Based on the case study of the special ecological environment and urban form of the loess gully region in Northern Shaanxi, this paper takes Ganquan county as an example and aims to determine the restrictive UGB and guiding UGB in its urban planning area and downtown area respectively. In terms of urban planning area, this paper proposes the delimitation of prohibited areas, which are measured by four factors - geological features, ecological protection, hydrological features and environmental safety, and the prohibited areas were overlaid and integrated into the restrictive UGB in order to form ecological security pattern. In terms of downtown area, this paper measures the performance of urban spatial expansion based on the change of urban form according to four indices, namely, compactness ratio, form ratio, negative elongation ratio and radial shape index, constructs the benchmark resistance surface and expansive resistance surface for future urban spatial expansion, and calculates the guiding UGB in immediate, mid-term and long-term plan based on GIS platform by referring to the total amount of land for urban development purpose of various stages as determined in the general plan of land use.%针对陕北黄土沟壑区特殊的生态环境与城市形态特征,以甘泉为例,分别在规划区和中心城区两个层面划定"约束性"与"引导性"城市增长边界.在规划区层面,构建地质地貌、生态保护、水文地质、环境安全4种单因子影响下的禁止开发建设区域,并叠加形成以生态安全格局保护为目标的约束性城市增长边界;在中心城区层面,选取紧凑度、形状率、负伸延率和圆形率4个指标来测度基于城市形态变化的空间拓展绩效,在此基础上构建未来城市空间拓展的形态基准阻力面和扩展阻力面,并结合土地利用总体规划中确定的未来城市发展各阶段的城市建设用地总量,通过GIS平台计算并划定城市近期、中期、远期的引导性城市增长边界.
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