黄河源发育不同类型、不同尺度和数量众多的弯曲河流，其频繁地发生颈口裁弯，快速降低原河道弯曲度和驱动新河道周期性演变，是弯道形态动力过程临界突变的拐点。颈口裁弯的持续时间短和冲刷过程强烈，遥感影像和野外观测均难以实时捕捉颈口裁弯事件，而且当前水槽实验尚不能实现颈口裁弯过程。本项目聚焦颈口裁弯的条件、过程与机理，旨在从野外观测及试验、水槽实验、理论分析和数值模拟突破当前颈口裁弯的研究瓶颈，实验研究不同水流、泥沙和植被条件下颈口裁弯过程，确定触发颈口裁弯的水流-泥沙-植被临界条件，理论构建单向崩岸和双向崩岸贯穿型颈口裁弯的形态动力学控制方程。采用黄河源实测数据和水槽实验塑造的逼近裁弯的弯道原型，建立颈口裁弯形态动力学模型，数值模拟并预测黄河源不同类型和不同尺度的弯道颈口裁弯发生、发展和周期演变，以及上下游河道对颈口裁弯的冲淤响应过程。本项目有利于丰富弯曲河流动力学和黄河源弯曲河流湿地的生态保护。

A great number of meandering rivers width different types and variable geometry scales develop in the Yellow River Source Zone, where the frequent occurrence of neck cutoffs is an inflexion point of the sudden change in the meandering river morphodynamics, i.e., quickly reducing the sinuosity of the old bend and driving the periodic evolution of the new channel. Neck cutoff has the short duration and induces intense scour process that result in difficultly real-time capturing the occurrence of neck cutoffs in nature based on satellite imagery and field survey, furthermore failing to produce neck cutoff in flume experiment so far. This study will focus on the condition, process, and mechanism of neck cutoff, aiming at outreaching the research bottleneck through field measurement and monitoring, flume experiment, theoretical analysis, and numerical simulation. Experimental studies on occurrence and processes of neck cutoff are performed under different input discharge, sediment supply, and planting riparian vegetation conditions, in order to determine the threshold condition of flow-sediment-vegetation that triggers the neck cutoff. A new concept of one-side and two-side bank collapse induced neck intersection is advanced to theoretically derive the morphodynamic governing equations of neck cutoff. Using the dataset of the bend prototype approaching neck cutoff in the Yellow River Source Zone and flume experiments, the process-based model of the morphodynamic processes of neck cutoff based the TELEMAMC model is established to numerically simulate and predict the occurrence, development, and periodic evolution of neck cutoff at different types and scales, as well as the erosion-deposition response of upstream and downstream channel to neck cutoff. This project is significantly helpful to enrich the knowledge of meandering river morphodynamics and of great importance to the ecological protection of meandering riverine wetland in the Yellow River Source Zone.