The effects of roading, harvesting and forest regeneration on streamwater turbidity levels in a moist eucalypt forest

Turbidity levels were measured in streamwater leaving eight small previousl y undisturbed eucalypt catchments near Dungog, NSW over seven pre-treatment and eight post-treatment years. Permanent roads were constructed in four o f these catchments prior to harvesting in 1983. The construction and use of permanent roads resulted in increased turbidity levels, but these increase s only persisted in the catchment containing a number of stream crossings. This result suggested that road-stream connectivity was the most important factor in sediment delivery in roaded catchments. Harvesting in the absence of roads generally reduced turbidity levels. This was possibly due to the effectiveness of the best management practices employed, and to the rapid a nd extensive revegetation of catchments after treatment. This revegetation by numerous pioneer ground cover species and eucalypts appeared to provide much better protection to the catchment surface from raindrop impact than t he previous old-growth forest. The range of site disturbances associated wi th the catchment treatments did not individually affect turbidity levels, b eing overshadowed by roading and regeneration influences. (C) 2001 Elsevier Science B.V. All rights reserved.