I used to work in the government in China and coordinated. I am living in US now.I did not take any money from government. Just tell you some truth.
Before discussing further, giving you very basic concept. The water in the city flow to the river and the river flow to the sea. If the surrounding rivers have high water level, the water in the city will be accumulated. Some time the water in the river might poure to the city. This seems tha case in Beijing.
1. I knew how difficulty to coordinate the department of water resource and department of urban-rural development It is not clearly defined who is responsible for the flood protection.
2.The technology in water resource and flood protection is quite mature. There is no 61 year difference between China and US. The real problem is money. Those engineering need huge amount of money. When designing the flood protection engineering, it is always arguable what standard should be used. The higher the standard, the safer the protection, but more expensive the cost. Normally a midian standard would be selected.
3. In some area, no engineering method might be used if the cost is too high to protect the whole area, i.e., to sacrifice some areas to protect the whole area in case of big but low probability rain.
4. The rain in Beijing rarely happened, over 1/200 or less? It is obvious that you can't invest large amount of money to protect the city from the rain that only happens once in 200 years (average).
5. Arid is the more serious problem in Beijing and the sourrounding areas. Most of the reservoirs have never been full since they were built. Beijing already took the big reservoiers from Hobei. So the government had to spend lots of money to guide the water from Long River to Beijing.
However, there would not be so many people died if the government had pay attention to flood protection and act quickly after the big rain came.