The UKC is the responsibility of the Ship's Master who must ensure that the vessel remains afloat at all times.It is essential that prior starting a voyage masters aware that their vessels have adequate under keel clearance during all stages of the voyage.
Calculating UKC: while calculating UKC specific factors must be taken into account during voyage planning and recorded prior to proceeding en route:
• Draft observations/calculations including estimates of hogging and sagging
• Increase in draft due to heaving, pitching and rolling motions
• The effects of squat
• Increase in draught due to change of water density
• Minimum charted depth available
• The predicted height of tide (minimum available during planned transit window)
• State of sea and swell
Guided by local knowledge and experience, it may be necessary for the Master to factor in an additional safety margin to make an appropriate allowance for the following variables the accuracy of the hydrographic data (references to reliability are often included on charts) and the vessel’s size and handling characteristics. In addition, changes in the predicted tidal height, caused by wind speed and direction and high or low barometric pressure and the nature and stability of the seabed – i.e. sand waves, siltation, pipelines, obstructions etc.
9Apps 4.9
