Stream bed sedimentation - observed cover at fish monitoring sites

Fine sediment is the collective term for inorganic particles smaller than 2mm that are deposited on the beds of rivers and streams. Urban development, agriculture, and plantation forestry around waterways can increase the amount of sediment entering river systems. Sediment can clog the spaces between pebbles used by aquatic insects and fish, and degrade food sources and sites used for egg laying. Excessive sedimentation can also affect the suitability of rivers and streams for recreation.

Stream bed sediment observations are visual estimates of the proportion of the river bed covered by fine sediment. This information was collected during fish surveys, and stored in the Freshwater Fish database managed by NIWA. Observed in-stream sediment values for 10,025 sites are provided, dating from 1990 to 2011 in order to represent contemporary cover. The exception to this date range is the Fiordland area where all available information (1970 to 2011) was used to fill a representation gap.

This dataset relates to the "Stream bed sedimentation" measure on the Environmental Indicators, Te taiao Aotearoa website.