High country river processes : a technical discussion of results from research on the Kowai River system, Springfield, Canterbury

Abstract

A sub-catchment (Torlesse Stream) of the Kowai River, Canterbury, has been the site of an interdisciplinary study of the relationships between erosion and stream sedimentation (Hayward 1975). It was logical to extend the stream sediment investigation of that study (Hayward 1978) into the Kowai system proper in order to establish changes in the nature and distribution of the stream sediments with distance downstream.

The sediment sampling study, comprising Part I of Paper A in this volume, analyses the changes in size, distribution, form and rock type of the river gravels from ahead water mountain stream to the wide braided river beds of the middle reaches of the Kowai River. Part 2 of Paper A discusses the possible implications for the management that these sediment studies have for this and other similar river systems. It is believed that if thought necessary it is possible to design a river training programme to guide the river towards a more manageable pattern.

Paper B of this volume compares the results of the present river gravel survey with those from a sedimentological analysis of fluvio-glacial outwash gravels deposited several thousand years ago within the lower reaches of the Kowai system. This comparative study is used to indicate differences in the hydrologic environment prevailing at their respective times of deposition, and aids in our understanding of the processes at work in hill and high country rivers today.

Both Papers A and B relate to the Kowai River system, but the authors wish to emphasise that the findings from these studies are believed to have application to other similar gravel bed river systems.