## 3 Results and Discuss
### Analysis of Snow Fences and Snow Cover Distribution
By comparing the distribution coefficient of snow cover under conditions of different snow fence rows and height, it is observed that the overall distribution characteristics upstream and downstream of the fence remain similar across different arrangements, with accumulation typically forming within 2-4 H upstream and 4-6 H downstream. If a small snow distribution coefficient on the subgrade surface is considered the criterion for effective snow fence protection, then two rows of 3 m high snow fences are superior to one row of 5 m high snow fences, and also better than one row of 3 m high snow fences. This is because two rows of snow fences can intercept more snow particles. The first row causes initial accumulation and, after a stable zone, the second row further decelerates the airflow, leading to a second accumulation, thus blocking a large number of particles outside the subgrade area. The main disadvantage of two rows of snow fences is the requirement for a larger area, while the protective effect is not significantly enhanced. Therefore, in areas where snowdrift disasters are particularly severe, prioritizing an increase in the height of snow fences may be preferable to increasing the number of rows. Previous studies [8; 23] have emphasized the role of cutting geometry in snowdrift formation, reporting an \"M-shaped\" snow distribution in cuttings. In contrast, our find  
Figure 15: Distribution of snow depth coefficient near the fence. (**a**) 2 row snow fence; (**b**) 1 row snow fence. ings reveal that embankments exhibit a \"U-shaped\" distribution, with maximum snow depth (38.3 mm) at the leeward slope foot. This divergence underscores the necessity of terrain-specific strategies: while cuttings benefit from snow platform widening (reducing distribution coefficients from 2.0 to 1.6), embankments require optimized snow fences to disrupt airflow and redirect snow deposition. For example, a 3 m-high fence with 50% porosity placed at 7 H reduces embankment surface snow depth by 60%, outperforming passive structural modifications alone. As the driving force and material source of wind-blown snow movement, wind field characteristics and snow availability directly influence snow depth. During snowdrifting, snow particles continuously gain kinetic energy from the airflow, causing them to become mobile and move with the air, thus increasing the snow concentration in the airflow. Simultaneously, snow particles near the surface reduce the average wind speed, and some particles lose momentum and settle, decreasing the airborne snow concentration. Snow particles are both lifted from the ground and deposited onto it. The change in airflow energy exists in a dynamic equilibrium with the momentum changes of the snow particles, forming a bidirectional feedback system where the movement of snow grains affects the airflow, and changes in airflow also affect the movement of snow grains. This equilibrium state is dynamic due to the fluctuating airflow energy and snow grain movement. The wind-blown snow movement causes both deposition on and erosion of the snow particle surface. In a state of dynamic balance, deposition and erosion can be considered equal. However, changes in flow conditions induced by snow prevention structures disrupt this balance, leading to a difference between the amounts of deposition and erosion, causing more snow particles to become airborne or settle on the ground. Under the influence of snow prevention structures, alterations in wind speed lead to changes in the flow field state. In areas of increased flow velocity, the wind-blown snow movement exhibits more pronounced erosion, and more snow particles become airborne. Conversely, in areas of weakened flow velocity, the wind-blown snow movement exhibits more deposition, and snow grains settle.