Mehdi Khalajzadeh; Gorban Vahabzadeh; Sadat Feiznia; Aliakbar Nazarisamani; Seyed Ramzan Mousavi
Abstract
Identification of hydrogeomorphic processes such as normal flood, debris flood and debris flow on alluvial fan (at the outlet of the watershed) is essential due to the type of sedimentary regime and various hazards. In recent years, the lack of field information has led to the need to use models based ...
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Identification of hydrogeomorphic processes such as normal flood, debris flood and debris flow on alluvial fan (at the outlet of the watershed) is essential due to the type of sedimentary regime and various hazards. In recent years, the lack of field information has led to the need to use models based on basic watershed information. The aim of this study is to develop a practical method for predicting the occurrence of various types of flood flow, using physical and geomorphological characteristics of watersheds. In this study, a descriptive-analytical method and some of tools, such as aerial photographs, satellite images, topographic maps were used. First, by descriptive method, field evaluation of sediments of various types of flood currents was carried out on July 19, 2015 in 70 sub-watersheds of in Karaj Dam Watershed. Results showed that out of 70 sub-basins, 30 sub-basins, debris flow, 16 sub-basin debris flood and 24 sub-basins were normal floods. Then, in the analytical method, 32 geomorphometric features of watersheds by 25-meter spatial digital model (DEM) and five geomorphological features of sub-watersheds by mass movement maps were extracted and then were transferred to the SPSS statistical program to determine the relationship with the type of flood flow. The results of ANOVA and Bonferroni multiple comparisons showed that four morphometric factors “main channel length, basin perimeter, mean basin width and basin length” were identified in differentiation of flood flow types. To achieve the two appropriate key parameters and threshold values, four variable pairwise were copaird by pair in six triple scatter plots. The results showed that “The main channel length (Lm) and the mean basin width (Wb)” has the least total errors of the observation streams, were selected as the most appropriate factors for predicting flood flows. In long basins with Lm>4 km, normal flooding occurs, and in short basins with Lm1 km, floods occur, and if Wb
Ghasem Mortezaii; jafar lotfi; shahram khalighi sigarodi; mohsen saravi; Aliakbar Nazari Samini
Abstract
In recent years, Kurdistan Province has faced a dramatic decline in groundwater levels. In this research, the time interval between the occurrence of meteorological drought and hydrological drought was determined for the necessary measures to cope with the drought caused by the lack of surface water ...
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In recent years, Kurdistan Province has faced a dramatic decline in groundwater levels. In this research, the time interval between the occurrence of meteorological drought and hydrological drought was determined for the necessary measures to cope with the drought caused by the lack of surface water and underground water resources. Therefore, the hydrological drought situation in Kurdistan Province was evaluated using Groundwater Resources Index (GRI) and Streamflow Drought Index (SDI) and compared with meteorological drought indicators. The GRI and SDI time series for the 30 years of studied period of 1982-2014 was inter-compared. The GRI showed the highest percentage of frequency of normal period. According to the results of Man-Kendall test, in all time scales, SDI has a higher variability than the meteorological drought indicators. Knowing the interval between the occurrence of meteorological drought and hydrological drought will help managers to cope with the drought caused by a shortage of surface water resources in the interior ministry, The Markov chain model used to predict the current state of a system with regard to the previous state in the statistical period showed good performance. According to the results of the study, on average, the probability of dry, wet and normal periods in the stations was 31, 29, and 40 percent, respectively. This means that in most cases, the region is in normal climatic condition, while the likelihood of wet and dry conditions is very similar. Also, SPEI with12 and 24 months’ time scales have the highest correlation with GRI index at 3 months lag-times, which showed the effects of meteorological drought on groundwater level even after two years or more. By considering the results of this study, the executive directors of water in the province can mitigate the effects of the crises caused by the hydrological droughts.
Ali Akbar Nazari Samani; Shahram Khalighi Sigaroodi; MAHSA abdolshahnejad; Sina Syadi Lotf Abadi; Majid Habibi Nokhandan
Abstract
Greenhouse gases have continued to increase in the atmosphere. This is largely due to industrial activities. The warming effect of greenhouse gas, increased over the last 200 years, due to carbon dioxide; hence the temperature of the lower levels of atmosphere will be increased. The climate change across ...
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Greenhouse gases have continued to increase in the atmosphere. This is largely due to industrial activities. The warming effect of greenhouse gas, increased over the last 200 years, due to carbon dioxide; hence the temperature of the lower levels of atmosphere will be increased. The climate change across the world resulted in an increased drought; disturbance in rainfall as well as desertification. Desertification has been caused by a variety of factors such as climate change. It is a significant natural resources problem. The aim of this study was to evaluate the desertification during five periods (1978-1987, 1978-2007, 2012-2041, 2042-2071, and 2072-2101) during the last, present, and future, using IMDPA model as well as climate and geology-geomorphology criteria. For each criterion, some indexes were selected, using area condition. First, air temperature and precipitation during the previous time was evaluated. Then, the climate change was estimated using two climatic models of HADCM3 and GFDL2.1 and three scenarios of A2, B1 and A1B of GCM as well as small scale exponentially. The land use map for four classes in two periods (1986 and 2010) was prepared and used for input data to the Markov chain for estimating future land changes through the three periods (1419, 1449, and 1479). Results were used as the land use index for working unit in geology-geomorphology criterion. It was assumed that the tolerance of stone to the erosion and slope of maps were constants. Hence, this criterion was studied during five periods. Results showed that the intensity of desertification was increased during the time.
Seid Saeid Ghiasi; Faezeh Rajabzadeh; Somayye Najirda; Sadat Feiznia; Aliakbar Nazari Samani
Abstract
Shallow landslide susceptibility assessment by using appropriate methods and determine of effective factors in reduce of its hazards is so effective. The aim of this study is to determine the effective factors on shallow landslide occurrence and investigation of Statistical Index Method (SIM) efficiency ...
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Shallow landslide susceptibility assessment by using appropriate methods and determine of effective factors in reduce of its hazards is so effective. The aim of this study is to determine the effective factors on shallow landslide occurrence and investigation of Statistical Index Method (SIM) efficiency for landslide susceptibility mapping. So, determination of each class of factors’ weights was accomplished by using SIM. That was done by adoption of inventory landslide map and ten initial factors including: slope, aspect, rainfall, altitude, drainage density, plan curvature, land use, geology, geomorphological faces and rock unit sensitivity to erosion in ArcGIS 9.3. Then model efficiency was evaluated by using percentage of area under ROC curve and the results showed high accuracy (0.95) of SIM. Principal Component Analysis (PCA) was used for determination of primary causative factors of shallow landslide occurrence. Results showed that five variables of rainfall, slope, aspect, rock unit sensitivity to erosion and plain curvature are the most effective factors on landslide occurrence, respectively.
