فصلنامه پژوهش های فرسایش محیطی
سال پنجم شماره 3 (پیاپی 19، پاییز 1394)

Predictions of total and even partial changes in rivers patterns are as the most essential issues related to rivers geomorphology. In this regarding, a lot of researches have been done by geomorphologists. This research has explored Kordan River aqueduct morphology changes in bights areas of Afkaneh cone surface. Kordan river is the one which has been affected by various factors and has changed a lot so that this changes has impressed on components an human activity around the river and on side erosion and channel. The research method is on analytical and time comparison method by which direct and indirect observations, maps and images are used, to the drainage characteristics in the two study periods. In this research topographic maps at 1:25000 scale and photogrammetry at 1:55000 and 1:40000 scale of studied region was used. Beside these, to exploit sack changes some software application such as Arc GIS , Excel and SPSS were applied. Research results show that river side changes in 37 to 165m are varied in river different parts that in average, river has gotten eroded 31583.4 m2 in 44 years that annual erosion amount has been 718.8 m2. It can be predicted for further 20 years that probably right side of the river will get eroded 14415 m2 in average. In 1999, developed and non-developed bights were added to river area, and high developed bights have been reduced from river than 1955. According to Leopold and Wolman index, bend coefficient more than 1.5 has bight pattern, therefore in studied bight parts of Kordan river 90% of bows has had evolved bight pattern in 1955 and this amount has arrived to 81% in 1999. Regarding to calculation, it can be concluded that bights had been increased from 1955 to 1999 but their sharpness were decreased.

Coastal and inland dune sands in desert environments are compositionally and texturally controlled by physical and chemical processes such as the wind action, marine/fluvial processes, weathering, air temperature and precipitation. The objectives of this research are study of sedimentological characteristics, calculation of CIA in the Aeolian sediments and classification of sand dunes in the Yazd-Ardakan plain. For study of sedimentological characteristics and calculation of the CIA were analyzed 88 and 20 samples, respectively. Major element component measured using XRF. Results showed that, sorting and mean grain size is weak and coarse to medium respectively, which it indicates sources of Aeolian sediments is local. According to classification of Besler (2008) sand dunes classified to strongly saline class. Amount of CIA in the all sample is less than 55, which it indicate there weren’t any weathering in the case study and the maximum of CIA is related to Kalot facies with 50.7.

In a watershed, land use As one of the most effective factors in basin hydrologic response, Can have significant role in the hydrological cycle and water resources. The knowledge of the effects of land use change on basin hydrology responses can help to determine the appropriate strategy to achieve sustainable development of water resources and a management model. The purpose of this study is to evaluate the hydrological effect of land use changes over the last 25 years in the Yalfan watershed. Swat model (2009) was used to simulate suspended load. Meteorological data, digital land use map and soil and digital elevation model of the research area was prepared. After calibration (2002 to 2007) and verification (2008 to 2010), In order to assess the impact of land use on suspended load, the 1989 and 2013 land use maps were created and introduced to the model. The result shows significant effects of land use change on suspended load. The changes in land use from 1989 to 2013 result in, increase of sediment load and runoff around 11 and 17 percent respectively and reduce ground water level about 16 percent. NS¡ R2¡ P-factor and R-factor were evaluated for calibration 0.54, 0.6, 0.48 , 2.3 , and 0.57, 0.65, 0.42 , 3.2 for verification respectively, approved that the model has a good ability to simulate sediment .

Requisite programs soil conservation and sediment control is requires identification of areas prone to erosion and today used fingerprinting method around the world to determine the contribution of sediments transported. In this study, in order to gain optimized share of the estimated sediment resources, used of tracking feature and finally presented the map susceptibility to erosion in the Fashand Catchment to area of 3247 hectares according to the mineralogical and geochemical studies. The results of mineralogical studies suggest that the Zagon formation with 17.13% of the watershed area has the greatest Sediment potential (57/1) in the region and the results of geochemical methods are also showing greater sensitivity Zagon formation the share of deposits has been 1.84. The results detection analysis suggest that of 11-element analysis in this research, have been appropriate the elements phosphorus, chloride, bicarbonate, lime, nitrogen and organic matter in order to separate the sediment sources. The results of mineralogical and geochemical methods have been largely fits together.

Ecosystem services are benefits that people obtain from ecosystems. Soil retention is one of the most important ecosystem services. The capacity of ecosystem to maintain soil can be estimated by quantifying this services. In this study, version 3.0.0 of the InVEST software was used to map this ecosystem service in the eastern part of Gorgan-Rud watershed. The InVEST model employs the Universal Soil Loss Equation (USLE) for estimation of the soil loss in which R is the rainfall erosivity, K is the soil erodibility factor, LS is the slope length-gradient factor, C is the land use/cover and crop management factor and P is the support practice factor. Soil retention was estimated through the RKLS-USLE equation. Findings revealed the total soil loss potential varied between 0 and66.3 (t/ha). The sum of soil retention in sub watershed varied between 0.5 to 4530.2 (t/ha). Forest cover provided the main supply of this service in the study area. In comparison with other hydrological models, this model requires minimal input data, but at the same time produces useful outputs.

Because Geno protected area didn’t protect enough, it cause to use lots of part for domestic animal productivity and this ecosystem with special plant and animal species degrade. This study was down with this goal: determining of proper region for soil protection, rehabilitation and special use according dry region potentials. We use these maps: slope, aspect, elevation, soil, plant cover and rural settle regions and then we categorized them with ArcGIS9.3 according Makhdom ecological modal and then we prepare shape earth units map and final zoning map. Although we numerated erosion factors according MPESIAC method and after adding numbers, sediment delivery identify determined. Results show that 12457.01 ha or %28.02 from total of region is protected zone, 203.82ha or % 0.45 from total of region is rehabilitation zone and 95.591ha or %0.21 from total of regions is special use zone. Results from identifying sediment delivery shows that Ziziphus spina-christi plant type with 87 numbers has forth sediment delivery class or high erosion that the most important factor depends on river erosion and slope. Results show that soils around one fifth of region is eroded intensively and a lot of plant and animals damaged in Geno region. This fact shows that human use a lot from Geno protected area that we must think for protecting more.