Abazar Esmali; Hasan Ahmadi; Mohammad Tahmoures
Abstract
The aim of this research is to describe the development of a methodology based on present knowledge and available data for evaluation of water erosion behavior and risk as well as modeling and estimation of soil erosion, which is compatible for other similar areas of Iran. Accordingly, the conducted ...
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The aim of this research is to describe the development of a methodology based on present knowledge and available data for evaluation of water erosion behavior and risk as well as modeling and estimation of soil erosion, which is compatible for other similar areas of Iran. Accordingly, the conducted research was based on four major types of water erosions including: sheet, rill, channel and riverbank which have considerable role on sediment yields of Baleghli Chay Watershed, Ardebil Province, were separately and spatially studied. In order to determine the inter-effects of effective factors, the study was conducted using stepwise multivariate statistical tests. For each erosion type, an individual model was then presented. In the next step, after determining of relations between sediment yield and environmental factors (fixed & variable) through statistical analyses and selecting of effective factors on erosion and sediment yields, was created an empirical structure for modeling erosion and sediment yields based on MPSIAC erosion model. In formulation of the new model, were used of eight effective factors on erosion in the area. These factors are susceptibility of geological formation, soil erodibility, rainfall erosivity, runoff erosivity, topography, hydrographic drainage, Normalized Difference of Vegetation Index (NDVI) and field conditions of erosion features. In the presented model, with summation of the scores of mentioned eight factors, obtains the M value, which can estimate the amount of erosion and sediment yields of the area, using exponential formula between sediment yield and M values. In addition, in order to obtain the confidence of presented model, it was used in "Nir" catchment for evaluation the precision. The results showed 11 percent difference. With accepting of this error value, the water erosion hazard map of the area was provided and presented using new model.
J. Sharifi; M. Akbarzadeh
Abstract
A major part of the rangelands of Iran are located in arid and semi-arid regions. In this climate, rainfall fluctuation is an important factor which affects vegetation and forage production. In dry years that rainfall decreases, surface vegetation and forage production is damaged. This study was conducted ...
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A major part of the rangelands of Iran are located in arid and semi-arid regions. In this climate, rainfall fluctuation is an important factor which affects vegetation and forage production. In dry years that rainfall decreases, surface vegetation and forage production is damaged. This study was conducted on semi-steppic rangelands of Ardebil over nine years (1999-2007), to study of vegetation changes with rainfall fluctuation. The results showed that canopy cover of Salsola gemmascens and Noaea mucronata species was decreased but Artemisia fragrans and Kochia prostrata species were increased.Generally density of shrub species was decreased about 40% and showed a positive correlation with seasonal precipitation (fall and winter). Grass species showed different response to precipitation changes over nine years period and in general, no significant changes were observed. Stipa hohenackeriana species was affected by winter precipitation but Poa bulbosa and Cynodon dactylon were correlated with spring precipitation. Density of perennial forbs species was increased considerably (about seven times), but in dry years (2000-2002) forage production reduced. Forage production over nine years increased from 296 kg to 747 kg per hectare, which is approximately 2.5 times higher. Meanwhile, proportion of plants in classes I, II and III, were respectively, 23.1, 51.9 and 25.2 percent of forage production. Also, forage production in wet periods increased from 747 to 1968 kg per hectare which shows an increase of about seven times.
