The location and orientation of coastal parabolic sand dunes in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Geography at Massey University
No previous research into either the spatial diversity of different coastal sand dune types, or the factors influencing the location and morphology of any particular dune type has been done in New Zealand. Vertical aerial photographs were used to locate Holocene dunefields around the New Zealand coastline. The locations of dunefields in general and the spatial diversity of dune types are able to be explained by identifying the conditions most suitable for sand dune development and examining the spatial variation in these conditions. One particular dune type, parabolic, was examined in more detail in order to discover the relative importance of different variables to the development of that dune type. The relationship between wind climate and the location and morphology of coastal parabolic sand dunes was examined in detail. Wind data from coastal sites around New Zealand were used to compute sand transport vectors using two methods - one proposed by Landsberg (1956) and the other by Fryberger (1979) - and these were compared with dune orientations obtained from aerial photographs. Although Fryberger's method has never previously been applied to coastal sand dunes, the two methods were found to produce very similar results. Spatial variation of other aspects of dune morphology, such as the shape of parabolic dunes, were also compared to wind climate characteristics. Such comparisons were permitted by applying further calculations proposed by Fryberger which allow the directional variablity of wind to be expressed in exact terms. The results of these studies indicate that morphological characteristics of parabolic sand dunes, such as orientation, shape and size, are largely controlled by the strength and frequency of onshore winds and the directional variability of winds. Sand transport resultants computed using the Fryberger method were found to be closely aligned to dune orientations in most cases. This study provides some insight into the processes and variables affecting spatial variation of coastal sand dune development in New Zealand but also highlights the need for more detailed geomorphic studies of coastal dunefields in New Zealand.