Sediment generation, transport, and impacts in the Motueka River

摘要: Decline in the Motueka trout fishery in the mid-1990’s has been linked by some observers to increased input of sediment into the river, mainly from the Separation Point Granite terrain. This is believed to have increased the proportion of the riverbed that is covered in sand and silt and affected trout spawning, food supply, and habitat (such as the density of pools in the catchment). However, there is currently no scientific evidence to support this contention, to determine where the major sediment sources are and whether they are natural or linked to land use practices, or to clearly determine whether other factors may have played a role in the observed decline in trout numbers. In addition, elevated sediment loads may also affect marine ecosystems and aquaculture, and there is a need to understand sediment delivery to Tasman Bay and redistribution within the bay. Further, understanding rates of gravel supply and sediment transport dynamics is fundamental to management of gravel extraction and bank stability within the catchment. This poster outlines the progress we are making to determine the spatial pattern of sediment generation, delivery and transport and its impacts on freshwater and marine habitats.