Studies On Settlement Characteristic Of “Secondary Gully” InLoess Plateau Of Northern Shaanxi

The hilly and gully areas of the Loess Plateau in northern Shaanxi are ecologically fragile,crisscross with gullies,and the distribution of human settlements is characterized by the gradual dispersion of the three gullies,namely,the Chuan Road,the Second Gully and the Zhimao Gully.At present,the rapid urbanization makes the Chuan Road space tends to be saturated,and the construction generally presents the characteristics of "plain style".As the direct extension area of the Chuan Road,the sub-gully is the primary expansion area for carrying the future residential space.The long-term evolution of Second Gully Settlement has basically adapted to the natural environment characteristics of the ecologically fragile area in northern Shaanxi and reflected certain locality.In recent years,the construction of human living space has spread to the sub-gully,but its construction does not adapt to the natural environment,and has the characteristics of unsustainable.Under the requirement of high-quality development of territorial space,it is particularly urgent to explore the characteristics and rules of primary sub-gully settlements in the hilly and gully areas of the Loess Plateau in northern Shaanxi,and to extract the appropriate spatial development path of sub-gully settlements.This paper takes Donggou,a typical sub-gully in Mizhi County,northern Shaanxi Province,as the research object for empirical analysis.First of all,the research objects were divided into 282(6*47)quadrats by using 100 meter grid method to measure the overall settlement and topographic index of Donggou.Then,the spatial distribution characteristics of Donggou were summarized in terms of the general characteristics,the variation law along the gully and the comprehensive index.It was found that there was a coupling distribution relationship between the topography and the settlement space of Donggou in different degrees.Secondly,a coupling degree model of settlement scale and terrain flatness was constructed by using the coupling degree of measuring the interaction degree of multiple indicators,so as to measure the spatial coupling characteristics of settlements and terrain more accurately.The measured results of the model include four types: extreme maladjusted decline,general maladjusted decline,general coordinated development and general coordinated maturity.The spatial distribution characteristics of the above quadrents were analyzed,and the formation factors of the "settling-terrain" coupling distribution characteristics were summarized and sorted out,including topography,roads,policies,flood control and other aspects.Based on the results of coupling coordination,30 typical settlement spatial samples were extracted to further study the spatial efficiency of the settlements themselves.Finally,the spatial performance characteristics of 30 samples in Donggou settlement were analyzed based on coupling coordination degree and three-dimensional fractal dimension correlation.According to the correlation results,the 30 samples were divided into different grades,such as high coupling-high fractal dimension,high coupling-low fractal dimension,low coupling-low fractal dimension and low coupling-high fractal dimension.On this basis,combined with morphological analysis,the corresponding typology characteristics of samples of each grade were summarized,including terrace parallel,free parallel and dense patch types,scattered point type and linear expansion type.Terrace parallel and free parallel with high coupling coordination degree and high three-dimensional fractal dimension were selected as the main reference model for the development of settlement space in Donggou in the future.After deeply analyzing the locality of typical samples corresponding to each model,some instructive experiences for the spatial development of sub-gullies in the hilly and gully region of the Loess Plateau in northern Shaanxi were extracted.