Study of urban green space and its changes using remote sensing techniques (Case study: Tabas city)
الموضوعات : فصلنامه علمی پژوهشی سنجش از دور راداری و نوری و سیستم اطلاعات جغرافیاییMahboubeh Shabani 1 , Seyedeh Razieh Keshavarz 2
1 - Master of Remote Sensing and Geographic Information System, Yazd Branch, Yazd Azad University, Iran
2 - PhD student in Geography and Urban Planning
الکلمات المفتاحية: Vegetation, green space, NDVI, Tabas, Sentinel 2,
ملخص المقالة :
Plant species used for urban green space in arid and semi-arid regions are not very diverse and many of them are drought sensitive and have high water requirements. This study was conducted to select new species as well as drought tolerant species for planting in green space and afforestation around cities in arid and semi-arid regions such as Tabas. To conduct this research, the required images of Sentinel 2 satellite in the period of 2017, 2018 and 2019 were prepared. Then, by performing the necessary processes, the amount of vegetation was calculated. And finally, maps and diagrams related to each year in the study area in Tabas city, which includes the area under municipal irrigation, Munshi Bashi Children's Park, Women's Park, Golshan and Anonymous Martyrs Garden, Anonymous Martyrs Boulevard and Social Security Boulevard, an area of Imamzadeh Musa Ibn Jafar Kazem and Razavi town were prepared and presented. The final results indicate that in 1996 there was an increase in vegetation, in 1997 with a decrease in vegetation and in 1998 there was a slight increase in vegetation. Also, the amount of water in 1996, 1997 and 1998 was estimated to be 11,250 cubic meters, 1433 cubic meters and 17,200 cubic meters, respectively. The results of the present study give us a worrying result that one of the reasons for these results could be due to improper use of water and improper vegetation in the target areas. In the end, suggestions were made to improve the current situation.
Study of urban green space and its changes using remote sensing techniques
(Case study: Tabas city)
Mahboubeh Shabani, Seyedeh Razieh Keshavarz, Seyed Ali Al-Modarressi
1- Master of Remote Sensing and Geographic Information System, Yazd Branch, Yazd Azad University, Iran
2- PhD student in Geography and Urban Planning, Yazd Branch, Yazd Azad University, Iran
3- Associate Professor, Department of Remote Sensing and Geographic Information System, Yazd Branch, Islamic Azad University, Yazd, Iran.
Email: (m.sh19931@yahoo.com)
Abstract
Plant species used for urban green space in arid and semi-arid regions are not very diverse and many of them are drought sensitive and have high water requirements. This study was conducted to select new species as well as drought tolerant species for planting in green space and afforestation around cities in arid and semi-arid regions such as Tabas.
To conduct this research, the required images of Sentinel 2 satellite in the period of 2017, 2018 and 2019 were prepared. Then, by performing the necessary processes, the amount of vegetation was calculated. And finally, maps and diagrams related to each year in the study area in Tabas city, which includes the area under municipal irrigation, Munshi Bashi Children's Park, Women's Park, Golshan and Anonymous Martyrs Garden, Anonymous Martyrs Boulevard and Social Security Boulevard, an area of Imamzadeh Musa Ibn Jafar Kazem and Razavi town were prepared and presented.
The final results indicate that in 1996 there was an increase in vegetation, in 1997 with a decrease in vegetation and in 1998 there was a slight increase in vegetation. Also, the amount of water in 1996, 1997 and 1998 was estimated to be 11,250 cubic meters, 1433 cubic meters and 17,200 cubic meters, respectively. The results of the present study give us a worrying result that one of the reasons for these results could be due to improper use of water and improper vegetation in the target areas. In the end, suggestions were made to improve the current situation.
Keywords: Green space, Sentinel 2, Vegetation, NDVI, Tabas
- Introduction
The expansion of urbanization, the vastness of urban space, and the pressure for more housing have brought about changes in land and natural environment. Spatial planning policies in cities and the need for more housing have reduced people's access to green spaces. Green space is a part of the physical vastness of the city that can have certain functions (Hatami Nejad et al., 2012).
Today, with the emergence and expansion of large cities, we are witnessing increasing growth and massive population movements. With the increase in urban population, urbanization issues and problems have also increased. Urban green space as one of the inseparable elements of a city is one of the factors affecting the sustainable development of the region (Ahmadi and Ahmadabadi, 2018).
Urban green space as a living thing is constantly changing and evolving. The concept of cities is no longer conceivable without the existence of green space in its various forms (Karam and Hajjeh Foroshnia, 2012). The consequences of urban development and the complexities of their environmental problems have made the existence of green space and its expansion inevitable forever (Majnoonian, 1995).
Urban growth is an important global phenomenon that occurs under the influence of environmental, human, economic and political factors. In most cases, this growth is associated with changes in urban land use, one of the most important of which is changes in green space, and often this growth leads to a decrease in green space (Majnoonian, 1995). Urban green space is a part of the physical scope of the city that can have meaningful functions. One of the main problems of cities is the lack of urban green space (Hataminejad et al., 2012). Knowing the ratio of land uses, land cover in a natural environment and how it changes over time is one of the most important things in planning. By knowing the ratio of changes in uses over time, future changes can be predicted and appropriate actions can be taken (Alavi Panah, 2003). Multispectral remote sensing images are very efficient to gain a better understanding of the earth's environment (Omidvar et al., 2015).
The purpose of this study is to investigate the changes in urban green space at different times using images and remote sensing techniques in Tabas.
Research background
The possibility of multi-time comparison of remote sensing data has made this technology the best tool for detecting changes. Using remote sensing images, the ratio of changes can be extracted and future changes can be predicted appropriately. Numerous studies have been conducted on this subject, some of which are briefly mentioned.
Zanganeh Shahraki et al. (2014), in a study examining the temporal-spatial analysis of the physical expansion of Mashhad and monitoring the changes in land use around them, the results of their research showed that 3343.67 hectares of agricultural land and 6964.11 hectares of barren land had been converted to urban use.
Gomeh et al. (2013) studied the trend of quantitative changes in the green space of Karaj metropolis using remote sensing data and landscaping measurements. Finally, the results of their research showed that the per capita green space decreased from 558 square meters in 1335 to 25 square meters. The results also showed that green space was not evenly distributed in the city and areas 5, 8 and 9 had the least green space.
Jafari et al. (2014) in the study monitored vegetation changes in Helen forest protected area and its reasons based on two-time NDVI analysis. The results showed that the rate of vegetation density increased from 12.4% of the total area from 1990 to 2009, which was 7.5% in the medium density forest sector and 4.9% in the low density forest sector. Also, in 0.63% of the total area, vegetation density has decreased, of which 0.17% was related to the medium-density forest sector and 0.46% was related to the low-density forest sector.
Mohammad Nejad et al. (2016) in their research examined the NDVI changes in Miandoab city in the period 1999 to 2014 using Landsat satellite images. Vegetation changes in this time period were compared in two images and calculated based on statistical indices of average mean, set, standard deviation and variance. Finally, the results showed that, in general, the vegetation index decreased significantly during 15 years from 1999 to 2014.
Sabz Ghabaei et al. (2015), in their research, investigated the detection of land use changes using remote sensing methods and GIS in Ghaemshahr. The results showed that the agricultural lands of Janga and the water areas became garden and residential lands. It was also shown that the use of satellite imagery to prepare land use maps, cover and change them to facilitate natural resource management planning was essential.
Alikhah Asl and Naseri (2015) studied the evaluation of the trend of land cover changes in the Kaftareh watershed using the remote sensing method and based on the results, the results showed that the use of additional information such as slope information and NDVI index, the region along with the processing of satellite images in a supervised method to prepare land cover maps, increased the accuracy of image classification.
Soodi and Jozi (2011) examined the qualitative changes of green space in Tehran from 1990 to 2006 (Case study: District 5 of Tehran Municipality). The results showed that in the period considered in the study, 186.48 and 0.9 hectares of land without vegetation had been converted into low and medium covered lands, respectively. 419.58 and 175.86 hectares of vegetated lands with low greenery were converted to uncovered lands.
Zu et al. (2005) used satellite imagery to study the green space of Baltimore and Maryland and obtain their area. In their work, they used high-resolution satellite images and digital aerial photographs. After analyzing the results, these researchers have emphasized the effectiveness of the object-oriented classification method in their work.
Satyakumar et al. (2019) examined the spatial approach to assess the spatio-temporal dynamics of urban green space distribution among neighborhoods in Mumbai. And the results showed that green space in Mumbai was generally reduced, divided and segregated between 2001 and 2011. Also, the green spaces in the western suburbs of the city had experienced the worst destruction.
Kai et al. (2019), the evolution of urban green space and its impact on the urban thermal environment based on remote sensing data: A case study of Fuzhou, China was studied.
Zhang et al. (2019) studied the spatial balance analysis of urban green space and human activities in Changdu, China.
The results showed that the coverage of urban green space reached 37.71%, while less than 27.49% of urban green space was used effectively. It also showed that human life and food behavior was highly dependent on urban green space and the poor balance between environmental services and the intensity of human activity in urban green space should be highly evaluated.
- Research Methods
Workflow diagram
Figure 1: Research workflow diagram
Study range
Tabas is the largest city in Iran, with an area of 55,808 square kilometers. Tabas was located in Khorasan province before 2001 (in that year Khorasan was not divided into three provinces) and in the same year, it separated from Khorasan and joined Yazd province. Finally, in 2014, it separated from Yazd again and joined South Khorasan. This city is located in the northeast of Yazd province and the east of Isfahan province; South of Khorasan Razavi and Semnan and west of South Khorasan province, in the orbit of 33 degrees and 35 minutes north and meridian 56 degrees and 55 minutes east, is located in an area with desert climate. And the cities of Bardaskan and Shahroud from the north, Ferdows and Birjand from the east, Kerman province from the south, and the cities of Nain, Ardakan and Bafgh from the west and southwest surround it. The study areas selected in Tabas include: Munshi Bashi Children's Park, Women's Park, Golshan Garden, Anonymous Martyrs, Anonymous Martyrs Boulevard, and Social Security Boulevard, an area of Imamzadeh Musa Ibn Jafar Kazem and Razavi Town.
Figure 2: Map of the geographical location of the study area
Method:
In this study, the purpose of studying vegetation changes in Tabas city is based on remote sensing analyzes. Sentinel 2 satellite data in 2018, 2017 and 2019 have been used. The first step to start work, considering that the study area was not in one image, so the mosaic images and then the desired pre-processions, including various corrections were done. Also, for each image, normalized vegetation index (NDVI) was calculated and their amount was recorded. Then, in Excel software, the numerical values for the normalized vegetation index in different ranges and time periods were regressed and their diagrams were drawn.
Table 1: Sentinel 2 image information
Direction of movement of satellite | Date | Image type |
Down pass | 14/07/2017 | S2MSI1C T39RWP/ S2MSI1C T39RWQ |
Down pass | 03/07/2017 | S2MSI1C T39RWP/ S2MSI1C T39RWQ |
Down pass | 04/07/2017 | S2MSI1C T39RWP/ S2MSI1C T39RWQ |
The Normalized Vegetation Index (NDVI) is a numerical index that is calculated and used using visible bands and near-infrared bands for remote sensing analysis.
This plant index, which is one of the most famous and simplest plant indices used, is defined in terms of two closely related red and infrared bands as follows. (Fatemi, 2017).
| Equation (1) |
|
|
| |
Figure 3: NDVI maps
In the map of 2017, the green color of the vegetation on the east side is condensed and the vegetation on the west side is narrowing. In the map of 2018, we have the most dense vegetation in the east and northeast, and in the map of 2019, you see the highest density of vegetation in the east, west and southwest. The following diagrams related to temperature, vegetation and water were drawn and displayed separately in Excel. (Figures 4, 5 and 6).
Figure 4: Temperature graph
Figure 5: NDVI chart
Figure 6: Water chart
Also, after calculating the amount of NDVI, regression was taken between the obtained values and the amount of this index was plotted in the desired ranges. (Figures 7, 8 and 9).
Figure 7: Graph of vegetation change in Golshan Tabas garden
Figure 8: Graph of vegetation change in Tabas Children's Park
Figure 9: Graph of the change in vegetation of the anonymous martyrs of Tabas
- Conclusion
Plant species used for urban green space in arid and semi-arid regions are not very diverse and many of them are drought sensitive and have high water requirements.
In this research, for changes in the vegetation of Tabas city and the area under irrigation of the municipality, which include Munshi Bashi Children's Park, Women's Park, Golshan and unknown martyrs Garden, unknown martyrs Boulevard and Social Security Boulevard, an area of Imamzadeh Musa Ibn Jafar Kazem and Razavi town. Vegetation rate in the period 2017, 2018 and 2019 was obtained using Sentinel 2 satellite data.
After performing calculations and processing, finally regression maps and graphs were prepared and displayed. The results showed that in 1996 we had an increase in vegetation, in 1997 we had a decrease in vegetation and in 1998 we had a slight increase in vegetation. Also, the amount of water in 1996, 1997 and 1998 was equal to 11,250 cubic meters, 1433 cubic meters and 17,200 cubic meters, respectively.
The results of the present study give us a worrying result that one of the reasons for these results could be due to improper use of water and improper vegetation in the target areas. According to the results obtained in the study, suggestions were made to improve the conditions of urban green space. Which includes the use of modern irrigation methods and accurate recording of irrigation in the municipal irrigation system and change of vegetation with extensive study and consideration of the indicators in remote sensing software as well as accurate monitoring of all stages of irrigation by relevant experts. The purpose of this paper was the ability of remote sensing to analyze and show understandable environmental changes. And the result obtained can be provided to the relevant officials of the institutions to fill the existing gaps, and the science of remote sensing has become evident indescribably.
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