What are the hazards of the Yellow River? What happened in recent years should be made clear.

"All previous major floods in the middle and lower reaches of the Yellow River were based on historical documents and flood trace surveys, especially in recent years, except for 1933, 1958 and 1982. Two others were sorted out and examined: 176 1 (twenty-six years of Qing Qianlong) and 1843 (twenty-three years of Qing Daoguang). " Cheng Gang said, "176 1 August 17, 17. The floods mainly come from the Yihe River, Luohe River and Qinhe River in the section from Sanmenxia to Huayuankou of the Yellow River and the small tributaries that directly flow into the Yellow River. There are many spillway in the lower reaches of the Yellow River. Huayuankou section 176 1 year peak flow is 32,000 cubic meters per second. Cities in the lower reaches of Luo Yi River and Qinhe River are suffering from floods. The whole beach area of Luo Yi River from Luoyang to Yanshi is more than ten feet deep. Yanshi, Gongyi, Qinyang, Wuzhi and Xiuwu are also flooded cities with water depths ranging from five or six feet to more than ten feet. According to the memorial of the governor of Henan at that time, ten counties in Henan Province were flooded, and another sixteen counties were flooded. "

Cheng Gang went on to say that in August of 1843 (July of the 23rd year of Qing Daoguang), a rainstorm occurred in the middle reaches of the Yellow River. The highest flood level appears in Tongguan-Xiaolangdi reach of the Yellow River. The flood was caused by a shear linear rainstorm in the southwest-northeast direction. According to the investigation of ancient sites and flood silt along the river, the flood level of 1843 is at least the highest in a thousand years. Its return period can be regarded as once in a thousand years. In the flood investigation, the residents on both sides of the Yellow River from Tongguan to Xiaolangdi have a deep memory of the flood, and there are many ballads that have been passed down to this day, such as "On the 23rd day of Daoguang, the Yellow River ascended to heaven, crossing the river in a rush to the sun, and taking Wanjin Beach". According to the then Governor of Henan Province, on the 8th of July, he said, "There are also records in Shaanxi, Xin 'an and Shandong. On July 14, the Yellow River rose by more than 20 feet, and the overflow tank was full, so that all the houses along the Tianhe River were washed away ... Now it has been reported that 23 counties were flooded, 17 counties were flooded by rain, 7 counties were flooded, and Surabaya and Chenliu counties were the most serious. The original situation is that the flood has been discharged to Zhongmou. A large number of floods flow from Zhongmou Koumen to the southeast, enter the Wohe River and Dasha River, capture the Huaihe River and return to Hongze Lake. The flooded areas include Fugou and Xihua in the west, Tongxu, Taikang, Lu Yi and Bozhou in the east, and Hongze Lake in the south. "

1933 In the first ten days of August, the biggest flood occurred between Hekou Town and Shan County in the middle reaches of the Yellow River 19 1933 Shan County Hydrological Station. The peak flow of Shan County Hydrological Station is 22,000 cubic meters per second, which is the largest flood since the station has measured data. As a result of this flood,

From July 1958 to July 18, heavy rain and flood occurred in Sanmenxia to Huayuankou section of the Yellow River. On the evening of July 17, the maximum flood peak flow at Huayuankou Station of the Yellow River since July 19 19 was 22,300 cubic meters per second.

Then, Cheng Gang introduced the situation of 1982 Yellow River flood in detail.

1982 Yellow River flood

From July 29th to August 2nd 1982 There was heavy rain from Sanmenxia to Huayuankou on the Yellow River, with heavy rain locally. From rainstorm to rainstorm, the main stream of Sanhuajian of the Yellow River and Luo Yi have risen successively. Huayuankou Station experienced a flood peak on August 2nd 18, with a flow rate of 15300 m3/s, with a flood of 5.02 billion m3 in 7 days, and the flow rate above 10000 m3/s lasted for 52 hours.

In this flood, the floodplain in the lower reaches of the Yellow River generally overflowed, and the flood peak was cut off by the sudden flood in Luo Yi and the floodplain on both sides. In order to reduce the flood control burden below Ai Shan, the old Dongping Lake was used for flood storage. Seven days later, the flood peak entered the sea on August 9.

The weather process started on July 29th, and the low-level southeast jet near Typhoon No.9 in Huanghuai area met with the cold trough that night, and heavy rain began to appear in Sanhua, and the local torrential rain expanded. From March 1 to August1,the typhoon low pressure moved to the south of Sanhua, and combined with the Shaanxi vortex, and the rainstorm and the rainstorm area continued to expand. On August 2, the rainy area moved north to Qin.

"This rainstorm is characterized by long duration, strong central intensity and uneven distribution," Cheng Gang said. "Its biggest rainstorm center is located in Luhun, Songxian County in the middle reaches of yi river. On July 29, the rainfall reached 544 mm, of which 1 1.5 hours of rainfall was 535 mm, the maximum intensity was 87 mm for one hour, and the maximum rainfall for five consecutive days was 782 mm. "

During the continuous rainstorm, there were three flood peaks in the main and tributaries of Sanhuajian. The first flood peak discharge at Huayuankou Station is 65438+6400 m3/s,1July 3, 9821day. On August 2nd, the second peak discharge of Huayuankou Station was 1 1200 m3/s, and the third peak discharge was 1982. Seconds Due to the inflow of water from Tan Jia and the flood plains on both sides of the strait, the flooded area is about 260 square kilometers, and the detention reservoir capacity is about 460 million cubic meters. The flood at Xiaolangdi, Heishiguan and Wuzhi Stations merged with the water from the main stream of Xiaohua Section (Xiaolangdi to Huayuankou), forming the peak of Huayuankou Station/kloc-0.53 million cubic meters per second, with a flood volume of 5.02 billion cubic meters in seven days.

At 4 o'clock on August 3rd, the flood peak arrived at Jiahetan Station, and the flood peak flow 14600 m3/s increased by 7.2% compared with the reduced 1958.

In order to reduce the flood control burden below Ai Shan, the old lake in Dongping Lake was used to store flood detention. Lin Xin sluice and Shilibao sluice were opened at 22: 06 on 6th and 1 10 on 7th, respectively, at 20: 00+02 on 9th and 23: 00+08 on 9th, with a total flood volume of 400 million cubic meters.

The sediment concentration of this flood is relatively small. The average sediment concentration at Huayuankou Station is 32 1kg/m3, and the maximum sediment concentration is 63.4kg/m3. The river below Huayuankou "silted up and washed away". The section from Huayuankou to Sunkou has deposited 800 million tons, including 67.6 tons from Gaocun to Sunkou. 38.2 million tons were excavated from the section below Sunkou.

According to Cheng Gang's analysis, the rainfall, rainstorm range and total flood volume of Sanhua are all greater than 1.954 and 1.958. The flood peak is slightly larger than 1.954 and smaller than 1.958. Along the way, the flood peak drops greatly and spreads slowly, and the flood level of most substations is higher than 1 958. Peak flow is less than 1958. The main reason is: 1. The rainfall intensity of Sanfang Rainfall Center (Sanmenxia to Xiaolangdi) is less than 1958, so the flood peak flow of Sanfang is 1 1000 cubic meters per second. And in 1982, only 4760 and 3520 cubic meters per second. 2. The distribution of rainfall time history is not as concentrated as that of 1958, which leads to the continuous flood peak of Luo Yi River and Sanxiao, and the flood peak of 1958 only occurs once. 3. The effect of water storage and flood detention of mixed reservoirs on land is better than that of 1958. 1982 decreased by 50% and 55%, that is, the combined flow of Baima Temple and Longmen Town was 7 100 and 9070 m3/s, and Heishiguan decreased to 3540 and 4040m3/s.. 4. The flood peaks of the main stream and tributaries are different, and the flood peaks of Xiaolangdi 1982 are different from those of Iraq, Luoyang and Luoyang.

1982 flood generally overflowed the beach, causing erosion and siltation, and the water level at the same flow rate decreased obviously during flood fluctuation. However, due to years of river siltation, the flood level of 1982 is generally higher than that of 1958, generally around 1 meter high, Liuyuan.