Suspended sediment and turbidity after road construction/improvement and forest harvest in streams of the Trask River Watershed Study, Oregon

Abstract

Transport of fine‐grained sediment from unpaved forest roads into streams is a concern due to the potential negative effects of additional suspended sediment on aquatic ecosystems. Here we compared turbidity and suspended sediment concentration (SSC) dynamics in five nonfish bearing coastal Oregon streams above and below road crossings, during three consecutive time periods (“before”, “after road construction/improvement”, and “after forest harvest and hauling”). We hypothesized that the combined effects of road construction/improvement and the hauling following forest harvest would increase turbidity and SSC in these streams. We tested whether the differences between paired samples from above and below road crossing exceeded various biological thresholds, using literature values of biological responses to increases in SSC and turbidity. Overall, we found minimal increases of both turbidity and SSC after road improvement, forest harvest, and hauling. Because flow is often used as a surrogate for turbidity or SSC we examined these relationships using data from locations above road crossings that were unaffected by roads or forest harvest and hauling. In addition, we examined the association between turbidity and SSC for these background locations. We found a positive, but in some cases weak association between flow and turbidity, and between flow and SSC; the relationship between turbidity and SSC was more robust, but also inconsistent among sites over time. In these low order streams, the concentrations and transport of suspended sediment seems to be highly influenced by the variability of local conditions. Our study provides an expanded understanding of current forest road management practice effects on fine‐grained sediment in streams and introduces alternative metrics using multiple thresholds to evaluate potential indicators of biological relevance.

Stream Mercury Export in Response to Contemporary Timber Harvesting Methods (Pacific Coastal Mountains, Oregon, USA)

“…The lack of increase in stream particulate THg and MeHg or TSS concentrations in clear-cut catchments is in contrast to what has been observed in other studies, where logging has been shown to increase catchment erosion and suspended sediment concentrations. , The absence of a response of these parameters in our study may result from the forestry BMPs that were used to reduce erosion, such as limiting new road construction, effective use of road prism drainage techniques, using cable logging where the felled trees are moved across the site suspended by a cable, and the practice of leaving a thick layer of slash materials covering the soil after harvesting. , These BMPs are widely utilized as part of forestry operations in the US and elsewhere; however, it is also not uncommon for slash to be removed or burned on-site. The removal of woody biomass, including stump harvesting, has gained interest in recent years for use as a renewable fuel or other products. , As such, the results from our study are believed to be representative of commonly applied contemporary forestry techniques; however, forestry operations not utilizing these BMPs may have larger influence on Hg mobilization and other water quality end points.…”

“…41,54 The absence of a response of these parameters in our study may result from the forestry BMPs that were used to reduce erosion, such as limiting new road construction, effective use of road prism drainage techniques, using cable logging where the felled trees are moved across the site suspended by a cable, and the practice of leaving a thick layer of slash materials covering the soil after harvesting. 42,55 These BMPs are widely utilized as part of forestry operations in the US and elsewhere; however, it is also not uncommon for slash to be removed or burned on-site. The removal of woody biomass, including stump harvesting, has gained interest in recent years for use as a renewable fuel or other products.…”

A Field-Based Experiment on the Influence of Stand Density Reduction on Watershed Processes at the Caspar Creek Experimental Watersheds in Northern California

“…As a result, current forest management has been designed to mitigate sediment delivery and minimize negative effects on aquatic and riparian ecosystems. Sediment delivery to streams under contemporary forest management can be very different from what was documented in past studies of historical management practices (Loehle et al, 2014;Arismendi et al, 2017). However, little is known about the consistency of fine sediment transport among neighboring watersheds, leaving questions about how sediment transport in streams varies spatially and temporally under contemporary forest management.…”

Comparative Study of Water Quality Parameters along NH, SH and Link Road of Shivalik Foothills in Himachal Pradesh

“…5 Furthermore, recent increases in urbanization and industrialization, in order to meet the requirements of an ever-growing population, have resulted in an increasing pace of constructional activities, which has had a significant negative impact on the water quality of many natural water bodies. 6 The current study aims to characterize the impact of road operations on local surface water sources, as well as to evaluate the impact of spatial variation associated with road pollutants on water quality and to investigate the relationship between various water quality parameters and seasons. The investigation's findings contributed in determining the extent to which water quality has deteriorated as a result of vehicular emission and other activities on road.…”