Alireza Motevali; Ali Talebi; Mehrdad Safaei; Mohammadreza Ekhtesasi
Abstract
Landslide is one of the most important geological phenomena in northern slopes of Iran (Alborz) which causes considerable damages gradually. In the last few years, due to unfavorable changes in land uses and increasing degradation of pastures, forests and farmlands as well as implementation of inappropriate ...
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Landslide is one of the most important geological phenomena in northern slopes of Iran (Alborz) which causes considerable damages gradually. In the last few years, due to unfavorable changes in land uses and increasing degradation of pastures, forests and farmlands as well as implementation of inappropriate development projects in areas prone to landslides, geology formation prone to landsliding, rainfall rate and steep slopes, the occurance of this destructive phenomenon has constantly increased. In this research, landslides which occurred around Sari-Kiasar road were investigated using physically based models i.e. SINMAP and SHALSTAB and the stability map of the region was determined applying these models. First, the physical and mechanical properties of soils in 13 points were measured and evaluated by 56 landslide points. The results of field studies, laboratory samples, running models and data analysis showed that these models (SINMAP and SHALSTAB) have success rate equal to 87.3 % and 69.5%, respectively for predicting the slope instability in ChaharDonge region. This means that the SINMAP model has more efficiency than SHALSTAB model for slope stability analysis.
Ali Talebi; Shahrbanoo Abbasi Jondani
Abstract
WEPP model needs a great deal of input data. Identifying the model’s sensitive parameters andtheir prioritization increases the accuracy and efficiency of the model. On the other hand, WEPPmodel can simulate processes affecting on runoff, erosion and sediment throughout the year. Thus,model sensitivity ...
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WEPP model needs a great deal of input data. Identifying the model’s sensitive parameters andtheir prioritization increases the accuracy and efficiency of the model. On the other hand, WEPPmodel can simulate processes affecting on runoff, erosion and sediment throughout the year. Thus,model sensitivity must vary based on the storm occurrence time and parameters value in differentsections of the year. To prove this assumption, two spring and autumn storm events related to 2008were selected and sensitivity analysis of the WEPP model was done in three plots with differentconditions in Sanganeh watershed. For sensitivity analysis, the OAT method was used andsensitivity degree of parameters was calculated. Obtained results show that the rate of sand is themost sensitive parameter of WEPP model. This parameter was followed by other parameters likeclay percent, effective hydraulic conductivity, height and intensity of rainfall, day degree ofgrowing, growing season and percent of growing season when leaf area index decreases. Mostvariations are observed in prioritization of sensitive parameter in the plant/ management file. Inmost cases, sensitivity degree of these parameters in autumn event comparing to the spring eventhas significantly reduced in all plots. In general, obtained results show that the rate of sensitivity ofthe WEPP model to different parameters varies during the time. Hence, for using this complexmodel in regions with data limitation, the user must be aware to this issue that regarding storm time,which parameter is more sensitive in the pilot area and need to be carefully measured in the field.
Masoud Eshghizadeh; Mohammad-Taghi Dastorani; Ali Talebi
Abstract
The management of sedimentation problems in rivers and reservoirs depend greatly on the sediment yield from the catchment land surface. In this research the effects of biological measures and ranges enclose on suspended load in two sub-catchments of Kakhk experimentalWatershed in Gonabad has been studied. ...
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The management of sedimentation problems in rivers and reservoirs depend greatly on the sediment yield from the catchment land surface. In this research the effects of biological measures and ranges enclose on suspended load in two sub-catchments of Kakhk experimentalWatershed in Gonabad has been studied. This catchment contains both control and experimental sub-catchments. These sub-catchments are similar in all aspects and differ only based on watershed management operations. Experimental sub-catchment has been under rangeland enclosures and operation of biological, biomechanical and mechanical measurements since 1998 whereas control sub-catchment is under normal operation. To determine the biological impact of management and biological measurements on sediment production, the yield suspended load on hillslopes in 18 experimental erosion plots during 4 rainfall events occurred in 2011-2012 has been analyzed in both control and experimental sub-catchments. Analysis was performed in SPSS software using independent-sample T test and ANOVAwith repeated measure test. Based on these comparisons, difference between the amount of suspended load in two sub-catchments was significant at 1 percent level, while runoff depth was significant at 5 percent level. Also results showed that correlation between the runoff depth and suspended load has been 94 percent in Control sub-catchment and 62 percent in Sample sub-catchment. Slope of the line changes between the runoff depth and suspended load in Control sub-catchment has been 5.3 times of the Sample sub-catchment. The research clearly showed the effect of the biological measures and ranges enclose on reduction of suspended load and runoff depth in experimental sub-catchment.
