黄河河口尾闾与三角洲演变过程机制解析

Evolution Processes and Mechanisms of the Yellow River Delta and Its Deltaic Channel

通过解析黄河河口尾闾摆动、大堤决口、三角洲演替过程与机制,认识到黄河河口尾闾每一次改道都再现了由地下河演变到地上河再决口改道的过程,而弯道环流裁弯取直过程中裁穿相对薄弱的悬河河岸,是近代三角洲以宁海为顶点自然决口与摆动的根本原因。1855年以来10条主要流路形成的整个近现代三角洲依次各存在第一代三角洲、第二代三角洲、第三代三角洲的自然叠加关系,1988年至今的现行清水沟流路第三代三角洲已成雏形。黄河尾闾摆动与三角州形成是黄河多沙河口几千年来的天性,要保障黄河河口的健康生命,不仅要为现行黄河河口尾闾留出一块可以摆动的第三代三角洲,规划流路河口也要留出第三代甚至第四代三角洲。

Based on the analysis of the processes of the Yellow River deltaic channel shift, levee breaches and delta evolution, the mechanisms of these processes were examined. A changing process from a normal river to a suspended river was illustrated during every shift of the deltaic river channel. The shortcut of the river channel due to secondary flow in river bend was the primary cause for the levee breach and deltaic channel shift near Ninghai. The modem Yellow River delta had been formed by the overlap of three phase subdeltas of each of ten deltaic river channels since 1855. The third phase of the current Qingshuigou deltaic channel had been formed since 1988. It is of importance to revel the mechanisms of the deltaic river channel shift and delta evolution. Furthermore, a future region for the third and even fourth phase subdelta should be planed for exten- ding the lifespan of the Yellow River mouth.