Differing Levels of Forestry Best Management Practices at Stream Crossing Structures Affect Sediment Delivery and Installation Costs
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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.Keywords:
Culvert
Bridge (graph theory)
Forest road
Sediment control
River management
The use of forest roads as foundations for dam construction by beavers is a recurrent problem in the management of forest road networks. In order to limit the damage to forest roads, our goal was to calculate the probability of beaver dam installation on culverts, according to surrounding habitat parameters, which could allow for improvement in the spatial design of new roads that minimise conflicts with beavers. Comparisons of culverts with (n = 77) and without (n = 51) dams in northwestern Quebec showed that catchment surface, cumulate length of all local streams within a 2-km radius, and road embankment height had a negative effect on the probability of dam construction on culverts, while flow level and culvert diameter ratio had a positive effect. Nevertheless, predicted probabilities of dam construction on culverts generally exceeded 50%, even on sites that were less favourable to beavers. We suggest that it would be more reasonable to take their probable subsequent presence into account at the earliest steps of road conception. Installing mitigation measures such as pre-dams during road construction would probably reduce the occurrence of conflicts with beavers and thus reduce the maintenance costs of forest roads.
Culvert
Forest road
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Forest road
Ditch
Sediment control
Revegetation
Road surface
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Recent controversies associated with ditched forest roads and stream crossings in the Pacific Northwest have focused national attention on sediment production and best management practices (BMPs) at stream crossings. Few studies have quantified soil erosion rates at stream crossings as influenced by road characteristics and compared them to modeled rates. Soil erosion rates were measured and modeled from forest roads that represented a range of road classes (permanent high standard to temporary low standard). Forty road approaches were identified in the Piedmont and Mountain regions of Virginia and categorized into four general road classes. Road attributes were characterized at each crossing (BMPs used, road width, grade, gravel, cover, cut and fill slope ratios, ditch characteristics, etc.). At each stream crossing, conveyor belts were installed as water-control devices across the road to divert sediment from the stream crossing approach into silt fence sediment traps. Sediment pins were installed adjacent to the silt fence to allow periodic measurement of sediment depths. Additionally, erosion potentials for approaches were modeled with the Universal Soil Loss Equation (USLE) as modified for forestry and compared to actual sediment deposition near the stream. Data presented represents < 1year of sediment measurements from the stream crossings.
Forest road
Ditch
Sediment control
Silt
Deposition
Erosion Control
Fence (mathematics)
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Obliterating high risk and unused roads is in response to underfunding of roadmaintenance budgets in the US Forest Service. Although many Forest Service specialists assumethat the long term economic and environmental benefits from road removal outweigh the short termsediment impacts, few studies have been done to verify this assumption. The Rocky MountainResearch Station and the Nez Perce National Forest conducted a study to measure short termimpacts. Stream flow rates and sediment concentrations were monitored at a stream crossing duringroad obliteration activity. The sediment yield from culvert removal during road obliteration was lessthan that from culvert installation during road construction which occurred between 1978 and 1979.Sediment concentration peaked at 28,000 mg/L directly below the culvert. Concentrations decreasedby 10 to 1,000 times over a distance of 100 meters, and by over 2,000 times at a distance of 800 m.The primary sediment producing activities were the removal of individual culvert sections from thestream crossing and the placement of riprap rocks in the channel. Additional measurements areplanned for the summer of 2004.
Culvert
Forest road
Riprap
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The communications surveying designing institute in Liaoing Province investigates minutely the an County's highway bridge-culvert,analyzes reasons for bridge-culvert damage.By experiences with the bridge-culvert design in Liaoning Province,the paper raises improvement of antiseismic measures for bridge design.
Culvert
Bridge (graph theory)
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In this study a new method of locating culverts is presented with the composition of achieved discharge from hydrological analysis and simulated forest roads in RoadEng 3D simulator to improve drainage condition. Locating culverts was performed on a small scale (1:20 000, using GIS) and large scale (1:2 000, road geometric design simulator). The small-scale study regarding the achieved discharge from streams shows that the installation of some culverts is not necessary. The large-scale study also showed that the geometric design of forest road has a significant effect on locating culverts and its accuracy. To improve drainage conditions 6 culverts and 2 waterfronts taking into account the geometric design of forest road, hydrological conditions and appropriate intervals (155 m) have been proposed. No installation or lack of accuracy to find the best location of culverts may result in the occurrence of creep and landslide, so the cost of destruction would be several times higher than the cost of technical buildings construction.
Culvert
Forest road
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This study was conducted to investigate and compare the existence cross drainage with its standards in forest regions of Savad kooh, Iran. Research was done according to the importance of the planning issue of technical structures in forest roads based on wildlife habitat. In order to assess the characteristics of considered ravine different analysis was respectively carried out to achieve flow direction, flow length, cumulate center and flow rate. The Roadeng software, which has been produced for road construction project, was used to design existent road, streams and culvert in our study area. In this software the level of water depth in culvert is determined with combination of topographic layers, ravine properties (length, direction, flow intensity and catchment area) and status of culvert installation. A result of investigations in study area showed that skew of mounted culverts is not accordance to flow direction. So that, when the culverts causes to skew water flow from its main route it can be a barrier against aquatic migration. In this study the culvert had suitable status in viewpoint of gradient and water level (suitable depth for fish passage). So that, this issue causes to even level flow and balance along culvert. According to the results of this study it can be concluded that the correct installation of culverts in forest roads need accurate scientific studies in field of road engineering, forest and fishing.
Culvert
Forest road
Ravine
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Forest road
Sediment control
Silt
Stream Restoration
Road surface
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Reducing forest roads sediment impact on the stream network requires a well-designed cross drain system. Washington State regulation has specific guidelines for cross drain design. To help in the process, several computerized sediment analysis packages are currently used to evaluate potential culvert locations with limited applicability. A specialized decision support tool, with an intuitive process flow and a friendly interface is introduced. PROBLEM Forest roads are held responsible for a large part of the increased quantities of sediment delivered to streams. The majority of the forest roads in mountainous regions are insloped with a side ditch. Most of these roads deliver sediment at stream crossings; therefore a wise placement of cross drains is essential for reducing road impacts on stream networks. When designing a new road or rebuilding an old one it becomes important to know how many cross drains are needed and where should they be placed in order to minimize sediment delivery. If a cross drain culvert is placed too far up the road from the stream crossing then a significant amount of sediment will still be delivered (Figure 1a). Conversely if the culvert is too close to the stream crossing part of the sediment dispersed onto the forest floor may still reach the stream (Figure 1b). Furthermore, the placement of intermediate culverts along the road alignment governs the amount of sediment moving along ditch and the sediment dispersed at specific locations.
Culvert
Ditch
Forest road
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Water quality issues surrounding sediment movement related to forest operations are a focus in forest management. The forest road system is a primary area of concern related to sediment movement because roads are a component of most forest operations. Controlling sediment movement is a common objective in most forestry best management practices (BMPs). However, there is a lack of information documenting the effectiveness of prescribed practices in reducing sediment loads from forest road systems. This is primarily due to the complexity of assessing the effectiveness of erosion and sediment control, stormwater control, and BMPs in the forest setting. Consequently, little sediment transport and BMP effectiveness information or data are available. Monitoring designs for effective evaluations of erosion and sediment control practices are critical to further reductions in sediment contributed from forest roads. This paper presents general engineering design aspects involved in evaluating erosion control, sediment control, and BMPs on the forest landscape. The paper discusses considerations involved with the selection of monitoring equipment and structures based on design storm and costs. Statistical considerations in the selection of an experimental design to optimize data collection and increase the probability of statistically valid results are presented. In addition, an innovative study design (real world) and application to address sediment control BMP issues will be reported. This study was initiated on the Tallulah District of the Chattahoochee National Forest that aims to evaluate the effectiveness of three road sediment control treatments (alternative BMPs) settling basins, sediment basin with riser control, and hay bale barriers in filtering sediment laden storm runoff. The BMP effectiveness study design utilizes stormwater samplers, trapezoidal flumes, automated flow level devices, flow dividers, and runoff tipping buckets to evaluate sediment transport through sediment control treatments. This design has the potential to set standards for forest road sediment control evaluations.
Sediment control
Forest road
Erosion Control
Sedimentary budget
WEPP
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