Road Prism Research Articles

A Review of the Sediment Production and Transport Processes of Forest Road Erosion

Forest roads are a common land use feature with a significant impact on sediment yield and the water sediment transport processes within a watershed, seriously disrupting the safety and stability of the watershed. Previous studies have focused on the sediment production processes within the road prism. However, there has been limited attention given to the transport processes of road-eroded sediment at various scales, which is crucial for understanding the off-site effects of road erosion. This paper reviews research conducted on forest road erosion over the past two decades. It summarizes the mechanisms of sediment production from road erosion and provides a detailed analysis of the transport mechanisms of eroded sediments from roads to streams at the watershed scale. The paper also examines the ecological and hydrological effects, research methods, and control measures related to sediment transport caused by forest road erosion. It identifies current research limitations and outlines future research directions. The findings of this review highlight several key points: (1) Most research on forest road erosion tends to be specific and unilateral, often neglecting the broader interaction between roads and the watershed in terms of water–sediment dynamics. (2) Various research methods are employed in the study of forest road erosion, including field monitoring, artificial simulation experiments, and road erosion prediction models. Each method has its advantages and disadvantages, but the integration of emerging technologies like laser scanning and fingerprint recognition remains underutilized, hindering the simultaneous achievement of convenience and accuracy. (3) The transport processes of forest road-eroded sediment, particularly on road–stream slopes, are influenced by numerous factors, including terrain, soil, and vegetation. These processes exhibit significant spatial and temporal variability, and the precise quantification of sediment transport efficiency to the stream remains challenging due to a lack of long-term and stable investigation and monitoring methods. The establishment and operation of runoff plots and sedimentation basins may help offer a solution to this challenge. (4) Both biological and engineering measures have proven effective in reducing and limiting sediment erosion and transport. However, the costs and economic benefits associated with these regulation measures require further investigation. This review provides a comprehensive summary of relevant research on sediment erosion and transport processes on unpaved forest roads, enhancing our understanding of sediment yield in watersheds and offering valuable insights for reducing sediment production and transport to streams.

Impact of Forest Roads on Hydrological Processes

The current review summarizes the knowledge generated by the recently published studies of the last twenty years, in the field of forest road networks, concerning the impact of forest road construction on hydrological processes. The currently applied methodology techniques/practices are discussed, the findings are highlighted and effective mitigation measures to mitigate the impact of forest roads are proposed. Critical for the minimization of the impact of forest roads on overland flow is the significant decrease in road surface runoff and overland flow velocity. The decrease in runoff energy reduces the detachment of soil particles and transportation in streams. The disturbances of forest roads in logging areas should be limited to decrease soil erosion. Additionally, aiming to minimize sediment transportation into the streams, it is very important to reduce the connectivity between the forest roads (or skid trails) and streams. The positive role of vegetation and organic matter on the road prism, naturally/technically established riparian buffers along the streams, and the use of appropriate bioengineering designs for each area significantly decrease the runoff generation and sedimentation. From a construction point of view, the decrease in short and long-term forest road-related impact could be achieved by reducing the depth of excavations and the use of soil compaction limiting technology during forest works. The road network design should be more efficient, avoiding hydrologically active zero-order basins. Techniques that minimize the length and connectivity among skid trails, unpaved roads and streams are highly crucial. Broad-based dips, immediate revegetation and outsloping of the road base are considered good road construction practices. Research should be focused on the hydrologic behavior of forest road networks and on the impact at the watershed scale, the degree of connectivity, utilizing plenty of qualitative field data, especially during intense rainfall events, which has been proven to exacerbate the runoff and sediment generation and transportation into the stream networks.

English

This study was conducted to investigate the interaction of soil properties and vegetation cover on soil loss from forest road prism. Rainfall simulations were carried out on road surface, fillslope and cutslope. Runoff and sediment samples were collected every 4 min and then total soil loss was measured. Samples from top soil were randomly collected for analysis and grouping soil into A, B and C. Results showed that on cutslope, the highest soil loss was detected for soil group B, where sediment concentration in runoff was 21.83 g L-1 and vegetation cover was 0 to 30%. On fillslope, the highest soil loss was detected for soil group C, where sediment concentration in runoff was 18.07 g L-1 and vegetation cover was 10 to 40%. On road surface, the highest soil loss was detected for soil group A, where sediment in runoff was 8.99 g L-1 and vegetation cover was 2 to 5%.   Key words: Forest road, sediment, soil groups, rainfall simulation, principal component analysis (PCA).

Use of Wicking Fabric to Help Prevent Frost Boils in Alaskan Pavements

AbstractBeaver Slide is on the Dalton Highway near 177.8 km (110.5 mi), and it is downhill when heading north. The road gradient is approximately 11% and the road prism is on a side hill. Each year, there are soft spots that usually appear in late April and remain all summer, which are also called “frost boils” by engineers at the Alaska Department of Transportation and Public Facilities (AKDOT&PF). The frost boils have resulted in extremely unsafe driving conditions and frequent accidents. Past repair efforts indicate conventional road construction methods do not work. A new type of geosynthetic wicking fabric has been recently developed that has a high specific surface area (consequently high wettability and high capillary action) and high directional permittivity. Preliminary laboratory tests indicate it has great promise as a cost-effective means to solve the frost heave-related problems on northern road systems. This study verifies the effectiveness of the wicking fabric to mitigate frost boils in Al...

Testing road surface treatments to reduce erosion in forest roads in Honduras

S. Rivera, J.L. Kershner, and G.R. Keller. 2009. Testing road surface treatments to reduce erosion in forest roads in Honduras. Cien. Inv. Agr. 36(3):425-432. Using forest roads produces more erosion and sedimentation than any other forest or agricultural activity. This study evaluated soil losses from a forest road in central Honduras over two consecutive years. We divided a 400-m segment of road into 8 experimental units, each 50 m in length. Four units were treated with Best Management Practices (BMPs) and four were left untreated. The BMP treatments included reshaping the road prism, installing culverts and reshaping of road ditches, compacting 20-cm layers of the road tread, crowning the road surface (3% slope, double drainage), longitudinal sloping (less than 12%), and adding a 10-cm layer of gravel (crush size = 0.63 cm). Soil movement was measured daily during the rainy seasons. The highest soil loss occurred in the control road, around 500 m 3 -1 per year, while the road treated with BMP lost approximately 225 m 3 -1 per year. These results show that road surface erosion can be reduced up to 50% with the implementation of surface treatments.

Relative contributions of runoff and sediment from sources within a road prism and implications for total sediment delivery

AbstractThis study examines runoff and sediment generation rates within the road prism on unsealed road segments in the Cuttagee Creek catchment near Bermagui in New South Wales, Australia. A large (600 m2) rainfall simulator was used to measure runoff and sediment yields from each of the potential sediment and runoff sources and pathways. These included the road surface, table‐drain, upslope contributing area and cutslope face, and the entire road segment as measured at the drain outlet. Experiments were conducted on two major types of road (ridge‐top and cut‐and‐fill) of varying traffic usage and maintenance standard for two 30‐minute simulations of increasing rainfall intensity. From the range of possible sources within the road prism, the road surface produced the dominant source of excess runoff and sediment at each site with limited contributions from the table‐drain, cutslope face or contributing hillslope. Sediment generation varied significantly with road usage and traffic intensity. Road usage was strongly related to the amount of loose available sediment as measured prior to the experiments. Table‐drains acted primarily as sediment traps during the low rainfall event but changes in sediment concentration within the drains were observed as runoff volumes increased during the higher rainfall event of 110 mm h−1, releasing sediment previously stored in litter and organic dams. The experiments demonstrate the potential roles of various features of the road prism in the generation and movement of sediment and water. Copyright © 2006 John Wiley & Sons, Ltd.

Forest road design with soil sediment evaluation using a high-resolution DEM

In this study, we combined a program to optimize forest road alignments with a method for prediction of surface erosion and related sediment delivered to streams. Combining the forest road design program with the high-resolution digital elevation model made it possible to estimate soil sediment based on a standard methodology, because a relatively accurate road prism could be generated. The combined program properly places and spaces drainage structures based on the Washington State Forest practice board manual. We applied the program to a part of Capitol State Forest in Washington State and optimized horizontal and vertical alignments while estimating movement of soil sediment from roads to streams. We discussed the effects of road surface materials, near-stream culvert distance to stream, and out-sloped forest road template on total road costs and soil sediment delivered to streams. Using lower quality rock surfacing reduced total costs, but the amount of soil sediment from lower quality rock surfacing was 1.5 times more than that on a higher quality rock traction surface. Therefore, lower quality rock surfacing should not be used near the stream. The placement of near-stream culverts 15m upstream and out-sloped road template were examined using a traction surface on 15-m sections upstream and lower quality rock surfacing on other sections in order to reduce soil sediments to the stream and total costs. As a result, placing near-stream culverts 15m upstream and using an out-sloped road template significantly reduced total road cost and soil sediment. Finally, we optimized horizontal and vertical alignments while limiting soil sediment to a specified maximum level. The model successfully optimized forest road alignments, which reduced total road cost as well as soil sediment.

Simultaneous Optimization of Horizontal and Vertical Alignments of Forest Roads Using Tabu Search

We developed a forest road design model that simultaneously optimizes horizontal and vertical alignments of forest roads using a high resolution Digital Elevation Model (DEM). Once an initial horizontal alignment is established by locating a series of intersection points, the model generates alternative horizontal and vertical alignments and cross sections along the road prism. The model also estimates earthwork volume and construction and maintenance costs for given road alignments and their spatial locations. The model then optimizes road alignments based on construction and maintenance costs using Tabu Search, one of the modern heuristic techniques. The model was applied to a part of Capitol Forest in Washington State, USA, where a high resolution DEM derived from LiDAR (Light Detection and Ranging) data was available. First, the program generated an initial horizontal alignment with the length of 827m and five horizontal curves based on manually selected intersection points. Then, the vertical alignment was optimized based on the initial horizontal alignment, which resulted in a total cost of $50,814, considering construction and maintenance costs. The optimized forest road alignment, whose horizontal and vertical alignments were simultaneously optimized during the search process, reduced the total cost and the road length by 36% and 19% compared to the initial horizontal alignment, respectively.

A comparison of landslide rates following helicopter and conventional cable-based clear-cut logging operations in the Southwest Coast Mountains of British Columbia

A comparison of landslide rates following helicopter and conventional, cable-based, clear-cut logging was carried out using results from two independent terrain attribute studies in the Eldred and Lois River watersheds in the Southwest Coast Mountains of British Columbia. Landslides initiating from directly within a road prism were excluded from the study in order to focus the comparison on landslides related primarily to conventional versus helicopter yarding methods. A landslide rate of 0.02 landslides/ha was observed in 162 terrain polygons logged by helicopter ∼8 years prior to this study. Landslide rates in 38 gullied polygons were 0.06 landslides/ha. No landslides were observed in 124 open-slope polygons. Over a similar 8-year average period, 0.03 landslides/ha were observed in 142 cable-yarded terrain polygons; 0.06 and 0.02 landslides/ha occurred in gullied and open-slope polygons, respectively. t-Tests indicate that total landslide rates are not significantly different following helicopter and conventional logging; however, a dichotomy exists between gullied and open-slope terrain polygons. Landslide rates are not significantly different in gullied terrain but are significantly higher on open-slopes following conventional cable logging. Consequently, landslides appear to have a greater potential to occur in open-slope terrain following conventional logging, but differences in gullied polygons are less likely. Increased post-logging landslide rates in conventionally logged, open slopes are more likely the result of undetected road-related drainage changes than differences between helicopter and conventional yarding-related ground disturbance.

Simplified Methods for Evaluating Road Prism Stability

Mass failure is one of the most common failures of low-volume roads in mountainous terrain. Current methods for evaluating stability of these roads require a geotechnical specialist. A stability analysis program, XSTABL, was used to estimate the stability of 3,696 combinations of road geometry, soil, and groundwater conditions. A sensitivity analysis was carried out to find the most important site-specific variables in estimating slope stability, and two regression equations were developed to predict the factor of safety ( FS) for a given road, one with the groundwater below the road fill and one with the groundwater in the road fill. The resulting equations predicted failures on road segments where failures were observed to have occurred. A comparison of the predicted FSs from the regression equations with the FS values predicted by the infinite slope equation showed that both methods predicted similar FSs.

Horton overland flow contribution to runoff on unpaved mountain roads: A case study in northern Thailand

AbstractTwo indirect methods are used to detect evidence of intercepted subsurface flow (ISSF) by the road prism in the Pang Khum Experimental Watershed (PKEW) in northern Thailand. During the 12‐month study period we failed to observe a soil moisture change that corresponds with ISSF being generated by the water table rising above the road surface. In support of the soil moisture data, δ18O signatures of rain water, road runoff, and stream water (a proxy for soil water) suggest Horton overland flow (HOF) generated on the road surface, not ISSF, is the dominant source of observed road runoff during typical rainfall events in the study area. This finding, which is contrary to the ISSF‐dominant road runoff regime found typically on unpaved mountain roads in the US Pacific NW, suggests that the use of a HOF‐based model to simulate runoff and sediment transport on unpaved roads in PKEW provides not only lower bound estimates of these processes, but realistic approximations for typical events. Copyright © 2001 John Wiley & Sons, Ltd.

Field evaluation of the long-term performance of geocomposite sheet drains

The long-term performance of geocomposite sheet drains has been monitored at three sites by measuring the effect of the drains on local groundwater hydrology during peak groundwater events. The study is on-going with the maximum record being 14 years at one location. One drain was placed 2.4 m deep in a vertical trench in soil that varies from clay and clayey gravel to silty sand. Over a three-year period, this drain has flowed as much as 100 l/min. Even during such extreme groundwater events, there has been essentially no rise in the water table just down gradient from the drain. The peak hydraulic gradient toward this drain consistently reaches 0.66–0.73 during major rainstorms and returns to a “base level” of 0.45–0.50 within 10 days after a storm peak. At a second site, a drain was installed 8 m deep in a silty sand soil behind a retaining wall. This geocomposite has flowed up to 15 l/min with no rise in the water table in the retaining wall fill. Performance of the drain has been consistently excellent over a 14-year period. Limited data suggest that the drain discharge is proportional to about 13 times the average hydraulic gradient toward the drain. At a third site, a drain was installed to a maximum depth of 2.4 m in a vertical trench in a silty sand soil. Performance of this drain is marginal because trench wall collapse during drain installation caused an uneven drain slope toward the outlet. This is a common issue where trench drains are installed at sites with a constantly high water table. The problem could be greatly mitigated by a geocomposite design in which vertical sections of the drain are completely independent units that could be quickly dropped into a trench immediately behind the excavator. Despite the construction problems, this drain is partially dewatering the road prism just down gradient from the geocomposite.

Runoff generation and sediment production on unpaved roads, footpaths and agricultural land surfaces in northern Thailand

Rainfall simulation was used to examine runoff generation and sediment transport on roads, paths and three types of agricultural fields in Pang Khum Experimental Watershed (PKEW), in mountainous northern Thailand. Because interception of subsurface flow by the road prism is rare in PKEW, work focused on Horton overland flow (HOF). Under dry antecedent soil moisture conditions, roads generated HOF in c. 1 min and have event runoff coefficients (ROCs) of 80 per cent, during 45 min, c. 105 mm h−1 simulations. Runoff generation on agricultural fields required greater rainfall depths to initiate HOF; these surfaces had total ROCs ranging from 0 to 20 per cent. Footpaths are capable of generating erosion-producing overland flow within agricultural surfaces where HOF generation is otherwise rare. Paths had saturated hydraulic conductivity (Ks) values 80–120 mm h−1 lower than those of adjacent agricultural surfaces. Sediment production on roads exceeded that of footpaths and agricultural lands by more than eight times (1·23 versus < 0·15 g J−1). Typically, high road runoff volumes (owing to low Ks, c. 15 mm h−1) transported relatively high sediment loads. Initial road sediment concentrations exceeded 100 g l−1, but decayed with time as loose surface material was removed. Compared with the loose surface layer, the compacted, underlying road surface was resistant to detachment forces. Sediment concentration values for the road simulations were slightly higher than data obtained from a 165 m road section during a comparable natural event. Initial simulation concentration values were substantially higher, but were nearly equivalent to those of the natural event after 20 min simulation time. Higher sediment concentration in the simulations was related to differences in the availability of loose surface material, which was more abundant during the dry-season simulations than during the rainy season natural event. Sediment production on PKEW roads is sensitive to surface preparation processes affecting the supply of surface sediment, including vehicle detachment, maintenance activities, and mass wasting. The simulation data represent a foundation from which to begin parameterizing a physically based runoff/erosion model to study erosional impacts of roads in the study area. Copyright © 2000 John Wiley & Sons, Ltd.

Runoff generation and sediment production on unpaved roads, footpaths and agricultural land surfaces in northern Thailand

Rainfall simulation was used to examine runoff generation and sediment transport on roads, paths and three types of agricultural fields in Pang Khum Experimental Watershed (PKEW), in mountainous northern Thailand. Because interception of subsurface flow by the road prism is rare in PKEW, work focused on Horton overland flow (HOF). Under dry antecedent soil moisture conditions, roads generated HOF in c. 1 min and have event runoff coefficients (ROCs) of 80 per cent, during 45 min, c. 105 mm h−1 simulations. Runoff generation on agricultural fields required greater rainfall depths to initiate HOF; these surfaces had total ROCs ranging from 0 to 20 per cent. Footpaths are capable of generating erosion-producing overland flow within agricultural surfaces where HOF generation is otherwise rare. Paths had saturated hydraulic conductivity (Ks) values 80–120 mm h−1 lower than those of adjacent agricultural surfaces. Sediment production on roads exceeded that of footpaths and agricultural lands by more than eight times (1·23 versus < 0·15 g J−1). Typically, high road runoff volumes (owing to low Ks, c. 15 mm h−1) transported relatively high sediment loads. Initial road sediment concentrations exceeded 100 g l−1, but decayed with time as loose surface material was removed. Compared with the loose surface layer, the compacted, underlying road surface was resistant to detachment forces. Sediment concentration values for the road simulations were slightly higher than data obtained from a 165 m road section during a comparable natural event. Initial simulation concentration values were substantially higher, but were nearly equivalent to those of the natural event after 20 min simulation time. Higher sediment concentration in the simulations was related to differences in the availability of loose surface material, which was more abundant during the dry-season simulations than during the rainy season natural event. Sediment production on PKEW roads is sensitive to surface preparation processes affecting the supply of surface sediment, including vehicle detachment, maintenance activities, and mass wasting. The simulation data represent a foundation from which to begin parameterizing a physically based runoff/erosion model to study erosional impacts of roads in the study area. Copyright © 2000 John Wiley & Sons, Ltd.

Erosion Control Techniques on Forest Road Cutslopes and Fillslopes in North Alabama

Road cutslopes and fillslopes account for approximately 50 percent of the total road disturbance area on steep terrain and contribute as much as 60 percent of sediment from forest roads. The significance of erosion control techniques on these vulnerable components of the road prism has become evident in recent years. A study to gain a better understanding of erosion control techniques on road cutslopes and fillslopes is detailed. Sediment and runoff yield from three erosion control treatments and a control were investigated on west-facing 2:1 and 1.5:1 cutslopes and fillslopes, respectively, on a newly constructed road during a 30-month study. The treatments evaluated were a wood excelsior erosion mat, native species grass, and exotic species grass. Factors detected to significantly affect sediment yield from road sideslopes were treatment, time, and treatment-time interaction based on analysis of variance. Significant reductions in sediment yield and runoff were found on all treatments on both the cutslope and fillslope. The erosion mat most effectively controlled erosion losses on both slopes for all study periods.

Hydrologic Impacts of Logging an Appalachian Watershed Using West Virginia's Best Management Practices

Abstract A 39 ha gauged watershed located in north-central West Virginia near Parsons was cut to a 35.5 cm stump diameter and logged using wheeled skidders to evaluate the effectiveness of West Virginia's Best Management Practices (BMPs). Roads initially occupied 10.6% of the watershed, but this percentage is decreasing as much of the original road prism reverts to forest. Reducing basal area by 44% in stems 2.54 cm dbh and larger had a negligible effect on maximum growing season stream temperatures, apparently because the stream remained shaded by residual trees and understory shrubs growing along it. Both growing season peakflows and total stormflow had small but significant increases due to treatment. Dormant season stormflows did not increase significantly. Although mean monthly exports of suspended sediment doubled the first year when the area was being logged, they remained within the range reported for carefully managed areas in the East. Sediment exports returned to pretreatment levels by the third posttreatment year. Long-term projections of current exports rates indicate that sediment exports from harvesting operations (3 entries) during a 100 yr rotation will account for less than 5% of the total sediment exported from the study watershed. Nitrate exports increased significantly during most of the monitored posttreatment years, but fertilizer applied to the roads during grass seeding is believed to have contributed to these increases. Actual concentration values remained low, with maximum concentrations well below standards for potable water. Calcium concentrations also increased during most years, but road liming during seeding probably was responsible for most of this increase. The BMPs used in this study were effective in minimizing adverse impacts to soil and water resources. North. J. Appl. For. 14(4):207-218.

Sedimentation associated with forest road surfacing in a bottomland hardwood ecosystem

Access systems are a necessary element of resource production in bottomland hardwood sites. However, road building may have a detrimental effect on hydrologic function of the site. This report describes initial results of a study designed to examine the effect of different road surfacing treatments on water quality. Four surfacing treatments installed on two test roads included native soil, native soil with vegetative stabilization, 6 cm of gravel, and 15 cm of gravel over geotextile. During the first flooding season periodic sampling measured floodwater suspended sediments and location of erosion and sediment deposition within the road prism. Initial results suggest that sediment movement was confined to the road right-of-way, with no statistically significant sedimentation effects detected beyond the clearing limits of the road. The study is continuing for another field season.