مجله مهندسی و مدیریت آبخیز
سال سوم شماره 2 (تابستان 1390)

Earth skin temperature including soil، water، snow، and vegetation surface temperature is one of the main variables in geo-science studies. Generally، spatial distribution of surface temperature is needed in such studies. Spatial monitoring of surface temperature is possible using remote sensing data، and the time series of images provide a continuous spatio-temporal framework required in modeling energy balance of regional evaporation، optimization of energy demands or dispersion of atmospheric pollutions. In this paper، some common methods of surface temperature estimation using satellite imagery were introduced and calibrations of several forms of split window equation were addressed for Sistan area، Iran. Split window method is based on the fact that the atmospheric transmittance varies with wave length and uses a combination of thermal infra-red brightness temperature and emissivity. To calibrate the split window equation، ground observations and 22 NOAA/AVHRR images during 1992 to 2002 were used to develop regression models. Statistical tests were performed to evaluate the equations and coefficients. Ten AVHRR images were used to verify the developed equations. The results indicated that three different forms of split window equations successfully passed the χ2 statistical test. Both، F and Kruskal-Wallis tests showed that they are not statistically different at 95 percent significant level. Therefore، the simplest form of equation was used to derive surface temperature maps in the Sistan region، and is recommended as the most applicable one.

This study is about the relation between erodibility rate and plasticity features of Neogene Marl deposits of Gatchab and Gitcha in southeast of Garmsar. The erosions al feature of Neogene sediments are rill، gully and waterway shapes. The depth of soil sampling for rill and waterway types is from surface to 30-centimeter thickness and for gully one is from head cut and all outcrop of gully bank. The engineering analyses for sediments include liquid limit، plastic limit and plastic index and engineering granulometry. On the basis of engineering classification of soil، the sediment of Gatchab and Siahkoh mountains are fine grained soils with low to very low degree cohesive، consequently low plastic limit and low internal consistency. The comparison of the results between marl units of Gatchab and Gitcha area have shown the M2 unit has low plasticity and high sensitive to erosion to other units M1 and M2. By the way، the M1 unit is high resistance to water erosion in comparison to M3 unit. From all aspect، Abundance of the lime and clay particle amounts is positive effects on decreasing of sensitivity rate to erosion of Neogene deposits. The above mentioned results base on plasticity features of Neogene deposits confirmed by field witness.

Erosion and sedimentation study and design of the distance between spreading channels are basic requirement in flood water spreading projects. Different environmental parameters including topography and slope، soil texture، vegetation cover and flow resistance affect the hydraulic characteristics of the flood water spreading area. So it is necessary to investigate the effect of environmental parameters according to natural conditions and simulation of overland flow. This study was done in the Gareh Bygone plain، in the south of Fasa city. An open hydraulic flume with 120 m length، 0. 4 m width and 0. 25 depth was used to simulate concentrated overland flow with 0. 1 m depth. Three experiments were examined and for each experiment، discharge flow and mean flow depth were measured directly and other parameters such as mean velocity and shear stress were calculated. Erosion or sedimentation depths were calculated by comparing flume bed elevations in the cross sections with one meter intervals. Results of this study show that erosion and sedimentation phenomena were changed with the increase or the decrease in trends of shear stress along the flume and shear stress parameter were also changed with bed slope and roughness coefficient and became maximum at 75 m from the top end of the flume. On the other hand، according to the bed elevations of cross sections in two steps maximum erosion depth occurred at 75 m from the start of the flume which was confirmed with maximum shear stress. So، we can conclude that channel erosion threshold was established in 75 m from the top end of the flume and it can be considered as channel spreading distance.

Due to the importance of water erosion in reducing soil fertility many studies have been done on the quantity of this destructive phenomenon. Tamura and Rogowosky found a meaningful relation between water erosion and Cs-137 loss in soil matrix. This report was the first of application of Cs-137 method to estimate soil erosion since 1974. From 1974، the method has changed gradually and now is used in many studies. In this study، aerial photographs with scale of 1:20000 and topographic maps with scale of 1:50000 were used. 12 transects on the hilly lands (compound and uniform slopes) and 3 transects on the piedmont plain were studied. Surface samples were collected from different slope situations. The situations were collected from different slope situations. The situations were summits، shoulders، back slopes، foot slopes and toe slopes; gamma spectrometer was used to determine the Cs-137 of the samples. Soil erosion and sediment were calculated by Cochanouski (1993) Equation. Results showed that in summit، shoulder and back slope of the compound slopes، erosion is 68. 42، 45. 46 and 51. 16 Ton/ha/yr respectively. On the same situations of uniform slopes 79. 6، 65. 3 and 84. 23 ton /ha/yr of soil losses were expected. In non-erosional situations (toe slopes)، soil loss has been deposited. In foot slopes، i. e. dynamic sites، sedimentation process is more dominant than destructive ones. The correlation between USLE and Cs-137 models were statistically signification with % 95 probability.

Geometrical parameters and river morphology are the main properties of each river which are used for river training، management and protection projects. So approaches to estimate these characteristics of Zohreh River are the main scopes of this research. Zohreh River as one of the permanent river of Persian Gulf basin has 64 km length in Hendijan delta and 169، 90 and 12 m3/s as maximum، average and minimum discharges respectively. Mean High High Water (MHHW) level is 2. 7 m that penetrates 17 km from river mouth upstream. Zohreh River banks are consisting urban، industrial، commerce and fishery activities which are sensitive to any changes on river regime and morphology parameters. Necessity of determining Zohreh River morphology and its changes led us to do research using GIS and field observations methods. Aerial photos (1967)، satellite images (TM، 1989 and ETM+، 2002)، topography map، previous studies and Ilwis and AutoCAD softwares were the materials used in this research. Results have shown two river cut offs which occurred since 1967 and channel meandering increased from 43 meanders to 48. Also sinuosity coefficient decreased from 3. 59 to 3. 06 and mean radius curvature and wave length increased 26% and 0. 06% respectively. According to Korins classification and mean central angle of Zohreh River، it is fallen in extreme developed meanders morphology category.

One of the main factors accelerating soil erosion in the watersheds in Iran is improper management including overgrazing and improper land use changes of pastures into agriculture. This problem is true in the whole Karoon watershed. Therefore، the objective was to study the effects of land use changes on soil loss in Gorgak sub-watershed. The statistical design was split plot design with pasture and rain fed agriculture as main factors. A drop maker rainfall simulator with 40 mm/hr intensity and 30-minute rainfall period was used on five field locations under two soil moisture conditions of air-dry and field capacity and three slope classes of 10-20، 20-30، and 30-40%. A total of 180 sediment and runoff measurements were made using the above rainfall simulator under field conditions for two land use systems of rain fed cereal and overgrazed pastures. All the measurements were done in triplicates (5 fields x 2 land uses×2 moisture content×3 slope classes×3 replicates = 180 plots). The results showed the soil loss under overgrazed and air-dry soil condition was 45. 6 times more than the rain fed agriculture under the similar soil moisture condition. However، the results showed the soil loss under overgrazed and field capacity soil moisture condition was 2. 33 times more than the rain fed agriculture under similar soil moisture condition. Once the soil loss was compared for different slope classes of 10-20، 20-30، and 30-40 slope percent، the results indicated the soil loss under overgrazed and air-dry soil condition were 4. 77، 5. 19، and 2. 34 times more than the rain fed agriculture under similar soil moisture condition. Overall، soil loss under overgrazed condition was 3. 38 times more than rain fed agriculture. Therefore، although most soil conservationists generally believe that the rain fed agriculture in Iran is very improper managed and it has high soil erosion rates but the results of this study showed the overgrazed pastures in the north Karoon watershed need much more priority for any soil loss measures and controls.

The water is life source and the main factor to human development. With increasing population and needs to food، day by day this needs to be evidence. Therefore، to prevent loosing this main source by planning should be done. One of the method to prevent from this lose is runoff control by micro catchments، keeping the moisture and reduce evaporation from soil surface. In this research، in order to introduce the most suitable method to reduce the evaporation from soil surface، to increase the perennial duration of soil moisture، to determine the performance of different treatments and to compare between them، lozenge shape micro catchments was made in sloppy hill side. The main duty of these micro catchments is collecting and conducting the surface water toward the end of the micro catchments and infiltrating the water into the soil which plus the humidity increase at micro catchments down، has considerable effects on increasing the level of the underground water tables and reducing the erosion and sediment production. In this research in order to increase the runoff coefficient، were made 6 treatments and 3 replications at the end of surface micro catchments were isolated by plastic cover so that end of each one of them has been isolated with common and available materials such as greenhouse plastic، gravel and fine and coarse sand and to infiltrate in depth of soil، a filter with 50 cm depth and 15 cm diameter was used. Soil moisture was measured and assessed in two depth 30 and 50 cm، during one year by TDR instrument. The result of research shows the treatment maximum or best treatment in purpose of soil moisture keeping in 30 cm depth is treatment b (plastic cover and gravel embankment) and in depth 50 cm are b، d (b+ with filter) treatments. The amount of keeping soil moisture resulted from kind of treatment than to control treatment in 30 and 50 cm depths are 2. 81% and 1. 62% respectively. The result of monthly variance shows b and d are the best treatments with 95 percent confidence in compare with other treatments. Because of low differences between in two treatment due to keeping moisture، and easy able and low cost، therefore b treatment is selected.