Wind wave characteristics at Lake Dunstan, South Island, New Zealand

Information on wave statistics, seasonal characteristics, and their distrib ution about lacustrine shorelines is virtually non-existent. The absence of such data limits the effective management of lake shores where issues of s horeline erosion are no less significant than on open ocean coasts. Results from instrumentally measured waves during seven storm events in 1995 are p resented for the Clutha Arm of Lake Dunstan, South Island, New Zealand. The significant wave height ranged from 0.07 to 0.57 m with a mean of 0.28 m, whereas the maximum wave reached 1.05 m. Peak spectral wave periods ranged from 1.7 to 3.6 s with a mean of 2.46 s. The largest and most destructive w aves are observed along the southern shore of the Clutha arm where fetch le ngths are at their maximum. These waves exhibit the longest and widest rang e of periods and are generally the steepest waves, making them highly erosi onal at the shore. Correlations of waves with those predicted by NARFET, a deepwater wave-hindcasting computer model, revealed reasonable predictions of the wave height (R = 0.77-0.81), particularly for sites exposed to longe r fetches, while the correlations with the wave period were lower (R = 0.56 -0.69). Wave hindcasting indicates that the wave regime in the Clutha Arm i s hi-directional, with most waves arriving from the north or south. Finding s from Lake Dunstan have important implications for larger lakes located th roughout New Zealand, where considerably larger waves can be expected to oc cur during severe storm events.