Zeinab Sheikhi; Aliakbar Nazari Samani; Haji Karimi; Reza Bayat
Abstract
Gully erosion is a typically threshold process which is important in land degradation and sediment contribution. Having knowledge on driving conditions and affected lands by gullies are crucial for land degradation management. In this research to prepare the gully erosion map over Iran land mass about ...
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Gully erosion is a typically threshold process which is important in land degradation and sediment contribution. Having knowledge on driving conditions and affected lands by gullies are crucial for land degradation management. In this research to prepare the gully erosion map over Iran land mass about scientific references (article, thesis and report) were investigated in order to scrutinizing of spatial data base and gullying map. Location of 2719 gully headcuts under different climate and land use were identified. Environmental attributes including: soil, climate, rainfall and temperature were collected through using of DEM (12.5 and 30 m), and landuse by using of maps, scientific reports, research studies were extracted. The frequency of gullies was investigated in relation to literature investigation. Topographic threshold conditions were determined and the relative frequency of gully area under mentioned environmental factors were analyzed. The results show that the total gully area in Iran is about 1,328,852 ha. The most occurrence of this erosion is in semi-arid climates, with annual rainfall is 250-350 mm, high silt content, low slope (<5%) and under dry farming landuse. The lowest threshold coefficient () in both arid and semi-arid climates is related to ranglands. The coefficient varies from 0.06 to 0.37 in arid climate and from 0.002 to 0.46 in semi-arid climate, which is indicating of mixing process (surface and subsurface) on gully developing. The resistance of sandy soils (due to permeability) and clay soils (due to cohesion) is higher than silty ones The degradation of canopy cover and runoff generating are two main driving forces, which will be more important under climate change in the near future.
heydar ebrahimi; Alireza Moghaddam Nia; Haji Karimi
Abstract
The runoff simulation in a watershed provides insight on the processes affecting runoff generation and the stream flow characteristics like spatial and temporal variability of stream flow. This insight helps managers and planners in informed decision-makings on water resources management and planning. ...
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The runoff simulation in a watershed provides insight on the processes affecting runoff generation and the stream flow characteristics like spatial and temporal variability of stream flow. This insight helps managers and planners in informed decision-makings on water resources management and planning. The objective of this study is to compare the performances of the complex SWAT model and the simple IHACRES model for simulating runoff in the Doiraj river basin, Ilam province. For this purpose, SWAT model due to having many parameters affecting stream flow and the use of GIS, and IHACRES model due to the low and easy access data requirements, are very practical. In this study, the data over a period from 1994 to 2004 and the statistical criteria of R2, bR2, and NS were used to evaluate performances of IHACRES and SWAT models. For IHACRES model, values of R2, bR2 and NS were estimated equal to 0.34, 0.112 and 0.33, respectively for calibration period and values of 0.47, 0.235 and 0.43, respectively for validation period. In addition, for SWAT model, the coefficients were estimated equal to 0.41, 0.314 and 0.12 respectively, for calibration period and values of 0.68, 0.632 and 0.56, respectively for validation period. Final results of this study showed higher performance of SWAT model relative to IHACRES model for simulating daily runoff in Doiraj river basin and can be used to simulate runoff in the watersheds with limited data and similar natural conditions.
Haji Karimi; Fathollah Naderi; Behrooz Naseri; Ali Salajeqeh
Abstract
Distinguishing the susceptible areas to landslide using different landslide susceptibility mapping (LSM) models is one of the primitive and basic works to reduce probable damages and reduce risk. The main purpose of this research is the efficiency evaluation of four methods including Information value ...
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Distinguishing the susceptible areas to landslide using different landslide susceptibility mapping (LSM) models is one of the primitive and basic works to reduce probable damages and reduce risk. The main purpose of this research is the efficiency evaluation of four methods including Information value (WINF), Valuing area accumulation (Wa), Analytical Hierarchy Process (AHP), Kopta-Joshi proposed method (LNRF) for LSM in Zangvan watershed, Ilam province. At first, all the effective factors in landslide occurrence were inspected. By analyzing the parameters, nine factors including slope, aspect, elevation, precipitation, distance from road, distance from fault, distance from drainage, land use and lithology were distinguished as the effective factors in landslides occurrence in the studied area. After preparing the information of these nine factors in GIS environment, the location of landslides were determined using areal photographs and satellite images and LSM performed by the above four methods. Finally, the landslide index was used for evaluation the ability of appropriate LSM model. Based on this Index, the information value method classified more 52 percent of occurred landslides in very high danger class. Therefore, this method is more efficient and proposed as the best LSM method in the Zangvan watershed because of compatibility of landslides with high danger classes and ability of differentiation of danger classes.
