Figs. 3 - 5 show the images of 2002, 2011, and 2022 of the QuickBird-2, WorldView-2, and Sentinel-2 satellite systems respectively, after performing, (1) the subset of all the satellite images to obtain the study area, (2) removing both of geometric and radiometric errors, (3) images rectification process between the reference image (QuickBird-2) and the slave images (WorldView-2 and Sentinel-2).
Change Detection and Urban Sprawl Monitoring
The figs. (6–8) indicate the applied outcomes of the classified images of QuickBird-2 satellite 2002, WorldView-2 satellite 2011, and Sentinel-2 satellite 2022, respectively. By adopting Envi software, a random sampling technique was used to collect training and testing sites from all the processed satellite images. The training sites were used in the Mahalanobis classifier in order to classify the three satellite images of QuickBird 2002, WorldView-2 of 2011, and Sentinel-2 of 2022 to detect the Land Use/ Land Cover change throughout the period of 2002 – 2011, and 2011- 2022. All testing samples were collected. These were checked using in situ checking and through the visual interpretation of the high-resolution image got in the fieldwork during July 2022. The testing sites were utilized to evaluate the accuracy of all the obtained results generated by image classification. The results showed an overall accuracy of about 85.94%, 89.82%, and 93.67% for 2002, 2011, and 2022 images, respectively. The classified maps’ accuracies showed results of more than 85%, and that gives a good manner about the image processing approaches that were adopted in conducting this study.
Also, the results illustrate the values of kappa coefficients, which were about 0.84, 0.86, and, 0.90 for 2002, 2011, and 2022 images, respectively. Figs. 9 and 10 indicate all the overall-accuracies and kappa-coefficient values of the classified images by the Mahalanobis distance classifier for all the applied satellite images of 2002, 2011, and 2022.
There are five major categories of interesting regions in AL-Hilla city: Roads, water bodies, urban area, vegetation, and soil were distributed in 2002, 2011, and 2022, all the obtained results are illustrated in Table 4.
Table4. indicates changes as extracted from the study area images.
Class Name
|
2002Area
(km2) / (%)
|
2011 Area
(km2) / (%)
|
2022 Area
(km2) / (%)
|
% of Increase
or Decrease
Since 2002
|
Roads
|
16.81
|
11.59
|
19.29
|
13.30
|
28.09
|
19.37
|
+ 07.78
|
Urban Area
|
16.59
|
11.44
|
34.37
|
23.70
|
45.88
|
31.64
|
+ 20.20
|
Water Bodies
|
07.93
|
05.47
|
04.29
|
02.96
|
02.42
|
01.67
|
- 03.80
|
Vegetation
|
51.21
|
35.35
|
43.15
|
29.76
|
28.59
|
19.72
|
- 15.63
|
Soil Area
|
52.42
|
36.15
|
43.90
|
30.28
|
40.02
|
27.60
|
- 08.55
|
The statistical comparison was utilized in this study to detect the changes in the patterns of the study area38. This method involves comparing multi-temporal produced classified Land Use/Land Cover maps from multi-temporal images over the period 2002 to 2011 and 2011 to 2022. In Figs. (6–8), the spatial urban sprawl is quite visible. The urbanization area increased dramatically and was distributed in the center part of AL-Hilla in 2002. The urbanization area category spread and is as revealed in the 2022 thematic map. The statistical comparison of categories indicates, that there is a notable urban expansion in the last 20 years between 2002 to 2022. Moreover, the outcomes show a substantial increase in two categories, Roads and Urban Area categories, and both of them together represent the urban area. For the last two decades, the urbanization region has rapidly increased in AL-Hilla as indicated in Fig. 11 and Table 4. It increased by 29.29 km2, from 16.59 km2 in 2002 to 45.88 km2 in 2022. However, Fig. 11 shows the total urbanization areas of both residential areas and roads in 2002 was 33.40 Km2 and it increased in 2022 to be about 73.97 km2. It increased rapidly from 2002 to 2002 by about 40.57 Km2. Table 5 shows the value of the average annual increasing rate of about 2.06%. The average annual rate of the 2022 urban region was about 1.91 times more than the size of the urban region in 2002. There are several phases to analyzing the urbanization in AL-Hilla city for the time from 2002 to 2022. In the first nine years of the study (2002–2011), the urban region sprawl was significantly high. In this time, the results of the Wars from 1980-2003, more than 600,000 persons returned to Babylon province, Iraq from surrounding country boundaries, and almost all of the coming people settled in urbanization regions, particularly in AL-Hilla city and surrounding areas. Those coming people built private houses, on their own lands or go through fragmented lands of orchards and agricultural lands, consequently, many new houses and buildings were constructed in that area. The urbanization area (roads and urban area) class has increased from 2002 to 2011 by more than 12.26% of the total area of AL-Hilla city. Figs. 6, 7, and 11 illustrate the burgeoning of the city’s spatial urban expansion, and its dramatic growth, which happened in the study area in different directions between (2002 and 2011). Moreover, in the case of considering the area of the roads is one side of the urban area. Therefore, the total area of both roads and urban area together will be increased for the period 2002 to 2011 was 33.40Km2 to 53.66 Km2 and that was equivalent to 37% of the total area of the AL-Hilla city as illustrated in Fig. 11.
Figs. 6–8, the second 10 years of this study area is (2011–2022), Although AL-Hilla city has hundreds of thousands of Syrian and Iraqi local refugees between 2013 and 2018, urban expansion rapidly accelerate at stabilized development rate. The Expansion of the Urban areas happened in approximately the first period (2002–2022), which shows a little growth in the rate after 2011, that was simply because of the Iraqi local refugees and Syrian refugees, those who ran away from the ISIS invasion, were settled inside and \ or near to AL-Hilla city. In the quantitative side, the urban regions and road classes together increased by 20.31 km2, from 53.66 km2 in 2011 to reach about 73.97 km2 in 2022, and that will be equivalent to 51.01% of the AL-Hilla city (Fig. 11 and Table 4). The Urban patterns expansion, and changes in other study area categories occur in the northwestern, and northeastern parts as well as, the southwestern, and southeastern parts of AL-Hilla city, where new housing and residential areas were settled between 2011 and 2022 (Figs. 7 and 8). So, the increase in Urbanization Areas (Urban and Roads classes) from 2002 to 2022 of about 27.98% of the area of AL-Hilla city (Table 4). In Figs. 6–8, 12 and Table 4, there was significantly decreased changes occurred in the classes of the study area for the period from 2002 to 2022 of the Water Bodies, Vegetation, and Soil Area with a decrease percent were about of - 03.80%, - 15.63%, and - 08.55% respectively. Fig. 12 illustrates the changes in each class between 2002-2022.
Urbanization Growth Analysis
Table 5 indicates the annual urbanization areas (urban and roads areas) growth percentage rate, from the period 2002 to 2022. (K) is represented as a key index to validate urbanization region growth, as indicates in (Eq.1) below27:
where, the (Ua), and (Ub) represent the urban region at the starting and end of the study interval times, respectively, and (T) is represented the entire time of the this study from (a to b).
Table 5. AL-Hilla’s annual urban region growth rate (2002–2022).
Date
|
Urban region (km2)
|
The annual growth (%)
|
2002
|
16.59
|
--------
|
2011
|
34.37
|
11.91
|
2022
|
45.88
|
03.39
|
The outcomes of this study show that urbanization growth of AL-Hilla city occurred in two phases in the period of (2002–2022). The first phase occurred from 2002 to 2011, and the second one occurred from 2011 to 2022. During the first stage, the urban area has been expanded over nine years by 17.78 km2 (or 1.96 km2 each year). The urbanization increased from 16.59 km2 (or 11.44 %) to 34.37 km2 (or 23.70%) of the study area from 2002 to 2011. In this stage, the dominant urbanization expansion was horizontal expansion in AL-Hilla city. However, with counting the areas of both urban and roads over the nine years from 2002 to 2011, the urban increased from 33.4Km2 to 53.66 Km2. The amount of annual growth of urban and road areas between (2002 – 2011) and (2011 – 2022) was recorded to be 6.7% and 3.8% respectively as illustrated in Table 6.
Table 6. AL-Hilla’s annual urban region growth rate (2002–2022).
Date
|
Urban region (km2)
|
The annual growth (%)
|
2002
|
33.40
|
------
|
2011
|
53.66
|
6.7%
|
2022
|
73.97
|
3.8%
|
The second period, which start from 2011 to 2022, urban area was dramatic growth. The urbanization areas expanded by 11.51 km2 (or 1.15 km2 each year). The infrastructures projects in Al-Hilla, including houses, residential, schools, universities, water supply stations, and electricity and service buildings, led to the increase in the urban center’s expansion. The dominant expansion in AL-Hilla was vertical urbanization between 2011 to 2022. The annual growth rate was 3.39%, which indicates that the urban growth in AL-Hilla has been almost steady for the study area between 2002-2022. However, with counting the areas of both urban and roads over the ten years from 2011 to 2022, the urban increased from 53.66 Km2 to reaches about 73.97 Km2. The annual growth rate was 3.8% as illustrated in Table 6. The results reported by17 & 38, investigating urban area sprawl, using satellite images from the Landsat satellite system of the MSS, TM, and ETM+, indicated, that the dramatic urbanization region growth occurred on the main roads and plantation land. The present research shows outcomes, that are better than those of 17 & 38.