Evolution of built-up land slope spectrum in plateau lake basin:A case study of Dianchi Lake Basin
Plateau lake basins are greatly restricted by natural geographical conditions,and built-up land inev-itably expands"towards the lake"and"uphill".Analyzing the spatiotemporal evolution rules of this process by constructing a slope spectrum for built-up land will help scientifically guide relevant land planning prac-tices.This study takes Dianchi Lake Basin and the 6 administrative regions involved as an example,based on land use data from 2000 to 2020 and elevation data converted from DEM,using methods such as steepness,evenness,and upper limited slope to analyze the evolution characteristics of the slope spectrum,and proposed the Weighted Built-up Land Climbing Index to quantitatively characterize the degree of climbing of built-up land,and deeply explores the spatial differentiation and evolution rules of built-up land expansion from the per-spective of altitude climbing.The results show that:1)The built-up land in Dianchi Lake Basin has expanded significantly,showing a distribution pattern of built-up land with the main urban area in the north of Dianchi Lake as the main core,Chenggong District in the east and Jinning District in the south as the secondary cores;2)The vertical spatial expansion of built-up land shows two-stage characteristics,that is,first expansion on flat land and then expansion on slope land.The period from 2000 to 2015 is the expansion stage towards the lake and decreasing altitude(WBCI＜0);the period from 2015 to 2020 is the expansion stage of climbing and in-creasing altitude(WBCI＞0).3)The slope expansion of built-up land and the elevation climb are consistent at the watershed scale,that is,the change trend of the slope climbing index is highly consistent with the altitude change trend of the distribution of built-up land.However,at the district scale,there are obvious spatial differ-ences in the expansion and elevation of built-up land.This study reveals the evolution characteristics of the slope spectrum of built-up land in plateau lake basin areas,provides new thoughts and perspectives for the two-dimensional expansion of urban space to three-dimensional expansion,and can also provide scientific refer-ence for urban land use planning and its ecological environment effect assessment.
built-up land expansionslope spectrum analysisterrain gradientelevation zoningDianchi Lake Basin
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