NAVIGATION TRAINING

1
NAVIGATION TRAINING Section 10 Currents and Waves
2
Table of Contents

• Section 1 Types of Navigation
• Section 2 Terrestial Coordinates
• Section 3 Charts
• Section 4 Compass
• Section 5 Nautical Publications
• Section 6 Navigational Aids

3
Table of Contents

• Section 7 Buoyage
• Section 8 Position Lines and Fixes
• Section 9 Tides
• Section 10 Currents
• Section 11 Weather

4
Ocean Currents
5
Ocean Currents

• Giant patterns of rotation gyres in each of the
  major ocean basins.
• Caused by natural effects salinity, temperature,
  the Coriolis Effect, etc.
• Described in the Sailing Directions
• Examples are the Gulf Stream, the Kuro Shio and
  the Owa Shio

6
Ocean Currents
7
Ocean Currents
8
Tidal Currents
9
Tidal Currents
10
Tidal Currents

• Caused by the rise and fall of tides in coastal
  waters.
• Speed and timing is dependent upon whether it is
  spring or neap tides, and the shape of the coast
  and the sea floor.

11
Tidal Currents
12
Relationship of Terms

• Flood Current
• A tidal current that flows towards shore (follows
  a low tide).

13
Relationship of Terms

• Ebb Current
• A tidal current that flows away from shore
  (follows a high tide).

14
Relationship of Terms

• Slack Water
• A period where there is no horizontal movement of
  water. Corresponds to the stand of the tide.

15
Set and Drift

• Set the direction of the current pushing
  normally expressed in oT.
• Drift the speed of the water, normally
  expressed in knots.
• Set and drift combined describe the current.

16
Waves
17
Waves

• If the wind is blowing from the water onto the
  land they are onshore winds. This causes waves to
  break a little earlier, thus pushing them over.

18
Waves

• If the wind blows from the land out to sea, they
  are offshore winds. They blow against the
  incoming swell and sustain the waves from
  breaking while they jack up a little higher and
  steeper before they break.

19
Water Temperature

• Water temperatures off Vancouver Island vary
  between the high 40s F in the winter and the low
  70's in the height of the summer, whilst
  temperatures in the inland waters can be a little
  cooler, some only getting up to only 55F.

20
Swell
21
Swell

• Most of the swells on the British Columbia coast
  are generated by storms that start in the
  Aleutians and spin down the coast of North
  America all fall and winter.
• They get dragged onto the continent by the jet
  stream anywhere from Alaska to California.

22
Swell
23
Swell

• This forces the water up and sort of trips the
  wave and it breaks, the top of the wave falls
  down in front of itself.
• Here in BC the storms fire swell at us over a
  shorter distance. As a result, because our
  beaches slope gradually, our surfing waves are
  comparatively scaled down in size and power.

24
Rip Currents
25
Rip Currents

• A Rip Current is a current of water flowing out
  to sea.
• Rips form when waves push large volumes of water
  onto the shore and the water returns seaward
  thorough channels between sand bars, behind
  islands and around rocky headlands.

26
Rip Currents

• On a sea coast, they can be identified by a line
  of discoloured water, foam and debris floating
  seaward or an area on choppy or confused water in
  the swell.

27
Rip Currents
28
Local Knowledge

• In all outings on the water, observe local
  currents and waves, what direction they flow at
  what times, where the areas.
• This will assist in
• 1. Plotting the best course in certain weathers.
• 2. Knowing where floating objects might end up
  going ashore under the effects of the current.