sediment yield

A Synthesis of the Impacts of Contemporary Forest Practices on Aquatic Ecosystems at a Watershed Scale: A Case Study from Hinkle Creek
Skaugset, A., M. Adams, D. Bateman, K. Cromack, L. Ganio, and B. Gerth

The Hinkle Creek Paired Watershed Study was initiated to carry out two overarching goals: to investigate the environmental impact of contemporary forest practices on non-fish-bearing streams and downstream in tributary and main stem fish-bearing streams. This presentation serves as a summary of some of the results for the studies in Hinkle Creek.  Statistically significant increases in water yield, summer low flows, peak flows, and storm flows were detected as a consequence of timber harvest and the subsequent silvicultural activities. Statistically significant increases in sediment yield were also detected. The increases in sediment yield were not consistent with the literature; however they were highly correlated with the observed increases in water yield. Statistically significant increases and decreases were detected in maximum and minimum daily stream temperatures in the non-fish-bearing tributaries, fish-bearing tributaries, and the main stem as a consequence of the two harvest entries. Statistically significant increases in nitrogen were detected as a consequence of the timber harvest and the subsequent silvicultural activities. Nitrogen was the only nutrient that responded to the silvicultural activities. In Hinkle Creek the pacific giant salamander was the only amphibian that was abundant enough to study. In the two years after the first harvest entry, the data did not support the hypothesis that there was any change in the abundance of salamanders.

DISCIPLINE: Disciplinary Results    STUDY: Hinkle Creek    TYPE: Presentations    TAGS: Paired Watershed, Watershed Hydrology, sediment yield, Stream temperature, Stream Chemistry
Local and Downstream Impacts of Contemporary Forest Practices on Sediment Yield
Skaugset A., N. Zègre, A. Simmons, and H. Owens

The hydrological impacts of forest management remains a primary concern to resources managers yet much of our understanding about these effects comes from historic paired watershed studies conducted up to four decades ago. While these early studies play a critical role in the development of current best management practices and forest harvesting practices, results do not necessarily reflect the effects of modern forest harvesting. In this presentation we show results of a study conducted at the decade-long Hinkle Creek Paired Watershed Study that examines the local and downstream impacts of forest harvesting on streamflow. Streamflow was measured at the outlet of six (4 treatment|2 reference) headwater catchments and two (1 treatment|1 reference) 3rd –order watersheds. Regression-based change detection models were developed between reference and treated catchments using mean monthly streamflow, instantaneous maximum peak flow, and storm quick flow. Contemporary forest harvesting practices, defined by the Oregon Forest Practice Rule, were used to clear-cut harvest trees in four experimental headwater catchments, while reference catchments remained untouched. Forest harvesting treatments were initiated in the experimental headwater catchments in 2005 (1st entry) removing trees from 13% to 65% of catchment area following a fifteen to eighteen month calibration period.

DISCIPLINE: Hydrology & Water Quality    STUDY: Hinkle Creek    TYPE: Presentations    TAGS: sediment yield, contemporary forest practices, Discharge
Local and Downstream Effects of Contemporary Forest Harvesting on Streamflow and Sediment Yield
Zégre, N. P.

This dissertation is a collection of three manuscripts that serve to fill the knowledge gaps and advance methods of detecting the effects of contemporary forest harvesting in experimental catchment studies. The objective of this research was to develop change detection models using time-series records to detect and quantify the effects of forest harvesting on streamflow and sediment yield. To accomplish this, it was necessary to characterize streamflow and sediment processes at a temporal scale capable of describing daily, monthly, and seasonal dynamics following forest harvesting; increase sample sizes used to construct regression-based change detection models; and develop alternative methods to the paired-catchment approach in order to discern changes in streamflow and sediment using highly variable time-series data. The paired-catchment approach was used to detect and quantify relative changes in streamflow and sediment yield in 5 harvested catchments. The ability to detect statistically significant changes at certain time-steps was a function of accounting for all sources of variability in change detection models. In this study, we aimed to develop robust change detection models using time-series data to increase sample size and decrease false/missed detections of true treatment effects.

DISCIPLINE: Hydrology & Water Quality    STUDY: Alsea, Hinkle Creek, Trask    TYPE: Theses    TAGS: forest harvesting, contemporary harvesting practices, detection models, paired-catchment, sediment yield
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