JOURNAL OF NATURAL ENVIRONMENT HAZARDS
Year:2020 | Volume:9 | Issue:25|Papers Count:10

Drought is known as one of the main natural hazards especially in arid and semi-arid regions where there are considerable issues in regard to water resources management. The focus of the present study is mainly on hydrological aspects of drought. For hydrological drought analysis, streamflow data is used as the key variable to identify drought events with reference to a demand specific threshold level, termed as truncation level. Thus, the objective of the present study is to (a) investigate the hydrological drought characteristics in Nesa River using streamflow data; (b) determine independent drought events, their duration, and severity using the variable truncation level approach; and (c) derive streamflow drought severity index. Based on expedience probabilities, the monthly flow duration curves for Nesa River were derived. These were utilized to estimate different dependable flows, and the values of variable truncation levels were obtained for a 75% probability level for each month. These values were used to distinguish the deficit and surplus flow periods independent drought events identified using the pooling procedure. Since 10 daily flow data were utilized, the minimum deficit flow duration was 10 days. In the following, have been identified some short duration (one or two 10-daily time step) surplus and deficit events. To decide on independent drought despite the short duration inter-event surplus has been used for a pooling procedure known as inter-event time and volume criterion (IC). Eventually, identified independent drought events and also describe their duration, severity, intensity, and DSI. Analysis of independent drought Characteristics in Nesa River indicated that are prolonged dry period in the hydrological regime of this river. In addition, based on DSI, Nesa droughts mostly are in sever category. Hence, it is suggested more realistic reload occurs in management programs of this river including storage, distribution and assign to various resources.

Heavy Rainfall is one of the natural dangers. Heavy rainfalls, directly or indirectly, affect human lives and their activities. In this study, the Talesh-Anzali wetland basin in the west of Guilan province has been investigated. To determine the probability of heavy rainfall events (seasonal) and the trend existence, non-parametric Men-Kendall test, to determine the probability of rainfall event ³ 30mm Poison’ s method and to identify local patterns of precipitation event IDW method has been applied. The data in this study include daily precipitation of ³ 30mm in 20 synoptic stations in a period of 30 years (1987-2016). The results showed the trend is mainly increasing, so that the stations located in the center towards the north of the study district in every four seasons and the stations in Anzali in spring and Masoleh in three seasons of summer, autumn and winter have increasing trend, but in some cases, some stations mainly toward the southern half of the area such as kasma in summer, Bashmahalleh and Rasht in winter and Ghalehroudkhan in autumn and winter have extreme decrease trend. Also, in all seasons of the year, in some stations, irregular and accidental changes are observed in the event frequency. This irregularity results from a lack of continuity increase or decrease of the event frequency and rainfall or lack of rainfall of ³ 30mm in some stations. Poison’ s distribution showed that the probability of lack of event in stations with non-humid climate is so high and the addition of lack of event with an event is more than 90% frequency of rainfall event ³ 30mm. Furthermore, in the north and central stations of the region, the most possibility for different events in all seasons of the year has been recorded. In the end, the results showed Poison’ s distribution has a proper evaluation of precipitation events in this region.

Desertification is defined as land degradation in arid, semi-arid and dry sub-humid that caused as a result of various factors including climatic variations and human activities. Desertification causes many restrictions in terms of agriculture, food security, livestock rising, industry and providing service costs. This phenomenon is a process that gradually developed and accelerated and adjustment costs are increasing exponentially, so according to resource constraints and the desert area sensitivity, providing optimal Combat desertification alternatives natively is necessary to achieve success in controlling and reducing the effects of this phenomenon among different regions. Therefore, this study was performed to provide a systematic and optimal alternative in a group decision-making model. To this aim, at the first in the framework of Multiple Attribute Decision-making (MADM), indices priority was determined using the Eigenvector model. Then, alternatives priority was evaluated by the VIKOR model. Assessing selecting conditions of optimal alternatives in the context of the mentioned model showed that Prevention of unsuitable land use changes (A18), vegetation cover development and reclamation (A23) and modification of groundwater harvesting (A31) with VIKOR index of Q=0, 0. 3083 and 0. 6241were selected as the main desertification hazards control alternative in the study area, respectively. Therefore, it is suggested that the obtained results and ranking should be considered in projects of controlling and reducing the effects of desertification and rehabilitation of degraded land plans.

Preparing a flood susceptibility map is necessary and the first step in reducing the damage caused by floods. Due to a lack of information in most of the basins, many researches uses data mining techniques for hydrological studies, especially floods. The aim study is to identify areas with flood susceptibility using a support vector machine (SVM) in the Nekaroud basin. For this purpose, 12 geomorphologic, hydrological and physiographic parameters including slope, aspect, elevation classes, temperature, land use, rainfall, density and distance from the fault, density and distance from the drainages, density and distance from the road, which are provided in the ArcGIS, SAGA GIS and ENVI software’ s environments. The GPS device was also used to acquire flood points. Finally, all variables and flood points were entered into the R software in ASCII format with the same pixel size (12. 5 m). To evaluate model accuracy, ROC was used in the R software environment. The results of the evaluation showed that the SVM model has good accuracy in identifying flood susceptibility areas in the study area. In addition, the results of this study showed that flood susceptibility areas are more in the northern and northwest regions of the basin and in portions where the concentration of human settlements is higher, while the central regions of the basin with dense vegetation have a low sensitivity to flooding. The results of this study can help planners and researchers to do appropriate actions to prevent and reduce future flood risks. It can also be used to identify suitable and safe areas for construction development.

Determination of the submergible area by flood provides a fundamental tool for reducing flood risks. Therefore, in this research, flood spreading modeling was designed using web-based software with the capability of zoning submerged areas by Google Maps DEM Data. For this purpose, at the first, a specified interval of a river is selected on the map. Then, at each selected section, the maximum cross-sectional area for passing flow is calculated. Then, based on the average of the cross-section area for the total interval and the physical properties of the selected river interval, the maximum flow rate is calculated. For this flow rate, the safe area of the flood is marked on the map. For a greater flow rate, the software determined the areas at risk of flooding, and ultimately the flood risk map is specified. For example, the software was applied for a seasonal river in Shiraz, which sinks to the Maharlu Lake with satisfactory results. Afterward, the October 2011 flood event of Ayutthaya River in Thailand was investigated, where satellite images of the flood-affected areas were available. Investigation of the satellite image of this flood along with the survey of topographic maps of the river route indicated peak discharge of the flood was 4113. 01 m3/s, which differed as 2. 1 percent as compared to a record of 4200 m3/s (real measured peak flow). If the flood occurs with the current situation in the area, the flooded area decreased by 17. 63% compared with the submerged area in 2011. Furthermore, simulation of the March 2019 Shiraz Flood by the model was in good agreement with the report of the Special Committee of 2019 Iran Floods.

Iran's location in the latitude of 25 to 40º N in the northern hemisphere has made the subtropical jet stream a factor in regulating humidity systems in Iran, making it easy for humidity systems to enter the country when this jet stream is in Southern Iran. But as it moves northward, its strength decreases. In recent years, it has been reported that the positioning of subtropical jet streams in the Northern Hemisphere is shifting. Therefore, the purpose of this study is to evaluate the position of subtropical jet stream location and its variability over Iran. In this study, data on zoning wind velocity ranged between 30 and 80º E in the Northern Hemisphere, at levels between 1000 and 10 hPa from NOAA, as well as outputs of circulation models including CanESM2 and GFDLCM3 for the historical period 1948 to 2005 and periods Future from 2006 to 2100 were received from IPCC in two scenarios RCP4. 5 and RCP8. 5. In this study, the main components of the jet stream include the central core velocity of the jet stream and its latitude position. Investigation of the position and velocity of the jet stream indicates that the subtropical jet position changes in Iran and its eastern regions are followed by significant incremental changes. Whereas in west Iran, there is a significant decline in jet stream velocity changes. The future of Jet Stream positioning in Iran based on the CanESM2 and GFDL-CM3 climate models in both rcp4. 5 and rcp8. 5 scenarios indicates that relative to the base period in both scenarios as well as the near and far future of its position to the north Moves.

The shortage of surface water resources has led to harvesting groundwater in many parts of the world and a sharp drop in groundwater aquifers. With an ever-increasing population, more and more harvesting has come from these resources, and these natural resources are facing a serious threat. On the other hand, land use changes affect groundwater resources and affect the quantity and quality of groundwater. The Mahidasht Plain is located in Kermanshah Province, which has been affected in recent decades due to the growing population of land use, has affected the process of exploitation of water resources, and has made important contributions to the groundwater resources. In the present study, by using the images of the Landsat and Sentinel 2, land use maps for the study area were identified in the four years of 1987, 2000, 2009, and 2017, and land use changes were also identified in 30 years. Then, according to 44 piezometric wells for the period 2000 to 2016, the amount and trend of groundwater level changes were determined and the number of changes was also estimated in existing uses in the area. The results of Satellite Images analysis in the areas of Firoozabad and Mahidasht during the years 1987 to 2017 indicate an increase in the area of agricultural land utilization, reducing the area of land use, agriculture, and forestry. However, decreased precipitation and increased extraction of underground water in the following years led to a severe drop in the water level. The precipitation rate and its change play a significant role in controlling the underground water level. As the rainfall increases, more water flows into the aquifer which leads to increased water feeding and rises in the underground water level.

Identifying the seasonal behavior of flood events and their changes over time in watersheds provide useful insights for a better understanding of flood processes, planning water projects, and managing flood risks. Directional statistics provide a good basis for determining the similarity between flood occurrence times and is useful for flood seasonality analysis. This method was applied to a set of 20 river gauge stations in the Gorganrud River Basin, located in the North of Iran, with a 48-year recording period, to identify the seasonality of flood occurrences as well as their variations. Two indices namely MDF and r which indicate the average time of flood occurrence and the uniformity of their occurrence date during the year (degree of seasonality), were calculated for the maximum instantaneous flow data, respectively. Also, in order to examine long-term changes in flood seasonality, the recording period of the maximum flow data was divided into three 16-year intervals representing the distant past, near past, and the present time and then the indices were calculated for each interval. The results show that the average time of flood occurrence in the Gorganrud River Basin is in springs and summers. Also, the majority of the stations (about 75%) have r values between 0. 3 and 0. 7, which indicates an intermediate degree of seasonality meaning that the time of occurrence of the events spreads over one, two or three seasons. Analysis of long-term changes in flood seasonality shows that the average time of flood events in the Gorganrud River Basin has not changed significantly from the past. The degree of seasonality, however, has decreased compared to the past period. A mixture of different flood generation processes such as snowmelt and summer or fall rainfalls and the combined influence of geographical location and the size of watersheds can be the possible reasons for the reduction in flood seasonality in this basin.

Now, in order to achieve sustainable development in the country and to prevent pollution and environmental degradation, all development and development activities in the country are taking into account environmental considerations. On the basis of this, before the implementation of many development and development projects, the impacts and consequences of such plans are identified and predicted on the environment of the region, and the necessary measures are taken to control and reduce them, and this is generally done through an assessment The environmental impacts of development projects are based on existing laws in the country. Saratoga Matrix was used to assess the environmental impacts of Qinarjeh Takab iron ore production unit design, and to analyze the two options for implementation and non-implementation of the project in two phases of construction and operation. In this study, the effects of the non-implementation option were evaluated with the option of implementation of the project, and in the executive option, the effects of all project activities on the environment were studied. The focus of attention in the environmental assessment is on the definitive effects, but the potential effects of the index are also considered important and studied. The results of the effects in the construction phase (-120) and in the exploitation phase (+142) indicate that the implementation and operation of the Qinarjeh Takab iron ore production unit have positive effects and, given the predominance of definite effects, the micro products of the unit production project Iron cane iron Takab is applicable.

Wildfire as a natural hazard is a major problem for forest and rangeland ecosystems of the world. In the Semi-Steppe Rangelands of Ardabil Province, severe wildfires can account for the adverse impacts on the ecosystems. These fires are the result of the combination of weather conditions, dry fuels, and topography effects. The Ghasre Dagh Yeylagh fire is an example of a severe wildfire that occurred with extreme environmental conditions, which was ignited on August 16, 2015, in the Meshgin Shahr municipality. In this study, weather conditions, fuels, and topography factors that strongly affected the fire will be accurately analyzed. The fire spread and behavior data including the observed final fire perimeter and fire arrival to the northern border of the fire perimeter (firefighting point) collected during the event will be also compared with the results of fire simulation obtained by FARSITE model. The average simulation accuracy for the burned area, as measured by the Sorensen coefficient and Cohen Kappa Coefficient was 0. 84. Simulation overestimation of flanking fire spread areas was expected and observed, since suppression activities that contained the fire spread were not considered in the model, due to the lake of this information. The main goal of this paper is to thoroughly study the behavior of a recent fire, to learn from it, and lessen the potential mistakes or hazardous fire-fighting operations in similar environmental conditions. Furthermore, a crucial point is to teach the fire crews not to be threatened by severe or abrupt fire behavior under extreme environmental conditions.