The glorious history of the ancient Shu civilization originated from a grain of rice sown by the ancestors of Baodun on this land more than 4,000 years ago. The rivers of the Chengdu Plain are vertical and horizontal, the soil is loose and fertile, and the ancient Shu ancestors lived by the water, making a living from farming, and cultivated a brilliant ancient Shu civilization. However, flood control has also become a long-term challenge for the ancient Shu ancestors. Recently, Meishan City, Sichuan Province, announced the discovery of the ruins of the ancient city of Dengyun, which was confirmed as the site of Baodun Cultural City. After preliminary archaeological investigation and exploration, archaeologists found that the ancient city of Dengyun was built along the river, surrounded by a ring moat outside the city wall, showing similar characteristics to other sites of the Baodun culture. The unique construction method of this city wall shows the life scene of the ancient Shu ancestors who competed with the water and moved forward bravely more than 2,000 years before Li Bing controlled the water.
Taking advantage of the terrain, the city wall and ditch were built to form a flood control system. Through the study of the shape of the ancient city, the structure of the city wall and the appearance of the ruins, it can be confirmed that the Dengyun site belongs to the Baodun culture period and is located in the southern part of the Chengdu Plain. Among the eight previously discovered Baodun cultural city sites, the cemetery of the ancient city site of Gaoshan is more than 4,500 years old. According to the dating of charcoal unearthed in the city wall, the age of the Dengyun city site is not earlier than 4800 years ago, which is a new discovery of the 9th Baodun cultural city site, which further expands the distribution range and age limit of Baodun culture. The ancient city of Baodun is one of the largest city sites with double walls inside and outside. It is understood that the site of Baodun Cultural City is usually built on the platform between the rivers on the Chengdu Plain, and the long side of the city wall is usually consistent with the direction of the river and the platform, showing a rectangular or nearly square shape, which is conducive to flood control and convenient for fortification. The ancient city of Dengyun is located on the secondary plain on the west bank of the Minjiang River, about 2 kilometers away from the east of the Minjiang River. There is at least one early river in the city, which may be slightly older than the city site, or has some connection to the early city construction. Outside the walls of the ancient city of Dengyun, archaeologists have also discovered a ring moat that surrounds the city wall. Similar to the inner and outer city walls of the ancient city of Baodun, Tang Miao, the head of the archaeological workstation of the Baodun site of the Chengdu Institute of Cultural Relics and Archaeology, once mentioned that the width of the trench outside the outer city wall of the ancient city of Baodun is more than 20 meters, and several meters of silt has been unearthed in the ditch, indicating that the ditch has been accumulating water. The ancestors of Baodun made full use of the natural advantages of the terrain and the river, and combined the tall and wide trapezoidal city walls with moats to build a powerful defense system. The unique construction method of the city wall reflects the advanced water control concept of the ancient Shu people.
In the view of archaeologist Tang Miao, during the Baodun culture period, the ancient Shu ancestors gradually formed an advanced concept of water control, which coincides with the way of "Minshan guiding the river, and don't be Tuo in the east" in Dayu's water control. He explained: "When the river flows from west to east and from high to low through the Chengdu Plain, the water flow is very fast. The use of blocking is equivalent to blocking the car with the mantis arm, which is tantamount to useless work for water. Therefore, the ancient Shu ancestors fully considered the benefits and abandonment of water when choosing the settlement place, built the city site on the earthen platform, and combined the city wall with the moat, which changed the water potential and realized the diversion rather than blocking. In addition, the city wall of the Baodun culture period is trapezoidal and has a gentle slope, which is different from the construction method of the city wall in the later historical period. Tang Miao pointed out that the construction of the city wall at the site of Baodun Cultural City adopted the "slope stacking method", that is, digging trenches in situ to take soil to build walls. Compared with the "plate construction method" usually used in the northern part of the Central Plains, which focuses on defending against the enemy, the "slope stacking method" pays more attention to the use of solid wall foundation and thick slope-like wall, which has a better effect on resisting the impact of the source of the flood and guiding the water flow. "The walls have a moderate slope for easy climbing, but the trapezoidal form is more stable in the face of flooding. Tang Miao said, "Therefore, the city wall of this period can effectively prevent the invasion of wild beasts or foreign enemies while defending against the northwest flood." In addition, we suspect that the wide platform at the top of the city wall could also serve as a temporary shelter. Chengdu **Jinguan News Reporter Wang Ruyi **Sichuan Provincial Institute of Cultural Relics and Archaeology, Chengdu Institute of Cultural Relics and Archaeology Editor-in-charge He Qitie Editor Wenzhu.