فصلنامه جغرافیای طبیعی
پیاپی 48 (تابستان 1399)

Floods are one of the most frequent and destructive natural disasters that cause severe financial and financial losses every year. Flood damage is on the rise due to human manipulation of river systems and river construction. In this regard, one of the most important non-structural measures to reduce flood damage is the preparation of flood risk zoning maps and their use in spatial planning. In this regard, the HEC-HMS model was used to simulate rainfall-runoff and identify flood zones and fuzzy logic was used to overlay the subject layers and prepare the flood line map. The simulation results show the high efficiency of HEC-HMS model in simulation of rainfall-runoff of Rudball catchment and estimation of peak flood discharges. The conversion of rainfall to runoff at the surface of the Rudball Basin is mainly controlled by geomorphometry and land cover. The highest peak runoff and peak flow rates are in the upstream sub-basins of the Rudball Basin. This is due to high slope, low soil permeability, abundance of impermeable surfaces and high CN. The combination of thematic layers using fuzzy logic showed that about 8.6% of the basin area was located in areas with high risk of flooding. These zones mainly correspond to the floodplain of the Rudbal River. These lands are always exposed to floods due to the low valley and low slope. Most of the settlements in the study area are located downstream of the basin. This has increased the risk of flooding.

One of the most important concerns in the world today is the debate over climate change and its consequences. In this study, in order to investigate the level of wheat and barley cultivation in past and future climatic conditions, first rainfall, average temperature, minimum and maximum temperature data in the statistical period (1998-2018) were received from the Meteorological Organization. The Kendall Mann test was used to study the trend of changes in meteorological elements. After that, the cultivation calendar was extracted from Landsat 8 images using the NDVI index and then using Tm, Etm, Oli, and Sentinel-1 sensor images in the Google Earth engine system by calculating the index. Monthly NDVI and SVM classification process Estimated crop area in different years was estimated. Finally, the SDSM model was used to simulate and predict meteorological elements by 2040.

According to the wheat and barley cultivation calendar, the cultivation of these crops in Izeh city starts in January and reaches its peak of greenery and growth in April, and finally from June the crop is harvested from agricultural lands. In Izeh city, there is an almost direct relationship between rainfall and cultivation area. With increasing rainfall, the area under cultivation increases. With increasing temperatures, the amount of cultivation area decreases to some extent. In the future climate conditions, all three scenarios predict an increase in the minimum and maximum temperature by 2040 by 0.7 degrees Celsius. In the rainy conditions of the past climate, in two decades, the area of ​​cultivation will decrease by about 7.4square kilometers, and in the conditions of the future climate, it will decrease by about 11.4 to 15 square رkilometers.That is the cultivated area decreased by 8 square kilometers per decade

Increasing water the demand for agriculture consumption, drinking and industry in recent decades has led to the drilling of water wells, which in many cases have been unlicensed. These uncontrolled withdrawals from groundwater sources in Isfahan province, along with the reduction of rainfall, have caused irreparable damage to the province's water resources and its dams are in danger of subsidence and sinking. Semirom city in the south of the province is one of the areas affected by uncontrolled abstraction of groundwater aquifers. In this study, by creating soil profiles in different parts of the region, identifying karstic environments, studying geomorphological characteristics and identifying authorized and unauthorized wells, groundwater level drop was investigated and the zoning risk map was prepared by fuzzy model. The results show the highest probability of occurrence of subsidence related to Kameh area located in Padna section in the southwest of Semirom city at a distance of 65 km from the city center. The subsidence hazard zoning map shows that 13.2% of the area in the risk zone is very high, 56.5% is high risk, 51.16% is medium risk and 13.2% is low risk. The results of hydrographic analysis and changes in the volume of water storage of aquifers and its evidence showed that the decrease in changes in the volume of aquifers in Semirom city is an average of 10.5 million cubic meters per year.

Landslides as one of the natural hazards can cause a lot of damage every year. Kahman catchment with potential mountainous features and different natural conditions has potential landslide potential. The purpose of this study was to investigate landslide hazard using fuzzy logic model in Kahman basin of Lorestan province. In this study, first, effective parameters on landslide occurrence were extracted and then the relevant layers were prepared. Then the landslide distribution map of the basin occurred. Then, by integrating the landslide map with the landslide distribution map, the effect of each of the slope factors, slope direction, lithology, precipitation, land use, distance from fault and waterway were calculated in ArcGIS software environment. In this study, fuzzy logic model with fuzzy community operator, fuzzy sharing operator, fuzzy algebraic multiplier operator, fuzzy algebraic sum operator, and fuzzy gamma operator were applied. Based on zoning using gamma-fuzzy operator, 64.37, 7.45, 8.93, 12.49 and 6.76 percent of the area were classified as very low, low, medium, high and very high risk classes has taken.

In this study, a part of the Gorganroud basin was selected to evaluate of the drought effect on 13 water physicochemical parameters. After collecting meteorological and hydrometric stations data in a period of 43-year (1350-1393), a 5-year drought index was determined using the standard precipitation index and moving average method. Then, the water quality parameters were obtained for a long-term and a drought period using the available hydrometric stations data. The average concentration of most of anions and cations, electrical conductivity, and sodium adsorption ratio have increased from upstream to downstream, so that, this increase in the downstream station is about seven times higher than its upstream station in the drought period. The average of anions, cations, electrical conductivity, and sodium absorption ratios were increase during the drought period compared to the long-term period. Using the Wilcox diagram, agricultural water quality is decreases in the direction of river flow, so that the water category changes from C2S1 (suitable for agriculture) in the upstream to C4S3 (harmful to agriculture) in the downstream. Therefore, it can be concluded that the occurrence of drought periods has a significant effect on the water quality factors in comparison with the long-term period, so that, the agricultural water quality drastically has reduced by a decrease in rainfall and subsequently decrease in river discharge within the drought period.

 Wind is one of the complex climatic variables whose changes can affect climatic characteristics on a global, regional and local scale. Although this variable is one of the important factors in climate change, it has rarely been studied to detect climate change. The purpose of this study is to analyze the temporal-spatial Distribution of surface wind speed in the geographical area of Iran (1982- 2019). For this purpose, the mean hourly, daily and monthly average wind speed data for the MERRA-2 model were used. The results show that there are fluctuations in wind speed and the trend was accompanied by an increase of 0.2 m / s. Statistical analysis also showed significant differences in time and location. Among the months, the highest average wind speeds occurred in the months (June, July and August) and the lowest in the months (October, November, December and January) and among the seasons the highest and lowest occurred in summer and winter. Locally, the highest intensity and persistence of wind current in eastern Iran and central Iran. Regression relationship between wind speed and temperature and pressure variables showed that wind speed is directly related to temperature (R = 81%) and inversely related to pressure (R = - 70%).

In this study, first, by studying the research, criteria and sub-criteria were identified that are effective in terms of environmental sustainability. After the Delphi stages, the criteria of environmental resources and services, environmental health and energy were selected as the most important criteria for assessing environmental sustainability in Babak, then using the neural network model to analyze and evaluate the environmental sustainability of Babak. In this study, drought in Babak city was analyzed with a SPI index of drought during a statistical period of 32 years 1361-1392. This index is specifically for time series six; Twelve and forty-eight months were calculated. The city of Babak has been facing drought during the statistical period of thirty-two years, especially the last seven years, and on an annual scale of six months, most of its droughts are mild to moderate droughts. But in the long-term Myas 48 months, 75% of the droughts were severe and very severe, which shows a high relationship with the quantitative and qualitative decline of groundwater in this area.