对坡面径流挟沙力研究的几点认识

坡面径流挟沙力是土壤侵蚀过程模型的核心输入参数。在系统界定坡面径流挟沙力概念的基础上，深入分析了坡面径流水动力学特性和泥沙特性对坡面径流挟沙力的影响及其机制，受降雨、地形、土壤、植被、土地利用、结皮形成、细沟发育和砾石出露等多种因素时空变异的综合影响，坡面径流挟沙力具有强烈的时空变化特征，导致坡面径流挟沙力的测定较为困难。将确定挟沙力常用的方法划分为河流挟沙力方程修正法、推理法、模型模拟法和测量法，比较分析了不同方法的优缺点。未来的研究应该重点关注挟沙力测定方法与技术、坡面径流输沙过程的动力机制、典型土壤的挟沙力、挟沙力方程构建与验证及变化条件下坡面径流挟沙力等方面。

Several understandings for sediment transport capacity by overland flow

Sediment transport capacity of overland flow, which is the maximum equilibrium sediment load that a flow can transport, is a key concept for developing process-based soil erosion models because it plays a pivotal role to determine soil detachment rate and sediment transport. Few studies have been conducted to investigate the mechanism of sediment transport capacity by overland flow on steep slopes. In this paper, based on the systematic definition of sediment transport capacity of overland flow, the influences and their mechanisms of hydraulic properties of overland flow and sediment characteristics on sediment transport capacity were deeply analyzed. Sediment transport capacity of overland flow has great spatial and temporal variations due to the comprehensive effects of precipitation, topography, soil, vegetation, land use, sealing formation, rill development, and gravel covering. Therefore, it is very difficult to measure sediment transport capacity of overland flow directly in field conditions. The commonly used methods to determine sediment transport capacity of overland flow can be categorized into the modification from river sediment transport capacity formula, the rational method, the model simulation, and the direct measurement. The advantages and disadvantages of each method were compared and analyzed. Further studies should be focus on the measuring methodology and techniques for sediment transport capacity of overland flow, the hydro-dynamic mechanism of sediment transport process, sediment transport capacities of typical soil types, transport capacity formula development and performance evaluation, and sediment transport capacity of overland flow under changeable conditions. It is helpful to summarize the conclusions of different studies, promote the research on sediment transport capacity of overland flow, and improve the prediction precision of the process-based soil erosion models for better service to water and soil conservation planning and design.