Hassan Moghim; Masoud Nejabat
Abstract
From the viewpoint of landslide occurrence, Parsian dam Watershed is one of the high risk regions for landslide hazard based on its geological and climatological conditions. Landslide occurrence usually make huge damages and also high amount of sediments. Landslide control and management is planned according ...
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From the viewpoint of landslide occurrence, Parsian dam Watershed is one of the high risk regions for landslide hazard based on its geological and climatological conditions. Landslide occurrence usually make huge damages and also high amount of sediments. Landslide control and management is planned according to Landslide Hazard Zonation (LHZ) that is obtainable through empirical models. The aim of this research was to assess the efficiency of two empirical models, Modified Nilsson and Relative Effect in LZH. First, prepared maps such as landslide distribution, slope, geology, land use, land cover, roads, drainages, faults, isohyet and hypsometric were imported into GIS environment and then the landslide hazard zonation was carried out by applying Modified Nilsson and Relative Effect models. Capability assessment of two models and determination of the more efficient one were evaluated using two statistical analysis methods namely quality summation (Qs) and correlation coefficient (R). Comparison of results from above two models with real map of happened landslides at Parsian dam Watershed showed that the relative effect model with quality summation of 1.00 and correlation coefficient of 0.941, is more efficient for landslide hazard zonation in Parsian dam Watershed.
Gholamreza Chamanpira; Gholamreza Zehtabian; Hasan Ahmadi; Arash Malekian
Abstract
Drought is the most hazardous natural phenomenon. Although not preventable, its negative effects can be reduced through taking some measures. One of the systems severely affected by drought while less considered is the groundwater. In this study, drought status and its impact on groundwater resources ...
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Drought is the most hazardous natural phenomenon. Although not preventable, its negative effects can be reduced through taking some measures. One of the systems severely affected by drought while less considered is the groundwater. In this study, drought status and its impact on groundwater resources was investigated in Alashtar Plain using Standardized Precipitation Index (SPI) at monthly, quarterly, and annual scales and the Groundwater Resource Index (GRI) during the statistical period of 1991-2010. After data collection, statistical errors were corrected by subtraction and ratios method. Then, to determine the status, SPI and GRI were calculated with DIP software on an annual, seasonal, and three, six, nine, 12, 18, 24, and 48-month time scales for Alashtar Plain. Then, according to SPI and GRI value, the moisture status were determined for each period. Results indicated that the trend of plain meteorological and groundwater drought is negative. Correlation between SPI at different time scales with and without the time delay and with average groundwater level and GRI was analyzed. Statistical analysis showed that SPI was significant at the level of 0.01, in the 24-month time scale without any time delay with mean groundwater level and GRI and had the highest correlation coefficient, suggesting the impact of drought on Alashtar plain groundwater. Regression relation between the mean level of the water table and SPI_24 showed that 64.4% of the variance at the mean level of water table was affected by SPI_24 and 35.6% was affected by other factors. Drought magnitude (DM) analysis showed that meteorological and groundwater droughts are consistent with winter and autumn, respectively. Undoubtedly, optimized utilization management, especially in spring and summer, may have a critical impact on preventing damages to the groundwater resources of the region.
