Seyed Hamidreza Sadeghi; Mohsen Zabihi
Abstract
Rainfall erosivity factor is the first noticeable point in soil erosion issues that plays very important role in detachment of soil particle from the origin bed. Hence, investigation of rainfall erosivity factor trend is necessary in decision-making and planning in order to manage soil and water resources. ...
Read More
Rainfall erosivity factor is the first noticeable point in soil erosion issues that plays very important role in detachment of soil particle from the origin bed. Hence, investigation of rainfall erosivity factor trend is necessary in decision-making and planning in order to manage soil and water resources. However, studies on various aspects of erosivity like trend and in interaction with precipitation and SPI index have not been attended well. The present study therefore aimed to investigate the rainfall erosivity factor trend based on the Fournier index in 28 stations throughout North-Khorasan Province during the period of 1987 to 2006 by using the Mann-Kendall test. In addition, the SPI and precipitation trend were comprehensively investigated for better characterization of erosivity trend analysis. Results showed that Noushirvan, Faruj, Ayerqayeh and Gholaman stations had decreasing trend and other study stations (71.85%) had increasing trend in the modified Fournier erosivity index. The SPI and precipitation in the study area indicated that most of the stations (89.28%) excluding Khartot, Noushirvan, Faruj and Ayerqayeh had increasing trend. The maximum and the minimum values of modified Fournier erosivity index with 70.97 and 33.44 mm were also assigned to Darkesh and Abiary Bojnourd stations, respectively.
Raoof Mostafazadeh; Mohsen Zabihi; Maryam Adhami
Abstract
Self-similarity characteristic of climate variables provides the spatial and temporal analysis, using fractal dimension. Therefore, the application of fractal geometry in predicting the nature of many natural processes (e.g. rainfall) in several areas is of great importance. The purpose of this study ...
Read More
Self-similarity characteristic of climate variables provides the spatial and temporal analysis, using fractal dimension. Therefore, the application of fractal geometry in predicting the nature of many natural processes (e.g. rainfall) in several areas is of great importance. The purpose of this study is to determine and calculate the fractal dimension of wet and dry periods, interpret and evaluate the spatial characteristics of dry and wet periods over 40 rain gauge stations in Golestan Province. Toward this attempt, the box-counting method has been employed to determine the number of wet-dry months at one to nine months temporal scales and the calculation of fractal dimension. Then, the regression lines are used to estimate the corresponding fractal dimensions over rainy and non-rainy periods. As well as the severity and duration of wet-dry durations were presented over the study area. The results indicated that variations of rainy/non-rainy durations vary in a range of 11 percent. According to the results, the number of consecutive wet-dry months decreased in coarser time scales (months). The analysis of fractal dimension showed that the dry periods have a lower frequency. The fractal dimension values were considered to determine the variations of precipitation regime over studied stations. Also, the intensity of wet durations is higher in central and eastern parts of the study area, while the western part of the Golestan Province had experienced more persistent wet periods.
Mohsen Zabihi; Seyed Hamidreza Sadeghi; Mehdi Vafakhah
Abstract
Soil erosion as a threatening phenomenon for the world population is mostly the result of the combined effects of unsuitable land use and climatic factors. Among climatic factors, rainfall is considered as one of the main causes of soil erosion and therefore detailed study of the different properties ...
Read More
Soil erosion as a threatening phenomenon for the world population is mostly the result of the combined effects of unsuitable land use and climatic factors. Among climatic factors, rainfall is considered as one of the main causes of soil erosion and therefore detailed study of the different properties of rainfall such as rainfall erosivity is necessary. However, investigation of spatial variability of rainfall erosivity factor at different scales at national level has been less considered. Therefore, the present study aimed to investigate the spatial variability of rainfall erosivity factor in Universal Soil Loss Equation (USLE) for monthly, seasonal and annual scales in Iran. Towards this attempt, the amounts of rainfall erosivity factor were calculated through calculation of kinetic energy and maximum 30-minute intensity over 12,000 showers occurred at 70 stations in the study period of 20 years (1984-2004) in Iran. The spatial patterns of temporal variation were also in different time scales. According to the results, existing stations in the south west and north of the country had the first priority of annual rainfall erosivity factor hazard. The west and south west stations and south east stations had also the highest and the lowest seasonal and monthly risk rainfall erosivity factor, respectively. Also, results showed Tangpich in Khuzistan, Anzali in Giulan and Poleshalo in Khuzistan had the maximum rainfall erosivity factor whereas Bande Enherafi in Semnan, Tabas in South Khorasan and Bam in Kerman Provinces had the minimum annual rainfall erosivity factor hazard country wide. The average annual rainfall erosivity factor in the country was ultimately obtained 14.13 tm.ha-1.cm.h-1.
