Research

Current work: Erosion sources and sediment pathways to streams associated with forest harvesting activities in New Zealand

The objectives of the study are to: 1) Quantify the spatial frequency of concentrated surface runoff and/or sediment to the stream (aka ‘breakthroughs’); 2) Identify common causes of breakthroughs; 3) Evaluate the geomorphic characteristics of areas that do and do not contribute sediment; and 4) Suggest BMP improvements to reduce connectivity between erosion sources and streams

Since the project began in Feb. 2016, stream channels associated with 17 recently harvested areas in Canterbury, Otago, and Southland have been surveyed for breakthroughs.  In total, 18 km of stream channel have been surveyed in association with 442 harvested hectares and 65 breakthroughs have been found.  Ground-based harvesting was associated with a higher spatial frequency of breakthroughs than cable-logging (i.e., 5.5 versus 1.5 breakthroughs per km of stream).  Ground-based harvesting is typically associated with increased ground disturbance in the form of bladed skid trails and extraction tracks.  In addition, 61% of breakthroughs were associated with forest roads (including road-stream crossings), skid trails, and vehicle tracking.

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Evidence of a sediment breakthrough resulting from ditch runoff at a road-stream crossing. 23% of breakthroughs were associated with stream crossing approaches.

Forest road management to protect water quality (Ph.D. dissertation):

Brown, K.R., Aust, W.M., and McGuire, K.J., 2013. Sediment delivery from bare and graveled forest road stream crossing approaches in the Virginia Piedmont. For. Ecol. Manage. 310: 836-846. DOI: 10.1016/j.foreco.2013.09.031.

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We used sediment traps to quantify annual sediment delivery rates associated with reopening legacy forest roads at stream crossings in the Piedmont Physiographic Region of southwestern Virginia, USA.  We compared these rates of sediment delivery with those of completely graveled stream crossing approaches (Brown et al. 2013).  Finally, we used field measurements of sediment delivery to evaluate model predictions by the Universal Soil Loss Equation modified for forested land (USLE-forest) and the Water Erosion Prediction Project (WEPP).

Brown, K.R., McGuire, K.J., Aust, W.M., Hession, W.C., and Dolloff, C.A., 2014. The effect of increasing gravel cover on forest roads for reduced sediment delivery to stream crossings. Hydrol. Process. DOI: 10.1002/hyp.10232

Brown, K.R., McGuire, K.J., Hession, W.C., and Aust, W.M., 2015. Can the Water Erosion Prediction Project (WEPP) model be used to evaluate BMP effectiveness from forest roads? (Accepted Jan. 2015). J. For.

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We conducted 58 rainfall simulation experiments to quantify event-based surface runoff and sediment yield from forest roads at stream crossings and to evaluate the sediment-reduction efficacy of different intensities of BMP implementations (i.e. different proportions of gravel surface cover).  We also estimated the cost of the different gravel treatments (Brown et al. 2014).  We used field measurements from the rainfall experiments (i.e., event-based total rainfall, total runoff, and total sediment yield) to evaluate WEPP model predictions of runoff and sediment yield, as well as uncertainty associated with model parameterization, and the model’s ability to distinguish between the different gravel treatments (Brown et al. 2015).

Nolan, L., Aust, W.M., Barrett, S.M., Bolding, M.C., Brown, K.R., and McGuire, K.J., 2015. Estimating costs and effectiveness of upgrades in forestry best management practices for stream crossings. Water. 7, 6946-6966. DOI: 10.3390/w7126668

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In Summer 2014, I assisted Lindsey Nolan (Master of Forestry Student) in evaluating BMP implementations at 43 forest stream crossings in the Piedmont Physiographic Region of southern Virginia.  Stream crossing BMPs were evaluated based on the following tools: 1) Virginia Dept. of Forestry’s BMP Audit spreadsheet for roads, skid trails, stream crossings, and streamside management zones; 2) a third-party audit that evaluated the implementation and functioning of water control structures, surface cover techniques, road profiling, and the adequacy of stream crossing structures; and 3) USLE-forest estimates of soil erosion.  Potential water quality problems were identified, and where applicable, improved stream crossing BMPs were proposed.  We then estimated the sediment-reduction efficacy and costs associated with the improved BMPs to quantify cost-benefit ratios.  This research will help the forest industry in Virginia to control sediment delivery associated with skid trail and haul road crossings with BMPs that are readily available and affordable (Nolan et al. 2015).

Evaluating timber harvesting BMP effects on streamflow and suspended sediment concentration (M.S. thesis):

We used a before-after-control-impact (BACI) design to evaluate the effects of timber harvesting BMPs on streamflow and sediment yield in low-gradient forested headwater streams of north-central Louisiana, USA.  My thesis research was part of a larger project to evaluate Louisiana’s contemporary harvesting BMPs with regard to hydrology, water quality, and benthic macroinvertebrates.

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