Study on Water Migration and Evolution Characteristics of Ecologically Protected Loess Slopes with Different Inclinations

Loess slopes are widely distributed in northwest China and are particularly susceptible to instability during heavy rainfall. Ecological protection has emerged as an effective means of safeguarding these slopes; however, varying ecological protection methods can lead to differences in the characteristics of internal water migration and overall protective efficacy. Therefore, this study aims to investigate the effects of different slope angles on the water migration and evolution characteristics of ecologically protected loess slopes. To achieve this, time series analysis and Hydrus-2D simulation software were utilized to elucidate the dynamic evolution of water within ecologically protected loess slopes, focusing on slope models with angles of 45° and 60°. The study revealed how rainfall intensity, duration, and plant growth stages impact the water content response model and examined the rules governing soil water transfer under different protection stages and slope angles. The results indicate that during the whole monitoring period, the overall moisture content of the 60° slope is slightly lower than that of the 45° slope, and the soil moisture distribution of the 60° slope with soil layer was more pronounced in the lower part of the slope, while the 45° slope is more obvious at the top. As rainfall intensity increased, the response lag time of internal slope water to rainfall significantly decreased, whereas extending the duration of rainfall events led to an increase in both the response lag time and the time to reach peak response. Vegetation protection effectively prolonged the lag time of the response of water inside slope to rainfall events. Additionally, the response of the 60° slope was slower than that of the 45° slope. For intense rainfall events, ecological protection can effectively reduce the water infiltration rate, and the water migration rate in different protection periods is as follows: early protection ＞ middle protection ＞ late protection. Furthermore, the effect of vegetation on the water migration rate was more significant on the 60° slope, where water infiltration occurred more slowly than on the 45° slope.