Beach cusp morphology on sand and mixed sand and gravel beaches, South Island, New Zealand

The morphology of beach cusps on a number of beaches around the South Islan d, New Zealand is described. Cusp dimensions such as spacing, elevation, am plitude, depth, and spacing variance are interrelated. Cusp dimensions co-v ary in regular fashion under different process conditions, such that the cu sp form displays a high degree of regularity. Beach cusp amplitude is an ex ception to this regularity, that appears to be controlled by factors such a s grain size and beach slope. Analysis of cusp spacing and elevation dimens ions on mixed sand and gravel beaches reveal that cusps having particular s pacings form at distinct elevations on the beachface, with the largest spac ings occurring at the highest levels on the beachface. The relationship bet ween cusp elevation and spacing provides a technique through which beach cu sp spacing can be used to infer mean sea-level. (C) 1999 Elsevier Science B .V. All rights reserved.