 3 nearby recording stations; Hamilton Airport, Hamilton RBG (Botanical Gardens) and Burlington Pier. It is important that the wind data used for hindcasting be representative of the actual overwater winds that cause wave generation on the body of water being hindcast. The preferred means of verifying the suitability of winds for hindcasting is through a calibration process that includes hindcasting to a site where waves have been measured. There is no suitable measured wave data within Hamilton Harbour so a comparison was made to Toronto Island wind data because that data has been successfully used for hindcasting on the western end of Lake Ontario. For the LaSalle Park Marina site the most important winds are those from east through to southwest. The Hamilton RBG data was eliminated from consideration because of the quality of the wind speed data. Over its 11 year period of coverage the highest recorded wind speed was 39 kph, and that it clearly not a reasonable approximation of the over-water winds that occur in this area. Figure 1 shows a comparison of wind exceedence curves for measured wind data at Hamilton Airport and Toronto Island Airport. Figure 2 compares Hamilton Airport and Burlington Pier wind data. These figures shows the percentage of time that measured winds speeds exceed a given speed. Comparing Figures 5 and 6 it can be seen that the Hamilton data is relatively consistent with the Toronto Island data although it shows a lower occurrence and lower peak wind speeds for easterly winds. The Burlington Pier wind data was judged to have reasonable easterly winds but poor westerly and southwesterly winds. Due to the importance of the southwesterly wind conditions at this site it was concluded that overall the Hamilton Airport winds were more representative of the winds that occur over Hamilton Harbour than the Burlington Pier winds. The Hamilton Airport wind data was therefore used to hindcast long-term wave conditions for this project. A second hindcast was also completed using the Burlington Pier wind data so the significance of the potential underestimation of east winds in the Hamilton wind data set could be examined. Environment Canada recorded hourly wind speed and direction data at Hamilton Airport from January 15, 1970 until December 15, 2011, which is just less than a 42-year period. Figure 3 shows a wind rose for that data set. Overall, approximately 2.2% of the data was either not recorded or judged to be erroneous and excluded from the data set. It can be seen that there is a higher frequency of occurrence of westerly and southwesterly winds than any other direction. The highest recorded winds speed also come from the southwest, with a sustained wind speed of 97 kph occurring on March 15, Figure 4 shows the highest predicted wave periods and Figure 5 shows the wave height and period exceedence curves. Only the easterly quadrant waves are shown for the Burlington Pier hindcast as that hindcast was only carried out to consider the potential under-representation of easterly winds within the Hamilton wind data set. It was concluded that the difference was not large enough to invalidate the Hamilton winds hindcast, but that easterly waves from the Burlington Pier winds hindcast should also be considered during the assessment of the various wave break alternatives. Figure 6 presents wave tables showing the average annual hours of occurrence of wave conditions grouped by wave height and period for the full year and for an operating season defined as April 15 to October 31. Figure 7 shows wave tables for a typical boating season defined as May 15 to September 30, and an extended boating season defined as May 1 to October 31.

3 Figure 1: Hamilton and Toronto Island Wind Speed Exceedance Curves

4 Figure 2: Hamilton and Burlington Wind Speed Exceedance Curves

5 Figure 3: Wind Rose for Hamilton Airport

6 Figure 4: Highest Hindcast Wave Periods per Direction Sector Peak Wave Period (s) Hamilton winds Burlington winds 0.0 North NE East SE South SW West NW North Figure 5: Wave Height and Period Exceedance Curves for Hamilton Winds Hindcast 100 Wave Period (s) Exceedance (%) wave height wave period Wave Height (m)

7 Figure 6: Hindcast Wave Tables, Full Year and Operation Season LASALLE PARK MARINA BREAKWALL EA Full Year Wave Data Average Annual Hours of Occurrence, Waves from All Directions Wave Height (m) Wave Period (seconds) Totals ,108 1,704 2, , > Totals 1,108 2,627 1, ,708 LASALLE PARK MARINA BREAKWALL EA Operational Season, April 15 - October 31 Average Annual Hours of Occurrence, Waves from All Directions Wave Height (m) Wave Period (seconds) Totals ,018 1, > Totals 665 1, ,827

8 Figure 7: Hindcast Wave Tables, Typical and Extended Boating Seasons LASALLE PARK MARINA BREAKWALL EA Typical Boating Season, May 15 - September 30 Average Annual Hours of Occurrence, Waves from All Directions Wave Height (m) Wave Period (seconds) Totals , > 1.0 Totals 476 1, ,848 LASALLE PARK MARINA BREAKWALL EA Extended Boating Season, May 1 - October 15 Average Annual Hours of Occurrence, Waves from All Directions Wave Height (m) Wave Period (seconds) Totals , > 1.0 Totals 571 1, ,315