长江中下游干流河道全长约 1773km ,两岸干堤总长 170 0km ,防洪标准很低。长江 1998年大洪水后 ,中游沿江两岸以前所未有的力度进行堤防加高加固。在堤防加高加固设计中 ,第一要素就是设计洪水位。在推求各堤段设计洪水位时 ,要注意上下游、左右岸的协调对应 ;对分蓄洪区的围堤 ,要考虑设计分蓄洪水位 ;城陵矶附近河段和湖口附近河段设计洪水位 ,因江湖关系的恶化 ,在修订长江防洪规划时应予适当调整 The total length of the mainstream river in the middle and lower reaches of the Yangtze River is about 1773km. The total length of the embankments on both sides of the Yangtze River is 170km, and flood control standards are very low. After the 1998 Great Flood in the Yangtze River, the embankments were heightened and hardened on both sides of the Yangtze River with an unprecedented intensity in the middle reaches. The first element in the design of embankment heightening and reinforcement is the design flood level. At the time of calculating the design flood level of each embankment section, attention should be paid to the coordination between upstream and downstream and left and right banks. For the embankment of the flood diversion area, the design of flood diversion points should be taken into account; design floods near the reach of Chenglingji reach and the vicinity of Hukou As a result of the deteriorating relations between rivers and lakes, they should be appropriately adjusted in the revision of the Yangtze River flood control plan