Layout optimization of rural settlements based on point-axis theory

Abstract: A rural settlement, with the spatial characteristics of point distribution and axis development, is an important land-use type that refers to construction in rural areas in China. Growth points (including town, key village and basic-level village) and development axis (including roads and river systems) play an important role in spatial optimization of rural settlements. To study the effects of point-axis on arranging the spatial layout of rural settlements, this paper analyzed the spatial action of point-axis on rural settlements using an improved gravity model. Three indexes, including population, gross domestic product, and development index of enterprise, were selected to calculate the gravity values among villages. The weights for population, gross domestic product, and development index of enterprise in the gravity model are 0.297, 0.540, and 0.163, respectively. The spatial gravity matrix of the villages was acquired using the gravity model. Five village groups were constructed and a key town, four key villages, and nineteen basic-level villages were identified. An index system, including growth point, life availability, and production convenience, was constructed to evaluate the action sphere of different growth points based on a weighted Voronoi diagram. The results show that there is an apparent difference between the action sphere of growth points and their administrative scopes. The action sphere of key villages (town) is greater than that of basic-level villages. The restriction of administrative scope was broken and the urban-rural construction was reconstructed using the weighted Voronoi diagram. Roads are important factors, which guide the development direction of rural settlements. A 500 m interval for roads is implemented to construct buffer layers by ArcGIS 10.1. The values range from zero to eight in nine buffer layers of roads, and the values range from two to five in four grades of slope. The layer with closer distances between rural settlements and roads holds a higher value. The layer, which is farther than 4000 m in road buffer, is assigned a value of zero. The interaction values of roads and slope for each rural settlement were calculated and three grades were classified based on Natural Breaks method. Rural settlements, with values between 0 and 4.647, were regarded as the potential consolidation objects. Considering the area of rural settlements, three optimization modes, including urbanization, removing and merging, and inner consolidation, were proposed for spatial optimization in Dajipu. Additionally, the mode of removing and merging was further sub-divided into two modes (construction of key village and construction of village center). The area of rural settlements for inner consolidation, urbanization, key village construction, and village center construction are 686.73 hm2, 56.18 hm2, 7.85 hm2 and 16.13 hm2, respectively. The modes for urbanization, removing and merging, are pivotal for land consolidation of rural settlements. Both of them play an important role in coordinating urban-rural development, whereas inner consolidation improves the level of intensified land use. Meanwhile, the spatial optimization of rural settlements should gather to the main roads properly. The results show that the proposed method can make the spatial optimization of rural settlements more scientific and intelligent with the consideration of growth point and axis action. It can offer an assist to decision-making in spatial optimization of rural settlements and New Countryside Construction.