Impact of the “23·7” extreme heavy precipitation on maize yield in the Hebei Plain

Flooding is a devastating natural disaster that poses serious threats to food production. Affected by Typhoons Doksuri and Khanun, between July 29 and August 1, 2023, the Beijing-Tianjin-Hebei region experienced unprecedented heavy precipitation and consequent enormous flooding, directly causing almost grain failure. To explore the impact of heavy precipitation on local grain yield, this study used the MODIS MOD09GQ product to compare the NDVI difference before and after heavy precipitation in the Hebei Plain (the main flood-submerged area), and the area of submerged farmland and the degree of grain failure were analyzed. The spatial distribution of maize (the main local summer crop), agricultural statistics, and NDVI data for 2016–2020 were also combined to estimate maize yields under the two scenarios, with and without heavy precipitation, by which we estimated the yield loss of maize due to heavy precipitation. The main conclusions were as follows: 1) After heavy precipitation, the NDVI of the affected farmland decreased in the range of 0－0.35, while the NDVI of the unaffected farmland showed varying degrees of increase on the Hebei Plain. 2) In the Hebei Plain, approximately 240 000 hm² of crops was affected by heavy precipitation, with complete crop failure in 130 000 hm² of farmland and moderate crop failure in 110 000 hm² of farmland. 3) The estimated 22 counties (city, district) around the flood detention basins were mostly affected by heavy precipitation. According to the results of the regression analyses, this heavy precipitation event caused a 220 000 t of potential loss of maize, and 92% of this yield loss was due to crop extinction. This study provides a fast and reliable assessment framework for the use of a remotely sensed approach to estimate flood-induced grain reduction and further emphasizes the harmful effects of extreme climate events on food security.