Xinyi River was completed in the winter of 1949, with a design flow of 3,500 cubic meters per second, which opened the sea passage for the flood in Yishusi basin and ended the situation of flooding. 1950 experienced five flood tests in flood season, with the maximum flow of 255 1 m3 per second; 1957 summer, however, it encountered an over-standard flood with a flow rate of 37 10, and narrowly escaped. 1958 heightens the flood dike on the backwater slope according to the standard of 5000 cubic meters per second, and the flood control standard is increased to 4500 flow. 1963, the levees were in danger, and the flood with the flow of 4 150 approached the critical point and finally turned the tide. 1964 decided to raise it to the once-in-a-thousand-year standard, which was designed according to the safety flood discharge of 6,000 cubic meters and checked according to 7,000 cubic meters. From 1965 to 1973, the Xinyi River extension project was completed after 9 years of construction. 1August 974 16 defended the historical maximum peak flow of 6900 cubic meters per second, but the levee was seriously damaged by water and the dangerous sections increased. Since then, some dikes in Chengwei, Dalu Lake and northeastern Sichuan have been reinforced. Due to the low safety and superelevation design of19646000m3/s, and after the flood of 1974, the dangers of Chengwei, Shawan and Dalu Lake are more prominent, and after the drought of 1978, the dike body generally cracked, so it was again from 1983 to/kloc-.
With the development of national economy and the improvement of flood control standards in the upper reaches, in June 5438+0993, the State Council approved the resumption of flood diversion project in Yishusi River Basin, and agreed to implement it in the near future according to the flood control standard of once every 20 years, requiring Xinyi River to discharge flood at the standard of 7000 cubic meters per second. From 1994, the reinforcement was carried out according to the flood discharge standard of 7,000m3 seconds once every 20 years (Phase I project). At this stage, the dangerous works and culverts with outstanding problems along the line are mainly reinforced, and the Haikou control hub is newly built. However, due to limited funds, the project failed to meet the safety flood discharge standard of 7000 cubic meters per second. By 1999, the first phase of the project was basically completed with an investment of 290 million yuan.
During the period of 1998, the flood peak discharge of Xinyi River was only 4360 cubic meters per second, and the water level below Shuyang River was generally high, reaching or approaching the design water level of 6000 cubic meters per second. High water level and moderate discharge make dikes in many places in danger, such as water seepage, sand break and slope collapse. In view of the fact that the 50-year once-in-a-lifetime project of South-to-North Water Transfer Project (Phase II) cannot be implemented temporarily, jiangsu provincial party committee and the provincial government decided to use loans to implement the Xinyi River dike project, focusing on solving the problems such as foundation leakage, insufficient flood discharge capacity and culvert danger of Xinyi River dike, laying a foundation for improving flood control standards in Yishu Sihe River basin and expanding flood discharge of Xinyi River. The main task of dike reinforcement design is to implement the 50-year return standard of Xinyi River in advance according to the problems found in dikes and the situation of dike-crossing buildings in flood season 1998 to ensure the safety of dikes and dike-crossing buildings. The project started at 1998 and ended at 200 1, with an investment of1.200 million yuan.
General Layout of Xinyi River Regulation Project (1 below)
Satellite map of Xinyi River Project (Figure 2 below)1990 shows that the flood discharge of Xinyi River has not exceeded the original design flow for many times, but many problems have been exposed, which poses a great threat to the safety of flood discharge. Although it was handled by the first phase of the project, it was limited by funds and failed to completely solve the problem. At present, the existing problems are mainly manifested in the following aspects: First, the roughness of the eastern part of Sichuan has become larger, and the original design flood discharge capacity cannot be achieved. Second, the top of some levees is too high. North dike 3 1 km, amplitude 0.06 ~ 0.31m; The south dike is 30 kilometers with an amplitude of 0.06 ~ 0.4 1 m. Third, the safety and stability of the dike body can not meet the requirements of the code. The main stream of Xinyi River is a 1 class dike, and the safety factor of anti-sliding stability under normal operating conditions is 1.30, but the east of Yanhe River can not meet the requirements of the code basically, and it needs to be strengthened urgently. Fourth, there are still dangerous sections in some embankment sections, and some buildings crossing the embankment are running with diseases. Fifth, the flood control infrastructure is weak, and the remaining problems such as beach property and cross-strait influence have not been solved for a long time. There are more than 300,000 mu of cultivated land in Xinyi River bed, which involves the production and living problems of 340,000 people along the coast. Due to years of flood discharge, the tidal flat project is seriously damaged and aging, which brings certain difficulties to tidal flat production.