98 flood history

Under the strong leadership of the CPC Central Committee and the State Council, millions of soldiers and civilians fought bravely and won a comprehensive victory in the Yangtze River flood fighting from 65438 to 0998. At present, people all over the country are concerned about how to further improve the Yangtze River. This is not only related to the long-term stability of the people in the Yangtze River basin, but also a huge project in the national economic construction. To this end, the two academies organized some academicians and experts outside the hospital, analyzed and studied the relevant information and opinions from all sides, and put forward the following report.

I. Understanding of the Yangtze River Flood and 1998 Flood Control

1998 flood is another basin-wide flood in this century after 193 1 and 1954 floods. According to preliminary data, compared with 1998 and 1954, the upstream peak flow and flood volume are close to 1954. Because the flood peak discharge in the middle reaches is not comparable, compared with the most concentrated 30-day flood discharge, the total inflow above 1998 Hankou is less than 1954 by more than 30 billion cubic meters. The downstream flood peak discharge ratio is less than 1954 1 10,000 cubic meters, and the flood volume is 50 billion cubic meters less. Because 193 1 lacks data, we can only make a rough comparison. The upstream may be slightly larger than 193 1, and the downstream may be smaller than 193 1.

It should be noted that in the last century and earlier, the Yangtze River suffered more floods than in this century. According to textual research, since 1 153, the flood peak flow at Yichang Station has exceeded 80,000 cubic meters for eight times (1998 is 63,600 cubic meters, and 1954 is 66,800 cubic meters), among which the flood peaks 1860 and/kloc.

At present, people are concerned that although the flood is not as big as 1954, why is the flood level of 1998 in the main stream of the Yangtze River higher than 1954 except Wuhan and Huangshi? Of course, there are many factors that cause the flood level to rise, but the most critical thing is that the flood diversion and storage capacity is greatly reduced compared with 1954. During the period of 1954, many dikes in the middle and lower reaches of the Yangtze River naturally burst due to their low flood resistance. In order to reduce the flood level and keep the key areas, except Jingjiang flood diversion project, a total of water was transferred and burst 1023 billion cubic meters, of which the storage capacity of flood peak was effectively reduced by about 70 billion. According to the flood inflow of 1998, if the water level of 1954 is to be maintained, the effective flood storage is about 40 billion cubic meters. However, the total flood diversion gap of 1998 is only about 1000 billion cubic meters, and the ability to effectively reduce flood peak is estimated to be about 5 billion cubic meters. This reduces the flood diversion by about 35 billion cubic meters, which is equivalent to reducing the flooded area by 7 million mu. In other words, the flood control of 1998 is to strengthen flood control and rescue, and strive to resist higher flood level, so as to increase flood discharge and reduce flood inundation losses. For example, 1954, under the condition of using Jingjiang flood diversion project, the highest flood level in Shashi of Jingjiang levee is 44.67 meters. According to the flood control plan of the Yangtze River, in order to reduce the application opportunities of Jingjiang flood diversion project, the design flood level of Jingjiang levee was raised to 45.0 meters. 1998, in order to avoid using Jingjiang flood diversion project, Jingjiang levee was used beyond the design standard, and the flood level in Shashi reached 45.22 meters. Another example is Lianhuatang Station at Dongting Lake exit. Compared with 1.954, the flood level is higher than1.85m.. This is because at 1.954, most of the dikes in Dongting Lake area above Lianhuatang and most of the dikes on both sides of the Yangtze River below Lianhuatang, including Honghu levee, have burst or raked to divert flood water, while at 65438+,

It should be said that this is an important decision in the flood control of 1998, and it is also a very difficult decision made under the specific conditions of 1998. 1998 flood control project is based on the completion of some water conservancy projects in accordance with the flood control planning of the middle and lower reaches of the Yangtze River. In addition to the controlled reservoirs of the tributaries such as Hanjiang River, Qingjiang River, Yuanshui River, Zishui River and Xiushui River, the heightening and reinforcement works of the key dikes in the main stream of the Yangtze River and the key dikes in Dongting Lake and Poyang Lake areas have been completed according to the increased design flood level (about 0.5m higher than 1954). All these provide a certain foundation for 1998 flood control. However, a considerable number of dikes were not completed as planned, especially the safety facilities of flood diversion and storage projects in plain areas were not considered enough in the original planning and were not implemented in the implementation, which brought great difficulties to flood control and put the decision-making in a dilemma: if flood diversion is carried out according to the original planning (according to the improved design flood level, the effective flood diversion amount is still 20 billion cubic meters), it will suffer great losses; If the flood is not divided according to the original plan, the dike will bear the flood level exceeding the design standard and bear great risks. Considering that the flood ratio of 1998 is smaller than that of 1954, and the military and civilians have great potential for fighting floods, the central authorities resolutely raise the flood level, strictly guard against death, and strive to reduce breaches and flood diversion losses. This is an extremely difficult decision, which has been proved to be correct in practice. Of course, it should be noted that this is only possible if the excess flood of 1998 is less than 30 billion cubic meters of 1954. If the flood in 1998 is equivalent to or even larger than that in 1954, it is still impossible not to divide the flood.

On 1998 Disaster in the Yangtze River Basin. According to the multi-stage and systematic monitoring and analysis of the middle reaches of the Yangtze River by satellite and aerial remote sensing, the maximum flooded area of Hunan, Hubei and Jiangxi provinces is about15.86 million mu, which is much smaller than that of the three provinces due to different statistical caliber. According to the statistics of the Yangtze River Water Resources Commission, five provinces in the middle and lower reaches of the Yangtze River have flooded dikes 1705, flooded 2.95 million mu of cultivated land and affected 2.3 million people. The above figures show that most breaches are small dikes, with an average of less than 2000 mu per dike. In the disaster statistics, most of the affected farmland is due to waterlogging. 1998 The death toll is 1432. This is very different from the disaster in 1954. At that time, except Jingjiang levee and Hankou levee, most other areas were flooded, and the death population was 33 169. It is completely different from the tragic situation of 193 1 boating on the streets of Wang Yang and Hankou in the middle and lower reaches, the downtown area of Nanjing being flooded and the death population145,000. Therefore, 1998 has indeed made great contributions to fighting floods.

People from all walks of life are generally concerned about whether the elevation of the flood level of the Yangtze River is due to the siltation of the Yangtze River bed. According to long-term observation data, the main channel of the Yangtze River is basically stable, which is essentially different from the Yellow River. Due to the influence of various factors, some sections of Jingjiang River have undergone erosion and siltation changes, the most obvious being Jianli-Honghu River section below Jingjiang River. This section is affected by the Xiajing River bend cutting project, with erosion above the bend cutting section and siltation below. According to the data of the Yangtze River Water Conservancy Commission, the water level of Luoshan Station, its representative station, rises due to sediment deposition at low water level, but at high water level, the rising trend is not obvious because the proportion of sediment deposition area to flood discharge area is small. 1998 the flood level of luoshan station is 19541.78m. According to the verification, it is mainly due to the flood diversion of Jiangjia Wharf below 1954 and the breach of Laowan, which greatly reduced the flood level.

About lake siltation. Since 1949, the capacity of Dongting Lake has decreased by more than 4 billion cubic meters, and since the reclamation of 1600 square kilometers, the capacity has decreased by nearly10 billion cubic meters. The siltation of Poyang Lake is very small, but since 1949, it has been reclaimed 1400 square kilometers, and the lake capacity has lost about 8 billion cubic meters. Because all the lakes on both sides of Hubei Province are closed, the area is reduced by 5,700 square kilometers. Since 1949, the cultivated land increased by reclamation in Hunan, Hubei, Jiangxi, Jiangsu and Anhui provinces is estimated to be about140,000 mu.

Soil erosion and sediment status in the Yangtze River basin. According to investigation and statistics, the average annual erosion amount of ground solid matter in the upper reaches of the Yangtze River is 65.438+0.568 billion tons, and the average annual sediment transport amount at Yichang Station in the main stream of the Yangtze River is 530 million tons, with a sediment transport ratio of 0.33. This is different from the Yellow River. Because the upper reaches of the Yangtze River are mainly rocky mountainous areas, the ground erosion materials are mainly coarse-grained weathered rocks, which are generally deposited in the form of piedmont slope deposits, depression deposits, gully mouth diluvial fans, pond reservoirs and small and medium-sized tributaries for a short distance, and cannot be transported by rivers for a long distance; The ground erosion material of the Yellow River is loess, with extremely fine particles, which can almost be transported to the main stream of the Yellow River. Below Yichang, the average annual sediment discharge of Hankou Station is 430 million tons, and that of Datong Station downstream is 468 million tons. The main difference between Yichang and Hankou is that it is deposited in Dongting Lake area in normal years, and it is deposited in Dongting Lake area, the state beach of the river and the levee that breaks in flood years. Most of the sediment transport at Datong Station is sent to the East China Sea. Due to the different distribution of rainstorm, the sediment discharge in Yichang varies greatly in different years. For example, during the eight years from 1990 to 1997, the average annual sediment discharge was only 380 million tons, which was a year with little sediment; However, the sediment discharge from June to August in 1998 reached 605 million tons, which was more than the sediment discharge from the same period in 1954 (527 million tons), and it was a sandy year. According to preliminary analysis, the sediment sources of 1998 are mainly Jinsha River and Jialing River, which is a phenomenon worthy of further study.

The above situation shows that the flood and drought disasters in the Yangtze River basin are serious, which are mainly due to the imbalance of the basin ecosystem in addition to objective meteorological reasons, mainly manifested in the over-utilization and unreasonable development of land resources under the condition of rapid population growth. In mountainous areas, deforestation and land reclamation are steep slopes; On the plain, blindly reclamation around the lake, occupy hongzhou beach. All these have caused revenge from nature. In the Yangtze River basin, soil erosion in mountainous areas is more harmful to the local area than the Yellow River. This is because the Yangtze River basin is a rocky mountainous area with very thin topsoil. After a certain period of scouring, the topsoil was washed away, and the rocks were exposed, forming "fossils", which completely lost the living conditions of the local people. There are many "petrochemical" mountainous areas in Guizhou Province, which is shocking.

Blind reclamation of lakes and occupation of beaches in plain areas are the main reasons for the rise of flood level in the Yangtze River in recent years. From the long-term natural law, the alluvial plain of the river is formed by sediment deposition carried by the river. The economy of the Chinese nation is also developed on the basis of developing the alluvial plains of seven major rivers. However, if the development is improper or over-developed, it will be punished by the flood. Now, we are faced with this problem in the development and utilization of land on both sides of the middle and lower reaches of the Yangtze River. Not only is the flood level getting higher and higher, but the flood control burden is getting bigger and bigger, and the flood control risk is getting bigger and bigger.

The fundamental reason for the imbalance of ecosystem in China is that there are too many people and too few people. The reconstruction of ecological system must be combined with the adjustment of economic structure, with the goal of comprehensively improving productivity and paying attention to the coordination of development, reform and stability. We believe that the policy of overall consideration, tackling both the symptoms and root causes and comprehensive management put forward by the central authorities is completely correct.

Second, suggestions for future work

According to the above understanding, the following suggestions are put forward from six aspects: ecosystem, forestry construction, engineering measures, application of new technologies, strengthening leadership and coordinating national water conservancy.

(1) Adjust the land use structure and rebuild the ecosystem of the Yangtze River basin. The imbalance of ecosystem in the Yangtze River basin is caused by population growth and economic development. Therefore, we should not simply restore the original state, but adjust the economic structure and population distribution structure from the perspective of sustainable development, solve the contradiction between population and land on the basis of comprehensive development of productive forces, and realize the adjustment of land use structure. On the one hand, it is necessary to take the flood control from 65438 to 0998 as an opportunity to publicize the necessity of adjusting the land structure in a big way; At the same time, it is necessary to formulate specific plans, steps, policies and measures to adjust the land use structure, so that returning farmland to forests, lakes and peaceful dikes can be truly implemented.

1. Through comprehensive investigation and necessary survey, the land in the whole basin will be comprehensively planned, the structure of agriculture, forestry and animal husbandry will be rationally adjusted, the river and mountain improvement and home reconstruction will be brought into the overall framework of ecosystem reconstruction in the basin, and a sustainable development model will be established according to local conditions.

2. In mountainous areas, returning farmland to forests should be combined with actively developing production.

The key to returning farmland to forests is to truly solve the production outlet of local workers and the masses. It is necessary to make clear the areas that must be converted from farmland to forests, formulate specific plans to solve the production outlet, specify the time limit and steps, determine the responsible units, do a good job of implementation, and regularly check and accept them. At present, we must first stop and prevent new deforestation and steep slope land reclamation. Special attention should be paid to prevent the Three Gorges immigrants from causing new ecological damage, and the resettlement should be planned in strict accordance with the Ecological Function Zoning of the Three Gorges Reservoir Area.

Vigorously develop efficient ecological agriculture in mountainous areas where farmland can be returned to forests. Promote measures such as changing slopes into ladders, hedgerows on sloping fields, and planting on horizontal slopes. Where conditions permit, support the construction of farmland water conservancy. Vigorously carry out small watershed management in mountainous areas, take small watershed as a unit, make overall planning, comprehensive development, combine ecological protection with economic development, and combine biological measures with engineering measures. This is an important way to improve and restore the mountain environment and make people get rid of poverty and become rich.

Vigorously develop grass and raise livestock. In mountainous areas with heavy rainfall, high humidity and steep slope, plateau areas with high altitude, sloping fields and dry-hot valleys unsuitable for afforestation, forage grass should be planted to develop animal husbandry. This is also an effective way to improve the ecological environment and get rid of poverty.

3. In the lake area, returning farmland to the lake should be combined with maintaining the sustainable development of the lake area economy.

Since 1949 in the middle and lower reaches of the Yangtze River, the cultivated land in the lake area has been developed14 million mu, plus tens of millions of mu of land developed in recent 1000 years, which is not only the agricultural base of the five provinces in the middle and lower reaches, but also the development of industry and transportation, the construction of prosperous towns and the contribution to the national economic development. However, according to the flood law of the Yangtze River, it is impossible for these tens of millions of acres of developed land not to be submerged under any flood situation. In the year when the flood is not too big, all or most of them can be saved; In the year of catastrophic flood, a considerable part must be sacrificed to keep the main points. Only in this way can we maintain the sustainable development of the economy in the lake area.

It is very difficult to return farmland to the lake, because a large number of people in the dike need to move. As far as the effectiveness of flood storage is concerned, controlled flood storage can reduce the peak flow more effectively than natural flood storage, and the required flood storage capacity is much less. Therefore, it is technically and economically reasonable to implement "empty dike water storage, low water cultivation and abundant water storage back to the lake" in Hunan Province. However, it is necessary to do a good job in the safe construction of flood storage dikes, formulate corresponding policies and insurance systems, and ensure that people's production and life are reliably guaranteed; At the same time, it is necessary to formulate economic development policies and specific measures to strengthen management that are compatible with "low-water farming and flood storage and detention at high water level" to ensure timely flood storage and detention at high water level. For some dikes in 1998 with low terrain, difficult drainage and serious water damage, it is necessary to resolutely return farmland to lakes, or change closed reclamation planting into semi-closed reclamation farming, and implement "returning farmland to fishing".

We must resolutely level the flood control dike. These dikes were built on the Yangtze River beach and Dongting Lake spillway, which became obstacles to flood discharge. The protected area is not large, but it has a great impact on the overall situation. They should be resolutely removed and put back into the river.

Establish an ecological economic accounting system and an ecological benefit compensation system. In view of the long-term and overall situation of ecological engineering, it is necessary to give support in finance, taxation and credit through policies and legislation. The State Council is establishing a forest price system and a forest ecological benefit compensation system, which is necessary and should be implemented as soon as possible. At the same time, practical regulations should be made on the management of grasslands and lakes, beaches and wetlands.