Effectiveness of forestry BMPS for stream crossing sediment reduction using rainfall simulation
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Recent decisions by the United States Supreme Court and United States Environmental Protection Agency (EPA) have re-emphasized the importance of forestry best management practices (BMPs) at stream crossings. Stream crossings are potential major sources of sediment due to their direct connectivity between the potential erosion source and the stream, which eliminates potential sediment reduction provided by filter/buffer strips and stream side management zones. The effectiveness of stream crossing BMPs for sediment control were tested for a permanent bridge crossing, culvert crossing, and improved ford crossing on three first-order streams in the Virginia Piedmont using rainfall simulation. The three crossings were located on a low standard legacy road having unimproved ford crossings before experimentation. All legacy fords received three levels of rainfall intensity via simulation prior to crossing installation. Following crossing installation, rainfall simulations were performed at each of the crossings under the following three treatments: (1) minimal levels of BMP erosion control (Low); followed by (2) installation of BMPs recommended by the Virginia BMP Manual (Medium); and (3) erosion control measures beyond the Virginia BMP Manual (High). Stream sediment (TSS) was monitored upstream and downstream during rainfall simulations to determine total sediment contribution from each individual crossing. The comparison of minimal BMPs, recommended BMPs, and extensive protection provides insight into the erosion associated with the crossing types and the effectiveness of current BMPs for nonpoint source pollution (NPSP) reduction. The Culvert crossing produced a sediment concentration (2.9 g/L) that was double the concentration produced by the Ford crossing (1.4 g/L) and over 10 times the concentration of the Bridge crossing (0.2 g/L).Keywords:
Culvert
Sediment control
Erosion Control
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Nuclear decommissioning
Forest road
Road surface
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Forestry best management practices (BMPs) are used to reduce sedimentation from forest stream crossings. 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.
Culvert
Bridge (graph theory)
Forest road
Sediment control
River management
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Abstract Direct sediment inputs from forest roads at stream crossings are a major concern for water quality and aquatic habitat. Legacy road–stream crossing approaches, or the section of road leading to the stream, may have poor water and grade control upon reopening, thus increasing the potential for negative impacts to water quality. Rainfall simulation experiments were conducted on the entire running surface area associated with six reopened stream crossing approaches in the south‐western Virginia Piedmont physiographic region, USA. Event‐based surface run‐off and associated total suspended solid (TSS) concentrations were compared among a succession of gravel surfacing treatments that represented increasing intensities of best management practice (BMP) implementation. The three treatments were no gravel (10–19% cover), low gravel (34–60% cover), and high gravel (50–99% cover). Increased field hydraulic conductivity was associated with maximized surface cover and ranged from 7.2 to 41.6, 11.9 to 46.3, and 16.0 to 58.6 mm h −1 respectively for the no gravel, low gravel, and high gravel treatments. Median TSS concentration of surface run‐off for the no gravel treatment (2.84 g l −1 ) was greater than low gravel (1.10 g l −1 ) and high gravel (0.82 g l −1 ) by factors of 2.6 and 3.5 respectively. Stream crossing approaches with 90–99% surface cover had TSS concentrations below 1 g l −1 . Reducing the length of road segments that drain directly to the stream can reduce the costs associated with gravel surfacing. This research demonstrates that judicious and low‐cost BMPs can ameliorate poor water control and soil erosion associated with reopening legacy roads. Copyright © 2014 John Wiley & Sons, Ltd.
Forest road
Total suspended solids
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Citations (35)
Urbanization generally leads to increases of impervious surfaces, changes of the natural hydrologic conditions and watershed's response to stormwater runoff. The application of Best Management Practices (BMPs) can provide a solution for on-site management of post-construction stormwater runoff. This study investigated the effectiveness of various BMP alternatives for retaining the first inch of runoff from highways and roads in Illinois with the Personal Computer Stormwater Management Model (PCSWMM) and idealized catchment areas. The modeled scenarios included pre-BMP construction when there is no BMP and post-BMP construction with bioswale, infiltration trench and vegetated filter strip. The effects of vegetated covers such as turf or prairie grass on infiltration of various soil types with and without BMPs were also evaluated. For all scenarios, one-inch rainfall 24-hour accumulated precipitation was applied. Typical dimensions and sizing for BMPs were extracted from Illinois Department of Transportation (IDOT) projects. This study found that runoff reduction for bioswale, infiltration trench, and vegetated filter strip are 70 to 83%; 100%; and 68 to 78%, respectively. Results also showed that prairie grass cover is more effective than turf grass in reducing runoff on various soil types.
Impervious surface
Bioretention
Low-impact development
Infiltration (HVAC)
Swale
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Today, many municipalities are implementing best management practices (BMPs). The most commonly used structural treatment BMPs that will be discussed in the presentation are ponds (detention/retention) and vegetated biofilters (swales and filter/buffer strips). Historically, structural BMPs were employed to capture peak flows, assist in local drainage, and manage the quantity of runoff produced during wet-weather flow (WWF), i.e., flood control. Current design typically still focuses on rainfall events that range from 2 to 10 inches of daily rainfall and occur at much longer return periods ranging from 2- to 100-year storm. These storms may contain significant pollutant loads, but their contribution to the annual average pollutant load is really quite small due to the infrequency of their occurrence. In addition, longer periods of recovery are available to receiving waters between larger storm events allowing receiving water systems to flush themselves and the aquatic environment to recover. Water quality control of urban runoff is still a relatively new and developing area of engineering and science. The addition of water quality considerations in the design of BMPs has introduced a new dimension to the traditional hydrologic considerations for BMP design. Water quality considerations have created a shift from flood events to a continuous long-term rainfall-runoff BMP design volume approach and the pollutant loads associated with these volumes. To treat the bulk of the pollutant loads from stormwater runoff, many states and municipalities specify a treatment volume that is designed to capture the initial component of the stormwater runoff. In practice this is achieved by specifying a rainfall amount (e.g., the first ½-inch or 1-inch) or the capture of a stormwater runoff volume that correlates to a design storm (e.g., 6-month, 1-year, or 2-year frequency storm). BMPs that encompass both peak discharge hydrology and small storm hydrology would optimally use a system that incorporates on-site treatment and storage of stormwater for the smaller storms while protecting downstream from floods. By including supplemental measures using either distributed and/or centralized controls, the peak discharge control strategies can be upgraded to perform water quality control.
Retention basin
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A forested headwater watershed in West Virginia was monitored to examine changes to in-stream turbidity following the construction of a 0.92 km (0.57 mi) haul road. Due to the design of the study, most of the sediment that entered the stream following road construction was known to result from the stream crossings and approaches to the crossings. Stream-water samples collected daily and sequentially during stormflow from 1999 through 2005 were used to interpret the effects of stream-crossing construction on turbidity and suspended-sediment concentrations (SSC). Daily and stormflow turbidity and SSC values increased as a result of the construction. Average sediment loads (kg per storm) and total annualized sediment loads (kg per year) also increased significantly, both by a factor of about 1.8. Sediment delivery to the stream was caused by mechanical introduction of soil during stream-crossing culvert installation and fill-slope construction in the crossing approaches, and by erosion of those areas due to delays in vegetation re-establishment. Inputs from stream-crossing construction affected the overall sediment regime of the stream; the turbidity-discharge hysteresis changed from the normal clockwise pattern to a counter-clockwise pattern for about seven months. As the crossing fills and approach fill slopes became re-vegetated, they stabilized, and annualized sediment loads declined. However, at the end of the study, sediment exports remained above pre-disturbance levels.
Turbidity
Forest road
Culvert
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Citations (19)
Stream crossings for skid trails have high sediment delivery ratios. Forestry Best Management Practices (BMPs) have proven to be effective for erosion control, but few studies have quantified the impact of various levels of BMPs on sedimentation. In this study, three skid-trail stream-crossing BMP treatments were installed on nine operational stream crossings (three replications) to evaluate the degree of sediment control associated with the different treatments. Treatments were: (1) slash, (2) mulch, and (3) mulch plus silt fence. Upstream and downstream water samples were collected daily at the stream crossings for 1 year following BMP installation. Samples were evaluated for total suspended solids. Both slash and mulch treatments applied to the stream crossing approaches after removal of temporary skidder bridges were effective at reducing the amount of sediment entering the stream after harvest. The mulch plus silt-fence treatment was the most expensive treatment, yet it allowed more sediment to enter the stream at the approach due to silt-fence installation disturbances. Thus BMP related disturbances should be minimized adjacent to a stream bank.
Sediment control
Silt
Erosion Control
Slash (logging)
Fence (mathematics)
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Abstract : The effectiveness of the Richland County Sediment and Erosion Control Ordnance is evaluated primarily through documentation of erosion and sediment response to suburban housing development. The Universal Soil Loss Equation (USLE) and the Modified Universal Soil Loss Equation (MUSLE) are used to predict soil erosion and sediment yield, respectively. Suspended sediment concentrations were monitored for three storms to test and compare the accuracy of predicted sediment yields. Stream channel cross-section surveys reveal aggradation and sediment storage in channels, but channel dredging during this study prevented accurate determination of storage volumes. Housing and road construction disrupts the natural erosion resistance and can accelerate erosion and delivery to channel systems. The primary objectives of this ordnance are to (1) insure that drainage channels remain clear of obstruction to storm water runoff, (2) control water pollution of streams and drainage channels by urban water runoff, and (3) prevent the encroachment into natural drainage channels by buildings or land improvements. Rapid soil erosion occurs during summer months when rainfall is intense. It is also during these months that construction activity is at it's highest peak. The quantity of sediment produced from construction areas has been shown to be from 2 to 200 times greater than for areas in a rural or wooded condition.
Dredging
Erosion Control
Sediment control
WEPP
Aggradation
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The Center for Dirt and Gravel Road Studies at Penn State University has been working to reduce sediment pollution generated by unpaved roads in Pennsylvania for over a decade. Runoff from unpaved roads is a large source of sediment pollution in many forested watersheds. The Allegheny Nation Forest, located in Northwestern Pennsylvania, has over 1,695 miles of unpaved access roads that serve the shallow oil wells in the Forest (USDA-FS unpublished, 2010a). The purpose of this study was to quantify sediment generation rates from these oil access roads in the Allegheny National Forest. In addition, the objective of phase II of the study was to determine differences in sediment production after new aggregate had been placed on 4 of the sites. The experimental approach taken in this study was to use a rainfall simulation device to create a repeatable rainfall event and collect sediment load data. The rainfall simulator was used to collect sediment in road runoff on 14 sites, each of which was 100’ in length. The simulated rainfall event was 0.61” in 30 minutes which has a return interval of slightly less than 2 months. The 14 sites tested showed sediment productions ranging from 3.2 to 60 pounds of sediment for each 30 minute simulated rain event. The average sediment runoff from the sites was 24.7 pounds, which equates to a sediment production rate of 1,300 pounds per mile for each 30 minute simulated rain event. Extrapolation of these results indicates that a single storm of similar intensity and duration to the design storm could be expected to produce over 1,100 tons of sediment from the oil access roads in the Allegheny National Forest. An estimated 385 tons of that sediment can be expected to enter directly into nearby streams during each storm. The study also identified a significant ‘first flush’ effect on the road segments studied. Additionally, road segments that received more traffic have been more compacted and exhibit higher structural strengths. Without traffic stress, the best indicators of sediment production from the roads tested were road slope combined with road width. If the road is stressed by traffic, then sediment production becomes less dependent on road width and slope, and more dependent on road strength as measured by the California Bearing Ratio. Finally it was observed that sediment generation would be greatly reduced from roads with very low usage by establishing vegetative cover on the road surface. After initial testing, 4 of the 14 sites were surface with new aggregate material. Two sites were surface with local “pit run” material as is standard procedure. Two of the sites were surfaced with Driving Surface Aggregate. The 4 sites were then tested a year later to determine sediment production. All four sites showd reductions in sediment production (39% and 65% for pit-run, 67% and 65% for DSA). The two pit-run sits averaged ten times as much sediment production as the DSA sites (26.1 lbs versus 2.5 pounds).
Dirt
Sediment control
Sedimentary budget
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Road runoff treatment is a challenge due to lack of space in the right of way. Therefore, it is imperative to understand the quality of runoff from roadways so that efficient stormwater control measures (SCMs) may be designed. In terms of TSS control, the particle size distribution of sediment in the runoff controls the amount of sediment (based on Stokes' Law) that may be removed through settling in a typical SCM. For best treatment of TSS, the flow depth in vegetated SCMs during the design storm should be limited to the height of the vegetation. Typical roadside stormwater controls (vegetated filter strips and swales) could be designed for water quality by calculating a hydraulic retention time for a particular removal of sediment. To do so, an understanding of average particle size distributions (PSDs) was needed for roads across North Carolina (NC). A field-monitoring study was conducted during May-November 2012 to obtain PSDs from roads in the three ecoregions of NC: mountains, piedmont, and coastal plain. Two sites in the mountains, six in the piedmont, and four in the coastal plain were monitored for TSS concentrations and PSDs for a minimum of six storms apiece. Roadway types were distributed across Interstate highways (six sites), four lane divided highways (one site), four lane primary roads (three sites), and secondary roads (two sites) to determine the effects that annual average daily traffic have on runoff PSDs. At the Interstate highway sites, two monitoring locations had a permeable friction course (PFC) overlay and one site had a NovaChip overlay, which may modify the expected PSD from a highway. Because nutrients are a concern in NC, nutrient concentrations (TN and TP) were monitored at four sites both in the stormwater and sorbed to the sediment. This will allow for modelling of nutrient removal performance for typical roadway SCMs by estimation of TSS removal from Stokes' Law. Gross solids (trash, debris, and particles greater than 5 mm in diameter) are often overlooked in loading of nutrients to waterways. Automated stormwater samplers are not able to capture most gross solids, and total maximum daily loads (TMDLs) for these pollutants have been established for some watersheds. Monitoring for gross solids was undertaken at four sites: one in the mountains, two in the piedmont, and one in the coastal plain. Three sites were Interstate highways while one was a divided four lane highway. Dry mass of gross solids and nitrogen and phosphorus content were determined in the laboratory. It was determined that gross solids are a substantial portion of the nutrient load, and that they cannot be disregarded in stormwater sampling for nutrient load estimation.
Settling
Total suspended solids
Retention basin
Swale
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