On Octorber 2nd ~ 5th ,1930, a rare torrential rain occurred at the DaLing River in weatern Liaoning Province (hereinafter referred to as "30.8" rainstorm), and the center was in Xihe River basin in the left tributary of the lower DaLing River in Liaoning Province. There was a catastrophic flood in the downstream of Daling River, all the rivers around Bo Sea coast and Raoyang River, also in the Qinglong River, which is the tributary of Luan River in Hebei Province. Floods had also spread to parts of southern Jilin Province.
This rainstorm is mainly distributed in Daling River, the middle and lower reaches of Liao River and the downstream of Luan River. The rain distributes from northeast to southwest. The east of this area is lower reaches of Liao River Plain, and the weatern terrain is gradually uplifted into a cutting low mountain area, which the average altitude is below 1000m. The east of rainstorm centre at the West River is YiWulv Mountain which locates north-south direction, and the main peak is 866m. The weatern part is Songling mountains which the average altitudes are 400-700m. The West River is located between the two mountains to form the open bell mouth terrain which provides good terrain conditions for the formation of rainstorm.
Because the western part of Liaoning didn’t have actual measured hydrological and meterological data, estimation of rainfall data based on survey data. After several investigations and verification by Liaoning hydropower Department, basically found out the date of the torrential rain, the central rainfall and regional distribution. The investigation field included Da Ling river, Rao Yang river and Liu Gu river etc.，more than 20000 square miles, covering city of Jin Zhou, Fu Yang Chao yang and other 12 counties 59 communities and 290 production units. The investigation got 111 rain raw data. According to certain converting method，investigation gets 25 credible data, 55 relative credible data and 31 reference data. Moreover, they choosed some river to investigate the flood and obtained 32 flood peak discharge results. Meanwhile, they still researched the disaster conditions made of this torrential rain.
Rainfall Process
In July, 1930, the western part of Liaoning province and Xiaoling River area began to rain and overcast. On Octorber 2nd, the measured rainfall in Luancounty, Hebei Province was 119.1mm. On Octorber 3rd, the rainfall in Lulong was 277.5mm in the Rong county was 195mm and in LuoJiaTun was 138,5mm. Meanwhile, the rain gradually expanded to the area in SuiZhong, Yi county and FuXin of LiaoNing Province. In August 3rd afternoon, the area of Yi County and FuXin started to rain, then the strength increased in the evening, and it didn’t end until 4th noon, stopping on 7th. The storm rainfall was moving from the northweat to the southeast. Rainfall in Hebei mainly concentrated on August 2nd-3rd. The rainstorm center in the western of Liaoning concentrated on August 3rd-4th, when the most strong was in the 3rd evening to the 4th morning.
The intensity of the storm was particularly heavy. According to local residents: The rain began at six or senven o'clock in the evening. The heavy rain was like trying to poke a hole in the sky. The rain dripping from the eaves was not a slip, but a piece of rain, which was like the curtain. It couldn't see the people three to four meters away, when you breathed you would feel suffocated. After the rain there were a large piece of dead birds in the field. It rained all night, so the second day the rain rushed to the BaiQiBao( renamed FuXingBao later).
There were 21 places where the rainstorm continued to fill three or four jar of water from 3rd night to the 4th. According to the residents who lived in FuXingBao, they said that the rain filled a jar of warter about 9 o'clock, then filled another jar at the chicken crowing as a rock, which the third jar was at the second day dawned. The accumulated rainfall was 1968mm after measurement. Considering about some factors such as the before rain or not clean the jar, the rainfall was estimated to be 1500-1700mm. According to the survey data analysis, the maximum rainfall in each period of rainstorm center was approximately 350-400mm two hours, 600-650mm four hours, 650-760mm twelve hours and1000-1300mm 24 hours, and the secondary rainfall was 1700-2500mm. The opportunity happened in China mainland which in 24 hours the rain was over 1000mm was few. It only had once record, which was 1060.3mm in the LinZhuang of Henan Province on August 7th ,1975. In addition, they have researched that the rain was 1400mm of 12 hours in WuShenQi MuDuoCaiDang ,Inner Mongolia on August 1st, 1977.
Torrential rain is mainly distributed in the front region of Nuerhu mountain in Liaoxi region, the rain was South-west and North-east tonal distribution. Liu river, Raoyang river as well as the large Ling river, small Ling river and Liugu river which were located on western side of liao river, all of them were shrouded in heavy downpour. It affects over 20 counties in Liaoning Province and more than 10 counties in Hebei Province. The centre of rainstorm nears Yi counties, the largest rainfall exceeds 2000mm, each rainfall at least 1500mm with the 496 square kilometre coverage; over 1000mm rainfall with the 3210 square kilometre coverage; over 500mm rainfall with 18000 square kilometre coverage.
Rivers in Torrential rain-zone occur flood or severe flood. The catchment area of region between Xi River and Fuxingbao River around 2862 square kilometre, the volume of flow in flood peak is 16200 cubic metre per second. The catchment area of region between Xiao Ling River and Jinzhou River around 3100 square kilometre, the flow volume in flood peak is 11700 cubic metre per second which ranked first in the last 100 years.
The information is provided by Disaster Risk Reduction Knowledge Service.
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