1- General Directorate of Natural Resources and Watershed Management of Golestan Province, Golestan, Iran
2- Vice-Chancellor for Research, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
2- Vice-Chancellor for Research, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
Abstract: (472 Views)
Extended Abstract
Background: Forest roads, as crucial developmental infrastructure in forested areas, play a significant role in the exploitation of natural resources, facilitation of transportation, and forest management. However, the construction of these roads has several environmental impacts, the most important of which include alterations in the hydrological regime, increased surface runoff, reduced soil permeability, and increased erosion and sedimentation. Over time, these changes can lead to decreased soil quality, habitat degradation, and reduced groundwater recharge, ultimately threatening the sustainability of forest ecosystems. Given that forest roads are divided into different sections based on topography and environmental conditions, such as the road shoulder, road surface, and side slopes, their impact on runoff and sediment production can vary across these sections. Therefore, quantitative and comparative assessment of these effects in different parts of forest roads is essential for sustainable natural resource management and mitigation of associated environmental damage. Considering the importance of this issue, the present study was conducted in the Kouhmian-Azadshahr forest to investigate changes in runoff volumes and sediment concentrations in different sections of a forest road.
Methods: Runoff and sediment were investigated using a rainfall simulator with one-square-meter plots. Experiments were conducted on three sections of the forest road: the roadbed, cut slopes, and fill slopes, with a rainfall intensity of 80 mm/hour for 32 minutes. Runoff and sediment were measured at 4-minute intervals, and soil samples were collected for physical analysis. Initial soil moisture was measured using an HB-2 moisture meter. After the experiment, runoff and sediment samples were transferred to the laboratory. The collected runoff volume in the designated areas was measured following each simulated rainfall event. Laboratory analyses included the determination of suspended solids, measurement of sediment concentration, and analysis of the physicochemical properties of the samples. Sediment samples were separated using Whatman No. 42 filters and dried in an oven at 105 °C. Soil physical parameters, including texture, organic matter content, and bulk density, were measured. Data were analyzed using the Kolmogorov-Smirnov test to examine data normality and Levene's test to assess variance homogeneity. To compare mean data between different road sections, the analysis of variance (ANOVA) and the least significant difference (LSD) test were used to determine the significance of differences in runoff and sediment yields among the sections.
Results: Runoff and sediment yields 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, high bulk density, lack of vegetation cover, and reduced permeability. In contrast, cut slopes produced the highest amount of sediment, which was attributed to the high proportion of silt particles, steep slope, and less vegetation cover. Fill slopes, on the other hand, had the lowest runoff and sediment yields, potentially due to the increased percentage of vegetation cover and higher organic matter content in these areas. During the experimental period, runoff volume on the roadbed showed a linear increasing trend, while cut and fill slopes exhibited fluctuating changes after an initial increase, indicating the influence of soil saturation and surface crust formation. The runoff coefficient reached its maximum value (0.49 to 1) on the roadbed and its minimum value (0.14 to 0.51) on the fill slopes. Changes in sediment concentration also showed different patterns; at the beginning of the experiment, cut slopes had the highest sediment concentration, which decreased over time due to particle settling. This trend is attributed to sediment deposition as runoff energy decreased. Conversely, the roadbed, due to its compacted structure and high impermeability, produced less sediment than the cut slopes.
Conclusion: The findings of this study demonstrate that slope, vegetation cover, soil texture, and organic matter content are the main factors affecting runoff and sediment yields in different sections of forest roads. The results highlight the importance of appropriate road slope design, conservation and development of vegetation cover on cut and fill slopes, and the use of sustainable methods to reduce erosion and sedimentation. However, implementing appropriate management practices, including increasing vegetation cover, soil stabilization, and optimal road slope design, can mitigate negative impacts. Implementing these strategies will not only improve road stability but also protect water and soil resources and reduce erosion. Finally, it is recommended to pay special attention to sustainable forest road stabilization approaches in macro-level natural resource policymaking. Furthermore, future studies using hydrological models and long-term assessments of road construction impacts on water resource quality are recommended to ensure sustainable management of forest roads and reduce environmental damage.
Background: Forest roads, as crucial developmental infrastructure in forested areas, play a significant role in the exploitation of natural resources, facilitation of transportation, and forest management. However, the construction of these roads has several environmental impacts, the most important of which include alterations in the hydrological regime, increased surface runoff, reduced soil permeability, and increased erosion and sedimentation. Over time, these changes can lead to decreased soil quality, habitat degradation, and reduced groundwater recharge, ultimately threatening the sustainability of forest ecosystems. Given that forest roads are divided into different sections based on topography and environmental conditions, such as the road shoulder, road surface, and side slopes, their impact on runoff and sediment production can vary across these sections. Therefore, quantitative and comparative assessment of these effects in different parts of forest roads is essential for sustainable natural resource management and mitigation of associated environmental damage. Considering the importance of this issue, the present study was conducted in the Kouhmian-Azadshahr forest to investigate changes in runoff volumes and sediment concentrations in different sections of a forest road.
Methods: Runoff and sediment were investigated using a rainfall simulator with one-square-meter plots. Experiments were conducted on three sections of the forest road: the roadbed, cut slopes, and fill slopes, with a rainfall intensity of 80 mm/hour for 32 minutes. Runoff and sediment were measured at 4-minute intervals, and soil samples were collected for physical analysis. Initial soil moisture was measured using an HB-2 moisture meter. After the experiment, runoff and sediment samples were transferred to the laboratory. The collected runoff volume in the designated areas was measured following each simulated rainfall event. Laboratory analyses included the determination of suspended solids, measurement of sediment concentration, and analysis of the physicochemical properties of the samples. Sediment samples were separated using Whatman No. 42 filters and dried in an oven at 105 °C. Soil physical parameters, including texture, organic matter content, and bulk density, were measured. Data were analyzed using the Kolmogorov-Smirnov test to examine data normality and Levene's test to assess variance homogeneity. To compare mean data between different road sections, the analysis of variance (ANOVA) and the least significant difference (LSD) test were used to determine the significance of differences in runoff and sediment yields among the sections.
Results: Runoff and sediment yields 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, high bulk density, lack of vegetation cover, and reduced permeability. In contrast, cut slopes produced the highest amount of sediment, which was attributed to the high proportion of silt particles, steep slope, and less vegetation cover. Fill slopes, on the other hand, had the lowest runoff and sediment yields, potentially due to the increased percentage of vegetation cover and higher organic matter content in these areas. During the experimental period, runoff volume on the roadbed showed a linear increasing trend, while cut and fill slopes exhibited fluctuating changes after an initial increase, indicating the influence of soil saturation and surface crust formation. The runoff coefficient reached its maximum value (0.49 to 1) on the roadbed and its minimum value (0.14 to 0.51) on the fill slopes. Changes in sediment concentration also showed different patterns; at the beginning of the experiment, cut slopes had the highest sediment concentration, which decreased over time due to particle settling. This trend is attributed to sediment deposition as runoff energy decreased. Conversely, the roadbed, due to its compacted structure and high impermeability, produced less sediment than the cut slopes.
Conclusion: The findings of this study demonstrate that slope, vegetation cover, soil texture, and organic matter content are the main factors affecting runoff and sediment yields in different sections of forest roads. The results highlight the importance of appropriate road slope design, conservation and development of vegetation cover on cut and fill slopes, and the use of sustainable methods to reduce erosion and sedimentation. However, implementing appropriate management practices, including increasing vegetation cover, soil stabilization, and optimal road slope design, can mitigate negative impacts. Implementing these strategies will not only improve road stability but also protect water and soil resources and reduce erosion. Finally, it is recommended to pay special attention to sustainable forest road stabilization approaches in macro-level natural resource policymaking. Furthermore, future studies using hydrological models and long-term assessments of road construction impacts on water resource quality are recommended to ensure sustainable management of forest roads and reduce environmental damage.
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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