Brief introduction and detailed information of flood season

Interpretation of basic information Flood season Flood season refers to the period in a year when the river water level rises regularly and significantly due to seasonal rainfall, melting ice and snow. Rainfall or melting snow in the basin will cause the river to rise sharply. In spring, the climate gets warmer, seasonal snow melts, river ice melts or spring rain causes the river to rise, which is called spring flood. In northern China, the phenomenon that river flow is blocked by ice in winter and spring is called ice flood. In summer, the torrential rain in the basin or the melting of snow in alpine glaciers make the river rise sharply, which is called summer flood. People are used to calling the floods around the dog days in summer the flood season. In autumn, due to heavy rain, the river surges, which is called autumn flood season.

Due to the different geographical location and weather system, the flood season of the seven rivers in China is different in the morning and evening. According to the analysis of rainfall and flood occurrence regularity and meteorological causes, the flood season can be roughly divided into: Pearl River: April-September, Yangtze River: 5- 10, Huaihe River: June-September, Yellow River: 6- 10, Haihe River: June-September, Liaohe River: June-September and Songhua River: June-September.

The flood season is roughly divided as follows: Pearl River: April-September, Yangtze River: May-10, Huaihe River: June-September, Yellow River: June-10, Haihe River: June-September, Liaohe River: June-September, Songhua River: June-September. Flood season refers to the period when the water level rises regularly due to seasonal precipitation and melting ice and snow in the basin. The flood season in China is mainly heavy rain in summer and continuous rain in autumn. Nationwide, the start and end time of flood season is different, which is mainly determined by the climate and precipitation in different regions. South China entered the flood season earlier and ended later; The flood season in northern China entered late and ended early. From May to September every year, the rainfall in the Jianghuai basin is obviously more than that in other months, which is customarily called the flood season. The flood season is the period with the largest precipitation in a year, which is easy to cause floods, so it is necessary to do a good job in flood control.

The floods in rivers and lakes are obviously concentrated in one year, which is easy to form a flood-prone period. Due to the different geographical location and flood season, the length and time sequence of flood season are also different.

The river rises regularly and dramatically throughout the year. Rainfall or melting snow in the basin will cause the river to rise sharply. Spring warming, seasonal snow melting, river ice melting or spring rain in the basin cause the river to rise, which is called spring flood. Because peach blossoms are in full bloom, it is also called peach blossom season (or peach blossom season). In northern China, the phenomenon that the water level rises due to the melting of river ice in spring is called ice flood. There are ice floods in the Ningmeng section of the Yellow River, the estuary section of Shandong and the lower reaches of Songhua River, which flow from south to north. In summer, the torrential rain in the basin or the melting of snow in alpine glaciers make the river rise sharply, which is called summer flood. In our country, it is customary to call the floods around the dog days in summer as the flood season. In autumn, due to heavy rain, the river surges, which is called autumn flood season.

The time, frequency and combination of rivers in different regions of China are different in flood season.

General types are generally divided into four flood seasons according to different seasons and causes of floods:

(1) The flood season with heavy rain in summer is called the flood season; (2) The flood season mainly caused by autumn rainstorm (or strong continuous rain) is called autumn flood season.

Headlights (3) The flood season caused by the thawing of ice plugs in winter and spring is called the ice flood season.

(4) The flood season is called the spring flood season, which is mainly when the iceberg at the source of Beijiang River melts or the ice sheet in the upper reaches freezes, and the south enters the rainy season at the turn of spring and summer. On the Yellow River, because Hong Ling, who speaks from the upper reaches of the river, spreads to the lower reaches, it is the season when peach blossoms are in full bloom, so it is also called the peach blossom flood season. Because flood season and autumn flood season follow closely, it is easy to form a big flood, which is generally called summer and autumn flood season, and is usually referred to as flood season for short.

Different Characteristics Rainstorms and floods in most rivers in China occur in the flood season of summer and autumn. The seasonality of rainstorm and flood is closely related to the north-south movement of rain belt and frequent typhoon activities, and the start and end time of flood season is different in different regions. The division of the start and end time of flood season (mainly refers to the flood season in summer and autumn) is generally reflected by the frequency of floods in this period. A flood that exceeds the average annual maximum flood peak discharge is called a "big flood". The determination of the flood season period is to ensure that more than 90% of the "big floods" occur within the specified period; The main flood season is determined by controlling more than 80% of the "big floods". For example, April to September is the flood season in Jiangnan, and May to June is the main flood season; The Pearl River is flooded from mid-April to September every year, with April to June as the first flood season, July to September as the second flood season, and May to June as the main flood season. The Yangtze River is in flood season from May to1mid-October, with the main flood season from July to August. The Huaihe River is in flood season from June to September, and the main flood season is from July to August. The Yellow River is in flood season from July to 10, and July to August is the main flood season. Haihe River is in flood season from July to August, and the main flood season is from late July to early August. Songhua River is in flood season from July to September, and the main flood season is from late August to early September. The analysis shows that with the change of rain belt, the start time of flood season in China is gradually delayed from south to north, while the length of flood season is gradually shortened from south to north. Pearl River, Qiantang River, Oujiang River, Yellow River, Hanshui River and Jialing River have obvious double flood seasons. The former is divided into pre-flood season and post-flood season, while the latter is divided into dormancy period and autumn flood season. July to August is the highest frequency of major floods in China.

The flood season is different all over the world. For example, the Nile in Africa is from July to 10, the Mississippi in the United States is from February to May, and the Amazon in South America is from June to July.

In addition, due to the rainstorm ahead of the flood and the need of flood control, the flood season stipulated by the * * * department is generally longer than the natural flood season. For example, according to the regulations of the * * department, the flood season starts and ends from April 1 to September 30th, the Yangtze River from May 1 to June 1, the Yellow River from July 1 to June 1, and the Songhua River from June.