Majid Kazemzadeh; Zahra Noori; Mohammad Jahantigh
Abstract
Occurrence of avalanches in mountainous areas is one of the most important natural hazards that cause a lot of human and financial losses. The study of affecting factors on avalanche occurrence and simulation is very important to manage this phenomenon. In this study, the affecting factors on the occurrence ...
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Occurrence of avalanches in mountainous areas is one of the most important natural hazards that cause a lot of human and financial losses. The study of affecting factors on avalanche occurrence and simulation is very important to manage this phenomenon. In this study, the affecting factors on the occurrence of snow avalanche (terrestrial and meteorological factors) and its simulation have been studied using the RAMMS simulation model in the Central Alborz Velayat Rood (Dizin Road), Alborz Province. Topographic and geomorphological factors such as slope, aspect, curvature, topographic position index (TPI), terrain roughness index (TRI) and topographic wetness index (TWI) using 6 ×6 cm2 pixel size of digital elevation model (DEM) were prepared by using a drone. Meteorological factors such as rainfall, temperature and wind were also considered. Then, using RAMMS simulation model, avalanche components such as avalanche speed, pressure and height were estimated in the study area. The results showed that the amount of slope and aspect as a topographic indicator have a great impact on the formation and occurrence of the snow avalanche. The largest part of the region with an area of 5.7 hectares (54.6% of the study area) with a northeast aspect and slope of 60 to 120%, the accumulation and track areas, has the greatest potential for avalanche. Also, the results of RAMMS simulation model showed that the average speed and maximum avalanche speed in the region were 5.3 m/s and 16 m/s. The average effective avalanche pressure was 7 and the maximum avalanche pressure in the region was 45 KPa. Estimation of avalanche height in the region also showed that the average avalanche height in the runout area (residential areas) was 4.5 meters and the maximum avalanche height in the region was 10 meters, which is classified as a large avalanche.
Majid Kazemzadeh; Ali Salajegheh; Arash Malekian; Abdolmajid Liaghat
Abstract
On average, 70 percent of the precipitation that reach Earth's surface, returns to the atmosphere through evapotranspiration, and this rate reaches 90 percent in arid areas. Meanwhile, watershed measures directly related to water, soil and plant, and ultimately to evapotranspiration on the natural resources ...
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On average, 70 percent of the precipitation that reach Earth's surface, returns to the atmosphere through evapotranspiration, and this rate reaches 90 percent in arid areas. Meanwhile, watershed measures directly related to water, soil and plant, and ultimately to evapotranspiration on the natural resources region (ecochydrology). In this study, in order to study the effect of biological activities of watersheds (enhancement and increase of vegetation) on the process of soil moisture and evapotranspiration changes, paired watersheds of Taleghan, Alborz Province were selected. In order to calculate evapotranspiration by soil moisture balance method, soil moisture monitoring points were selected using field and laboratory studies in three main areas (northwest, eastern and southeast) and three replications and at three depths of 0-20, 40-20 and 40 -60 cm during plant growth period in 2017. Data were analyzed by ANOVA method, and Duncan test. The results showed that the actual evapotranspiration in the treated watershed and control watersheds were not statistically significant and, respectively, they showed 181 mm and 159 mm in a period of growth. In other words, the actual evapotranspiration value in the treated watershed was 14% higher than the control one during the growth period. Also, the results showed that evapotranspiration under different aspect slopes had a significant difference. The total actual evapotranspiration in the northwestern slopes were 229 and 226 mm, in east slopes were 207 and 171 and in the southeastern slopes were 109 and 80 mm in the treated and control watersheds, respectively.
Majid Kazemzadeh; Javad Akbari
Abstract
One of the most important last century challenges in the world was drought and monitoring and assessing drought severity and duration to combat and mitigate its impacts is very necessary. In recent decades, with developing of remote sensing issues, satellite-based estimating drought with high spatial ...
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One of the most important last century challenges in the world was drought and monitoring and assessing drought severity and duration to combat and mitigate its impacts is very necessary. In recent decades, with developing of remote sensing issues, satellite-based estimating drought with high spatial resolution and different time steps were widely used. Hence, the aim of this study was focused on the analyzing drought and error distribution of TRMM satellite data-based estimation with ground data over the period 1998 to 2014. In this regard, in order to assess the accuracy of meteorological drought index based on the TRMM satellite data, 41 synoptic stations were used in Iran. In this study, error assessment criteria were included NSE, RMSE, ME, Bias and correlation coefficient and also the IDW interpolation method in ArcGIS 10.3 was used for spatial analysis. Results of drought index showed that in terms of severity, Kerman, Bushehr, Kashmar, Ghazvin, Bojnurd, Kashan stations have suffered from at least one extreme status for 1998 to 2014 and in terms of frequency, the most frequent drought was in Karaj station. Results of spatial analysis of error criteria showed that the drought index estimated of TRMM satellite had the lower error in northeast of Iran (around Mashhad and Kashmar stations) and southwest of Iran (around Shahrkord, Esfahan, Yasouj, and Shiraz stations) while the most error was in central region of Iran (around Biarjomand, Tabass stations), respectively. In most areas of the country, drought index estimated by TRMM data had acceptable agreement with ground stations data. Calibrating the TRMM data with ground stations can be used for drought monitoring in areas without stations for networks 0.25*0.25 latitude and longitude degrees.
