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Dr. Hamid Gholami, Hasan Fathizad, Ata Safari, Mehdi Biniaz,
year 5, Issue 4 (2016 winter 2016)
year 5, Issue 4 (2016 winter 2016)
Abstract
Today, soil erosion is considered as one of main subjects of watershed management at national and global levels. Assessment of decreasing risk of soil and it spatial distribution are one of key factors for successful evaluation of soil erosion. The objectives of research were calculation and modeling of rain erosivity factor in Ilam province using data of number of 28 pluviometry stations during of 23 years period. After that, rain erosivity factor was calculated, map of rain erosivity factor was provided using geostatistical algorithms. Spatial correlation between data of rain erosivity was drawn using Variogram. In order to, studying of erosivity index were used (IDW), (GPI), (RBF), (LPI) and kriging. The best algorithm was selected using statistical indices of Root Mean Square Error (RMSE) and MAE. Results showed that, GPI was the best algorithm with RMSE and MAE equal to 28.93 and 20.95, respectively.
Yaser Safari, Zahra Noori, Mohammad Rahmanian,
year 11, Issue 2 (Summer 2021)
year 11, Issue 2 (Summer 2021)
Abstract
Extended abstract
1- Introduction
Land-use change has been extensively considered by farmers as an easily available approach with the aim of finding new resources for producing more agricultural products. Deforestation, the most common type of land-use change, has led to the extensive parts of productive lands in different parts of the world being highly degraded. Rainfed farming can be listed as one of the most important substitutes for the forests which have been destroyed. In this scenario, as time goes on, the productivity of the land might be decreased due to the problems arising out of inappropriate land management strategies or inexorable climate changes, leading to the lands being abandoned. Given the prevalence of this issue in the Southwest part of Iran, the present study aimed to monitor the changes of selected soil fertility properties following the oak deforestation in the Miankooh region, Southwest Shahrekord City.
2- Methodology
The study area is located in 31° 44′ N and 50° 34′ E, 150 kilometers far from Shahrekord City, Southwest Iran. The area has a semi-arid climate with an annual average temperature and rainfall of 16.3 °C and 439.5 mm, respectively. This area is naturally covered with semi-dense oak forests, considerable parts of which have been partly destroyed and then assigned to rainfed wheat by local farmers. A substantial loss in crop yield in recent decades, mainly due to the decreased precipitation, has persuaded the young farmers to abandon the less productive lands. Aimed at assessing the impact of land-use change on soil fertility, a total of 30 surface soil samples (0–25 cm) were collected from the lands under wheat cultivation, semi-dense oak forest, and abandoned lands. The soil samples were air-dried and sieved through a 2-mm sieve and then analyzed for soil pH, organic matter content (OM), total nitrogen (N), available phosphorus (P), and exchangeable potassium (K) using standard methods. The data was statistically analyzed applying the Duncan test at the probability level of 5%, one-way ANOVA, and the multivariate approach of the Hotelling test.
3- Results
The studied soils contained a fairly high content of clay and can be classified as alkaline soils, possibly due to their relatively high content of calcium carbonates. A high soil buffering capacity caused by the accumulation of calcium carbonates in surface layers would have contributed to enabling the studied soil to undergo different uses without any significant changes in soil pH. Following the land-use change from oak forest to rainfed wheat and then to abandoned (uncultivated) lands, soil organic matter and total nitrogen decreased from 2.33% and 0.11% to 1.0% and 0.05%, respectively. This observation may be arisen out of the fact that the soils under wheat cultivation receive a relatively deep plowing almost every year, which can substantially reduce the percentage of soil total N or OM by mixing the rich surface layer of the soil with the less enriched subsurface layer. As far as the abandoned soil is considered, receiving the negligible inputs of organic matter caused a further decrease in soil total N and OM. The investigated soils benefited from acceptable amounts of available P so that the insignificant fall in their P contents due to land-use change may not affect their fertility potential. When it comes to K, unlike soil OM and N, it significantly rose from 615.0 mg/kg in forest lands to 633.4 in the soils under wheat cultivation. It appears that the addition of manure to surface soil by local farmers has provided a good source of this important nutrient. Applying the multivariate approach of the Hotelling test aimed at simultaneous comparing of different land-use types according to all of the studied soil properties, it was observed that the three types of land use investigated could be considered as different units.
4- Discussion & Conclusions
Even though deforestation generally leads to soil degradation, some soil fertility properties might remain unchanged or even be improved based on the management strategies applied. In fact, applying purposeful and appropriate techniques in the field may be helpful to alleviate the unavoidable consequences of land-use change. Compared to substituting the semi-dense oak forests with rainfed farming, abandoning the croplands may result in more problematic soils. The pretty fast degradation of the crucial soil fertility properties caused by land-use change gives a serious warning about the possibility of further destruction of soils in the area studied, which may make them entirely unsuitable for any kind of agricultural use. Considering the complexity of soil environment, comparing the soils under different land use in terms of each individual soil property may not necessarily lead to reliable results. Accordingly, multivariate approaches, like the Hotelling test, maybe more consistent with the complex nature of the soil.
Mahboobeh Karimi, Ali Abbaspour, Yaser Safari, Vajiheh Dorostkar,
year 13, Issue 1 (Spring 2023 2023)
year 13, Issue 1 (Spring 2023 2023)
Abstract
1- Introduction
Identifying the accurate patterns according to which the important properties of soils are impacted by various factors considering the local situations would be a prerequisite for the precise estimation of soil behavior and site-specific management. Topographical conditions of any given area are among the main factors which influence the variations of soil attributes, especially in small spatial scales. The influence of topography and its different aspects may vary depending on the local situations and also on the interactions of its effects with other soil-forming factors. Slope length and width, slope position and aspect as well as slope gradient would be considered as the most important topographical conditions which influence soil properties. By now, the previous researches conducting relevant studies to the impact of these factors on soil quality in different regions of the world have reported some inconsistent results. The current study was carried out with the aim of investigating the influence of slope and position aspects on the soil quality considering the local situations by comparing the amounts of soil pH, organic matter (OM), available phosphorus (P), mean geometric diameter of soil aggregates (MGD), and water-dispersible clay (WDC) in the soils located in the south-facing and north-facing slopes in five different slope positions, including the summit, shoulder, backslope, footslope, and toeslope in the forests of Kalpoosh area, in the Northeast of Shahrood.
2- Methodology
Kalpoosh area, 173 kilometers far from Shahrood City towards the Northeast, has a semi-arid climate and experiences snowy and freezing winters followed by cool summers. The study area is located in 36° 32′ N and 56° 41′ E, with an average altitude of 1270 meters above sea level. The area under investigation is naturally covered with semi-dense forests that, in recent years, considerable parts of these forests have been partly destroyed and then assigned to rain-fed farming by the local farmers. For sampling, two slope aspects, including south-facing and north-facing were selected and the five main slope positions, including the summit, shoulder, backslope, footslope, and toeslope were separated. Then, surface soil samples (0 – 20 cm) were taken up from three different points which were two meters far from each other in every slope position, and each individual sample was considered as a replication. Accordingly, considering the two selected slope aspects, 30 samples were gathered and after being passed from a 2-mm sieve, their mentioned properties were measured using standard methods. The data were statistically analyzed by applying the Duncan test, and one-way ANOVA in SPSS software, and the relevant diagrams were plotted by applying Excel software.
3- Results
The results indicating the combined effects of slope aspects and positions were significant on soil pH, OM and MGD (P < 0.01). Furthermore, the soils on shoulder position in north-facing slopes had the highest pH (8.17), whereas the minimum pH (7.73) was observed in the soils located on toeslope in south-facing slopes. The highest soil OM content was found in backslope position in south-facing slopes (4.79 %) and the lowest OM content was observed in toeslope position in south-facing slopes (0.62 %). Similarly, the soils located on shoulder and backslope positions in south-facing slopes had the highest MGD (1.23 mm), whereas the soils located on summit position in north-facing slopes showed the lowest MGD (0.79 mm). On the other hand, in contrary to the most of previous researches, the amounts of OM (2.64 %), P (10.13 mg/kg), MGD (1.30 mm), and WDC (2.23 %), in south-facing slopes were relatively more favorable compared to their corresponding values in north-facing slopes (2.13 %, 8374 mg/kg, 0.95 mm, and 3.90 %, respectively). Sites on backslope had significantly more favorable soil properties than other sampling sites, probably because of a gentle slope and the semi-dense plant cover in these sites. Correlation analysis revealed a significant relationship among OM with P (0.49, P < 0.01) and equivalent calcium carbonates with MGD (0.37, P < 0.05). Accordingly, it seems that soil OM is the premier factor controlling P distribution in soil, and similarly, soil carbonates curb the flocculation and soil aggregate creation in the studied soils.
4- Discussion & Conclusions
Considering the fact that Iran is located in the northern hemisphere and as it is well documented in previous papers, it is anticipated that the soils on north-facing slopes would be more mature with more favorable attributes in comparison with south-facing slopes. Unlike this estimation, comparing almost all of the soil properties in the two different slopes indicated that aside from slope position, the soils located on south-facing slopes had more favorable properties compared to north-facing slopes. Considering that the area under investigation undergoes early coldness in fall as well as heavy snows, low soil temperature in north-facing slopes seemingly hinders plant growth and soil evolution. On the other hand, receiving more radiation, soils located on south-facing slopes can modify the impacts of early coldness so that they provide the appropriate temperature for plant growth and the development of soil-forming processes.
Sara Mohammadi Issaabad, Amir Safari , Ali Ahmadabadi, Sahar Darabi Shahmari ,
year 14, Issue 1 (Spring 2024)
year 14, Issue 1 (Spring 2024)
Abstract
1- Introduction
Flood is one of the most common and widespread natural disasters that occur frequently around the world (Patra et al, 2016). In recent years, the damages and casualties caused by floods have been affected by various factors. However, increased population, land use change, and the development of residential areas are considered to be the boosters for the increase in damages. The decrease in the active width of rivers by different factors especially human interventions has increased the vulnerability facing floods. The damages are classified into tangible or intangible types. Tangible damages, including the destruction of buildings, agricultural lands, roads and transportation systems, infrastructures, environmental ecosystems, and human casualties impose a major negative emotional burden on the target society (Tiryaki and Karaca, 2018). Among the natural disasters, floods cause the most damage to the agriculture, fisheries, housing, and infrastructure sectors and severely affect economic and social activities. Despite the natural cause of the floods in Iran, the main cause of the damages may be due to the human settlement in the high-risk areas (Mustafa et al, 2018, Nga et al, 2018). In recent years, about 70% of the annual budget dedicated to decreasing natural disasters have been allocated to recovering the damages by flood and this trend is increasing, so the 250% growth of flood damages in the last five decades confirms this claim (Demir and Kisi, 2016).
3- Results
This applied quantitative research was carried out in the Cheshme kile river, located in Tonekabon City in 2021-2022. In the first stage, indicators affecting flood vulnerability were prepared using the study of the research background. In this regard, the data of 6 indicators of aging ratio, sex ratio, youth ratio, land use, population density, structure quality, and material quality were prepared as effective indicators of flood vulnerability. Data were collected using the statistical yearbooks by referring to the National Statistics Center of Iran, which was recorded in the last census in 2016. In the next step, the relationships defined according to Table 1 were used to prepare each index. Zoning the floodplain area is applicable to detect the vulnerable area. The map of floodplain zoning is the result of modeling based on the HEC-RAS model (Saffari et al, 2023). The data of each of the indicators was overplayed with the layer of urban blocks of Tonekabon using ArcGIS 10.3 software. Then, the Vikor method was used to prepare flood vulnerability zoning maps. The data normalization was carried out due to the different data spectrums. Then, the weight of each index and sub-index was prepared using the AHP method. After determining the weight of each index, positive and negative ideals were determined. Positive ideals are the highest values of each index and negative ideals are the lowest values of each index. The result of subtracting the positive ideal from other sub-indices is the index of usefulness, and the result of subtracting the negative ideal from each of the sub-indices is the regret index (Table 2). The regret and usefulness indicators were classified (very high, high, medium, low, and very low) for each of the layers using the reclassify tool through ArcGIS software. (Figures 2 and 3). The classification spectrum for each of the layers is presented in Table 2. After calculating the indices of usefulness and regret, a flood vulnerability map was prepared for the study area using Equation 5 (Figure 3). In this map, values close to zero show the highest vulnerable area, and values close to one show the lowest vulnerable area conditions. To better understand the distribution of risk zones, the target map was classified into 5 spectrums of very high risk, high risk, medium risk, low risk, and very low. According to the findings, the area of risk zones in very high, high, medium, low, and very low classes were 0.36, 0.26, 0.34, 0.28, and 0.19 kilometers, respectively. The largest and lowest area of risk zones were observed in the very high and very low classes.
4- Discussion & Conclusions
The aim of this study was to investigate the vulnerability of the Cheshme Kile River in the area of Tonekabon City facing floods using the Vikor multi-criteria decision-making method based on the geographic information system (GIS). Effective criteria in flood vulnerability included land use, population density, youth ratio, aging ratio, gender ratio, and quality of structures and materials. The findings show the low vulnerability facing floods in the southern areas on the left side and the northern areas on the left and right sides of the Cheshme kile river due to the low population density, the low active width of the river channel, and the presence of green spaces. On the other hand, the density of the population and the dense building texture on the left banks in the western and northwestern margins have led to a decrease in soil permeability levels and an increase in the volume of urban runoff. Therefore, these areas are more vulnerable to floods and urban runoff. According to the findings, the highest and lowest areas were observed at very high risk and very low zones.
The width channel of the river has increased downstream, while the slope of the river has decreased, which
increases the water level and the possibility of financial and human losses. As can be seen in Figure 4, areas with high vulnerability can be seen on the left and right banks in the downstream section of the river. In these layers, factors such as population density at the range of 192-67 and 192-408, youth ratio in the ranges of 19.21-26-43 and 14.19-21, structure quality in the very unfavorable range, the aging ratio in the range 9-18, the gender ratio in the range of 27.56-44.74 and building and industrial lands have increased the risk of flood vulnerability in this area. Naturally, by reducing the range of investigated indicators, the risk of flood vulnerability also decreases. For example, in a factor such as the youth ratio, the lower the relative spectrum, the greater the risk of flood damage.
Flood is one of the most common and widespread natural disasters that occur frequently around the world (Patra et al, 2016). In recent years, the damages and casualties caused by floods have been affected by various factors. However, increased population, land use change, and the development of residential areas are considered to be the boosters for the increase in damages. The decrease in the active width of rivers by different factors especially human interventions has increased the vulnerability facing floods. The damages are classified into tangible or intangible types. Tangible damages, including the destruction of buildings, agricultural lands, roads and transportation systems, infrastructures, environmental ecosystems, and human casualties impose a major negative emotional burden on the target society (Tiryaki and Karaca, 2018). Among the natural disasters, floods cause the most damage to the agriculture, fisheries, housing, and infrastructure sectors and severely affect economic and social activities. Despite the natural cause of the floods in Iran, the main cause of the damages may be due to the human settlement in the high-risk areas (Mustafa et al, 2018, Nga et al, 2018). In recent years, about 70% of the annual budget dedicated to decreasing natural disasters have been allocated to recovering the damages by flood and this trend is increasing, so the 250% growth of flood damages in the last five decades confirms this claim (Demir and Kisi, 2016).
3- Results
This applied quantitative research was carried out in the Cheshme kile river, located in Tonekabon City in 2021-2022. In the first stage, indicators affecting flood vulnerability were prepared using the study of the research background. In this regard, the data of 6 indicators of aging ratio, sex ratio, youth ratio, land use, population density, structure quality, and material quality were prepared as effective indicators of flood vulnerability. Data were collected using the statistical yearbooks by referring to the National Statistics Center of Iran, which was recorded in the last census in 2016. In the next step, the relationships defined according to Table 1 were used to prepare each index. Zoning the floodplain area is applicable to detect the vulnerable area. The map of floodplain zoning is the result of modeling based on the HEC-RAS model (Saffari et al, 2023). The data of each of the indicators was overplayed with the layer of urban blocks of Tonekabon using ArcGIS 10.3 software. Then, the Vikor method was used to prepare flood vulnerability zoning maps. The data normalization was carried out due to the different data spectrums. Then, the weight of each index and sub-index was prepared using the AHP method. After determining the weight of each index, positive and negative ideals were determined. Positive ideals are the highest values of each index and negative ideals are the lowest values of each index. The result of subtracting the positive ideal from other sub-indices is the index of usefulness, and the result of subtracting the negative ideal from each of the sub-indices is the regret index (Table 2). The regret and usefulness indicators were classified (very high, high, medium, low, and very low) for each of the layers using the reclassify tool through ArcGIS software. (Figures 2 and 3). The classification spectrum for each of the layers is presented in Table 2. After calculating the indices of usefulness and regret, a flood vulnerability map was prepared for the study area using Equation 5 (Figure 3). In this map, values close to zero show the highest vulnerable area, and values close to one show the lowest vulnerable area conditions. To better understand the distribution of risk zones, the target map was classified into 5 spectrums of very high risk, high risk, medium risk, low risk, and very low. According to the findings, the area of risk zones in very high, high, medium, low, and very low classes were 0.36, 0.26, 0.34, 0.28, and 0.19 kilometers, respectively. The largest and lowest area of risk zones were observed in the very high and very low classes.
4- Discussion & Conclusions
The aim of this study was to investigate the vulnerability of the Cheshme Kile River in the area of Tonekabon City facing floods using the Vikor multi-criteria decision-making method based on the geographic information system (GIS). Effective criteria in flood vulnerability included land use, population density, youth ratio, aging ratio, gender ratio, and quality of structures and materials. The findings show the low vulnerability facing floods in the southern areas on the left side and the northern areas on the left and right sides of the Cheshme kile river due to the low population density, the low active width of the river channel, and the presence of green spaces. On the other hand, the density of the population and the dense building texture on the left banks in the western and northwestern margins have led to a decrease in soil permeability levels and an increase in the volume of urban runoff. Therefore, these areas are more vulnerable to floods and urban runoff. According to the findings, the highest and lowest areas were observed at very high risk and very low zones.
The width channel of the river has increased downstream, while the slope of the river has decreased, which
increases the water level and the possibility of financial and human losses. As can be seen in Figure 4, areas with high vulnerability can be seen on the left and right banks in the downstream section of the river. In these layers, factors such as population density at the range of 192-67 and 192-408, youth ratio in the ranges of 19.21-26-43 and 14.19-21, structure quality in the very unfavorable range, the aging ratio in the range 9-18, the gender ratio in the range of 27.56-44.74 and building and industrial lands have increased the risk of flood vulnerability in this area. Naturally, by reducing the range of investigated indicators, the risk of flood vulnerability also decreases. For example, in a factor such as the youth ratio, the lower the relative spectrum, the greater the risk of flood damage.
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