Objective  Through centuries of military defense and construction, a large number of fortress settlements with military defense functions have been formed along the Great Wall, most of which survive today as natural villages. The more than 140 Great Wall fortresses established since Ming Dynasty are mostly built in mountainous environments. The influence of seasonal rainfall, mountain confluence and river systems endows the area where the aforesaid fortresses are located with greatly varied water environments and frequent droughts and floods, leading to the formation of various water adaptive landscape patterns with outstanding value within and outside the fortress settlements therein. This research summarizes and refines the water adaptive landscape characteristics and patterns of the Great Wall fortress settlements, with a view to providing reference and inspiration for the planning and conservation of mountainous village settlements.

Methods  This research analyses the siting of fortress settlements based on precipitation and distance between city and water, and proposes three types of city-water relationships: water flowing through city, city building near water, and dryland fortress. To be more specific, the research firstly collects precipitation information in the research area to analyze the precipitation situation where the settlements are located. Then the research adopts the ArcGIS 10.6 software platform to conduct a confluence analysis of the digital elevation model (DEM) and accordingly figure out the grade and distribution of the confluence river network concerned, based on which the research conducts a city-water distance analysis in combination with the distribution of settlements to outline the type of city-water relationship. In addition, the research conducts a comprehensive analysis of the drought and flood situation in the settlements, taking into account such information as river level, city-water distance and precipitation, drought / flood records in local chronicles and other relevant literature. Finally, the research selects three typical cases to analyze the presentation characteristics and adaptation methods of corresponding water adaptive landscape from such aspects as spatial pattern, storage pattern, crop type and ritual belief.

Results  Through fieldwork and systematic combing of related chronicles on the Great Wall fortress settlements, the research derives three water adaptive landscape patterns (terrace pattern, pond pattern and ditch pattern) respectively in response to three different disaster threats, namely the dual threat of drought and flood, seasonal drought and seasonal flooding. The water adaptive landscape patterns are linked to the type of city-water relationship without strictly corresponding to each other. The terrace pattern and the pond pattern are mostly associated with the city-water relationship where water passes through the city, with terraces being reclaimed on both sides of the river as a space for agricultural production and rainwater storage, and ponds being dug around the river for water storage; the ditch pattern is mostly associated with the city-water relationship where ditches are dug to divert water from the river for irrigation. The research selects three typical examples of water adaptive landscape for in-depth analysis, and summarizes the spatial patterns, storage patterns, crop types and ritual beliefs thereof under different landscape patterns.

Conclusion  The Great Wall fortress settlements in Beijing have developed diverse water adaptive landscape patterns under the influence of the complex water environment and military defenses. The traditional wisdom of water adaptation has guided the siting of the settlements, how droughts and floods are managed and the evolution of local folk rituals and beliefs. With the passage of time, the spatial organization logic and landscape pattern of the fortress settlements have undergone significant changes, and the traditional adaptive landscape is at risk of destruction in the process of rural construction and economic development. As to the conservation and construction of modern settlements, contemporary strategies for the transformation of traditional water adaptation wisdom can be implemented at three levels. 1) Integration of traditional water adaptation wisdom into rural planning. The planning of mountainous villages in Beijing should fully draw on the traditional experience of the water adaptive landscape of the Great Wall fortress settlements, enhance the disaster resilience of the mountainous villages through the clever layout and flexible use of space, take into account the comprehensive benefits of flood risk, ecological safety and the livelihoods of residents in the planning and design, and plan and build the production, living and ecological spaces of the villages in a rational manner. 2) Systematic conservation of water adaptive landscape patterns and value networks. Focus on the comprehensive examination and systematic excavation of water adaptive landscape elements and value networks within the fortress settlements; carry out systematic identification and value assessment of landscape patterns and targeted conservation for settlements with different water adaptive patterns and spatial types; conduct research on spatial patterns and storage methods for key fortresses. 3) Revitalization and utilization of traditional engineering facilities and humanistic elements. In the process of preserving the heritage of the Great Wall fortress settlements, traditional water engineering facilities should be systematically examined and registered, and spiritual elements such as beliefs in water gods, rituals and festivals, and the culture of geomancy should be inherited in a living form within the settlements. In the context of the construction of the Great Wall National Cultural Park, this research is of important referential significance for the conservation and development of the Great Wall Cultural Belt and the transmission and continuation of traditional Chinese water adaptation wisdom.