Using negative exponential function to characterize built-up land density along slope gradient for 19 urban areas in China

In China,numerous cities are expanding into sloping land,yet the quantitative distribution patterns of urban built-up land density along the slope gradient remain unclear,limiting the understanding of sloping land urbanization.In this paper,a simple negative exponential function was presented to verify its applicability in 19 typical sloping urban areas in China.The function fits well for all case urban areas(R^(2)≥0.951,p<0.001).The parameters of this function clearly describe two fundamental attributes:initial value a and decline rate b.Between 2000 and 2020,a tends to increase,while b tends to decrease in all urban areas,confirming the hypothesis of mutual promotion between flatland densification and sloping land expansion.Multiple regression analysis indicates that the built-up land density and the ruggedness of background land can explain 70.7%of a,while the average slope ratio of built-up land to background land,the built-up land density and the built-up land area can explain 82.1%of b.This work provides a quantitative investigative tool for distribution of urban built-up land density along slope gradient,aiding in the study of the globally increasing phenomenon of sloping land urbanization from a new perspective.

Examining Rate of Built-Up Areas on the Vegetation Cover along River Riara Riparian within Kiambu Town, Kenya

Urban river riparian spaces and their natural systems are valuable to urban dwellers;but are increasingly affected and ruined by human activities and in particular, urbanization processes. In this research, land sat and sentinel satellite imagery apt for change detection in vegetation cover, both landsat and sentinel imagery, covering the period between 1970 and 2021 in epochs of 1973, 1984, 1993, 2003, 2015 and 2021 years were used to establish the correlation between vegetation cover and built-up area along River Riara river reserve. The images were analysed to extract the built-up areas along the river reserve, including the buildings, and the rate of human settlements, which influenced vegetation cover. Normalized Difference Built-Up Index (NDBI) and Normalized Difference Vegetation Index (NDVI) were computed using the Short-Wave Infrared (SWIR) and the Near Infra-Red (NIR) bands to show the rate of change over the years. Results indicate NDVI values were high, compared to NDBI values along river Riara in the years 1973 and 1993 implying that there was more vegetation cover then. However, in the year 2021, the NDVI indicated the highest value at 0.88, with the complementary NDBI indicating the highest NDBI value at 0.47. This represents a significant increase in built-up areas since 2015 more than in previous epochs. Either, there was a significant increase in NDBI values, from 0.24 in 1993 to 0.47 in 2021. More so, the R-squared value at 0.80 informed 80% relationship between NDBI and NDVI values indicating a negative correlation.

Rainwater harvesting systems: An urban flood risk mitigation measure in arid areas

Rainwater harvesting (RWH) systems have been developed to compensate for shortage in the water supply worldwide. Such systems are not very common in arid areas, particularly in the Gulf Region, due to the scarcity of rainfall and their reduced efficiency in covering water demand and reducing water consumption rates. In spite of this, RWH systems have the potential to reduce urban flood risks, particularly in densely populated areas. This study aimed to assess the potential use of RWH systems as urban flood mitigation measures in arid areas. Their utility in the retention of stormwater runoff and the reduction of water depth and extent were evaluated. The study was conducted in a residential area in Bahrain that experienced waterlogging after heavy rainfall events. The water demand patterns of housing units were analyzed, and the daily water balance for RWH tanks was evaluated. The effect of the implementation of RWH systems on the flood volume was evaluated with a two-dimensional hydrodynamic model. Flood simulations were conducted in several rainfall scenarios with different probabilities of occurrence. The results showed significant reductions in the flood depth and flood extent, but these effects were highly dependent on the rainfall intensity of the event. RWH systems are effective flood mitigation measures, particularly in urban arid regions short of proper stormwater control infrastructure, and they enhance the resilience of the built environment to urban floods.

Analysis of the Relationship between Land Surface Temperature and Vegetation and Built-Up Indices in Upper-Hill, Nairobi

Designing “liveable” cities as climate change effects are felt all over the world has become a priority to city authorities as ways are sought to reduce rising temperatures in urban areas. Urban Heat Island (UHI) effect occurs when there is a difference in temperature between rural and urban areas. In urban areas, impervious surfaces absorb heat during the day and release it at night, making urban areas warmer compared to rural areas which cool faster at night. This Urban Heat Island effect is particularly noticeable at night. Noticeable negative effects of Urban Heat Islands include health problems, air pollution, water shortages and higher energy requirements. The main objective of this research paper was to analyze the spatial and temporal relationship between Land Surface Temperature (LST) and Normalized Density Vegetation Index (NDVI) and Built-Up Density Index (BDI) in Upper-Hill, Nairobi Kenya. The changes in land cover would be represented by analyzing the two indices NDVI and BDI. Results showed the greatest increase in temperature within Upper-Hill of up to 3.96&#176C between the years 2015 and 2017. There was also an increase in impervious surfaces as indicated by NDVI and BDI within Upper-Hill and its surroundings. The linear regression results showed a negative correlation between LST and NDVI and a positive correlation with BDI, which is a better predictor of Land Surface Temperature than NDVI. Data sets were analyzed from Landsat imagery for the periods 1987, 2002, 2015 and 2017 to determine changes in land surface temperatures over a 30 year period and it’s relation to land cover changes using indices. Visual comparisons between Temperature differences between the years revealed that temperatures decreased around the urban areas. Minimum and maximum temperatures showed an increase of 1.6&#176C and 3.65&#176C respectively between 1987 and 2017. The comparisons between LST, NDVI and BDI show the results to be significantly different. The use of NDVI and BDI to study changes in land cover due to urbanization, reduces the time taken to manually classify moderate resolution satellite imagery.

Dynamics of Urbanization and Its Impact on Land-Use/Land-Cover: A Case Study of Megacity Delhi

The rapid expansion of urban areas due to rise in population and economic growth is increasing additional demand on natural resources thereby causing land-use changes especially in megacities. Therefore, serious problems associated with rapid development such as additional infrastructure, informal settlements, environmental pollution, destruction of ecological structure and scarcity of natural resources has been studied carefully using remote sensing and GIS technologies for a rapidly grown megacity namely, Delhi. The present work evaluates the land use/land cover (LULC) changes and urban expansion in Mega city Delhi and highlights the major impact of rapid urbanization and population growth on the land cover changes which needs immediate attention. The results indicate that the city is expanding towards its peripheral region with the conversion of rural regions in to urban expansions. Built-up area of Delhi witnessed an overall increment from 540.7 km2 to 791.96 km2 or 16.86% of the total city area (1,490 km2 ) during the study period 1997 to 2008 which mainly came from agriculture land, waste land, scrub-land, sandy areas and water bodies. The increment in forest cover of 0.5 % is very small when considering the increment in built up category to 17%. Total area of waterbodies has reduced by 52.9% in a ten year period (58.26 km2 in 1997 to 27.43 km2 in 2008) with shallow waterbodies now having a dismal presence. LULC changes are studied with the urban growth parameters such as population, vehicles, gross state domestic product etc. The results lay emphasis on the concepts of urban planning to be applied such that more consideration is towards the preservation and management of natural land use classes which will increase the quality of life in an urban environment.

Statistical Change Detection in Water Cycle over Two Decades and Assessment of Impact of Urbanization on Surface and Sub-Surface Water Flows

Urbanization is termed as physical transformation of landscapes that alter the natural regime of the environment of its surrounding resulting in further changes in macro as well as micro climate of the region [1]. Urban areas are continually facing problems of water scarcity and urban flash floods. Recent news from IPCC report 2010, CIESIN’s Global Rural Urban Mapping Project [2] and World Water Vol. 7 2007, it is clear that urban land area has doubled and affected the hydrological cycle. The components of hydrological cycle affected are Infiltration, Runoff and Evaporation and the causing components are derived by studies as land use, land cover, water withdrawal and urban developments. Thus water availability, water recharge and water cycle are all destabilized in course or urban development. The paper is an attempt to correlate and identify the periodical changes in urban water cycle, during urbanization of Bhopal City, India, during last twenty years and above. The observations are based on GIS mapping of the study area from 1991 to 2009 using rational method of runoff and recharge calculations and statistical analysis of related built-up areas. Also change in natural course of drainages with the help of GIS imageries which have been detected during twenty years that help to observe the adaptation of natural system to urban course. Also the observations show an interesting relation which can be used for further research and sustainable development [3].

Chinese City Size Ranking: A Comparative Study of the Urban Built-Up Area Based on Remote Sensing Data

Without a clear and unified definition of the urban built-up area, many city rankings by area are inconsistent, giving rise to confusion among the general public and even scholars. This paper summarizes various definitions of the urban built-up area and proposes three definition methods: all urban built-up areas in a municipal administrative area, concentrated contiguous built-up areas, and urban built-up areas in central cities. From the latest Landsat 8 satellite images, the paper obtains the data of urban built-up area in some of China’s big cities and makes a comparative study between the results of the urban built-up areas by the three definition methods and three other common statistical data. It finds that neither the area data nor the ranking is consistent. Finally, it further explores what causes differences in rankings and gives some advice for improving the definition of the urban built-up area.

Impact of Urbanisation on Land Use/Land Cover in Puducherry City, India

The change of land use plays a major role in the developmental activity of a developing country. Due to rapid growth of urbanisation and dramatic increasing population, the fertile agricultural land has been converted to built-up area with respect to the demand for housing requirement and to the need for basic infrastructure facilities. The quantum of open space and surface water bodies has also been encroached. There has been a rapid growth of population in Puducherry city from 3.48 million in 1991 to 5.44 million in 2011. Hence the conservation of natural resources becomes one of the major challenges especially in small and medium town. This study was conducted to assess the effect of change on land use in urban agglomeration area of Puducherry city for the duration period from 1997 to 2017. There has been an increase in population in Puducherry city mainly attributed to higher scale of migration from adjoining rural areas and medium town for better education, job opportunities and quality life. Hence, it has been strongly recommended for stringent Development Control Regulations to quantify the urban sprawl and manage the impact of urbanisation of land use/land cover in Puducherry city.

基于混合用地模式识别的济南市老城区典型片区绿色空间降温效应分析

城市绿色空间可以通过生态系统服务调节功能有效缓解城市热岛效应,降低高温健康胁迫风险。城市中心城区特别是老城区建成环境具有高度异质性,复杂建成环境中绿色空间的降温效应,特别是混合用地模式中绿色空间的降温强度、阈值、形状等还需进一步明晰。在厘清城市热环境影响因素和绿色空间降温机制基础上,构建了“冷热岛分析提取-混合用地模式聚类识别-混合用地模式热效应分析-典型绿色空间降温效应分析”的研究框架。针对当前城市绿地指标失实、结构失衡、功能失调等现实问题,选择济南市老城区典型片区进行实证研究,重点分析了中层建筑混合用地模式中绿色空间的降温强度、降温面积阈值、形状及植被覆盖度等,总结了具有高降温效能的绿色空间模式,为促进城市健康人居环境发展提供借鉴。

城市轨道交通对容积率影响的定量分析——以东京为例

以东京为例研究城市轨道交通对容积率影响的定量关系,可为我国城市轨道交通站区土地资源的合理配置与优化利用提供指导依据。选取区位、建筑类型、到车站距离、地价作为影响地块容积率的因素,并构建了带交互项的线性回归模型进行分析。p值检验结果表明带交互项模型更适用。研究显示“到车站距离”对商业建筑容积率的影响大于居住建筑,商业建筑“核心区”与“到车站距离”间交互影响程度最大,居住建筑“市区”与“到车站距离”间交互影响程度大于郊区。研究结果为调整国内城市轨道交通站区商业建筑物布局,优化城市核心区轨道交通站点周边商业建筑物容积率及调控城市市区与郊区轨道交通站点周边居住建筑物差异化规划提供依据。

景观格局汇水单元法与城区水量水质模拟研究

景观多样性有助于提高城市韧性,但其可能带来的透水斑块破碎化和廊道连通度的改变,会影响城区非点源污染的产生输移特性。传统对非点源污染的定量评估忽略了汇水单元内部景观格局(形状、比例和空间配置)对物质输移的影响,是导致模拟精度偏低的主要原因。针对这一问题,本研究结合遥感影像和城市景观格局分布特征,构建了基于景观格局的汇水单元划分方法(景观格局法)。采用SWMM模型,以巢湖一级支流十五里河为对象展开研究,结果表明:(1)基于实测数据进行验证,采用景观格局法模拟各项指标(水量、COD、TP和NH 3-N)的纳什效率系数(NSE)均大于0.7,结果可靠;(2)与传统方法(泰森多边形划分汇水单元)相比,水量模拟精度(以NSE计)提高8%,水质模拟精度提高6%;(3)与泰森多边形法相比,景观格局法计算的入河总水量和污染总负荷较低,且污染物浓度峰值滞后;(4)景观格局法通过改变汇水单元之间的水力联系,模拟出污染物冲刷减弱,初期雨水冲刷效应降低,且随着重现期的加大,降低初期雨水冲刷强度的效果越明显,表明一定程度上景观类型多样化有助于缓解瞬时高强度污染影响。本研究构建的方法充分考虑了城市斑块内部的景观格局分布特征和水力联系,可为城区面源污染输出控制提供新的评估手段。

利用珞珈一号提取城市建成区的方法对比分析

采取单独使用珞珈一号(Luojia1-01)夜间灯光数据、构建植被调整NTL城市指数(VANUI)、Luojia1-01和兴趣点(Luojia1-01&POI)指数3种方法提取了2018年成都市的建成区,并利用总体精度和Kappa系数对比了3种方法的提取精度。结果表明,Luojia1-01的高分辨率在建成区提取方面有广阔的应用,但单独使用会产生信息误提的问题;VANUI提取的建成区在内部和边界细节信息方面表现更优,但存在孔隙较多、图斑破碎的问题;Luojia1-01&POI指数提取的建成区范围效果最好、精度最高。研究结果为Luojia1-01与其他类型数据的结合提供了参考,进一步证实了POI数据结合夜间灯光数据提取建成区的高精度与可靠性。

Examining the influence of the implementation of Major Function-oriented Zones on built-up area expansion in China

China had implemented the national strategies for Major Function-oriented Zones （MFOZs） to realize the goal of national sustainable development since 2010. This study analyzed and compared spatio-temporal characteristics and differences in built-up area for China＇s MFOZs using a China＇ s Land Use Database （CLUD） derived from high-resolution remotely sensed images in the periods of 2000-2010 and 2010-2013. To sum up： （1） The percentage of built-up area in each of the MFOZs was significantly different, revealing the gradient feature of national land development based on the distribution of the main functions. （2） Annual growth in built-up area in optimal development zones （ODZs） decreased signifi- cantly during 2010-2013 compared with the period 2000-2010, while annual growth in built-up area in key development zones （KDZs）, agricultural production zones （APZs） and key ecological function zones （KEFZs） increased significantly. （3） In ODZs, the average annual increase in built-up area in the Yangtze River Delta region was significantly higher than in other regions; the average area increase and rate of increase of built-up area in KDZs was faster in the western region than in other regions; average annual area growth of built-up area in APZs in the northeast, central and western regions was twice as high as the previous decade on average; the annual rate of change and increase in the dynamic degree of built-up area were most notable in KEFZs in the central region. （4） The spatial pattern and charac- teristics of built-up area expansions in the period 2010-2013 reflected the gradient feature of the plan for MFOZs. But the rate of increase locally in built-up area in ODZs, APZs and KEFZs is fast, so the effective measures must be adopted in the implementation of national and regional policies. The conclusions indicated these methods and results were meaningful for future regulation strategies in optimizing national land development in China.

城市建成区海绵容量评估与排水系统优化设计

低影响开发理念成为解决我国城市化所带来的洪涝灾害、面源污染、水生态破坏等城市水问题的新思路。灰-绿基础设施联用可同时达到削减径流量和污染负荷的目的。但区域本底海绵容量、绿色基础设施调蓄量与关键设计参数缺乏定量依据。该研究通过SWMM模型模拟、数值计算和现场实测评估研究区域本底海绵容量,结合综合径流系数法明确了研究区域水敏感区分级,其海绵容量分级为优、良、中、差、极差5级的子汇水区占比分别为8.6%、9.1%、24.6%、55.0%和2.7%,绝大部分子汇水区分级为中和差;结合现场实测和RECARGA模型模拟,明确了绿色基础设施海绵容量及灰色基础设施入流参数,结果表明:相较于填料厚度变化,绿色基础设施对降雨量大小的响应更为明显。从排水管道系统优化和灰-绿组合排水系统优化两个方面进行了系统方案设计,构建了灰-绿联用雨水调蓄技术路径,为其关键设计参数的选取和管道改造方案的制定提供了有效依据。

《城区范围确定规程》应用中的关键技术问题

围绕城区范围划定3个工作阶段的关键技术,综合运用文献资料法和个案调查法,分析了《城区范围确定规程》在应用层面表现出的问题。研究发现:⑴部分城区范围划定作业单位对《规程》的技术逻辑理解不深不细,基础数据清洗工作存在纰漏;⑵通过指定相关参数和阈值确实对遏制作业单位主观性有所帮助,但在城区实体地域范围和城区范围划定阶段表现出的过度扩张问题值得高度重视;⑶叠加分析环节导致的城区空间扩张可能深刻影响甚至改变《规程》既定的技术逻辑。研究认为,城区范围划定具有基础研究性质,要尝试通过增设社会经济指标、赋予作业单位参数设置权等多项措施检测和预防过度扩张问题,提升城区范围划定成果的应用价值。

城市土地混合利用测度及空间格局研究——以合肥市建成区为例

通过利用系统思想构建土地混合利用的内涵与测度框架,揭示城市建成区土地混合利用现象的空间分布特征。利用地理信息系统(Geographic Information System,GIS)空间分析技术对多源数据进行整合,量化测度合肥市建成区土地混合利用的情况,通过空间自相关和聚类以及异常值探讨建成区土地混合利用的空间格局。结果表明:合肥市整体土地混合利用现象分布不均衡,空间上呈现“中高外低”的分布,分布上呈现高度混合多中心分散以及中度混合集中连片的格局;土地功能混合度较高的区域主要集中在合肥市建成区中心区域、区域的生活中心和生态环境较好的区域,土地功能混合度中高度混合的格网个数低于土地数量混合度与土地空间混合度中高度混合的格网个数;土地混合利用现象呈现一定的空间聚集效应,表现为较高度混合和高度混合的空间集聚特征,形成了由中心向外围降低的离心式结构,并且边缘有分散的点状聚集区域。

基于夜间灯光数据的城市空间动态扩张分析——以江苏省为例

引用改进动态阈值法和重心模型,分析江苏省城市动态扩张时空特征,得到江苏省城市建成区的空间分布情况及区域差异。结果表明,2000—2021年,提取的城市建成区面积与实际符合,演变规律与城市经济发展相贴合,形成以南京市、苏州市、徐州市为中心的“放射状”集聚形态,不同城市、不同阶段扩张速度差异明显,发展重心逐渐由南向北推进,由南京都市圈和苏锡常都市圈为主的发展模式逐渐向均衡发展模式转变。

人本视角下多维数字技术在总体城市设计中的集成应用探索--以太原市总体城市设计为例

数据环境和数字技术的协同发展极大地促进了城市设计的技术方法创新,为在城市尺度范围分析人本尺度的高精度数据带来可能。基于空间格局、空间秩序、风貌品质和公共活动等城市设计重点关注领域,对既有城市设计研究中的数字技术进行梳理,构建一个重点适用于存量地区总体城市设计实践的数字技术应用“工具箱”,为城市设计从业人员结合具体现状问题和规划目标,进行定制化的数字技术和多源数据选择提供参考。最后以太原市总体城市设计为例进行数字技术集成应用示范,以期为存量地区城市设计实践提供数字技术应用方面的借鉴。

基于多源遥感卫星数据融合的城市建成区提取研究

以某城市为研究区,结合城市建成区特性,构建了一种利用NPP/VIIRS高分夜间灯光数据提取的城市活跃区与城市不透水区域融合的城市建成区提取方法。结果表明:根据提出的融合算法提取城市建成区,具有较高的精度,能有效揭示城市建成区与区域不透水率、夜光数据活跃度的内在关系,是一种可行的城市建成区提取方法,也能为城市蔓延分析等的进一步研究奠定良好的数据基础。

郴州市市辖区建成区扩张时空变化特征及驱动力分析

以湖南省重要城市郴州市的市辖区为研究对象,选取1989年、2000年、2009年、2018年4期Landsat遥感影像,通过最大似然法提取了土地利用类型信息,运用转移矩阵分析了各年份间土地利用变化趋势,基于阈值分割图像确定了市辖区建成区范围,分析了建成区变化趋势及其与人口、经济的关系.结果表明,1989-2018年间建设用地增长147.39 km^(2),建成区面积增长32.32 km^(2),主要来自林地和耕地转化,且耕地转化占比不断增大.受“南延东进、西扩北提,东进优先”政策影响,建成区各年份间扩张强度依次为4.86%、6.45%、5.74%,主要向南、东南方向持续快速扩张.受地貌限制,建成区总体呈近南北向线性形态,属不规则圈层式+廊道式结合的扩张模式,人口、经济增长皮尔逊相关系数为0.9756、0.9751.政策、自然地貌、人口、经济构成了该城市扩张的重要驱动因素.研究可为郴州市城市高质量发展精准施策提供参考.