The Waimakariri riverbed changes in vegetation 1850 - 1982

Abstract

Since settlement of Canterbury in 1850, the vegetation and general appearance of the landscape has been markedly altered through efforts to use the land more intensively. Riverbed land has not been developed as much as adjacent lands because of its floodable, unstable nature and the harsh environmental conditions which prevail.

Distinctive plant communities, which were able to survive in the environmental conditions, existed along the riverbed but these have been altered directly and indirectly by man. This study attempts to discover what changes have occurred to the vegetation along one such Canterbury river and how these changes have come about, whether as direct modification of the riverbed or as effects of land use practices in the surrounding catchment.

The Waimakariri River has played an important role in Canterbury's history. Due to its length from the Southern Alps to the east coast, the river is influenced by different environmental conditions and has experienced various degrees of human impact. It has always been of considerable economical and physical importance to the city of Christchurch, and to large areas of agricultural land. The river provides a continual supply of water to the lowland region (of particular importance during summer), But it also acts as a physical barrier across the plains and has the potential to flood extensive areas with widespread damage. The Waimakariri is distinguished from other Canterbury braided rivers by its tendency to aggrade in the lower reaches, thus increasing the chance of flooding. Since flooding has tended towards the concentrated population of Christchurch, the lower part of the river has been markedly altered by man in an attempt to control it.