We present a simple image analysis technique for measuring the sediment composition of the bed surface during flow with bedload transport in flume experiments. The bed was composed by a bimodal mixture of natural sediments and the flow conditions were such that both fractions were mobile. A camera placed 2.5 meters above the flume framed the central part and took pictures every minute, allowing for a high-resolution data acquisition. The two sediment fractions had different colors, thus we developed an image analysis technique based on color detection. This technique provided the areal fraction content of each fraction and the detection of patterns of sorted sediments, namely patches of each grain size, and it was applied in three laboratory experiments conducted to study the influence of lateral width constraint on channel morphology, sediment sorting, and bedload transport. The three experiments were carried out under constant feeding rate conditions, in particular a sediment supply equal to the transport capacity was provided, thereby matching dynamic equilibrium conditions. The image processing was implemented through a code written in Matlab and made available for other users.

我们提出了一种简单的图像分析技术，用于在水槽实验中利用床载运输来测量流动过程中床面的沉积物成分。该床是由天然沉积物的双峰混合物组成的，流动条件使得两个馏分都是可移动的。位于水槽上方2.5米处的照相机将中央部分框起来并每分钟拍摄一次，从而可以进行高分辨率的数据采集。两种沉积物组分具有不同的颜色，因此我们开发了一种基于颜色检测的图像分析技术。该技术提供了每个馏分的面积馏分含量，并检测了分类的沉积物的模式（即每个粒度的斑块），并将其应用于三个实验室实验中，研究了横向宽度约束对通道形态的影响，泥沙分选和基床运输。这三个实验是在恒定的进料速率条件下进行的，特别是提供了等于输送能力的沉积物，从而匹配了动态平衡条件。图像处理是通过用Matlab编写的代码实现的，并可供其他用户使用。