Showing 3 results for Vegetation Cover
J. Abdollahi, N. Baghestani, M.h. Saveqebi, M.h. Rahimian,
Volume 12, Issue 44 (7-2008)
Abstract
The present study discusses a method used to produce updated information about vegetation cover in arid and semi-arid zones, using RS data and GIS technique. In this method, Landsat ETM+ data in 2002 was collected in an area of about 60000 ha in Nodoushan basin, Yazd, Iran. To collect the necessary ground data, 50 sites of different vegetation types were selected and the percentage of vegetation cover in each one was determined. Also, different vegetation and soil indices were derived and crossed with located sampling points using ILWIS software capabilities. To get the best fitted curve, the relationship between vegetation cover, as a dependent variable, and satellite data bands, vegetation indices and environmental factors, as independent variables were assessed. Therefore, a multiple linear regression model was established for the prediction of vegetation cover percentage in the studied area. Finally, a vegetation cover map with high a precision was produced. As a conclusion, it can be said that mapping of vegetation cover via remote sensing is possible even if its vegetation cover is sparse.
A Masjedi, M Fathi Moghadam, B Shomalnasab,
Volume 12, Issue 46 (1-2009)
Abstract
Tamarix sricta plant grows in riversides of Karun river. Outer body plant in the flood times causes decrease in water velocity, preventing erosion. One of the factors by which the hydraulic resistance is expressed is the roughness coefficient. Measurement of roughness coefficient of the existing plants in these riversides and floodplains, and surveying their effects on the velocity decrease and shear stress of the flow are important. The present research studies roughness coefficient of the plants manning existing in the riverside. Tamaix sricta was studied in non-submerged and sub-critical conditions in a flume with the length of 12.6 m, width of 0.5 m and height of 0.6 m in different velocity, discharge and depth ranges. The height of plants in this study was 35 cm with a natural arrangement in a bench of 2.8 m in length put in the bed of the flume. The total number of the experiments is 22. The results of this study show that roughness coefficients of plants are functions of velocity, depth, hydraulic radius and type of plants. Roughness coefficients in non-submerge condition change nonlinearly with changes in velocity, depth, Reynolds number, submerge depth and (VR) in natural conditions.
Engineer H. Talebikhiavi, Engineer M. Zabihi, Dr. R. Mostafazadeh,
Volume 21, Issue 2 (8-2017)
Abstract
Effective soil conservation requires a framework modelling that can evaluate erosion for different land-use scenarios. The USLE model was used to predict the reaction of appropriate land-cover/land-use scenarios in reducing sediment yield at the upland watershed of Yamchi Dam (474 km2), West Ardabil Province, Iran. Beside existing scenario, seven other land-use management scenarios were determined considering pattern of land-use through study area within a GIS-framework. Then, data inputs were prepared using terrain data, land-use map and direct observations. According to the model results, the generated erosion amount was 3.92 t/ha/yr for the current land-use (baseline scenario). For this purpose, conservation practices in dry farming slopes and implementing the scenario 5 (contour farming and remaining crop residuals) can reduce the sediment to 2.02 t/ha/yr. The lowest and highest decreases in sediment yield are projected to be through implementation of scenario 6 (irrigated farming protection with plant residuals) and 7 (biological soil conservation in dry and irrigated farming). The results indicated that, implementing scenario frameworks and evaluating appropriate land-use management scenarios can lead to the reduction of sediment entering the reservoir, and prioritizing soil conservations in the studied area.
