Dynamical analysis of the mud-belt formation in the Bohai, Yellow and East China seas

Abstract

Mud belts commonly occur on the coast and shelf environments worldwide. It requires a point source (river) and a residual current, all together constituting a tripartite configuration of the mud-belt system. This mud-belt system is analyzed for its basic sedimentological and hydrodynamical parameters to be interrelated under the steady-state conditions. The parameters include the length (L) and sedimentation rate (A) of a mud belt, water depth (h), residual current velocity (ur), and settling velocity of suspended particles (ws). The analysis shows that L is proportional to h, ur and ln A but inversely proportional tows. In addition, the mean sedimentation rate of a mud belt (A¯) is a function of only the sedimentation rates at its head and toe.To test the analytical relationships, three mud belts studied extensively are chosen from the Bohai, Yellow and East China seas. Each of these mud belts follows the ideal tripartite configuration. For all the mud belts, residual currents have been reported to be the strongest during winter seasons. The calculated A¯ gives a constraint to the otherwise wide range of the previously estimated riverine contributions to each mud belt. The two mud belts in the East China Sea and the Bohai Sea are analyzed to receive 30 and 7% of riverine sediment discharges from the Yangtze and Yellow rivers, respectively. In comparison, the Huksan Mud Belt in the southeastern Yellow Sea, on debate concerning its origin, analytically proves to be in a source-sink relationship with the Geum River. The calculated ws suggests that suspended particles are composed dominantly of fine-silt-sized single grains or micro-flocs for the three mud belts. As a result, the derived relationships may be a useful tool to understand dynamical processes of the mud belt. They also may be instrumental in anticipating the possible changes in the mud-belt evolution with A and ur that are likely to vary with the globally warming climate.