Abstract:
In Sri Lanka, nearshore wave climate is influenced by the simultaneous occurrence of
swell waves approaching from a more or less southerly direction and sea waves
mainly influenced by monsoonal weather pattern. Some nearshore areas are also
vulnerable for occasional impact of cyclonic wave conditions. This complexity and
high degree of temporal and spatial variability of waves clearly emphasize the need
for accurate assessment of nearshore wave climate.
The lack of wave recordings at nearshore location restricts the assessment of
nearshore wave climate to some extent. This deficiency in wave data can be overcome
by transforming waves from location at which wave data are available through wave
propagation modelling. This research study is aimed to develop two dimensional
mathematical model based on an irregular wave description capable of simulating
wave propagation from offshore to nearshore considering wave transformations due to
shoaling, refraction , wave breaking and bottom friction dissipation. The wave
conservation equation and the model of Battjes and Janssen were used as the basis to
develop the model.
Galle (70m depth) is considered as offshore location which represents the entire deep
water wave climate off the southern offshore coast. Hambantota (17m depth) and
Kudawella (15m depth) were selected as nearshore locations to establish the
directional wave statistics for swell and sea waves by applying the developed
mathematical model.
Finally based on obtained nearshore wave data base, predictions for extreme wave
conditions were made as design wave parameters for coastal and harbour structures.
Extreme wave heights analysis were done for both offshore and nearshore locations in
southern coast of Sri Lanka using two statistical extreme value probability
distributions, namely Gumbel (Fischer-Tippet Type 1) distribution and the Weibull
distribution
