Objective As a kind of special historical and cultural landscape, coastal defense settlements in Ming Dynasty were often distributed along the coast. Considering the special geographical characteristics of the coast, in addition to meeting the basic functions of military defense, coastal defense settlements should also meet the water environment requirements for flood control and drainage, which may affect their siting and spatial layout. Minjiang River Estuary is the estuary of the capital of Fujian Province, which has important strategic significance in the coastal defense system of Fujian Province. Meihua Fortress is an important military defense post guarding the entrance of Minjiang River Estuary. This research may contribute to the protection and development of coastal settlements including Meihua Fortress, to the exploration of local cultural value. and also to the protection and research of regional settlements under the influence of water environment. It may also expand research perspectives on the protection and utilization of cultural landscape about the relationship between human and environment.

Methods Taking Meihua Fortress in Fujian in Ming Dynasty as an example, this research conducts a field investigation and integrates the science of human settlement environment with such disciplines as history, military science, hydraulics and geography. Moreover, the research conducts a quantitative analysis by using ArcGIS tools to analyze slope, slope aspects, reclassification and cost distance based on digital elevation model (DEM) data and using DepthMapX software to analyze street characteristic based on space syntax. Starting from the man-land relationship, the research explores the spatial construction characteristics of coastal defense settlements under the influence of water environment in the aspects of enemy resisting, flood control, moisture protection, drainage, and water intaking, so as to supplement and deepen the research on coastal defense settlements.

Results The results show that Meihua Fortress leans against mountain while facing water, which is sited in consideration of such factors as sea control, altitude control, risk control and accessibility conducive to military defense. Relying on the natural environment, Meihua Fortress was off the coast in Ming Dynasty to effectively monitor the northern sea area of the Minjiang River Estuary District and form a good observation post. Being mostly located above the highest tide level in history by then, Meihua Fortress can basically resist the invasion of tides without the consideration of embankments. Considering factors such as terrain and topography, Meihua Fortress was built on high ground in avoidance of low-lying stagnant areas. Meihua Fortress had no river inside, with only the Meihua River located 200 meters away from the southwest side of the city to reduce the impact of flooding and waterlogging. Meihua Fortress built multiple layers of defense, including the barbican entrance in the east gate as an important core site, the firm city walls constituting the peripheral defense system together with the trenches around, as well as relevant stone houses and stone retaining walls. Meihua Fortress strengthened resistance to enemies and the ability to resist flood and sea salt erosion in the construction of multiple building details. Thanks to the high terrain, the external flood around Meihua Fortress can be directly discharged into the downstream low-lying areas through the main ditches around Meihua Fortress. Meihua Fortress adopted streets and alleys for internal drainage. Specifically, it leveraged the elevation difference of terrain, slope and slope aspects of Mount Gui to divert rainwater from the southeast of the city to the low and flat areas in the northwest, and leveraged its own street ditches to dredge rainwater and strengthen drainage in order to reduce the pressure of rainstorm and flood on buildings and streets, and ensure the safety of villages, streets and buildings for drainage. Meanwhile, the buildings in Meihua Fortress also contributed to drainage by setting drain under the stone steps and on the walls and oblique roofs overhanging wall surface. Because of the distance away from the river, the water intaking resource was mainly from the wells in Meihua Fortress. The wells reasonably built inside the city could meet the production and living needs of the soldiers and civilians, while protecting them from being poisoned by enemy forces outside the city and ensuring water supply in case of siege to keep water safe. According to the results of the analysis of the cost distance from each designated location to water well points in Meihua Fortress in ArcGIS and the analysis of the global integration, regional integration (R=3) and connectivity value of Meihua Fortress, the research figured out that the distribution of wells affected the layout of streets. Using the methods mentioned above can achieve the effect of no waterlogging arising from heavy rain, and meet the needs of local residents to resist floods in the face of less manpower and single production and life mode in Ming Dynasty.

Conclusion Coastal defense settlements represented by Meihua Fortress in Ming Dynasty were sited on the basis of the influence of water environment, which contributed to the formation of a special spatial layout meeting local needs for defense and development. Such spatial layout is characterized by the combination of flood control and drainage with defense against enemies, which may provide reference for the protection and research of historical cultural landscape such as coastal defense settlements, and provide inspiration for the construction of modern resilient cities.