فصلنامه پژوهش های فرسایش محیطی
سال سوم شماره 3 (پیاپی 11، پاییز 1392)

Landslide is one of the natural disasters which causes a lot of annual damage directly or in directly in the world. Landslide zones are extended in the northern and the western part of Iran. Land use change and high rainfall are two effective factors on mass movement in Beheshtabad basin. This paper follow to compare two method AHP and FAHP that is used in landslide hazard zonation. First of all، hazard zonation map was prepared with AHP method using inconsistency rate 7%. Then، fuzzy membership function definded for each the parameters، and hazard zonation map was prepared to the base of FAHP method. Finally، two maps were compared and results show that FAHP method has higher accuracy than AHP. In addition،57. 7% of landslide have been located in moderate elevation with 680-760 mm rainfall in Beheshtabad watershed.

Nowadays watershed catchments have been introduced as the main point of permanent development in many management discussions. Watershed catchments ecological power assessment and their rankings according to different Ethological criteria is one of the important factors in watershed catchments planning and management. Taxonomy method is one of the most comprehensive planned systems for assessing the power of related variables in planning and decision making for the future. In this research، four subcatchments of Zidasht catchment located in Taleghan region has been selected. Based on Taxonomy method، four effective variables in watershed catchments management plans (plant composition index، soil protection index، erosion and sediment index، and water quantity index) has been selected. Results demonstrates that the most effective index is the soil protection index and the ranking and the first priority among four selected sub catchments to perform management plants according to four mentioned indexes is D1 zone. The most important indicator of soil conservation index، the D2 sub and DINT1 and DINT2 are next in priority.

Fingerprinting is emerged as a new method widely used all over the world to shed lights on land unit''s contribution in suspended sediment production. According to common method، a suitable combinations of features separating sediment sources، the contribution of sediment sources in sediment production is determined. The present study was carried out in catchment area of 3278. 91 ha called Tulbaneh in the southern Golestan province (Northern Iran). Having average annual suspended sediment yield of 140709. 97 ton/ha، this basin characterized as critical in sediment production. The X-ray fluorescence (XRF) test was applied and number of 17 compounds were used as tracer. To this end، the basin was divided into five units as well as three sections of the main river from which three samples were taken. Samples of the sediment source area from two samplings taken at different times on outlet sediments as well as a combination of two sediment samples were compared. In order to data analysis، factor and discriminant analysis were considered. Compounds CaO، SiO2، Rb2O and X2 taken in to consideration as tracers. Results indicate that the channel 5 margin with an average 54. 19 percent accounted for the largest contribution in suspended sediment production. Results good confirmation with field data introduce source routing method used in this study as a promising and valuable approach to determine the contribution of suspended sediment source in watershed.

The most areas in Iran including arid and semiarid regions which have high soil erosion and sedimentation. Therefore، the study of soil erosion and sediment yield possesses and evaluation of its effective factors is very important in a proper management of a watershed catchment. The present study wants to evaluate efficiency of MUSEL model to estimate of sedimentation in storm scale and also modeling by using storm and runoff characteristics relating to four subcatchments of Doviraj river watershed in Ilam province. We finally optimized a model to estimate storm and sediment. We used two storms in two dates (2012. 11. 22 and 2013. 1. 30). According to results، in calibration stage، there was the appropriate correspondence between observation and estimation in terms of sediment yield. While، in validation stage there was a high difference between observation and estimation in 1، 2 and 3 subcatchment compared to 4 subcatchment، and therefore the reason of impracticality of the model in validation stage is related to the vastness of subcatchment. In order to present the appropriate model of the whole area regression relation has been used، in which the power of runoff factor changed from 0. 56 to 0. 34، which has a high correlation coefficient. In this case if other subcatchments of Doviraj watershed catchment have similar vegetation cover، physiography and geology conditions، the MUSEL modified can be used.

The growing population led to greater human need to use natural resources such as sand and gravel mines. Direct removal of sands from the bed river leads to increase suspended sediment concentrations in downstream of harvested area and creates other problems viz. filling reservoirs، change in hydraulic characteristics of the channel and environmental damages. However، the range of temporal and spatial effectibility of such human interferes has been rarely considered. The present study، therefore، aimed to investigate the spatial and temporal variation of suspended sediment concentration in the Kojour River in Educational and Research Forest Watershed of Tarbiat Modares University in Mazandaran Province، Iran. Towards this attempt، the effect of a conventional sand and gravel mining on suspended sediment concentrations was studied in a range of 0 to some 4 h and 0 to some 200m from the beginning and location of mining، respectively. The results showed that the exploitation from a local small sand and gravel mines had remarkable impact on suspended sediment concentration at a distance of approximately 100m and 2 h after mine exploitation. The statistical results by General Linear Model in Repeated Measure factor verified the increasing trend in suspended sediment in range of 50m after about 30 min of mining (P=0. 05)، while the effect of mining on increasing suspended sediment concentration could be recognized up to 200 m from the location of study up to about 10 min (P=0. 01) of time of sand mining.

The exact identification of the limiting factors is necessary for recognition of environmental crisis in every region. The invasion of quicksand into human centers is considered one of the important problems of the Sirjan salt playa. Each year the Mobility of quicksand entered damage to settlements، roads and farmland. Nebkas، in local scale، are representing potential of quicksand stabilization by vegetation، in the other word، ecosystem is trying to adjust the pressure of windy erosion and stabilize quicksand by creating this feature. The aim of this study is comparative assessment of Nebkas of Sirjan salt playa and introduction of appropriate type for quicksand stabilization، using analysis of nebka morphometric parameters via Analytical Hierarchy Process model. First morphometric parameters such as volume of nebkha، nebkha elevation، vegetation canopy cover، plant height، nebkha diameter and nebkha slope، 392 nebkhas for species tamarix mascatensis، Reaumaria Turcestanica، alhagi manifera and seidlitzia florida was sampled with transect method. The results show that Tamarix Macatensis Nebka، with weight of 0. 615، has the highest importance in stabilization of quicksand. Seidlitzia Florida Nebka، with weight of 0. 249، has secondary order. If that is developed and implemented، will have the highest productivity. Reaumuria Turcestanica and Alhagi Mannifera Nebkas، respectively with weights of 0. 070 and 0. 064، have the lowest efficiency and their development is not suggested in any way.