مجله مهندسی و مدیریت آبخیز
سال پنجم شماره 3 (پاییز 1392)

Sediment concentration in rivers, especially in seasonal ones, is affected by flood situation due to changes of rainfall or snowmelt events. Due to the importance of flooding flows in inundation and the useful age of reservoirs built on seasonal rivers, the study and assessment of this issue seems to be essential. In the present research, suspended sediment concentration variation in spring and autumn floods and runoff from snowmelt in spring, have been studied for Abshine River in Ekbatan Dam Watershed. Over the forecast period, three storms in autumn, two storms in spring and five snow melt events were selected and compared. Analyzing 226 suspended load samples showed its variability in the area. Sediment rating curves in different base times showed different trends. The correlation coefficient (r) were 0.79 and 0.50 for storms and snowmelts and 0.81 for all data, respectively. Also, coefficient and power value analysis of sediment rating curve, presented the same erodibility for hill slope in both seasons (spring and autumn). Separating falling and rising limbs of flow hydrograph and assessing their effect on discharge explains a better Q-sediment concentration relationship. The hysteretic shape of discharge and sediment concentration had clockwise and anticlockwise form and compound pattern of both forms that reflected the distribution of probable sediment sources throughout the catchment.

Improper land use management has inverse impacts on available resources. To reduce these environmental and economic effects of soil erosion, there is a need for proper watershed plans. Land use optimization is of the solutions for achieving sustainable development and reducing the loose of resources. The main objective of this research was determining the optimal level of land use to increase the income of residents and reducing the effect of erosion in the Sana Dam Watershed. To apply an optimal pattern of land used for minimizing soil erosion and maximizing land income by a multi-objective programming model, optimal scenarios were chosen proportion to the shape of objective functions and constraints. For this purpose a linear programming model was used for three different scenarios of a) present land use conditions b) present land use condition with some applied land use management and c) standard land use conditions according to principles and scientific criteria. The results showed that present land use is not in optimal level and should be changed. Also, results demonstrated that the amount of soil erosion could be decreased by 5.3, 31.7 and 43.4 percent and the amount of net income could be increased by 47.73, 242.57 and 242.57 percent by land use optimization in present land use conditions, present land use condition with some applied land use management and standard land use conditions, respectively.

Many on-site and off-site problems occurred due to irregular human use of natural resources leading to increasing sediment loads in watersheds. Understanding relative importance and source of erosion and sediment is essential for effective control of aforesaid problems. Todays, there are different techniques for determining sediment sources. However, the evaluation of their relative agreement has been less considered. Towards his attempt, the present study aimed to compare the results of fingerprinting, soil erosion feature map and direct field measurements of soil erosion. According to the results of fingerprinting technique, the red gysiferouse marl geological unit with 85 percent contribution in sediment yield was most important sediment source. It was in the same line with that reported from soil erosion feature map with code of CS23R41G42. The results of field measurements also showed that the red gysiferouse marl geological unit with soil erosion rate of 34.4 t ha-1 and 14023 t annual erosion had the highest proportion in sediment yield. Other geologic units viz. young alluvial deposits and old alluvial clastic lied in second and third orders. These were also consistent with those of fingerprinting technique. Totally, the differences in the results of fingerprinting technique, soil erosion feature map and field measurement techniques referred to their quantitative or qualitative approaches and not considering sediment delivery ratio concept and other sediment transition processes. It clearly confirmed the necessity of simultaneous use of all aforesaid techniques to get access to reliable results.

The present research is looking for determining and evaluation of water balance in Sanjabi Watershed located in Kermanshah Province due to a variety of problems raised by the population increase. For this purpose, the SWAT model parameters have been calibrated by applying required information layers in a period extending from 1995 to 2004 and their sensitivity were analyzed by SUFI2 program. The flow parameters’ sensitivity was computed by P-Value and t-State in SUFI2. The most sensitive parameters were calibrated and thereafter model was validated for a period extending from 2005 to 2007. The model evaluation results showed that the value of NS (Nash Sutcliff), R2 (Coefficient of determination), Mean Absolute Relative Error (MARE) and Percent Difference (D) for calibration period were 0.78, 0.78, 0.2 and -0.2, respectively and for validation period were 0.74, 0.86, 0.3 and 0.01, respectively. Results showed the desired accuracy of SWAT for runoff simulation. Discharges for calibration and validation periods were generally under and overestimated, respectively. The water balance values are calculated as the amount of water available in the soil. So that the water balance resulted as negative in years 2005 (normal year), 2006 (wet year) and 2007 (dry year). Nevertheless, in these three years, autumn and winter monthly water balances were positive while in spring and summer were negative. The results also showed that most water losses were due to evapotranspiration in this watershed.

Differential synthetic aperture radar interferometry (D-InSAR) has become a useful technique for monitoring ground movement. The technique enables the analysis of very small ground movements in continuous and large areas and has the advantages of high accuracy, high resolution, all-weather adaptability, low cost and inaccessible area coverage. Thus, D-InSAR has been widely used for investigation of geologic hazards, such as subsidence, landslide, earthquake, and volcanic activity. In this research, D-InSAR technique was applied for detection of unstable slopes and determining moving displacement rate. For this purpose, eight SAR images of PALSAR sensor of ALOS satellite were selected for processing based on D-InSAR approach. Obtained results were validated by field observations prates. This paper is only represented results related to image pair processing of 5th July to 5th October 2007 with 92 days interval. Garm Chay watershed with 940 km2 area is located in North Eastern and 40 km far from Miyaneh in Eastern Azerbyjan, Iran. This region with 380 landslides is considered as one of the unstable landslide proven area in Eastern Azerbyjan. Occurrence of these slides caused heavy damages to rural properties and arable lands. As a result, Sovin village in north western part of this watershed was moved to other safesite. The results clearly showed that some old stabilized landslides were still active. Because of their proximity to local stream networks (check the possibility for stream displacement), they can be considered as important sources of sediment yield. Before mentioned period, the maximum displacement was calculated 5.8 cm in landslide surface near to Avin, Atajan and Benavaran villages. The results from this method should be validated by geodetic methods and field obsevations.

One of the most important problems that empirical model users in Iran are facing with, is that these models are prepared for countries with special conditions such as lithology factor, which scores are given based on geology condition of origin country that are not compatible for a vast country like Iran with a great lithological variation. This research was conducted to reduce such problems and increase the efficiency and localization of these kind of models and provides rock erosion sensitivity factor for their special conditions. In PSIAC and EPM as a common experimental models, lithology factor is an important agent among other effective factors. In this research, a comprehensive classification of erodibility has been produced in 10 orders, based on mineralogy, chemistry, texture, structure and mechanical properties. Regarding to aridity of many parts of the country, and low rate of soil generation, erodibility rates of geological formations would be an important tasks. Results showed that, about 70 percent of the area covered with very low to low strength lithology to erosion and have a high potential of sediment yielding. Geological formations’ erodibility has been classified in 30 Tamab watershed with order of 4 and the results are compared with EPM results and monitored values in river gauging stations. Results also indicated a good agreement with high confidence with natural conditions and with respect to other important factors of the watersheds such as topography and rainfall.

Dust is one of the drought consequences which during recent years has been emerged as one of the important factors affecting wheat growth and its production yield beside other climatic fluxions. In this research, the drought intensity has been studied at nine synoptic stations of Lorestan province, during a ten years period of 2000-2009 and its dominant effects on dust frequency rate and its effects during seasons on the wheat cultivation performance rate, as one of the most important agricultural products sensitive to climatic variations,. The drought intensity analysis has been conducted by SPI index, for a six months’ time scales led to January and its relation with dusty day’s frequency distribution has been examined in horizontal sight less than 2000 m at the province stations. Also, the mutual correlation rates have been analysed using Pearson correlation test and multiple regression method with SPSS software and clustering was studied using Ward method in S-plus software. Results demonstrated that even during normal wet-spell, dust days happen and wheat performance in drylands falls below1000 kg ha-1 (2004, 2005 and 2007). Whereas, the dust days reached to zero and the wheat performance exceeded kg ha-1 (2006), when the wet-spell exceeds its normal rate and reaches to reduced domain. The frequency of dust days and wheat performance are directly correlated in most stations like Khoramabad, Koohdasht and Broojerd with a rate of 0.784, 0.626 and 0.933, respectively and completely adverse in Azna with a rate of -0.926.

The vortex settling basin is a sediment control structure in conveyance water system which can be more economical than other designs in specific conditions. Deposition of sediment in the basin is a major problem. Mechanism of separates solids and water in these basins, based on flow vortex and difference of density between water and sediments. Therefore the sediment increases in the basin for long time. In this study the hydraulic characteristics of these basins are investigated and offered a method to increase the efficiency of it. In this offer the submerge vans were used on the bed of the basin. Experimental results were showing that increase in deposition with a decreasing vanes interval (rR/2), vanes with guidance sediments toward orifice bottom, flashing from bottom occur more than another. Results also indicated that located vanes with constant total flashing efficiency and flow losses, and has been able to change bottom sediments in the basins. Experiments show that if the vanes are placed in less radial intervals, the discharge loss increases. As well as increase input flow because that total deposition efficiency, hydraulic efficiency and vanes efficiency in flashing have been increased.

Keywords: Deposition efficiency, Flow losses, Radial distance, Orifice, Sediment