Managing Across Borders

During the Chinese history, attempts to control the Yellow river have been categorized by different strategic approaches. One strategy is to confine the river within a narrow channel by high levees. The narrow-channel concept carries the danger of active erosion of the levee, but it encourages the fast flow that keeps sediment in suspension, and therefore, allows only slow silting of the river bed. However, there is little reserve capacity for absorbing a major flood crest, and even the high levees will inevitably be overtopped. On the other hand, one might adopt a strategy of confining the river in a wider flood plain, between lower levees. This is cheaper to construct, but requires that more land be sacrificed to river control. It also permits a slower flow, and promotes silt deposition. Over time the river will inevitably build up its bed. However, there is much more reserve capacity for flood water in a wide channel, and there is room to build small diversion dams to keep the river course to the center of the channel, avoiding the problem of scouring against the levee foundations.