Development on large scale foliation-controlled landslides in the Wakatipu Basin

Geotechnical engineering in the Wakatipu Basin is unique, with the area posing a variety of geomorphological environments where practitioners need to thoroughly understand the geological history and genesis to provide robust engineering solutions. Glacial processes and waning of the last glacial maxima have resulted in a spectrum of terrains, from flat benign terraces to undercutting of schist bedrock cliffs, and everything in between. The region has undergone unprecedented urban growth where geotechnically simple sites are becoming limited. Continued pressure for development has led to expansion into more geotechnically challenging terrain.

This paper focuses the Coronet Peak Landslide Complex (CPLC) which extends from Arthurs Point towards Arrowtown. It is an example of regional dip-slope foliation induced landslides which typify the southern slopes of the Wakatipu Basin. These macro-scale landslides are initiated by glacial de-buttressing during and prior to the last glacial maxima (~20,000 years ago). The CPLC surface geomorphology is dominated by hummocky terrain with a series of secondary reactivations. Typical landslide geomorphology is prominently observed on the slopes of Mt Dewar (Figure 1), with multiple foliation landslide scarps observed at the crest of Mt Dewar. The CPLC has been subject to various studies since the 1990’s and is widely considered suitable for development with no significant global movement observed within recent records.