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• We examine eight steep slope forested headwater catchments (15–100 ha). • Bedload organic carbon (OC), soil carbon and dissolved OC was measured. • OC in the bedload was found to be significantly related to catchment area. • Dissolved OC export in stream water declined with catchment area. • There was no difference in OC export from the harvested and non-harvest catchments. Qualitative and quantitative understandings of the origin, transport and fate of organic carbon (OC) in forest systems is needed to advance our understanding of biogeochemical cycling as well as catchment management and forest harvesting. Here we present the findings from eight steep slope forested catchments dominated by headwater streams (size range 15–100 ha) in south eastern Australia where bedload, organic carbon in bedload, hillslope soil carbon together with dissolved organic carbon has been measured over multiple years. OC in the bedload was found to be significantly related to catchment area (p < 0.02). Dissolved organic carbon export in stream water declined with catchment area. Combined bedload organic carbon and dissolved organic carbon export was significantly related to catchment area. There was no significant difference between hillslope soil organic carbon and bedload organic carbon concentration. When corrected for area, OC export by bedload was not significantly different to that of dissolved OC export. Using the environmental tracer 137Cs it was found that there was no significant difference in tracer concentration between bedload and hillslope soil. This suggests a direct link between hillslope and channel and delivery of organic carbon to the channel. Of the eight catchments examined here, six had been harvested for timber in previous decades (with area of forest removed ranging from 25 to 60%) while two catchments had minimal disturbance (Control catchments- no harvest). There was no difference in organic carbon export from the harvested and Control catchments. The results demonstrate that although land disturbance had previously occurred the management practices employed in each catchment were effective in the long term. [ABSTRACT FROM AUTHOR]

The article discusses the bedload transport data from planebed and step pool reach types that are used to find out the grain size transport thresholds for chosen upland streams in southeast Australia. Structural deviation between the reach types let the effects of frictional losses from bedforms, microtopography and bed packing to be incorporated into the dimensionless critical shear stress value. Also included is a local sediment transport data in a regime model and applied to mountain streams to investigate whether empirical data improve the delineation of reach types on the basis of dimensionless discharge per unit width and dimensionless bedload transport.

Summary: A severe wildfire burnt over 1 million ha of forested land in southeastern Australia in early 2003. Included in the burnt area were two 136 and 244ha hydrologic research catchments in the East Kiewa valley that had been decommissioned following a 10 year study, and an adjacent larger (10,050ha) gauged catchment, the West Kiewa River. The three catchments were re-instrumented to measure discharge and suspended sediment fluxes at 15min timesteps, with additional measurement of bedload at the East Kiewa sites. Analysis of annual rainfall–discharge relationships and of flow duration curves for the first 2 post-fire water years indicated annual flow increases of around 65–75% for Slippery Rock Creek in both post-fire water years and 40% and 76–94% for Springs Creek in 2003–2004 and 2004–2005, respectively. The flow impacts on the less severely burnt West Kiewa River were far more subdued, and did not exceed pre-fire variability in annual flows. Flow duration curve analysis did not indicate changed runoff generating processes at the daily timescale, with the curves shifting upward uniformly over the flow regime. Total sediment exports increased by factors of 8–9 (up to 2.96tha−1 yr−1) from the East Kiewa catchments in year 1 after the fire, diminishing to a 2–4-fold increase in year 2. Flow increases accounted for much of the year 2 exports as suspended sediment concentrations decreased toward pre-fire levels. Post-fire suspended load exports from the larger West Kiewa catchment were much lower per unit area, probably reflecting the smaller area of high intensity burn, less intensive burning of riparian areas and possible scale effects. The results were observed under near-average rainfall conditions, with the exception of one short duration high intensity storm that produced almost 50% of the combined sediment loads from the East Kiewa catchments. [Copyright &y& Elsevier]