فصلنامه پژوهش های فرسایش محیطی
سال چهارم شماره 2 (پیاپی 14، تابستان 1393)

Multiciplity inputs of different analysis of digital data in modern methods of map processing causes the changes in results of erosion and sediment models. In this context، selecting a cartographic scale as the major input of spatial data has become a challenge issue in erosion and sediment modeling. Therefore، in this study، using topographic maps and selecting to spatial scales (1:25000 and 1:50000) and nine pixel size (10، 15، 20، 25، 30، 50، 75، 80 and 100) in digital elevation model derived from two mentioned cartographic scales in Jamash watershed، we tested the hypothesis of non-uniform of output regarding to sediment delivery ratio. In this manner، first by entering raw data in ArcHydro extension and processing them، we ordered the stream by Strahler method. Then، by calculating the ratio of drainage area، we tested the relationship between drainage area and estimated sediment delivery ratio in each scale in a logarithmic model. The result show that changes in cartographic map scales and DEM pixel sizes، have significant effect on Jamash watershed sediment delivery ratio. Due to not having a definite and comprehensive basis in choosing the map scale in erosion and sediment studies، especially estimation of sediment delivery ratio، more over exact determination of sediment delivery ratio by means of observed data in watersheds with statistic، would not be challengeless; Consequently it seems that future researches should focus on defining the appropriate scale of erosion and sediment studies by analyzing physical processes of sediment، transport and deposition and it’s correspondence to cartographic scale in each watershed.

Floodwater spreading (FWS) has an important role in floodwater control, groundwater recharge, restoration and enhancement of vegetation and desertification control. Since the flood causes the transporting of soil particles including organic materials, the floodwater spreading project can be a suitable place to sequestration of organic carbon in sediment yielded by flood. The knowledge of soil organic carbon stock (SOCS) changes affected by different process can be important in realizing of these process roles in world carbon cycle and consequently in greenhouse gases effects mitigation. Therefore, the objective of this study was to evaluate SOCS in floodwater spreading project in the Zahab Plain. In view of this, 9 FWS strips based on random block design divided into three higher, middle and lower strips as well as each strip divided into three initial middle and final sections and sampling carried out in 0-20 cm depth. Soil organic carbon concentration and bulk density in 42 samples from FWS project and control areas were measured and SOCS were calculated. The results showed that SOCS in the three divided strips of floodwater spreading and control area as well as three sections of each strip with control area was significantly different. But the SOCS within divided strips and sections were not significantly different. The mean of SOCS in 0-20 cm depth in the three sections and control area were 1.29, 1.02, 1.53 and 4.61 Kg m-², respectively (P < 0.05) and the mean SOCS in three sections of strips initial middle and final sections was 1.04, 1.16 and 1.64 Kg m-² respectively (P > 0.05). Overall, transported sediment with low organic carbon concentration from upstream catchment or exporting of organic carbon as dissolved organic carbon have been caused to low increasing of SOCS in Zahab Plain floodwater spreading.

The dimensions, shapes and the patterns of natural rivers change according to their dynamic properties. These unavoidable changes cause the rivers imbalance and a new balance will be formed. The around lands will be affected by this dynamic and dangers such as instability of the bed. In this research we used chronological inference method to study Kashkan River morphology. Kashkan river is located in a region between Lorestan province and Gavmishan bridge in a reach of 25 kilometers. The aero photos of 1334, 1376, the sensing images of liss3 obtained from IRS P6 satellite in 1385 and the Geo Eye image of the land were digitized in Arc GIS software. In the second step geometrical parameters such as wave length, valley length, sinuosity, central angle and radius tangent on the river arch were calculated. Then these geometrical parameters were statistically analyzed and were compared in 4 stages. We Using HEC-RAS investigated flood zonetion as an important factor in river bed changes. The results of this study and comparing these parameters during the 4 reaches showed that in the abovementioned year's kashkan river pattern was meandering in the reaches of 1, 4 and 5 and also it was developed meandering form in the reaches of 2 and 3. Those river’s arcs which had the most changes in those years were located in the reaches of 2 and 3. At the end it was concluded that the geology factor and the river’s flood in the reaches of 2 and 3 were the most important factors in forming the bed’s changes and bank erosion. Topography factor was the most important factor in causing the most changes in the reaches of 2 and 3 which were located in floodplain.

Greenhouse gases (GHG) are a serious threat to humans and environment. Greenhouse gases have been different sources، but main factors are fossil fuels، industrial processes، deforestation and agriculture. What is now more than ever before should be considered according to the role of forests and rangelands in atmospheric carbon sequestration. Carbon sequestration is to changes in atmospheric carbon dioxide to form organic compounds with carbon by plants and capture for a certain period of time. Based on this research project in a completely randomized factorial experiment format was done. This study estimated and compared the amou nt of carbon sequestration by Atriplex canescens and Hulthemia persica، determine the economic value of carbon sequestration and determine the contribution of soil and plant carbon sequestration. In order to measure the organic carbon in soil and plants، respectively Walki Black and Combustion methods were used. The results showed that carbon sequestration by Atriplex canescens (41،626 ha) more than Hulthemia persica (32،461 ha) and bare area (26،654 ha) is. Therefore، the amount of organic carbon in areal biomass more than underground biomass and rate of soil organic carbon in first depth more than second depth. Share of soil in carbon sequestration in the planted region by Atriplex canescens، 87% and in an area with dominant cover of Hulthemia persica is 97%. So we can conclude that the soil in ranglands، most organic carbon reservoir is considered.

Soil mapping is one of the basic studies in the natural resource sector. The purpose of this study was to analyze spatial of soil properties on the map of arid areas and deserts. For this purpose, a region with an area of 600 hectares in Qom that considered Salt Lake watershed. Specified methods used include inverse distance methods, radial functions, and prediction local general estimate.Kriging and geostatistical methods used include a variety of types Cokriging. The results show the advantages of using geostatistical methods to determine the mapping of soil for methods of defined the maximum is 9.87 and minimum 1.26 and for methods of kriging the maximum is 9.48 and minimum 1.19 and for methods of Cokriging the maximum is 9.64 and minimum is 1.2. In this parameter has the highest correlation with the desired parameter was considered as a covariate. Landsat ETM + data have also been used as a covariate in the interpolation parameters. The results show that the use of satellite data for mapping soil parameters is increased accuracy. Most accurate method was different for each parameter and evaluatedhave different for mapping soil properties.In most of surface parameters the best method was geostatistical methods and in silt parameters the best methods was local estimation method. The best way in most deep parameters was geostatistical methods.

The erosion is one of the waster factors of land sources. Understanding of erosion danger provides possibility of identifying critical regions and priority of administrative and protective plans. The aim of this research is providing of soil Endanger map by GIS, RS and multi criteria division systems in Doab basin of Lorestan province. For purpose, data of 8 important factors in soil erosion including: slope aspect, slope, lithology, land use, vegetation cover, precipitation, soil was provided by GIS. Then weight of each factor and weight of classes each layer was calculated in super division by Analytic network process and pair comparison methods. Then, case study was classified for each factor by GIS overlaying functions. Finally, final map was provided in 5 classes of very much danger, much danger, middle danger, low danger, and very low danger by classified maps combination based on obtained weight from Analytic network process method. Results indicated that%11, %13, %16, %28, and%32 of case study are very much danger, much danger, middle danger, low danger, and very low danger respectively. Also, for results validity, position of 93 points of erosion was determined in field investigation with GPS. Then, these points compared with erosion map by ArcGIS overlaying functions. Results of this overlay indicated that from these points, %24, %51, %13, 3 and 9 point has laid in very much danger, much danger, middle danger, low danger and very low danger respectively. So Data obtained during the field study is accordance with ANP method results that are indicator precision of Analytic network process method in investigation of erosion.