mojtaba jannatrostami; mohammad rahimi; hassan kaboli
Abstract
Most of the studies on dust storms are concentrated in the western-eastern provinces of the country and less research has been done in other parts of Iran. In this research, some of the southern plains of Alborz; which have the potential to produce dust were selected. Daily data of 18 meteorological ...
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Most of the studies on dust storms are concentrated in the western-eastern provinces of the country and less research has been done in other parts of Iran. In this research, some of the southern plains of Alborz; which have the potential to produce dust were selected. Daily data of 18 meteorological stations with long-term statistical period from 2008 to 2017 and to calculate the indicators of agricultural drought, MOD13Q1 and MOD11A1 products were used in the same period. Standardized precipitation index and standardized precipitation-evapotranspiration index were calculated and from the dust hourly meteorological codes, the experimental dust storm index was obtained. Then the relationships between climatic indices, vegetation and experimental index of dust storm were investigated using Pearson correlation and multivariate regression statistical method. The highest frequency of DSI index during 10 years is related to Imam Khomeini station with a value of 30.5 and the lowest is Taleghan station with 0.05. The Year-on-year changes in the dust index show that in the early years, the central and southeastern parts of the region were affected by dust storms, and sudden decrease had a significant effect on the results and reduced the long-term trend. The highest and the lowest correlation is respectively wind speed and Temperatur .Regarding the results of monthly multivariate regression, are somewhat variable in different months of the year, so that the effect of climatic elements and vegetation changes in different months, in general wind speed, TCI and SPEI have the most important effect on increasing
mojdeh mohammadi; Hossein Malekinezhad; Mohammad Taghi Dastorani
Abstract
Main problems in flood frequency analysis are limited number of gauging stations and recorded data, together with the inaccurate at-site estimations in the study area. These problems have caused increasing application of regional methods. Regional analysis seems to be a useful method for estimating peak ...
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Main problems in flood frequency analysis are limited number of gauging stations and recorded data, together with the inaccurate at-site estimations in the study area. These problems have caused increasing application of regional methods. Regional analysis seems to be a useful method for estimating peak flow at an area of no data or low-recorded length. Regional flood frequency analysis relies on physical and climatic characteristic of basins and applies statistical method to study flow records. The methods of regional analysis are numerous that the selection of each one of them in any study area depends on data length, climatic factors, data type and expected return periods. In this study, four techniques of regional analysis were used to evaluate the priority and importance to estimate the peak flow for different return periods. The Hybrid, Multiple regression, L-moments and Canonical Correlation Analysis are the four approaches applied for some watersheds of Isfahan–Sirjan and Yazd-Ardakan Basins. A number of 16 stations were selected and their data were analyzed to find out peak flow. The results of this analysis were compared to the Hybrid and Multiple regression approaches using RRMSE and MAE statistics. The results showed better performance of the CCA method rather than other methods in all return periods. After CCA, Multiple regression methods were selected to estimate the peak flow (Model 2, 3). Therefore, CCA method can be adopted as regional flood frequency method for the study area.
ALIREZA Arabameri; kourosh shirani; Mahdi Tazeh
Abstract
Present study seeks to identify effective factors in landslide occurrence and landslide sensitivity zonation using logistic regression and multivariate linear regression. Accordingly, through the interpretation of arial photos with scale of 1:40000, geological, topographic maps, and field survey using ...
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Present study seeks to identify effective factors in landslide occurrence and landslide sensitivity zonation using logistic regression and multivariate linear regression. Accordingly, through the interpretation of arial photos with scale of 1:40000, geological, topographic maps, and field survey using GPS, landslide hazard map was prepared as dependent variables. For determination of effective factors in landslide occurrence, using Support Vector Machines in Rapid Miner Software, the numerical values of the parameters were analyzed and from 21 selective data layers, 15 data layers were selected and were prepared and digitized for zonation map as the independent variable in ArcGIS 10.1. After weighing the layers, zonation map was prepared using selective method in five classes: very low, low, moderate, high and very high. Result of weighting layers showed that in both methods, land use and aspect have the greatest impact on landslides. The ROC (Receiver operating characteristic) curves and area under the curves (AUC) for landslide susceptibility maps were constructed and the areas under curves was assessed for validation purpose and its values showed that multivariate linear regression model (0.890) has a higher efficiency than the logistic model (0.829) for landslide hazard zonation. According to result of superior model (multivariate linear regression), 16046.1 hectare (20.13%) of the region was found to be located in high risk class and 15671.2 hectare (19.66%) was in very high risk class.
Elham Meshkati; Hassan Ahmadi; Aliakbar Nazari Samani; M.H Davoodi
Abstract
Landslide occurs inevitably and naturally in many slopes due to sensitive formations, moisture, andother factors. Taleghan watershed is prone to landslide due to the presence of huge Miocene marlmasses. After construction of Taleghan reservoir dam, moisture and ecological condition of theregion changed. ...
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Landslide occurs inevitably and naturally in many slopes due to sensitive formations, moisture, andother factors. Taleghan watershed is prone to landslide due to the presence of huge Miocene marlmasses. After construction of Taleghan reservoir dam, moisture and ecological condition of theregion changed. In this paper, factors impacting upon landslide hazard (slope, aspect, hypsometry,geology, land use, distance to road, distance to lake) were studied and their role and importance onthis phenomenon were verified in a large (maximum distance of 1500 meter from lake) and a small(maximum distance of 450 meter from lake) spatial scale. Thus, GIS maps of the above mentionedparameters were provided using satellite and aerial images and field activities. All maps werecrossed with a resolution of 100m*100m. It was found out that the distance to the lake didn’tinfluence upon landslide in a large spatial scale but it falls effective as the distance to the lakereduces. In fact lake has a local effect and mostly influences at maximum 200 meter distance.
