Khosro Shahbazi; Ali Salagegheh; Mohammad Jaafari; Mohammad Khosroshahi
Abstract
Gully erosion affects land degradation, particularly in the semiarid reigns. Topographic thresholds are strongly affected by landuse change and destroy of vegetation. The objective of this study was to evaluate topographic thresholds of gully erosion in different landuse including agriculture (AG), fair ...
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Gully erosion affects land degradation, particularly in the semiarid reigns. Topographic thresholds are strongly affected by landuse change and destroy of vegetation. The objective of this study was to evaluate topographic thresholds of gully erosion in different landuse including agriculture (AG), fair rangeland (FR) and weak rangeland (WR) which carried out in Ghasreshirin, Kermanshah, Iran. The topographical parameters were measured in the field and relationship between gully catchment area and slope was analyzed for each landuse. The results revealed that some main topographic characteristics mainly cross-section, width, depth and gully branches length in the FR was significantly lower than in the AG and WR (p<0.05). Furthermore, analysis of gully threshold based on catchment area-slope showed that the critical area for gully formation in AG, FR and WR was 1300, 1689 and 1233 m2, respectively which was significantly lower in FR reducing by vegetation cover. The respective slope threshed was 1, 3 and 3 percent in AG, FR and WR. However, the affected area by gully erosion in AG, FR and WR was 12.4, 14.1 and 21%, respectively. The gully in the agricultural land was more dipper compared with other land uses. The volume of gully channels in FR was 3.4 and 2.2 times less than AG and WR, respectively. It is concluded that rangeland degradation and thereby removing vegetation attribute to severe gully erosion and consequently environmental problems such as soil carbon dioxide emission.
Meisam Alizadeh; Behrouz Malekpour; Hamid Arya; Samaneh Verdian
Abstract
In near future, earth's temperature fluctuation will be considerable. This phenomenon is the result of concentration of greenhouse gases in the earth's atmosphere. Therefore, it seems necessary to prevent of its happening. The biological methods including plant biomass and phytomass and soil are proposed ...
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In near future, earth's temperature fluctuation will be considerable. This phenomenon is the result of concentration of greenhouse gases in the earth's atmosphere. Therefore, it seems necessary to prevent of its happening. The biological methods including plant biomass and phytomass and soil are proposed as the best and practical ways. Watersheds are the greatest physical and geomorphologic units which are contain two important factors soils and plants. So that the current trend of climate change is a double challenge and threat to the sustainability of watersheds. Soil and plant carbon sequestration are economic feasibility act and adaptable to their environment which they can be provided with land management ways by kind of scientific method. Therefore by scientific method of landuse planning, this research has been carried by aims of study of kind landuse on soil carbon sequestration and determines best of landuse in Vaz watershed of Nour city. Soil sampling was carried at the selected different landuse area at two depths of 0-15 and 15-30 centimeters and after analyzing soil organic matters were calculated. Results showed that forests are rich at both depths. But on the farms and orchards, rangelands and rural areas have had least amounts of organic material. Therefore Vaz watershed has 741666 tons of reserve of carbon.
Khosro Shahbazi; ali salajagheh; mohammad jafari; hassan ahmadi; ali akbar nazari samani; mohammad khosro shahi
Abstract
Negative impacts of gully erosion in marl areas are severe due to improper landuse practices such as irrigation, tillage, overgrazing and degradation of vegetation cover. The objective of this research was to evaluate hydraulic flow thresholds of gully erosion in the agriculture (AG), fair rangeland ...
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Negative impacts of gully erosion in marl areas are severe due to improper landuse practices such as irrigation, tillage, overgrazing and degradation of vegetation cover. The objective of this research was to evaluate hydraulic flow thresholds of gully erosion in the agriculture (AG), fair rangeland (FR) and poor rangeland (PR) areas in the Qasre-shirin, Kermanshah, Iran. Nine flumes were performed in the field to determine the critical values of hydraulic parameters including flow discharge, velocity, Froude and Reynolds numbers, Darsi resistance coefficient, shear tension, head-cut dimensions as well as vegetation cover. Results showed that respective critical value of discharge as the gulling thresholds for AG,FR and PR was 1.53, 12.0 and 4.49 li/s indicating significantly higher (p<0.05%) in the FR due to higher vegetation cover. In addition, there were no significant differences for flow disturbance based on Froude number, while the respective value of Rinuldze number in the AG, FR and WR were obtained 3113, 26092 and 9525 significantly higher in the FR. Furthermore, the critical level of shear tension for gully formation in the AG, FR and WR were found 12.12, 14.01 and 9.28 Nm-2, respectively showing significant differences among them. Finally, it is concluded that hydraulic flow parameters as the gully triggering are strongly affected by vegetation cover through landue practices so that higher plant cover in the FR was the key factor resulting in significant enhancement of gully.
D Talebpoor Asl; S Khezry
Volume 63, Issue 3 , December 2010, , Pages 341-358
Abstract
The Mahabad River Watershed has been exposed to severe erosion as a result of landuse change. The aim of this study is to quantify the amount of sediment yield and the relationship between land use change and slope. Different sources such as geologic and topographic maps, satellite images, hydrometric ...
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The Mahabad River Watershed has been exposed to severe erosion as a result of landuse change. The aim of this study is to quantify the amount of sediment yield and the relationship between land use change and slope. Different sources such as geologic and topographic maps, satellite images, hydrometric as well as meteorological data were used to extract and gather the information needed for this research. Six factors including altitude, slope, precipitation, rock erodibility, time of concentration and land use were specified as the most effective factors. The overlapping of the six factors maps resulted in the preparation of sediment delivery potential map. The distribution maps prepared on each of these parameters and their overlaps have shown that areas with more severe slopes are categorized as highly susceptible to erosion. However, in areas with resistant rocks, change of land use has been the determining factor. Comparison of water and sediment discharge data of 1996-97 with 2001-02(similar annual water volume) showed that the sediment yield has increased. Studying land use map prepared using satellite imagery of 1987 and 1998 showed that land use of the area has severely changed from pasture to dryland farming. This factor has also caused the intensification of mass movement recently occurred in the area. Landuse is the only parameter modified by human, and it is the only one which can be quickly and effectively changed. Hence, it seems that the upstream areas in the south and southwest of the basin with low concentration time, steep slope, high erodibility, high amount of precipitation, and the landuse of forest and pasture mixture as well as alluvial terraces with fine and granular sediments are the most sensitive areas which need protecting and control measures.
