Submarine-fan channels can build the largest sediment accumulations on Earth, but our understanding of flow and sedimentation processes related to channel evolution remains limited. Results from physical and numerical modelling predict dominantly downstream channel bend migration. However, observations and evolutionary models for aggradational submarine channels on passive margins suggest that bends are dominated by lateral expansion. This paradox may be due to limitations induced by the use of constant width channels in process studies. Constant width has been used for two reasons: partly because this is the simplest possible case, but primarily because the width variation around submarine channel bends is unknown. Channel width variations are examined from an active channel reach with 49 bends and three inactive but unfilled channel reaches with a total of 35 bends from the Congo Fan. Each bend was divided into 13 cross-sections, and for each cross-section, channel width was measured for the channel base, and at 10 m vertical increments up to the height of the channel banks. The results indicate that channels are typically wider around bend apices than around inflections. We argue that this morphology suggests that channels are controlled by bank-pull (outer bank erosion), with later deposition at the inner bend, similar to many rivers. The implications of these spatial changes in channel width around bends for sedimentation and channel evolution are explored, and we suggest that such changes may account for the contradictions between physical and numerical modelling, and seafloor observations. Integration of these channel width data with the known climate history of the Congo Fan, further suggests that the magnitude of channel width variation at bend apices may be controlled by allogenic forcing, with larger flows associated with greater width variations around bends.

海底扇形通道可以在地球上建立最大的沉积物堆积，但是我们对与通道演变相关的流量和沉积过程的理解仍然有限。物理和数值模拟的结果主要预测下游河道弯道迁移。但是，被动边缘上的海底消融通道的观测和演化模型表明，弯曲主要由侧向膨胀控制。这种矛盾可能是由于在工艺研究中使用恒定宽度的通道而引起的限制。使用恒定宽度的原因有两个：部分是因为这是最简单的情况，但主要是因为未知海底河道弯道周围的宽度变化。通道宽度变化是从刚果扇的活动通道到达49个弯道和三个非活动但未填充的通道到达总共35个弯道中进行检查的。将每个弯头分为13个横截面，并针对每个横截面，测量通道底部的通道宽度，并以10 m的垂直增量测量直至通道堤的高度。结果表明，弯曲顶点周围的通道通常比拐点周围的通道宽。我们认为，这种形态表明河道是由河岸拉力控制的（河岸外侵蚀），后来在河内弯道沉积，类似于许多河流。探索了弯道周围河道宽度的这些空间变化对沉积和河道演变的影响，并且我们建议这种变化可能解释了物理和数值模拟与海底观测之间的矛盾。将这些河道宽度数据与刚果民主共和国已知的气候史相结合，进一步表明，弯道顶点处河道宽度变化的幅度可以通过同种异体强迫来控制，更大的流量与弯道周围较大的宽度变化相关。