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Floods

Like a hole in the sky

Hardly a year goes by without floods in China. Rivers are being forced into narrow courses and urban areas are becoming increasingly impermeable. After several years without any historic flood disasters, 2016 saw exceptional flood damage once again.

27.03.2017

China’s last devastating flood disaster took place in 1998, when flooding on the Yangtze and Songhua rivers kept entire regions in suspense for weeks on end. Losses came to some US$ 20bn and almost 4,000 people lost their lives. Just like in 1998, an exceptionally strong El Niño event preceded the 2016 floods. The Chinese authorities had issued warnings back in the spring about the possibility of a particularly intense flood season in the central and lower Yangtze regions. Starting in June – earlier than usual – new flood flashpoints developed on an almost weekly basis.

Flash floods: a nasty surprise

Although there were similarities ­between the events of 1998 and 2016, there were also striking differences. The 1998 floods were primarily a result of river flooding that plagued the Yangtze and Songhua rivers and their major tributaries. In contrast, the 2016 catastrophes were a combination of many different, intense and often localised individual events. Critical flood stages were reached on 363 small and me­­dium-sized rivers.

At over 600, the number of fatalities was remarkably high. One reason is that you generally have very little time to save yourself in a flash flood, as these develop much more quickly than river floods. A second is that people increase the risk further by attempting to rescue their prized possessions when time is of the essence. What’s more, flash floods develop much more power than river floods and are therefore more dangerous.

Hardly a year goes by without floods in China. Rivers are being forced into narrow courses and urban areas are becoming increasingly impermeable. After several years without any historic flood disasters, 2016 saw exceptional flood damage once again. © dpa picture-alliance / Photoshot
It was China’s cities that suffered most from the extreme rainfall during the 2016 mei-yu season. One eyewitness said it was as if “someone had poked a hole in the sky”. Flash floods brought life in many places to a complete standstill.

Floods in the Yangtze region

The most costly period of flooding started in mid-June in the Yangtze catchment area in central China. For almost a month – during the season known locally as the plum rains (“mei-yu” in Chinese) – it was one rainstorm after another. Nanjing, situated on the lower Yangtze, received 1,055 mm of precipitation between January and July, the second-highest amount on record and twice the ­normal figure. The whopping 550 millimetres that fell during the ­mei-yu season (June and July) even smashed the old record. The floods wreaked great damage in the city.

The mei-yu period is typically characterised by rather steady rain, but the 2016 season was interspersed with a large number of thunderstorms, with localised torrential rain and even hail in some areas. There were landslides in many places and a total of 179 dyke breaches. Although major rivers like the Yangtze ran dangerously high, this did not lead to catastrophic losses. Overall, the floods in the Yangtze region cost around US$ 20bn, of which just 2.5% was insured. At least 237 people died.

Flood causes in China

One of the most spectacular local events befell the city of Wuhan, at the junction of the Yangtze and Han rivers. More than any other city, Wuhan exemplifies the river flood risk in China. From 1 to 6 July, precipitation in the city’s four districts was between 930 and 1,087 mm, a new record. Roads, railways and underground lines were flooded. Wuhan is also a symbol of the unbridled expansion of Chinese cities, where drainage infrastructure is unable to keep pace. Since 1949, the city’s built-up area has grown by some 200 square kilometres to approximately 550 square kilometres (2015 figure). As a result of this expansion, one third of the retention volume of the surrounding lakes, where many million cubic metres of water had been held temporarily during floods, was lost.

Did the Three Gorges Dam help?

Whereas the floods on the Yangtze in 1998 came mainly from Sichuan through the Three Gorges, on this occasion they occurred downstream of the mighty dam. Nevertheless, the Three Gorges project still played a pivotal role in 2016. During the flood period on the middle and lower course of the Yangtze, a significant amount of the water coming from the upper reaches of the river was held back by the dam, thereby lowering the flood peak by almost 40%. Without the retention in the Three Gorges reservoir, the critical water level in the Yangtze upstream of Wuhan would have been exceeded for seven days. This illustrates that a reservoir can play a key role in flood management, even if it is not used to reduce a flood wave flowing into it. That said, the Three Gorges project cannot prevent all floods.

Rainstorms over large cities

The second billion-dollar event in 2016 hit the northeast of China, affecting provinces that are together home to over half a billion people. From 18 to 21 July, an easterly-moving corridor of precipitation hit Taiyuan, Zhengzhou, Shijiazhuang, Tianjin and Beijing. In just three days, well over 50 millimetres of rain fell on an area covering 900,000 square kilometres, with as much as 250 millimetres descending on an area covering 36,000 square kilometres. Historic records were exceeded in 22 districts. The town of Dongshan near Beijing experienced 454 millimetres of rain, and up to 140 millimetres fell in some places in the space of an hour. 149 towns and districts in the province of Hebei suffered damage, and almost 15 million people were affected by the floods, which left 164 dead. Overall losses amounted to US$ 4.5bn, 85% in Hebei alone.

The district of Xintai in the southwest of the province was particularly badly hit. Here, a sudden flood wave topped the dyke, flooding a neighbourhood in the middle of the night without warning. One example in the same district highlighted serious shortcomings, with the illegal development of a riverbed that had dried up only a few years before. The area suffered extensive damage.

Increase in flood protection and prevention measures

Following the traumatic events of 1998, China launched an extensive flood protection programme. Over the following ten years alone, the government invested more than 620 billion yuan (US$ 87bn). Centres were set up for data collection, flood forecasting and early warning, and a flood management strategy was drawn up. By the end of 2006, 85,800 dams, retention basins and polders had been built or retrofitted, together with 280,000 kilometres of dykes, providing protection for 550 million people and 45 million hectares of farmland. As a result, the impact of the annual floods has diminished, even though values have risen.

Lessons learned from the floods

In rural areas, greater emphasis must be placed on more sustainable development, taking account of the local environment. Improvements also need to be made to flood and water management in general. Advanced planning and improved early warning possibilities are essential. Likewise, planning of emergency management measures can – and must be – improved.

In megacities like Wuhan and Beijing, the objective must be to optimise the entire spectrum of disaster prevention and risk reduction measures. This includes not only suitably designed rainwater drainage systems, more efficient early warning capabilities and flood defence measures, but also efforts to ensure a rapid return to normality following a catastrophe. Particular emphasis must be placed on increasing resili­ence: supply lines and traffic routes must not be left unusable for days, but instead be able to perform their key tasks again within a very short time.

Great potential for insurers

The low proportion of insured losses to overall losses (2%) in the summer of 2016 highlights the enormous gap in cover, despite efforts by the government over the years to promote insurance protection. Often, cover is only found in the industrial sector, primarily at international companies. Very few private households are insured. The reason for this, especially in rural areas, is a lack of financial resources in conjunction with a lack of risk awareness. What’s more, most people trust that the government will assist them if they suffer serious personal damage.

There have, however, been some tentative efforts to enhance resilience, with local authorities trying to obtain insurance protection for their communities. In this way, at least some of the losses can be compensated after a disaster, and those affected put in a position from which they can return to a normal life. There is enormous potential and a corresponding need in this regard in China. Thus far, however, there has been very little recognition that this type of insurance is good for everyone concerned. Efforts are still needed to convince people of this, as is greater awareness of what is needed for an insurance solution to be effective. Specifically, this includes hazard maps, claims statistics, and data on value distributions in regions at risk of flooding.

Topics Geo – Natural catastrophes 2016
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Munich Re Experts
Wolfgang Kron
Head of Research, Hydrological Hazards in Geo Risks Research
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