calculated for the head and beam seas separately for a wide range of vessel sizes。 The limiting wave heights H5% as well as the significant wave height He were used in the downtime calculations。

Wave climate varies throughout the year resulting in different operational downtime at different months of the year。 Annual downtime assists with the financial feasibility analysis of a new berth whereas a month by month downtime assessment assists with port management such as planning for storage capacity。 Therefore, besides an annual downtime assessment, it was also assessed for each month of the year。

The paper describes a practical technique for preliminary assessment of downtime based on numerical modelling results。 The methodology has been successfully applied to a real project and the results presented in this paper are from this project。 The methodology and lessons learnt from the study would be useful for the development of any sea port or bulk terminal worldwide。

2。Meteorological  Conditions

2。1Bathymetric Conditions

The assessment site is situated between the -12 m and -14 in seabed contour lines。 However, a dredged depth of -17。3 in will be maintained at the berths, in the turning circle and the navigational approach channel。

2。2Offshore  Wind Conditions

Three-hourly time-series wind data for 10。83 years (January 1, 2000 to October 3 1, 2010) were purchased from BMT ARGOSS [2]。 The wind data were analysed using the MIKE2I software developed by DHI [I]。 The wind rose based on the purchased data is shown in Fig。 l 。

Winds blow predominantly from the north-east and south-west sectors with the highest wind speed of 21 mls。 The higher wind speeds are generally from the south-westerly  sector。

2。3Offshore Wave C'oudifions

Three-hourly time-series offshore wave data also purchased from BMT ARGOSS [2]。 The location and the duration of this wave data was the same as for the wind data (Section 2。2)。

The study site is affected by wind-waves (shorter-period waves generated by winds close to the study site) and swell-waves (longer-period waves generated at more remote locations)。 Therefore, both wind-wave and swell-wave data purchased。

Data on resultant-waves (a combination of wind-waves and swell-waves) also purchased to understand the combined wave conditions at the study site。

The offshore wave data also analysed using the MlKE2l software developed by DHI [I]。 The wave roses based on the purchased data are shown in Fig。 2。 Most of the small wind-waves come from the north-easterly direction。 However, larger wind-waves primarily propagate from  the south-easterly to south-westerly sectors, with the south-westerly sector being the more dominant。 The highest wind-waves in the data are from the south-westerly sector。 Most of the swell-waves are from south-westerly directions with the highest waves also from this sector。 The figure

Preliminary Assessment of Operational Downtime of Sea Ports and Berthing Facilities through 119

Numerical Modelling

site is negligible and does not exceed 50 mm。 Water levels at the study site are given in Table l 。

The global sea level rise for various scenarios was extracted from the IPCC (Intergovernmental Panel On Climate Change) [3]。 A sea level rise of 0。5 in has been adopted for the next century。

3。Numerical Modelling of Waves

3。11 Purposes ofNumerical Modelling

Knowledge of the inshore wave conditions is required to assess the downtime of the proposed bulk terminal。 The aim of the numerical modelling was to transfer offshore waves inshore to derive wave conditions at various locations for the proposed bulk terminal。