Browsing by Author "Morris, Brian C."

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    Differing Levels of Forestry Best Management Practices at Stream Crossing Structures Affect Sediment Delivery and Installation Costs
    Morris, Brian C.; Bolding, M. Chad; Aust, W. Michael; McGuire, Kevin J.; Schilling, Erik B.; Sullivan, Jay (MDPI, 2016-03-10)
    Forestry best management practices (BMPs) are used to reduce sedimentation from forest streamcrossings. Three BMP treatments (BMP, BMP-std, and BMP+) were applied to three forest road stream crossings (bridge, culvert, and ford). BMP did not meet existing BMP guidelines, BMP-std met standard recommendations, and BMP+ treatments exceeded recommendations. Following BMP applications, three simulated rainfall intensities (low, medium, and high) were applied in order to evaluate sediment delivery from crossing type and BMP level. During rainfall simulation, sediment concentrations (mg/L) were collected with automated samplers and discharge (L/s) was estimated to calculate total sediment loading. Costs of stream crossings and BMP levels were also quantified. Mean sediment associated with the three stream crossings were 3.38, 1.87, and 0.64 Mg for the BMP, BMP-std, and BMP+ levels, respectively. Ford, culvert, and bridge crossings produced 13.04, 12.95, and 0.17 Mg of sediment during construction, respectively. BMP enhancement was more critical for sediment control at the culvert and ford crossings than at the bridge. Respective costs for BMP , BMP-std, and BMP+ levels were $5,368, $5,658, and $5,858 for the bridge; $3,568, $4,166 and $4,595 for the culvert; and $180, $420 and $1,903 for the ford. Costs and sediment values suggest that current standard BMP levels effectively reduce stream sediment while minimizing costs.
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    Effectiveness, cost, and implications of forest haul road stream crossing structures and best management practices in Virginia
    Morris, Brian C. (Virginia Tech, 2015-07-06)
    Forest roads and stream crossings have the potential to be sources of sediment from forest operations. Recent litigation has renewed interest in furthering research related to forest road Best Management Practices (BMPs). Three legacy (100 year old) forest road stream crossings were monitored for suspended sediment for nine months before and six months after upgrading three unimproved ford crossings with one bridge, one culvert, and one improved ford. During construction, rainfall simulation was utilized to estimate the sediment contribution of each crossing with minimal BMPs (BMP-), BMPs equal to state recommendations (BMP), and BMPs beyond state recommendations (BMP+). Construction costs were recorded to quantify the change in cost with a change in BMP level. Three levels of rainfall simulation were used on each BMP treatment for each crossing resulting in 27 rainfall simulations. Water samples collected by an automatic sampler downstream of the crossings were analyzed for suspended sediment. Pre - and post- construction time periods were compared to assess how the improved crossings altered total suspended sediment concentrations downstream of the crossings. The number of stream crossings constructed per year in Virginia was also estimated using satellite imagery on 400 harvest tracts. Site visits were conducted on 240 harvest tracts where data were collected on the presence of crossings, the types of crossings, and the level of BMP implementation. Rainfall simulation experiments showed decreased sediment with increased BMP level and daily total suspended sediment concentrations measured over 15 months showed a decrease in mean daily sediment concentration after construction of the bridge and culvert crossings. There was no decrease in sediment concentration for the ford crossing. Statewide crossing construction and BMP implementation rates were estimated. Approximately 67% of the audited stream crossings were characterized as having BMPs that were equal to or beyond state recommendations. Increased BMPs and upgrading of stream crossings resulted in decreased total suspended sediment. However, increased BMP implementation also increased stream crossing construction costs. Effectiveness of increased levels of BMPs and the pre and post construction analysis suggests the improvement of a legacy stream crossing may reduce total suspended sediment concentrations.