Following an earthquake on 18 June 1994, a large slip partially blocked the Bealey River in Arthur's Pass National Park, South Island, New Zealand, and introduced a large quantity of silt and terrestrial organic matter into the river. The effects of this slip, and in particular the effects of increased sediment loads, on the biota of the river were monitored to assess likely effects of proposed road construction works in the area.
Impacts of the increased sedimentation appear to be short lived and unlikely to disrupt the ecosystem very much. Other rivers of a similar, or greater, size that drain catchments in high rainfall areas like the Southern Alps, are likely to show similar reactions to natural sedimentation episodes.
Proposed road works alongside the Bealey River are expected to increase sediment inputs, and have the potential to affect aquatic biota. These impacts, however, are greatly reduced by the frequent rainfall and associated flood events which quickly remove silt from the river, and thus minimise the build-up of fine sediments.
Keywords: alpine, biota, construction, ecosystem, environment, fauna, hydrology, invertebrates, land slip, New Zealand, periphyton, sediment, river, road