The 1.2 sluice is built in the estuary, and the flood discharge is not smooth. Building sluices in estuaries can prevent salt water from accumulating, which is very beneficial to irrigation, aquaculture and shipping in estuaries and beaches. Therefore, China has built more than 65,438+000 culvert gates along the coast. But at the same time, there are also problems such as river siltation, poor flood discharge and aggravated waterlogging. 1958 A Yaojiang sluice was built in Yuyao, Zhejiang Province, which played a certain role in developing agricultural production, but it stopped 12 from entering Yaojiang! The tidal volume of × 1m (accounting for 46% of the Yongjiang tidal volume) greatly reduces the tidal intake of Yongjiang River, resulting in serious siltation of Yongjiang River, narrowing of the whole riverbed, reduction of the average cross section of mid-tidal level from 2 560 m to 1 460 m, and reduction of the average flood discharge in flood season from 2 500 m/s. Because the flood discharge capacity of the river is greatly reduced, the drainage time in the coating area is prolonged and the waterlogging is aggravated. At the same time, the flood level in Ningbo city has risen by 50 ~ 70 cm, which brings great difficulties to urban flood control.
1.3 Environmental pollution and ecological imbalance. In recent ten years, with the accelerated development of tidal flat resources, pollution industries have been introduced into tidal flat in some places, and even tidal flat has been regarded as a natural pollution receiving field, resulting in pollution incidents from time to time. The use of pesticides and fertilizers, especially high-efficiency pesticides, and the discharge of domestic sewage in planting and breeding have brought serious pollution to the natural ecological environment of beaches and caused huge economic losses. Nantong City, Jiangsu Province1997,20,000 tons of cultured Meretrix meretrix died due to environmental pollution, and the direct economic loss was about 200 million yuan. In 1960s and 1970s, the annual output of natural Pseudosciaena crocea was 5000 ~ 1000t, which is now extinct. Bitter brine is an important chemical raw material, but due to the technical level and other reasons, the utilization rate of bittern in China is only about 25% at present, and most of the rest is discharged into the sea as wastewater, causing the death of beach and offshore organisms and destroying the ecological balance.
1.4 Wetlands decrease and species are endangered. Coastal beaches provide a good natural ecological environment for the life and reproduction of biological populations, so there are rich species here, and there are many kinds of national first-and second-class protected wild animals. However, with the reclamation and plunder of beaches, the species of organisms gradually decreased and biodiversity was seriously damaged. The yellow mud snail produced on the beach in Dafeng City, Jiangsu Province is famous both inside and outside the province. In previous years, the fishing period lasted for more than two months, but in recent years, the number of people on the beach was as high as 10000 ~ 20000 every day, and it was difficult for large and small snails to survive, and the fishing ended about10d. The city is known as "the freshest Meretrix meretrix in the world", with a reserve of 9 000 t 1979, but the resources of Meretrix meretrix in Shanghai beach are less than 30 t; At present. Sulongdan, a Chinese herbal medicine produced in this city, bought 22,550 kg at 1963, and the price dropped to 100 kg at 1983. At present, this species is on the verge of extinction on coastal beaches.
1.5 was improperly introduced, which affected the disaster. In order to promote siltation and reclamation, protect banks and dikes, and improve soil, Spartina japonica has been introduced in many places, because Spartina japonica is salt-tolerant and waterlogging-tolerant, and has wide adaptability, and can almost grow in intertidal zone. The stems and leaves of Spartina alterniflora are elastic, and the root system is developed, and it grows down several tens of centimeters or even several meters, which has the functions of wave absorption, slow flow and sand retention. Spartina has strong tillering and reproduction ability, and the number of tillers can reach dozens or even hundreds every year. At the same time, its seeds can spread outward and quickly spread around. Because of these characteristics of Spartina, in fact, some places have spread into two disasters. In Sandu Bay, Fujian Province, Spartina has invaded more than 4 000 km of breeding ground, and its leaves and seeds drift with the waves and accumulate in seaweed and kelp breeding ground, which has caused huge economic losses to beach aquaculture. In addition, in some harbors along the coast of South China, due to blind reclamation, the tidal capacity in the harbor is reduced, the tidal channel is silted, and the navigation channel becomes shallow, resulting in poor navigation. Coastal beaches are most vulnerable to direct attacks by typhoons, so the more the beach economy develops, the greater the disaster losses caused by typhoons.
References:
Negative Effects of Tidal Flat Reclamation and Sustainable Development Strategies (Feng Lihua, Bao Yixin)