IALA Risk Management Tool The IWRAP Model

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IALA Risk Management ToolThe IWRAP Model

• Mr. Ian Gillis
• Risk Assessment Officer
• Canadian Coast Guard

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The IWRAP Model

• Comprises
• 1. Means to determine the minimum safe channel
  width for vessels taking into account aids to
  navigation and the effects of wind and current.
• Probability equations based on vessel track
  information and its distribution
• 3. Under Keel Clearance assessment based on depth
  of channel, ships draught, speed and squat.

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Calculation of Minimum Safe Channel Width

• The minimum safe channel width is based on
• Quality of position from the mix of aids to
  navigation provided (CCG Marine Aids Study)
• Channel geophysical conditions (PIANC)
• Vessel size (PIANC)
• Angle of turn (PIANC)

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Selection of Aids to Navigation
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Derivation of the Effects of Wind and Current
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The basis for assessment of the minimum safe
channel width
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Channel Width Ratio

• A ratio is developed using the calculated minimum
  channel width and the actual channel width.
• If the ratio is greater than 1.0 then the channel
  is considered to be adequate
• If the ratio is less than 1.0 then the Mariner
  should proceed with a heightened degree of
  awareness

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Development of Probability Equations

• Actual vessel track information is gathered
• A histogram is built based on the track
  information
• The distribution of the vessel tracks are then
  quantified in terms of the Standard Deviation
  (STD)

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Collection of Vessel Traffic information Fehmarn
Belt Eastbound
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Histogram of Vessel Traffic information Fehmarn
Belt Eastbound
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Probability equation for Collisions

• Probability of collision
• Pcol Pc x Na
• Pc Causation Factor
• Constant derived from Dr. Fujiis work
• Meetings per year (Na)

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IWRAP Output information
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Flexibility of the IWRAP model

• Any changes to
• Aids to Navigation,
• Vessels size or speed, Traffic volume,
• Channel width or length,
• Wind or current
• Are reflected instantly in
• the output information.