A Study Of The Human-Environment Relationship In Lanzhou Basin Based On Topography

Man-land system is an huge and complex system formed by the interaction between human activities and geographical environment on the surface of the earth.In this giant system,people are always in a dominant position.The coordination process of the contradiction between man and land has been a comprehensive subject of geography and other related scientific research since prehistoric times.Urban human-land relation is a dynamic relationship,which is formed by mutual influence of human activities and geographical environment in the specific urban areas.City,as the most concentrated place of human activities,is the most affected region by human activities.The man-land relationship in this area is very complex.With the accelerated development of urbanization,human activities have stronger influence on the urban terrain environmental change,which will lead to complex environmental problems and seriously affect the further development of city.Therefore,analyzing the relationship between natural environment and the human activities in urban area has great practical significance to promote the sustainable development of cities.Valley City is the urban main body that formed and developed in a valley.Because of the restrictions and impacts of valley terrain,the valley cities forced to develop along terrain and river.The topography of such cities,which are an important part of the urban natural environment system,have a profound impact on city's geographical structure,function,landscape,evolution and urban socio-economic activities.Meanwhile,valley cities have narrow basin space and the land resources are very scarce.Human activities have larger impact on urban terrain environment,and contradictions between man and land are prominent.Therefore,it is necessary to study the relationship between man and land in valley cities based on terrain.The Lanzhou City is the representative of valley cities,so we selected typical valley basin,the Lanzhou basin,as our research object.In the perspective of terrain,study on man-land relationship of Lanzhou city has stronger representative and scientificsignificance.The study can provided scientific reference for understanding and evaluation of man-land relationship in valley city.First of all,through methods of data collection,field investigation and remote sensing image interpretation,we extracted the terrain situation,urban agglomeration evolution,landform disaster,land use and other basic data of the study area,and we established a geographic information database by using GIS method.Secondly,using ArcGIS spatial analysis and statistical analysis methods,we analyzed the impact of topography on settlements evolution,the urban landform disaster of Lanzhou city,and the deformation process of urban terrain under the influence of human activities.It can provide a scientific basis for the planning,environmental management and disaster prevention of Lanzhou city.The results were shown as follows.(1)Study area has typical valley terrain,where distributes two larger basins.The minimum elevation is-1500 m in this region and the highest is 2926 m.Slope is mainly concentrated in the range of 0-65°.The terrains are relatively flat on river floodplain and one or two terraces,where the slope is concentrated in 0-7°.The aspect is mainly concentrated in the range of 90-270°.(2)Place names carry a lot of information about the terrain,and it can reflect the terrain situation and the reasons of terrain formation.Place names like “Tan”,“Ping”and “Tai” can reflect a special landforms of Yellow River terraces,while “Shan”,“Gou”,“Wan”,“Wa”,“Ling”,“Xian”,“Liang”,“Gang” and “Ju” can reflect that Lanzhou lies in the Loess Plateau.These results further illustrate the relationship between place name system and the landform,and we can understand the terrain characteristics of the area through the place names.(3)From Neolithic to modern times,the characteristics of temporal and spatial distribution of human settlements are that the slope of human habitation is gradually decreasing,the average elevation and the average distance from the Yellow River are gradually reducing and then increasing.However,the average elevation and average distance from the Yellow River in study area Where the human settlements are located in modern time are much smaller than that in the Neolithic period.The trends of human settlements concentration in these three periods are along the Yellow River,and the gathering direction is close to the water source.Topographic factors,such as altitude,slope,aspect and distance to the river,have a large impact on the distribution patterns and evolution of the human settlements.While from the Neolithic Period toModern Times,the effects of each factor are various.According to our analysis and many other records of Lanzhou,we infer that the development of productive forces is the main reason for these difference and the change of settlements distribution.Meanwhile,with the improvement of productive forces,the ability which human beings adapt to the natural environment is gradually increased.(4)During the last one hundred years,Lanzhou basin debris flow and flood disaster are serious,and terrain elements have a significant impact on the occurrence of urban disasters.River channel flood disasters mostly occur on the floodplains of the Yellow River.Compared with the river channel floods,flood passage disasters and debris flow disasters occur more frequently and on smaller scales.Through establishing predictive formula of river channel flood disaster,flood passage disasters and debris flow events using logistic regression,we found that the occurrence probability of these events have a negative correlation with the elevation and distance from the river.(5)We found that there are topographic deformations in most areas of the Chengguan District during 1970-2012 on Lanzhou East Basin.Terrain deformations are mainly manifested as ground subsidence,and this phenomenon is serious in Yantan area.The natural factors and human activities caused urban land subsidence from1982 to 2012 year.The reduction of terrain elevation is related to the intensity of precipitation and the human activities.The reinforcement of precipitation and the intensity of human activity can cause the increases of land subsidence.In addition,we further explored the impact degrees of human activities and natural environmental change on urban terrain changes,it is showed that the impact of human activities greatly transcend natural factors on the terrain,so that the phenomenon of ground subsidence is more serious.