جستجوی مقالات مرتبط با کلیدواژه « vegetation » در نشریات گروه « عمران »

Today , the high temperature is one of the main problems in the city, which affects the thermal comfort of pedestrians. Therefore, urban designers and planners should consider the effect of various urban elements such as water elements on thermal comfort. In this study, to investigate the effect of vegetation and water levels on thermal comfort of pedestrians in the city, Envi-met environmental software has been used. The result showed that vegetation and water have a better effect at the same time than when they are used alone and there is a difference of about 0.5-1 degrees in their effectiveness. It is worth to mention that vegetation is a more powerful solution to reduce the air temperature in the hot season of the year. The extent of these cooling effects of vegetation and water levels depends on the distance from them. The radius of the effect of these two elements on air temperature can be observed up to 200-300 meters. The water level has a better effect when it is close to the ground level, and these effects also depend on artificial environment around it including the height and density of the surrounding buildings.

Vegetation has traditionally been viewed as a nuisance and obstruction to channel flow by increasing flow resistance and water depth. However, in recent years, vegetation has become a major component of erosion control and stream restoration. Most of research efforts focus on describing vegetation roughness , determining drag coefficients and empirical formulas for resistance under various vegetation configurations. While the development of experimental solutions for vegetative resistance is important, it is also important to understand the detailed characteristics of flow through vegetation. Yang et al.(2007) conducted flume experiments with different types of vegetation, and found that, in the cases of non vegetated floodplains, all measured streamwise velocity distributions followed the logarithmic distribution, but for vegetated floodplains, they followed an S-shaped profile Nezu and Sanju(2008) have investigated turbulence structures and coherent motion in vegetated canopy open-channel flows. They divided the whole flow region into three sub-zones, i.e., the emergent zone, the mixing-layer zone and the log-law zone. In the present study, some experiments were undertaken herein under different conditions to elucidate the flow structure. The main focus is to examine how the vertical velocities, are affected by simulated vegetation arranged in emergent and submerged conditions. In addition, the effect of dowel density, configuration, and relative depth are examined.

The experiments were conducted in a fixed bed rectangular flume, 9 m long and 0.6 m high and 0.8 m wide. The slope of bed flume was 12 ×10-5. The main channel and floodplain had widths of 24 and 28 cm, respectively, and the main channel had a side slope, s, of 0. The bankfull height, h, was 6 cm. Vegetation were simulated by wooden dowels. The wooden dowels were 140 mm tall and 7 mm in diameter. The dowels were attached to a PVC sheet bolted to the bottom of the flood plain in linear and staggered arrangement. The spacing of the dowels varies from 2.5-10 cm in both lateral and streamwise directions forming stem density of 0.41, 1.64%, 6.04%. The flume was operated under a uniform flow condition, and measurements of discharge, point velocity and flow depth were taken. Flow depths were measured by means of a pointer gauge, discharges were measured by a digital flowmeter, installed upstream of the channel, and a micro propeller current meter were used to velocity measurements. Within the measurement cross section, located at 5.6 m, the authors arranged ten verticals, where the lateral values of y from the first vertical to the last were 0, 4, 8, 12, 12.2, 26 and 34 cm. When the vertical distance from the measurement point to the bed was less than 175 mm, the measurement interval was 10 mm and 5mm in the main channel and floodplain, respectively.

The experimental results are presented in three parts, flow through non-vegetated floodplain first, flow through emergent vegetation second, followed by the submerged case. The effects of density and dowel configuration are included in each of the sections. Each section ends with a discussion on the effects of rigid dowels on logarithmic profile. In the cases of nonvegetated floodplains, all measured streamwise velocity distributions followed the logarithmic distribution, but for vegetated floodplains, they followed an S-shaped profile. It is seen that after implanting the vegetation over the floodplain, the velocity over the floodplain decreases whereas it increases in the main channel. Also, as the vegetation density, λ, increases, velocity increases in the main channel and decreases in the floodplain. In the presence of emergent vegetation on floodplain, logarithmic profile does not exist even in the main channel, however it seems that the formation of the S-shaped profile in the main channel is under the bankfull height and above the bankfull height the vertical velocity profile takes on a logarithmic profile again. Under Submerged flow conditions, the velocity characteristics in all locations above the dowel array are well illustrated by the semi-logarithmic expression that has a slip velocity initially near the inflection point. On the basis of the present experimental results, the whole flow region is divided into the following three sub-zones: (1) Emergent zone (0 ≤ z ≤ hp), (2) Mixing-layer zone (hp < z ≤ hlog), (3) Log-law zone (hlog < z ≤ H). In the present study, hp was equal to 0.2 H and hlog was equal to 0.5 H. In the emergent zone (0 ≤ z ≤ hp) the velocity is almost constant due to strong wake effects of vegetation stems although it may behave slightly in a counter-gradient fashion. In the second zone (hp ≤ z ≤ hlog), the vertical velocity profile are similar in both submerged and emergent conditions, and the effect of bed roughness is completely eliminated and the velocity gradients are reduced and almost fixed. The velocity in the third zone (hlog < z ≤ H) is significantly higher than the velocity in the second zone. In the log-law zone (hlog < z ≤ H), the log-law of velocity distribution for rough beds is reasonably applied even to vegetated flows. Comparison the longitudinal velocity profiles for linear and staggered dowel arrangements indicates an increase in the resistance due to the linear arrangement compared to the staggered arrangement.

In the cases of non vegetated floodplains, all measured streamwise velocity distributions followed the logarithmic distribution, but for vegetated floodplains, they followed an S-shaped profile. However, in the main channel, higher than the bankfull height the velocity profile is logarithmic. The results shows that as the vegetation density, λ, increases, the velocity increases in the main channel and decreases in the floodplain. Linear arrangement resulted higher resistance compared to staggered vegetation arrangement. The velocity profile at all locations above the dowel array are very well represented by the following semi logarithmic expression. In fully submerged vegetation, the whole flow region was divided into three sub-zones, i.e., the emergent zone, (0≤z≤hp) the mixing-layer zone (hp < z≤hlog), and the log-law zone(hlog<z≤H). In the present study, hp was equal to 0.2 H and hlog was equal to 0.5 H.

Rivers can be classified as straight, meandering and braiding, Meandering is the most common plan-form acquired by natural rivers. The meandering channel flow is considerably more complex than the straight channel. Compound meandering channels are abundant in nature that including the main channel for the flow in normal times and one or two floodplain (usually covered with plants) at the sides during floods. Vegetation is an important property of many rivers, enhancing amenity values for people and providing habitat for other organisms. Vegetation stabilizes stream banks, provides shade that performs an essential role in nutrient cycling and water quality and supports wildlife. Therefore, it is necessary to study this issue in order to better understand the flow during floods. This study is focused on the influence of vegetation on overbank flow characteristics. In this research, the effect of non-submerged rigid artificial vegetation in the floodplain on two relative depths of 0.35 and 0.55 has been studied in the laboratory.

The experimental research was carried out in a non-mobile bed meandering channel constructed in a 10 m long and 0.78 m wide flume which included the main channel and two floodplains on its sides. The channel wavelength and meander belt width were one meter and 0.58 m, respectively with the sinuosity of 1.3. The geometrical parameters for the main channel were: width, Bmc=0.2 m and depth, Hmc= 0.1 m. Plastic cylinders of 9mm diameter are used to simulate the emergent floodplain vegetation. A movable weir located at downstream of flume controlled water level. Velocity data were extracted and analyzed using Acoustic Doppler Velocimetry. The minimum recording time for each point velocity was 60s. ADV measures the 3D velocities of water particles located 5 cm below its probe. The measurement sections located 6 m downstream of channel inlet, with the names of S1 to S5.

The results showed that the presence of vegetation in the plain flood for a constant relative depth has reduced the flow capacity. The decrease in discharge for depths of 0.35 and 0.55 is equal to 23 and 12 percent, respectively, for a density of 0.77 percent per unit area of one square meter. The pattern of contour lines of the longitudinal velocity in the main channel in the presence of vegetation changes at both relative flow depths relative to the uncovered state. The absolute values of velocity in the main channel in the uncovered state are greater than in the covered state. Also, the values in the transverse and vertical velocity components in plain floods with vegetation are much higher than in uncovered conditions. The directional secondary vectors of the flow in section S1 indicate a counter-clockwise flow in the main channel. The presence of vegetation at a relative depth of 0.55 has reduced the size and values of these vectors in both the main channel and the floodplain. It seems that the presence of coverage, as observed during the experiments, has changed the patterns and directions of vectors on the floodplain. These changes are also observed at the relative depth of 0.35, but specifically the presence of vegetation at this relative depth has caused the flow transfer from the right floodplain to the left floodplain. For all sections, the average values of longitudinal velocity on both sides of the floodplain are greater than the uncovered state and increase by moving away from the main channel to the glass wall of the channel. Although the capacity of covered flow is less than the uncovered one, flow velocities in and around the main channel seem to be close to those measured in uncovered channel. This indicates the high impact of floodplain vegetation on the hydraulics of the flow in the compound meandering channels. Also, the presence of cylinders has increased turbulence and consequently increased shear stress. The values of shear stress at the bottom of the main channel and the convex coast of the floodplain are higher than other areas. In addition, the cover has increased shear stress in the floodplain and reduced the kinetic energy of turbulence (TKE) in the floodplain.

In this study, using a laboratory model, the effect of non-submerged rigid artificial vegetation on the floodplain of a compound meandering channel was investigated. The following is a summary of the results of this study. The presence of vegetation reduced the water transfer capacity, due to the increased resistance to flow. The average longitudinal velocity of the flow in the cross section of the channel in the uncovered state is higher than in the case with the cover. Due to the non-submerged rigid artificial vegetation used, the shear stress in the floodplain has increased. Keywords: Flood, Flow Pattern, Meander Channel, Relative Depth, Vegetation

of this Research is the study and evaluation of the relationship between vegetation area and water area with the number of birds in Band-e-Alikhan wetland between 2011 and 2015. Due to the importance of Band-e-Alikhan wetland as a seasonal wetland with fresh water, which is located 35 km south of Varamin city, it has been used as a study area. In the present study, first, the necessary pre-processing, ie radiometric corrections, which include atmospheric corrections, banding errors, etc., were performed on Landsat 7 and 8 images, and then the normalized differential plant index maps (NDVI) and water index. Normalized difference (NDWI) was generated using pre-processed images. Then, by examining the histogram of plant and water indicators produced for each year, the appropriate threshold for each index was selected and by limiting the threshold on plant and water indicators produced, vegetation and water area maps were obtained for the year, respectively. . Each year, the maps obtained by the reference data selected manually in this study by satellite imagery were evaluated, the results of which show that the average overall accuracy and capability coefficient of vegetation surface extraction and of water over five years, with89/37% and 81/89%, which demonstrates the successful extraction of these parameters are. By obtaining the effective parameters, ie the level of vegetation and water, between the number of birds and the effective parameters of linear regression, two variables were formed and its coefficients were estimated by the least squares method. The results of studies and evaluations show that the model and regression formed between the number of birds and the parameters of vegetation surface and water area have a coefficient of determination of 0.861 and an adjusted coefficient of determination of 0.582 and indicate the appropriate fit of regression. Then, by the obtained coefficients and regression, the number of birds in 1394 was estimated using the level of vegetation and water area of the same year and was compared with the actual amount of birds in 1394, the results of which showed that the bird population is 93 . 1. It is predicted. The results also show that changes in the environmental conditions of the wetland provide a clear response to changes in bird populations and bird migration.

Vegetation in compound channels by increasing factors such as roughness in the floodplains rather than main channel, velocity difference and momentum exchange between the sub sections, leads the transverse velocity gradient and apparent shear stress of interface to increase. In natural rivers by changing the cross section, uniform flow converts to non-uniform. In prismatic channels, shear stress in the interface between main channel and floodplains, influences the transfer capacity and velocity distribution pattern significantly. This effect in non-prismatic channels, due to the extra momentum exchange between the sub sections is more intense. In such condition identifying the flow hydraulic is very complex. Although forming the vegetated and non-prismatic floodplains at the same time in natural rivers is highly probable, but there are no specialized studies yet to investigate the hydraulic of flow in such conditions. Therefore in the present study, experimental measurements were conducted in a compound channel with non-prismatic and vegetated floodplains simultaneously and flow behavior is investigated on it.

The experiments were conducted in a 10 m long, 2 m wide compound channel located at the National Laboratory for Civil Engineering (LNEC) in Lisbon, Portugal. The channel cross section consists of two equal rectangular floodplains (floodplain width Bfp=0.7 m) and one trapezoidal main channel (bank full height, hb=0.1 m, bottom width bmc = 0.4 m, bank full width Bmc = 0.6 m and side slope of 45°, sy= 1). The channel bed is made of polished concrete and its longitudinal slope is S0= 0.0011 m/m. The vegetated floodplains were obtained by covering their bottoms with a 5 mm hight synthetic grass. For the polished concrete, n= 0.0092 m-1/3s and ks=0.15 mm and for the synthetic grass, n=0.0172 m-1/3s and ks=6.8 mm. Measurements were performed for relative depths of 0.21 and 0.31. The experiments in the non-prismatic channel performed at two convergent angles of floodplains (θ=7.25◦ and θ=11.3◦). In this cases, the mentioned relative depths were set up in the middle sections of convergences by changing the downstream tailgate. The velocity measurements performed for Entrance, Middle and End sections of convergent angles.

high velocity distribution pattern’s gradients are observed in non-prismatic rather than prismatic channel for a given relative depths. Comparisons between similar sections indicates by increasing relative depth, the interaction intensity through the main channel and floodplain decreases. Because, presence of vegetation on the floodplain leads to channel transfer capacity decrease and in high values of relative depth, this effect decreases. Except the areas close to wall and interface, the flow on floodplain is two-dimensional while in main channel and especially in low relative depths is three-dimensional. This issue has also been affected by different convergence angles. The maximum velocity generally occurs near the outer wall of the main channel. But, by increasing the relative depth, position of the maximum velocity moves to the floodplain. In the lower relative depth, in vicinity of interface, a bulge is visible in isovel lines that is already reported in previous works. Due to the mass transfer from the floodplain towards the main channel, this bulge occurred more intensively in the middle sections in both the convergent angels. In non-prismatic channel, for all the flow cases, at the interface, the intensity of the secondary flows is more apparent and in the down part main channel flow, a vortex is formed that by increasing the relative depth from 0.21 to 0.31 and convergent angels from 7.25◦ to 11.3◦, moves from the outer wall of the main channel towards the floodplain. Also at the beginning of the floodplain, one vortex is formed that becomes more apparent by increasing the convergence angles. Due to converging floodplains, in the upper layers, a transverse current is directed from the floodplains to the main channel. This transverse current enters the main channel from both sides and, due to symmetry of flow, plunges to the channel bed and as a result, two helical secondary flows are generated in the main channel, rotating in the channel length which is very important in terms of sediment and pollutant transport. By increasing relative depth, velocity gradient between the main channel and floodplains decreases.

In present study, using an experimental model, flow behavior in a prismatic and non-prismatic compound channel is investigated. Non-prismatic channel consists of two convergence angles; 7.25° and 11.3°. All the experiments are conducted at two relative depths of 0.21 and 0.31. In order to investigate vegetation cover effects, floodplains are covered with synthetic grass and a vecterino (ADV) is used to measure the fluctuations of instantaneous flow velocity. Variations in the streamwise velocity distribution, secondary currents and Reynolds stresses based on proportions of vegetation and non-prismaticity in the flow hydraulic are investigated. Results show for high relative depth, by increasing convergent angles, the floodplains are less involved in discharge carrying and transferring. The maximum velocity values which occur at the main channel center, by increseang the relative depth and extending secondary currents, towards to the floodplains. By increasing the convergent angle, the roughness values in the main channel and floodplains increases. Distribution of flow mean kinetic energy shows that by increasing relative depth, its values in the middle section decreases for both the convergent angles.

Land surface temperature plays an important role in the physics of surface atmosphere interactions. It is at the same time a driver and a signature of the energy and mass exchanges over land. Land surface temperature is highly variable in both space and time mainly as a result of the heterogeneity of the meteorological forcing, land cover, soil water availability, surface radiative properties and topography. Therefore, satellite-derived land surface temperature is widely used in a variety of applications including evapotranspiration monitoring, climate change studies, soil moisture estimation, vegetation monitoring, urban climate studies and forest fire detection. The normalization of the surface temperature relative to environmental parameters is essential in scientific studies and management decisions of urban and non-urban areas. For the first time, a normalization method for topography-induced variations of instantaneous solar radiation and air temperature has been applied to satellite land surface temperature. While land surface temperature data are widely used over relatively flat areas, this new approach offers the opportunity for new applications over mountainous areas. As a significant perspective, such a normalization method could potentially be used in conjunction with land surface temperature-based evapotranspiration methods over agricultural and complex terrain, soil moisture disaggregation methods and forest fire prediction models, among others. In practice, when applyingthe normalized land surface temperature as into to energy balance models, the energy balance would be driven by the mean (instead of the spatially-variable) downward radiation within the study area as it is commonly done over flat areas. The aim of the current study is to utilize the physical model based on the soil and vegetation energy balance equations for normalizing the land surface temperature relative to environmental parameters. For this purpose, Landsat 7 satellite bands, AST08 Surface kinetic temperature, MODIS water vapor product, ASTER digital elevation model and meteorological and climatic data sets were used. In the current work, topographic factors, the radiation which reached the surface, albedo, environmental lapse rate and vegetation, were considered as environmental parameters. For calculating the surface temperature, the single channel algorithm was used. Moreover, for calculating the downward radiation to the surface, the albedo of the surface, lapse rate and vegetation; respectively, direct and diffuss radiation of the solar and neighboring surfaces, a combination of Landsat 8 reflective bands, the digital elevation model, and NDVI index, were used. Finally, by creating the energy balance equations for dry bare soil cover, wet bare soil, fully stressed vegetation and unstressed vegetation, the temperature of various coverages was extracted by exploiting Newton's method and by optimizing parameters of the model in both global and local optimizations and combining resultant temperatures; modeled and normalized surface temperature was obtained. The environmental parameters normalization model is calibrated in two main steps using Landsat land surface temperature observations. The first step minimizes the mean difference between observed and modeled land surface temperature. The second step adjusts environmental lapse rate, surface soil dryness index and vegetation water stress index by minimizing the RMSE between Landsat land surface temperature and model-derived land surface temperature. For evaluating the accuracy of the proposed model results, coefficient correlation indexes and RMSE were used between the modeled and observed surface temperature values as well as the variance of normalized surface temperature values. The results of this study indicate that in global optimization, the values ​​of the correlation coefficient, RMSE and variance for AST08 data were 0.89, 2.6 and 6.44, respectively for Landsat 7 data 0.93, 2.08 and 1.1 and in local optimization mode, the values ​​of these criteria for AST08 data were 0.962, 1.61 and 0.71 respectively and for the data of Landsat 7, 0.977, 1.2 and 0.13. The results of the study showed that, in both global and local optimization methods, the performance of Landsat 7 for normalizing the land surface temperature is higher than ASTER. Also, the use of local optimization method for global optimization to estimate the optimal values ​​of the missing parameters increased the accuracy of normalization results. The investigation of results of the relation between the surface temperature and considered environmental parameters in this study before and after the normalization indicate that the effect of environmental parameters on the surface temperature noticeably reduced after the normalization. Results of the current study imply the high efficiency of the proposed model for normalizing the surface temperature relative to environmental parameters. Generally, the results of the research were an indicator of the efficiency of the proposed model for normalizing the surface temperature relative to environmental parameters.

Rate of change and the destruction of resources of previous years and the feasibility and predict changes of future could be an important step in planning and optimum use of resources and control of non-normative changes for the future. In the last few years due to vegetation changes in the country's western regions fine dusts entry has created many problems for residents in western and central. For this reason, this work focuses on the westernmost region of the country. We apply ETM Landsat satellite images of 2002 and 2012 to predict vegetation changes. Vegetation changes zoning map of the area of study was prepared after geometric correction and radiometric images through combining comparison of images classifications of every two years Using matrix multiplication applications method and appropriate vegetation indices. Our results show among vegetation indices, the SAVI index has the highest correlation coefficient between the quantitative data of canopy cover and its numerical values based on which this index was used to investigating the region vegetation coverage. The vegetation coverage can be categorized in three classes of poor, medium, and fine. In the period of 2002-2012, area of the poor and fine vegetation coverage classes has increased whereas that of the medium class has decreased. The greatest reduction has been occurred in the medium class where the area of coverage decreased from 304 km2 to 173 km2 and the reason for this is the conversion of vegetation areas to desserts. Areas with poor vegetation are the source of fine dusts to the country that require attentions to prevent their extension.

Flow in a compound channel differs from a simple channel due to the strong interaction of flow between the main channel and the floodplain. In this research, flow pattern was investigated in a compound channel without vegetation and with vegetation by parallel arrangement. To study the effect of vegetation density on flow pattern, the ratio of inter-plant distance and plant diameter (L/D) was used, which was set to 3, 8, and 16. Results indicated that longitudinal velocity and depth-averaged velocity of flow in the main channel were lower in the non-vegetated condition than the vegetated one. However, this condition was reversed for the floodplain. Under the non-vegetated case, by moving from the center of the main channel to the floodplain, the depth-averaged velocity decreased until it increased at the interface between the main channel and the floodplain. Later the decreasing trend continued. In the parallel arrangement, with a reduction in L/D ratio, vegetation density increased while longitudinal velocity, depth-averaged velocity of flow, shear stress and flow rate at the floodplain decreased by about 65%.

Studying the extent of resource changes in the past years and assessing and predicting these changes in the coming years can be an important step in environmental planning, land preparation and sustainable development in the future. The catastrophic earthquake at the Sarpole-Zahab occurred on November 21, 2006 in Kermanshah province. This earthquake has caused changes in land cover and consequently changes in natural vegetation and rangelands of the region, in addition to life and infrastructure damage. It is usually difficult and limited to study and monitor vegetation on a global scale and areas of access to field or field data. It is also time-consuming to estimate vegetation in a conventional way that includes an overall estimate of vegetation and does not provide very accurate information. Therefore, remote sensing is a very useful technology that has features such as providing a wide and integrated view of an area, repeatability, easy access to information, high accuracy of information obtained and time saving over other methods. Is preferred. Therefore, satellite data is one of the most effective tools in the field of rangeland and vegetation science. Vegetation indices such as NDVI as well as SAVI soil effect modifier vegetation index were calculated from the VRR vegetation improvement index to evaluate the effect of earthquake on vegetation area and to evaluate natural vegetation recovery rate. The natural recovery rate of VRR plants for the year after the earthquake was 40% for the study area using NDVI index and 39% using SAVI index.

Vegetation can be a significant factor for improving water quality and reducing the concentration of pollutants. In this study, the longitudinal dispersion coefficient and variations of the tracer concentration have been studied using Potassium permanganate (KMnO4) as a non-decayable tracer. The experiments were conducted in a straight rectangular compound cross section with 8 m length, 0.25 m width, and 0.6 m height. Two rows of metal cylinders were used over the floodplain for simulating rigid vegetation. Digital image processing technique with imaging from tracer cloud in Matlab software was used for measuring tracer concentration in three sections downstream of the injection. The results showed that shear flow between vegetation and floodplain wall was invigorated in the presence of two rows of vegetation. Consequently, this shear flow had a significant impact on longitudinal dispersion coefficient. Accordingly, two rows of trees increase the longitudinal dispersion coefficient up to 39.2% in specific relative depth (0.56) compared to non-vegetated case and causes reduction in the concentration of contaminants downstream of the injection section. The results of non dimensional longitudinal dispersion coefficient obtained in this study compared with the empirical relationship proposed by different researchers and the accuracy of each method for estimating the longitudinal dispersion coefficient of waterways combined with vegetation over the floodplain were also investigated. The results showed that the models of Elder (1959) and Deng et al. (2002) predict the longitudinal dispersion coefficient with two rows of vegetation over flood plain with higher accuracy.

Formation of bed forms, such as dunes, is a prominent feature in natural open channel flows with sediment transport. Knowledge of turbulent flow over sand dunes is needed to understand the interaction between the flow, the bed forms and the associated sediment transport. This study presents results of an experimental work aimed at investigating the effect of different dunes and vegetated banks on flow velocity, Reynolds stresses and turbulence intensities. Experimental measurements were made over fifth and sixth dunes in a series of ten of 2-dimensional asymmetric gravel dunes which had dune height of 4 and 8 cm, respectively. These dunes had a mean wavelength of 100 cm, mean lee slope angles of 28º, and width equal to the flume width. Rice stems with a median diameter of 2.7 mm and a stem distribution density of 400 stem/m were used to cover the flume banks for simulating vegetation on riverbanks. From experimental measurements, the effect of different heights of crest of gravel dunes on the characteristics of flow in vegetated flume; and the reattachment points for different heights of crest of gravel dunes were investigated.

Floodplain vegetation affects the flow and pollutant transport in waterways. In this paper, the effect of submergence of floodplain vegetation on the transverse mixing coefficient (ε) in a compound channel with asymmetric section is investigated experimentally. The experiments were carried out with different vegetation densities and relative flow depths. Tracer concentration was measured using MATLAB’s image processing toolbox in three sections downstream of the injection point. The transverse mixing coefficients were calculated by standard method of moments according to the variations of variance of tracer concentration. The results showed that ε increases in the emergent vegetation compared to the bare conditions up to 127 and 114% in the main channel and floodplain, respectively, while these values are 43 and 37% for the submerged vegetation. Also, ε increases with the flow relative depth for both submerged and emergent vegetation conditions. As the relative depth increases from 0.15 to 0.25, the lateral mixing coefficient in the floodplain and main channel increases to 97 and 45% for submerged and to 91 and 42% for non-submerged vegetation, respectively. For a specific relative depth, ε increases with the vegetation density. Finally, it was found that as the vegetation density increases, the difference between ε values for submerged and emergent vegetation conditions increases too. In general, the results showed that both submerged and non-submerged floodplain vegetation affect the lateral mixing coefficient significantly.

Hyperspectral images، with high spectral resolution، have caused vast progress in remote sensing extensions. One of the most important applications of these images is agriculture and forest. The purpose of this research is improvement in classification of various vegetation types over Botswana region by using combination of target detection algorithms and Hyperspectral image. In the first step، target detection algorithms implemented over the preprocessed Hyperspectral image. In the second step، information of target detection algorithms was combined by using the proposed method. Results of the proposed method were implemented for different windows size. The best overall accuracy of the method was 96. 16 percent for 3*3 windows size that its overall accuracy has approximately improved at least 8 percent and uttermost 20 percent with respect to the results of target detection algorithms.

Vegetated floodplains frequently occur in natural rivers. The presence of vegetation plays an essential role in bank stabilization and ecological restoration. The hydraulic resistance due to vegetation on the floodplain typically causes a further reduction of flow velocity and increases the velocity difference between the main channel and the floodplain. As a consequence, a strong lateral shear layer leads to the exchange of mass and momentum between the main channel and floodplain which in turn affects the overall channel conveyance and certain fluvial processes. The goal of this study was to simulate flow velocity in compound channels with vegetated floodplains. The present paper builds on previous work by Tang and Knight and applies it to simulate flow on a vegetated floodplain. This model includes the effects of bed friction, drag force, lateral turbulence and secondary flows, via four coefficients ƒ, C􀭈, λ and Γ, respectively. To validate the 2D model, flume experiments have been conducted in straight compound channel with vegetated floodplains. Six series of tests were undertaken at 2 different bed slopes (S􀬴) and three depth ratios (Dr). The results of a comparison between calculated and measured values of the velocities showed that Colebrook-White equation cannot correctly predict values of friction factor (ƒ) and thus use of Nudging’s equation would be recommended. Five eddy viscosity models were selected from the literature and the best model was introduced, through the best-fit to the observed data.