Design wave estimation considering directional distribution of waves

The design of coastal and offshore structures requires design significant wave height having a certain return period. The commonly followed procedure to estimate the design wave height, does not give any consideration to the directions of waves approaching a site. Based on available one year measured data for three locations along the Indian coast and 18 years ship reported data for regions covering locations 1 and 3, the design wave height was estimated based on the method taking into account the directional distribution of H s. The conventionally obtained omni-directional 100-year design H s value was found to be marginally lower with a reduction factor of 4.6% at 23 m water depth and 0.5% at 15 m water depth when recalculated using directional H s distribution as basis.