4.2.4. Kaifeng City in the Qing Dynasty and the Yellow River Flood in 1841 AD

This Yellow River flood overflowed from the South Gate with flood waters proceeding northward from east to west, converging in the north of Longting Pavilion, resulting in serious water accumulations in some parts of the city [44,45]. It was not until February 8, 1842 AD that the closure of the Yellow River's breached embankment was completed. The flood between Kaifeng brick city and the moat and the accumulated water in the city gradually subsided, but the city was besieged by floods for eight months. This Yellow River flood did not cover the whole city, so Kaifeng city was not completely buried underground. For example, the ML core which is located in Gongyuan of Henan Province, showed no signs of deposits from this flood, whilst the deposits in SZ and YZ cores are not too thick, being less than 1 m. The surface of Kaifeng city therefore comprises the upper parts of the sediment layers from both the 1642 AD and 1841 AD Yellow River floods. Nowadays, the surface of the Xiangguo temple and the Yanqing Taoist temple before the whole uplift is higher than that of its base (Figure 11). However, the flood besieged Kaifeng for 8 months, and deposited a large amount of sediment between the outside of the brick city and the moat, as evidenced in the JM core, where the corresponding sedimentary thickness is 3.2 m. This is basically the same as the burial depth of the two Qing dynasty courtyards at the Xinzheng Gate site (Figure 12).

**Figure 11.** Comparison of the Yanqing Taoist temple before and after the 1841 AD flood which resulted in the lifting of the ground surface by some 3.1 m. The photograph on the right was taken in 2009.

The evidence derived from these stratigraphic, archaeological, and literature investigations, all indicate that there are at least "three and a half ancient cities" located underground in Kaifeng city today; namely, the Daliang City of the Warring States (the representative time is before 225 BC, and the depth is 10–15 m), the Dongjing City in the Northern Song Dynasty (the representative time is 225 BC–1387 AD, and the depth is 9–13 m), the Kaifeng city in late Ming dynasty (the representative time is 1387 AD–1642 AD, and the depth is 3.5–8 m) and the ancient ground, of the Qing dynasty, which existed in certain areas (the representative time is 1662 AD–1841 AD, and the depth is 1–4 m).

**Figure 12.** The Qing courtyard at the site of Xinzheng Gate in Northern Song outer city wall.
