Multi-time scale analysis of loess landform evolution for Dongzhi tableland, southwestern Loess Plateau, China

Study region Dongzhi tableland, southwestern Loess Plateau, eastern Gansu Province, China. Study focus The loess tableland has shrunk greatly over the past thousand years, and this trend is expected to continue. Predictions of loess tableland evolution can support the design and implementation of adequate mitigation measures. To address the limitations of generic Landscape Evolution Models (LEMs) in loess regions, this paper establishes a modified LEM tailored for loess landforms. The model incorporates water as an actual flowing medium in real-time computations, capturing the effects of soil creep, soil detachment, sediment transportation, and sedimentation on loess landscape evolution in a relatively simple and practical manner. Field observations validated that the stream incision law could be modified by adjusting the erosion incision index to make it more suitable for loess regions. The evolution processes of two watersheds with different scales were calculated and analyzed with the established loess geomorphic evolution model. New hydrological insights for the region The numerical results show that the loess geomorphic evolution model can effectively describe the process of erosion and expansion of loess gullies. In local areas, the model can also describe the evolution process from loess tableland to loess ridge to loess hill. When the erosion incision index m is less than 0.3, the model can better balance the proportions of lateral erosion and downcutting erosion in loess regions. The parameters that control the rate of erosion in the model were verified using archaeological evidence and data on similar landforms presented in the scientific literature. When the selected gully advance rate is 0.26 m/year, the time accuracy of the model can reach 95.4%. This model may be extended to other loess areas to assess the extent of landform evolution.