1- General Directorate of Natural Resources and Watershed Management of Golestan Province
Abstract: (6 Views)
Introduction and Objective: Forest roads, as one of the most critical infrastructural developments in forested areas, play a significant role in the exploitation of natural resources, facilitating transportation, and managing forests. However, the construction of these roads entails numerous environmental consequences, among which the most significant are alterations in the hydrological regime, increased surface runoff, reduced soil permeability, and heightened erosion and sedimentation. Over time, these changes can lead to soil degradation, destruction of natural habitats, reduced groundwater recharge, and ultimately, threats to the sustainability of forest ecosystems.Given that forest roads are divided into different sections—such as road surface, road shoulders, and side slopes—based on topography and environmental conditions, their impact on runoff and sediment production may vary across these sections. Therefore, a quantitative and comparative assessment of these effects in different sections of forest roads is crucial for sustainable natural resource management and mitigating environmental damage. Considering the importance of this issue, the present study was conducted in the Kouhmian-Azadshahr forest with the aim of investigating variations in runoff volume and sediment concentration across different sections of a forest road.
Materials and Methods: To analyze runoff and sediment, a rainfall simulator with one-square-meter plots was utilized. Experiments were conducted on three sections of the forest road: the roadbed, cut slopes (excavated areas), and fill slopes (embankments) under a rainfall intensity of 80 mm/h for 32 minutes. Runoff and sediment were measured at four-minute intervals, and soil samples were collected for physical analysis. Initial soil moisture was determined using an HB-2 moisture meter, and after the experiments, runoff and sediment samples were transported to the laboratory. Following each rainfall event, the volume of collected runoff in designated areas was measured. Laboratory analyses included determining suspended particle concentration, measuring sediment concentration, and analyzing the physical and chemical properties of the samples. Sediment samples were separated using Whatman 42 filters and dried in an oven at 105°C. The physical parameters of the soil, including texture, organic matter content, and bulk density, were measured. Data analysis involved the Kolmogorov-Smirnov test to assess normality, Levene's test to examine variance homogeneity, and analysis of variance (ANOVA) along with the Least Significant Difference (LSD) test to compare runoff and sediment variations among different sections of the road.
Results: The results indicated that runoff and sediment production in different sections of the forest road were significantly influenced by soil physical properties, vegetation cover, and slope gradient. The roadbed exhibited the highest runoff volume due to high soil compaction, greater bulk density, lack of vegetation cover, and reduced infiltration capacity. In contrast, cut slopes generated the highest sediment yield, attributed to the high silt content, steep slopes, and lower vegetation cover. Conversely, fill slopes exhibited the lowest runoff and sediment production, likely due to increased vegetation cover and higher organic matter content in these areas. During the experiment, runoff volume in the roadbed followed a linear increasing trend, whereas in the cut and fill slopes, after an initial rise, fluctuations were observed, indicating the effects of soil saturation and surface crust formation. The runoff coefficient ranged from 0.49 to 1 in the roadbed, while in the fill slopes, it ranged from 0.14 to 0.51. Sediment concentration patterns varied, with cut slopes initially exhibiting the highest sediment concentration, which decreased over time due to particle settling. This trend resulted from sediment deposition as runoff energy diminished. In contrast, the roadbed, due to its compacted structure and low infiltration, generated lower sediment yields compared to the cut slopes.
Conclusion: The findings of this study revealed that slope gradient, vegetation cover, soil texture, and organic matter content are the primary factors affecting runoff and sediment production in different sections of forest roads. The results emphasize the importance of appropriate road slope design, the preservation and enhancement of vegetation cover on cut and fill slopes, and the adoption of sustainable measures to reduce erosion and sedimentation. However, implementing effective management strategies, such as increasing vegetation cover, stabilizing soil, and optimizing road slope design, can mitigate adverse effects. Applying these strategies will not only enhance road stability but also contribute to soil and water conservation while reducing erosion. Ultimately, it is recommended that sustainable forest road management be given special consideration in national natural resource policies. Furthermore, future research employing hydrological models and long-term assessments of road construction impacts on water quality is suggested to ensure sustainable forest road management and minimize environmental degradation.
Materials and Methods: To analyze runoff and sediment, a rainfall simulator with one-square-meter plots was utilized. Experiments were conducted on three sections of the forest road: the roadbed, cut slopes (excavated areas), and fill slopes (embankments) under a rainfall intensity of 80 mm/h for 32 minutes. Runoff and sediment were measured at four-minute intervals, and soil samples were collected for physical analysis. Initial soil moisture was determined using an HB-2 moisture meter, and after the experiments, runoff and sediment samples were transported to the laboratory. Following each rainfall event, the volume of collected runoff in designated areas was measured. Laboratory analyses included determining suspended particle concentration, measuring sediment concentration, and analyzing the physical and chemical properties of the samples. Sediment samples were separated using Whatman 42 filters and dried in an oven at 105°C. The physical parameters of the soil, including texture, organic matter content, and bulk density, were measured. Data analysis involved the Kolmogorov-Smirnov test to assess normality, Levene's test to examine variance homogeneity, and analysis of variance (ANOVA) along with the Least Significant Difference (LSD) test to compare runoff and sediment variations among different sections of the road.
Results: The results indicated that runoff and sediment production in different sections of the forest road were significantly influenced by soil physical properties, vegetation cover, and slope gradient. The roadbed exhibited the highest runoff volume due to high soil compaction, greater bulk density, lack of vegetation cover, and reduced infiltration capacity. In contrast, cut slopes generated the highest sediment yield, attributed to the high silt content, steep slopes, and lower vegetation cover. Conversely, fill slopes exhibited the lowest runoff and sediment production, likely due to increased vegetation cover and higher organic matter content in these areas. During the experiment, runoff volume in the roadbed followed a linear increasing trend, whereas in the cut and fill slopes, after an initial rise, fluctuations were observed, indicating the effects of soil saturation and surface crust formation. The runoff coefficient ranged from 0.49 to 1 in the roadbed, while in the fill slopes, it ranged from 0.14 to 0.51. Sediment concentration patterns varied, with cut slopes initially exhibiting the highest sediment concentration, which decreased over time due to particle settling. This trend resulted from sediment deposition as runoff energy diminished. In contrast, the roadbed, due to its compacted structure and low infiltration, generated lower sediment yields compared to the cut slopes.
Conclusion: The findings of this study revealed that slope gradient, vegetation cover, soil texture, and organic matter content are the primary factors affecting runoff and sediment production in different sections of forest roads. The results emphasize the importance of appropriate road slope design, the preservation and enhancement of vegetation cover on cut and fill slopes, and the adoption of sustainable measures to reduce erosion and sedimentation. However, implementing effective management strategies, such as increasing vegetation cover, stabilizing soil, and optimizing road slope design, can mitigate adverse effects. Applying these strategies will not only enhance road stability but also contribute to soil and water conservation while reducing erosion. Ultimately, it is recommended that sustainable forest road management be given special consideration in national natural resource policies. Furthermore, future research employing hydrological models and long-term assessments of road construction impacts on water quality is suggested to ensure sustainable forest road management and minimize environmental degradation.
Type of Study: Research |
Subject:
فرسايش خاک و توليد رسوب
Received: 2025/02/4 | Accepted: 2025/10/1
Received: 2025/02/4 | Accepted: 2025/10/1
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