Simulation of utilization and construction suitability of gentle hillsides based on risk evaluation in Banan District of Chongqing
LIJing1,, LIAOHeping1,2,, CAIJin1 1. School of Geographical Sciences, Southwest University, Chongqing 400715, China2. Institute of Land Resources, Southwest University, Chongqing 400715, China 通讯作者:通讯作者:廖和平,E-mail:liaohp@swu.edu.cn 收稿日期:2017-07-12 修回日期:2018-03-6 网络出版日期:2018-05-10 版权声明:2018《资源科学》编辑部《资源科学》编辑部 基金资助:国家科技支撑计划项目(2013BAJ11B02)教育部人文社会科学重点研究基地重大项目(16JJD790064) 作者简介: -->作者简介:李靖,男,四川绵阳人,博士生,主要从事国土资源与区域发展研究。E-mail:freelj@qq.com
关键词:低丘缓坡土地;适宜性评价;有序加权平均方法;GIS;情景模拟;重庆市巴南区 Abstract Utilizing gentle hillside areas is an effective way to alleviate land use pressure and optimize the allocation of land resources and avoid potential risks. In order to explore dynamic simulation to evaluate suitability of gentle hillsides under different policy scenario, promote scientific and rational use of gentle hillsides and reduce utilization risk, we studied Banan District in Chongqing. Eleven indices were selected to establish the evaluation index system representing landscape risk, social risk and ecological risk. Simulation results of the utilization and construction suitability of gentle hillsides under five policy scenarios were carried out based on OWA (ordered weighted averaging) and GIS (geographical information system) methods. With increasing α (the decision risk coefficient), the level of utilization and construction suitability of gentle hillsides is higher. Suitability of the western part of the study area were overall better than that of the eastern part, while the suitability of areas around streets and towns were better than remote areas. Under non-extreme policy scenarios, suitability partition was more scattered. In the current period of land use planning, new urban construction land was mainly distributed in areas not comprised of gentle hillsides. Land use planning of gentle hillsides present a prudent and conservative attitude. To some extent, this research enriches the theory and methods of suitability evaluation of gentle hillside land. This work provides a reference and practice support for utilization and management of gentle hillsides in similar areas.
Keywords:gentle hillside;suitability assessment;ordered weighted averaging;GIS;scenario simulation;Banan District;Chongqing -->0 PDF (22412KB)元数据多维度评价相关文章收藏文章 本文引用格式导出EndNoteRisBibtex收藏本文--> 李靖, 廖和平, 蔡进. 基于风险评价的低丘缓坡土地开发建设适宜性情景模拟——以重庆市巴南区为例[J]. 资源科学, 2018, 40(5): 967-979 https://doi.org/10.18402/resci.2018.05.10 LIJing, LIAOHeping, CAIJin. Simulation of utilization and construction suitability of gentle hillsides based on risk evaluation in Banan District of Chongqing[J]. RESOURCES SCIENCE, 2018, 40(5): 967-979 https://doi.org/10.18402/resci.2018.05.10
巴南区位于重庆主城区南部,地处106°26′2″E—106°59′53″E、29°7′44"N—29°45′43"N,下辖8个街 道办事处,14个镇,全区幅员面积1822.84km2(见 图1)。区域内地质地貌形态多样,有石马向斜、南温泉背斜等10余个向斜和背斜,地势总体北低南高、西低东高,起伏甚大,区内最低点海拔154m,位于北部边缘华光村冉家湾,最高处为东南方斗山,海拔1132m。境内有大小低山和山脉11座,丘陵地貌遍布于各个向斜与背斜中。全区社会经济发展和土地利用均受地形的影响明显。2015年,巴南区实现GDP568.30亿元,三次产业比例为7.9:46.1:46.0,完成固定资产投资733.50亿元,实际利用内资566.60亿元,实际利用外资24.64亿元,进出口总额为85.64亿元,人口城镇化率达78.28%。当前,巴南区既承载重庆市都市功能南拓,又肩负着耕地保护粮食生产和主城生态屏障的重任,科学合理地开发、利用和保护区内低丘缓坡土地资源将成为必然选择[35]。 显示原图|下载原图ZIP|生成PPT 图1研究区示意 -->Figure 1The study area -->
低丘缓坡土地作为承载人类活动的自然-经济-社会复合系统的特殊资源载体,具有高度敏感性特征[36]。土地开发建设将给该复合系统中所有组成要素造成不同程度的扰动,通常,低丘缓坡区域内复合系统对扰动作用的抗干扰能力较弱,当扰动作用突破适宜性限定阈值将导致复合系统面临变异风险,引发灾害并威胁人类健康[37]。在低丘缓坡开发建设过程中,对地表景观改造将面临来自于基本农田保护、饮用水源保护、地质灾害防范、生态破坏等多方面风险,本研究结合研究区实际,基于差异性、可操作性和地块评价的原则选取坡度、农地、林地、农村建设用地、水源保护、农用地利用等、公路通达性、距城镇距离、植被绿度、灾害易发度、距河流距离等11个风险评价指标,分别归纳到景观风险、社会风险和生态风险三个准则层(图2)。 显示原图|下载原图ZIP|生成PPT 图2低丘缓坡土地开发建设适宜性情景模拟框架 -->Figure 2Framework for suitability simulation of utilization and construction of gentle hillside -->
景观风险层面中,考虑坡度、农地、林地和农村建设用地四个方面。坡度作为自然基底要素,低丘缓坡开发建设将改变原有地表地形,坡度越大对开发的限制性越强,开发风险也随之增大;另外,开发建设也将全面改变地表覆被现状,目前未开发建设的低丘缓坡土地表面现状多为农地、林地以及农村建设用地,选用农地表征农地景观被用于开发建设造成的农业生产及粮食安全风险,农用地中耕地开发风险大于园地开发风险,已划定为基本农田的区域开发风险最高;选用林地表征林地开发风险,以自然保护区和生态空间管护等级确定风险大小,保护力度越大风险越高;选用农村建设用地用来表征农村建设用地的承载强度情况,承载强度越高风险越大。 社会风险层面中,考虑水源保护、农用地利用等、公路通达性和距城镇距离等四个方面。饮用水安全与否关系群众健康,对集中供水保护区的开发建设将不可避免地造成污染,通常,离取水区越近开发风险越大;农用地利用等越高的地块其土地生产效益越高,开发建设应尽可能避免占用或少占利用等高的农用地地块,农用地利用等风险值按其利用等大小赋值;采用距城镇距离和公路通达性表征待开发地块与现状城乡聚落的空间联系程度和交通便利程度,往往距离城市建成区越近或交通便利程度较高的低丘缓坡地块开发适宜性越高,反之,开发距城镇远或通达性不高的地块成本风险相应越大。 生态风险层面中,NDVI反映植被生物量的空间分布情况,可以衡量低丘缓坡土地开发的生态成本,开发NDVI值越高的地块生态风险越大;地质灾害是土地开发建设选址极力避让的重要因素,开发建设选址应避开地质灾害高发区,地质灾害风险按其易发程度大小赋值;选取距河流距离作为评价指标,主要考虑地块开发建设造成的污染,同时也需要避免洪水灾害,距河流距离越近的生态风险越高。 研究涉及的指标均按一定规则(表1)归一化处理后生成分辨率30m的栅格图层(图3),并统一为西安1980坐标系。运用AHP进行指标间两两比较,确定标度,得到判断矩阵,赋予指标准则权重,见表1。由计算结果可知,三种风险的AHP判断矩阵一致性指标CR值分别为0.0825、0.0534和0.0825,均小于0.1,通过了一致性检验。 显示原图|下载原图ZIP|生成PPT 图3低丘缓坡土地开发建设适宜性评价指标 -->Figure 3Suitability evaluation indices of utilization and construction of gentle hillside -->
Table 1 表1 表1指标体系及归一化方法 Table 1The index system and the normalization method
通过以上情景对比发现,风险程度系数α同样可以用于表征政策偏好情景,研究区低丘缓坡土地建设的适宜性随之调整而呈动态变化态势。根据前文分析,本研究拟将α=1时的综合权重用于表征决策者对低丘缓坡土地开发建设过程中面临景观、社会和生态等风险时一种平衡城镇化、工业化、耕地保护和生态安全等发展目标的综合权衡决策。不同于α=0.1和α=10,α=0.5和α=2时的综合权重计算结果表明,部分指标作用虽受到明显抑制,但在加权后仍能参与适宜性评价。因此,本研究认为α=0.5和α=2可分别被视为现实决策中风险控制型和城镇建设型政策的极端状态,命名为“风险控制型极端政策”和“城镇建设型极端政策”。因此,风险控制型政策和城镇建设型政策应介于以上3类情景节点之间,即α∈(0.5, 1)时为风险控制型政策,α∈(1, 2)时为城镇建设型政策。本研究选取α=0.8和α=1.2分别作为“风险控制型政策”和“城镇建设型政策”的静态表征。 为防止重分类分区时栅格属性值过于偏向某一方向,研究将采用自然间断点分级法(natural breaks)将以上设置的3种开发建设政策情景栅格图按风险属性大小划分为5级,风险属性值越小的开发建设适宜性越高,划分为最适宜区、高适宜区、中适宜区、次适宜区、不适宜区。转为矢量图后与低丘缓坡区域范围进行叠加,将10hm2以下的图斑融合到相邻面积最大的图斑中,得到不同政策情景下的适宜性分区结果(图5),可以发现,5类设置情景呈现出的适宜性空间差异显著。 显示原图|下载原图ZIP|生成PPT 图5不同政策情景下低丘缓坡开发建设适宜性分区 -->Figure 5The utilization and construction suitability division of gentle hillside under different policy scenarios -->
4.3 低丘缓坡土地适宜情景模拟结果分析
风险控制型极端政策下,全区低丘缓坡土地开发建设适宜性由中适宜区和次适宜区占主导,主要分布于全区东部。东部槽谷区域虽地势相对平坦,但区域内城镇建成区的辐射能力较弱且地块交通通达性水平总体不高,同时该区域低丘缓坡分布着大量的农田,植被覆盖水平也相对较高。此时,全区最适宜区和高适宜区主要分布在西北部区域,该区域低丘缓坡土地地块开发建设的主要优势为距离城镇建成区近且交通通达性水平高。城镇建设型极端政策下,除地质灾害易发程度较高的区域外,全区适宜性分区由高适宜区和最适宜区占主导。距城镇距离、交通通达性、植被绿度等风险属性值较高的要素均不被决策者重视,东部槽谷区域低丘缓坡土地多被划入高适宜区和最适宜区。平衡型政策下,决策者对各类开发建设的风险要素持更谨慎的态度,适宜性分区格局相对均衡,分区以中适宜区为主。高适宜区和最适宜区主要分布在城镇建成区附近,东部槽谷区域低丘缓坡土地多数被划为了中适宜区。从图5可以看出,相较于以上两类极端情景,现实决策中出现可能性较大的“风险控制型政策”和“城镇建设型政策”(α=0.8和α=1.2)情景下的适宜性分区格局更加接近平衡型决策情景,各类参评风险要素在分区图上的体现程度更高,其主要特征有:中适宜区、高适宜区及次不适宜区的面积比重更大;各级分区空间分布更加零散,图斑更加破碎。 对比分析5类开发建设情景发现,随着α增大,政策导向从风险控制型向城镇建设型过渡,适宜性等级较高的分区面积所占比重增大,低丘缓坡土地开发建设适宜性等级总体更高;不同情景下研究区西部片区的适宜性情况总体优于东部片区,同时城镇建成区周边区域的适宜性高于偏远区域;不同政策情景下地质灾害易发度均能在适宜性分区中体现,适宜性级别低于其他区域;不同情景下东部槽谷区域的适宜性分区情况差异明显,对于东部槽谷区域的低丘缓坡土地开发建设应加强论证;在两种极端政策情景下,各级别适宜性分区在空间上的集中连片程度更高,而在另外3种非极端政策情景下,适宜性分区更加零散,地块破碎程度更高。 根据前文分析,巴南区新增规划城镇用地布局在低丘缓坡区域内的总量为1741.42hm2,仅占新增城镇用地总量的22.68%,本轮规划期内对城镇化、工业化等方面的城镇建设用地保障仍然以占用非低丘缓坡土地为主;与低丘缓坡土地适宜性情景模拟分区图进行叠加分析可以发现(表3),在不同的决策情景中,巴南区规划期内(2006—2020年)新增城镇用地分布在最适宜区的比重呈现出随着α增大而增大的态势,值得注意的是,在5类决策情景中,规划新增城镇用地均主要分布在最适宜区、高适宜区和中适宜区三个分区内,面积比重均约为90%,由此可见,在本轮规划期内,巴南区在对低丘缓坡土地利用规划布局的决策方面总体上仍表现出较为谨慎和保守态度。 Table 3 表3 表3不同情景下规划新增城镇用地在低丘缓坡区域中的适宜性分区情况 Table 3Result of suitability partition of new urban construction land in gentle hillside area under different scenarios(%)
(1)在传统静态评价的基础上,采用OWA算法可将决策者偏好带入到权重体系中对原权重进行加权修正以实现动态的多情景模拟,模拟结果更加接近实际,一定程度上弥补了传统静态评价结果的单一性,然而模拟结果的准确性高度依赖指标选取和AHP确定准则权重的合理性,因此,丰富完善评价指标体系和探索客观赋权法与OWA方法的结合是今后研究的重要内容。 (2)适宜性分区结果可为研究区土地利用规划编制提供不同政策偏好下的低丘缓坡土地开发规模与空间布局的专项研究支撑,可促进区域内低丘缓坡土地资源合理开发与保护。鉴于研究区在现实的政策情景下适宜性等级较高的低丘缓坡地块破碎,今后区域内低丘缓坡土地开发建设决策应优先鼓励发展占地规模不大的工业园区、旅游地产、养老地产等产业项目,以规避大面积开发建设可能带来的风险。 (3)今后可开展关于低丘缓坡土地开发政策与区域城镇化和工业化演进规律、生态环境保护策略等相关因素的多维度耦合系统研究,量化在不同发展阶段耦合系统达到最优运行状态时表征决策者所持态度的决策系数(α值),进一步提升基于OWA算法的决策情景模拟结果的准确性。 The authors have declared that no competing interests exist.
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