China floods: "Plum Rain" and Typhoon In-Fa

A series of recent flood events have caused widespread devastation across multiple provinces in China. Spanning the last two months, the floods started in late June in the provinces of Sichuan (CNA, 2021), Jiangxi (Floodlist, 2021a) and Heilongjiang (Floodlist, 2021b) following successive occurrences of heavy rainfall.

This was followed by unprecedented rainfall in July as flooding occurred in Henan province (Earth Observatory, 2021). The largest rainfall event observed in Zhengzhou city, located in Henan province, has been classified as a 1-in-1,000-year flood (Reuters, 2021a), making it one of the worst events to affect China this year. (CNN, 2021a). The severe floods in July were attributed to the prolonged rainfall deposited in a short period of time across widespread areas (please refer to section on Rainfall Analysis for more information).

Next, Typhoon In-Fa made landfall on the Zhoushan Archipelago in Zhejiang Province, on the central coast of eastern China, on 25 July at 12:30pm (local time) with the centre of the storm being 40km south of Shanghai. Maximum sustained winds of 74 km/h (tropical storm) were recorded (ReliefWeb, 2021).

As of 2 August 2021, 302 deaths were officially reported. Economic losses for Henan alone are likely to reach at least USD $13.79 billion (SCMP, 2021b).

Figure 1: An overview of provinces affected by floods from different events in 2021: late June (blue-purple), July (orange), and Typhoon In-Fa (purple) in late July. (Insert) China experiences the annual “Mei Yu” season during the summer months. The mean position of the monsoon front rainband for May (light purple), June (purple) and July (dark purple) are illustrated in the insert, and are based on the ERA5 climate reanalysis dataset from 1979-2014 (Chevuturi, 2021).

The Plum Rain

During the summer months, between June and August, China and Japan experience the Mei Yu (Plum Rain) season.

Also known as the East Asian rainy season, it is a result of warm moist air coming from the East of China, in the Pacific Ocean. As this air meets the cooler continental air from China, the interaction between the two air masses causes the weather front to move back and forth across mainland China.

This combination of high humidity, heat and rain provides the perfect conditions for plum harvest, leading to the colloquial name of ‘plum rain.’ The insert in Figure 1 illustrates the mean position of the Mei Yu monsoon rain bands for the months of May, June and July (Chevuturi, 2021).

The prolonged rainfall experienced in July was a result of high pressure in the western Pacific Ocean, combined with moisture carried by strong winds from Typhoon In-Fa that came from the east of China (SCMP, 2021a).

Furthermore, as Zhengzhou is located in the foothills of Taihang mountains, orographic uplift likely further intensified the rainfall in July (Yale Climate Connections, 2021). When prevailing winds meet a higher terrain, the air mass is forced to rise from low elevation to high elevation, which causes it to cool and result in clouds and precipitation.

Areas affected – Late June 2021

Figure 2: Areas severely affected in the late June 2021 floods. The map depicts total rainfall accumulation from 22 June to 3 July 2021; the highest rainfall is represented by red. (Data source: NASA PPM. 2021. NASA Precipitation Measurement Missions. [online] Available at: [Accessed 22 Jul. 2021].

The three major provinces affected were the Heilongjiang, Sichuan, and Jiangxi provinces. Floods in Sichuan, which sits upstream of the Yangtze River, have impacted eight cities in the province, with damage to 230,000 hectares of crops and economic loss estimated at USD $440 million.

These floods further up the Yangtze have also caused severe floods downstream. For example, nearly 1.1 million people have been affected in Jiangxi province, which sits downstream on the Yangtze. More than 156 houses have been destroyed, 219 houses damaged and 63,000 people relocated, alongside damage to 70,300 hectares of crops in the province. These floods have resulted in an estimated USD $160.68million of direct economic losses. The highest recorded rainfall in Jiangxi was 185.8mm within a 24-hour period at Jingdezhen city and 112.8mm at Nanchang, the capital city of Jiangxi (4, Floodlist, 2021a).

In Heilongjiang, in Northern China, heavy rainfall over the Greater Xing’an mountains caused the Amur River that borders Russia and China to overflow its banks (17, Teller Report, 2021). This led to floods in the Daxing‘anling and Mudanjiang prefectures downstream of the Amur River (5, Floodlist, 2021b). This displaced 42,000 people and damaged thousands of hectares of crops (5, Floodlist, 2021b).

Areas affected - July 2021

Figure 3: Rainfall accumulation from 10 July to 1 Aug 2021; the highest rainfall is represented by red, with a maximum of 714mm over the 7-day period. (Data source: NASA PPM. 2019. NASA Precipitation Measurement Missions. [online] Available at: [Accessed 2 Aug. 2021].

During the July 2021 flooding, the three major provinces affected as a result of prolonged rainfall and Typhoon In-Fa were the Henan, Shanghai, and Zhejiang provinces.

Between 10 and 23 July 2021, Henan province was the worst affected by floods. Zhengzhou City, with a rainfall return period estimated to be greater than 1,000 years, reported 292 deaths because of floods and landslides (CNN, 2021b). Direct economic losses are estimated at USD $24 billion, with 580,000 hectares of farmland affected by floods (ABC News, 2021).

This catastrophic flooding was worsened by Typhoon In-Fa (Figure 4), which affected Shanghai and Zhejiang.

Typhoon In-Fa first made landfall near Putuo district, in Zhoushan City (25 July 12:30pm local time). It made a second landfall north of Shanghai, near Qidong district, the following day (26 July 9:50am local time) (BBC, 2021a; BBC 2021b).

A total of 951mm of rain was recorded at YuYao station over four days (Equal Ocean, 2021) when it landed in Qidong, Zhejiang province, resulting in further floods (New York Post, 2021). This resulted in 69 deaths, while more than 1.65 million people in Zhejiang were displaced (Global Times, 2021b).

In Shanghai City, the Qidong and Pudong districts were the worst affected as businesses and the airport were forced to close. However, the presence of existing typhoon defences prevented extensive damage (DW News, 2021).

Figure 4: Video showing daily rainfall between 15 and 30 July 2021 at the eastern coast of China, with Typhoon In-Fa coming from the east of China (Data source: NASA PPM, 2021; video produced by JBA Risk Management Limited™.)

Rainfall Analysis in Henan and Zhejiang provinces

According to rainfall gauges, several locations in Henan province experienced 120-400% more rainfall in just 24 hours than the historical average for the whole month of July (Table 1). Over four consecutive days from 17 July, 4,098 weather stations in Henan received 50mm or more of rainfall, with 47% of the stations (1,923 stations) receiving at least 100mm and 15% (606 stations) receiving more than 250mm of rainfall (SCMP, 2021a).

250mm of rainfall is equivalent to the average total July rainfall for the worst affected cities in Henan (Table 1). For comparison, the average total rainfall in the month of July ranged from 150 – 350mm on average for Zhengzhou, XinYang and SongShan (World Weather Online, 2021).

The city of Zhengzhou was particularly hit, recording a maximum of 617mm of rain in a 24-hour period (Table 1) – equivalent to its average rainfall for an entire year (Yale Climate Connections, 2021). Maximum 1-hour rainfall recorded at Zhengzhou meteorological station was 201.9mm (20 July 09:00-10:00 UTC) (Sohu, 2021) which has exceeded the highest 1-hour rainfall record in mainland China, recorded at 198.5mm on 5 August 1975 (Global Times, 2021a).

Table 1: Rainfall return period analysis conducted by JBA Risk Management for high rainfall recorded in some known locations. A Weibull distribution curve was fitted to historical records available for each location. The historical rainfall records were obtained from gridded rainfall between 1970 and 2020. Daily maximum and historical rainfall records obtained from SCMP (2021a).

Average flood losses in China

Insured losses for this flood event could reach up to USD $1.7 billion (SCMP, 2021d). But as flood insurance coverage for property remains relatively low in China, the vast majority of the claims relate to motor claims (Artemis, 2021). For example, the insurer Ping An states that only 3% of the 46,000 claims made so far were for damage related to properties, farms or accident claims (SCMP, 2021d).

Based on a report by Swiss Re in 2019, residential insurance penetration in China accounts for around 0.01% of China’s GDP. The total insurance premiums for residential properties in China is USD $1.41 billion, which makes up 20% of all property insurance in China (Swiss Re, 2020).

Total economic loss from the 2021 July floods is estimated to be at least USD $24 billion (ABC News, 2021). This is comparable to losses from previous summer floods in China. For example, floods in June 2016 had an estimated loss of USD $25-$38 billion (Table 2). Total economic loss in summer 2010 reached approximately USD $50 billion from losses in 18 provinces (Table 2).

Table 2: Historical events and reported losses for severe flood events in China 1998–2020. (Sources: Swiss Re Sigma Explorer (2021),Du et al., (2019), SCMP (2020), Reuters (2020), Wunderground (2016), Artemis (2021), The Guardian (2010), ADB (2012)).

Figure 5: JBA has modelled for all countries in Asia against flood risk. The loss ratios generated from the average annual losses are plotted against the modelled insured values. We have specifically highlighted China (CN), India (IN), Indonesia (ID), Thailand (TH), Malaysia (MY), Vietnam (VN), Bangladesh (BD) and Cambodia (KH).

Using JBA’s probabilistic flood modelling for China, we estimate that the country’s average annual economic loss (AAL) from flooding is USD $58 billion a year. Given China’s unprecedented growth in the last 30 years, the economic toll of flooding has progressively increased; in the 1990s, it’s estimated that flood had an AAL of between USD $24-39 billion, between USD $7.2-30.6 billion in the 2000s, and between USD $24-56 billion in the 2010s (Du et al., 2019).

With rapidly increasing urban development and exposure, previous flood events would undoubtedly be more costly if they occurred today. The devastating floods of 1998 cost the country USD $80 billion (Du et al., 2019), a value which represented 3% of China’s Gross Domestic Product (GDP) at the time. If an event of similar size and severity reoccurred today, based on contemporary GDP, it may constitute an economic loss in the range of USD $225-275 billion. As Figure 5 highlights, based on JBA’s modelling and a contemporary market portfolio, the 1998 event could represent a return period in the range of 175-300 years.

Figure 6: Modelled flood loss exceedance curve based on JBA’s flood modelling for China. (Source: JBA Risk Management)

The impacts of urban development and population growth on flood exposure will also be exacerbated by climate change, with flooding likely to get more frequent and severe around the world.

It’s vital that organisations act now in response to flood risk. We offer flood mapping and probabilistic flood modelling worldwide, providing flood risk insights at any location globally. This can help re/insurers, financial organisations, and the International Development sector to better understand and manage flood risk.

To find out more about our flood data and how it can help you, get in touch with the team.

This report is covered by JBA’s website terms – please read them here.


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