An Investigation on the Effects of DEM Resolution and Stream Delineation Thresholds on the Performance of the Kinematic-wave-based GIUH Model
اصغر
عزیزیان
دانشجوی دکتری سازه های آبی، دانشگاه تهران
author
علیرضا
شکوهی
دانشیار گروه مهندسی آب، دانشکده فنی و مهندسی، دانشگاه بینالمللی امام خمینی (ره)، قزوین
author
text
article
2013
per
Digital elevation models (DEMs), due to their capacity for extracting many of geomorphologic parameters such as: streams network, sub-watersheds area,slope of streams and sub basins have obtained a very important rolein rainfall - runoff modeling. One of the most important issues that affect the results of these models is the DEM resolution and the assigned threshold for artificial river network delineation. In this study, the effect of DEM resolution on the geomorphologic parameters of watersheds and the performance of a kinematic wave based model, called as GIUH, is investigated. The results show that by decreasing the DEM resolution, parameters such as sub-basins' mean slope and the number of streams (specially of order 1 and 2) decrease and the area of the i-th order sub basins and the mean length of the overland flow increase. Moreover, the results indicate that the reduction of the DEM resolution at a fixed threshold causes the peak flow and hydrograph time base to decrease up to cell size of 100 meters and then after experiencing a jump, again decrease with increasing cell size. According to the results obtained, above the threshold of 2%, the difference between the peak flows of different hydrographs at different resolution is meaningful. In a fixed threshold, the time to peak flow is independent of DEM cell sizes.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
8
v.
3
no.
2013
1
18
https://jhyd.iha.ir/article_6411_5c4e4bbd8942d20ce9061f3868a76e0e.pdf
dx.doi.org/10.30482/jhyd.2014.6411
Experimental Study on the Effect of Different Concentration of Wastewater on the Deposition Rate of Cohesive Sediments by using Rotating Circular Flume
میلاد
خواستار بروجنی
کارشناس ارشد سازههای آبی، دانشگاه فردوسی مشهد
author
حسین
صمدی
استادیار گروه مهندسی آب دانشگاه شهرکرد و رئیس مرکز تحقیقات منابع آب
author
text
article
2013
per
Sedimentation in water conveyance channels is one of the main problems in the operation of irrigation systems. In recent years, wastewater has been used in agriculture. This may affect the rate of the channel sedimentation. In order to assess this matter, some experimental tests were conducted in an annular flume. In these experiments the velocity and the shear stress profiles were measured using an Acoustic Doppler Velocimeter (ADV). During the experiments, deposition rate of the sediments were determined by using the measured suspended sediment concentration. The results showed that adding 30% to 60% wastewater caused deposition rate of the sediments to be increased at a rate of 39%. In this work a significant difference between the effect of 30% and 60 % wastewater concentration was not observed. For all experiments, it was observed that the arrival time for deposition of a certain amount of suspended sediment in a fluid- containing wastewater occurred in a shorter period of time.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
8
v.
3
no.
2013
19
28
https://jhyd.iha.ir/article_6412_993fee656cb070de815675ed7b723ed1.pdf
dx.doi.org/10.30482/jhyd.2014.6412
The Effect of Diversion Angle on Flow Pattern and Sediments Transportation around the Intake Mouth in Sinuous River
منصور
ابوالقاسمی
استادیار، مؤسسه تحقیقات آب
author
text
article
2013
per
Secondary current in the river bend causes transportation of the river bed sediments towards the convex bank. Several parameters affect the rate of sediment diversion to the intake. In this research, the effects of intake angle on sediment rate were investigated in two extreme angles, 52 degrees (the gentle angle) and 90 degrees (the sharp angle), under various discharges and flow diversion rates. The results show that the outflow capacity of intake in 52-degree is higher than 90-degree about 21 percent for various discharges. Therefore, it is possible to decreases the width of intake mouth in 520 diversion angle proportionally. Comparison of the sediment diversion rates in two angles shows that, in case of intake with 90-degree diversions angle, up to 22 percent, less sediment diverts into intake mouth, compared with 52-degree diversion angle. At this angle because of the quick rotation of flow surface towards intake mouth, the angle between surface flow and bottom flow increases (about 90 degree), and the power of secondary flow, increases, and consequently decreases sediment entry into intake. Secondary flow power in intake mouth causes by secondary flow in the bend and diversions angle that is identified by Psec Index. By increasing the flow rate diversion in 900 diversions angle, the domain of flow diverted into the intake mouth expands more than the width of bend and approaches to the moving sediment bar in the inner part of the bend. This flow acts the same as flow in the outer bend of the river but with higher potential for sediment transportation progression. At the 52-degree angle, the flow rotates with a minimized angle by diverting a part of river flow into the outer bend. Therefore, at the lower angle in flow diversion and intake alignment, the power of secondary flow becomes weaker than the 90-degree angle. This results in lower rate of up to 22 percent more sediment diversion into the intake compared with 90-degree diversion angle.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
8
v.
3
no.
2013
29
43
https://jhyd.iha.ir/article_6413_543587d0c120dd2a8fc1620f89b01cc0.pdf
dx.doi.org/10.30482/jhyd.2014.6413
Analysis and Prediction of the Kashkan River Flow using Chaos Theory
مسعود
انیسحسینی
دانشجوی کارشناسی ارشد مهندسی رودخانه، دانشگاه صنعتی جندیشاپور، دزفول
author
محمد
ذاکرمشفق
استادیار گروه مهندسی عمران، دانشگاه صنعتی جندیشاپور، دزفول
author
text
article
2013
per
In this paper, flow of the Kashkan River was analyzed through chaotic viewpoint regarding the daily discharge time series. At first, time series noise level was evaluated by the Gaussian Kernel estimation and wavelet transform methods. In addition, statistical behavior of time series was studied using autocorrelation and partial autocorrelation functions. Then, in phase space reconstruction by lags method, Average Mutual Information and False Nearest Neighbors methods were used to recognize the optimal delay time and embedding dimension, respectively. Subsequently, fractal dimension of system had been estimated using the correlation dimension method. In addition, sensitivity to initial conditions examined by Lyapunov exponent method and finally, prediction has been made using the local approximation method. Decrease of false neighbors due to increasing the embedding dimension, shows the existence of fractal attractor in system's phase space, which beside positive Lyapunov exponent obtained, suggests the condition of a chaotic system for river flow in the Kashkan basin. Following these results, forecasting had been made using local approximation method in the base of reconstructed phase space and satisfactory accuracy obtained, indicate the usefulness of chaos theory-based methods to analysis and prediction of river flow in the Kashkan basin. This efficiency was emphasized using comparison between local approximation and genetic programming results.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
8
v.
3
no.
2013
45
61
https://jhyd.iha.ir/article_6414_dbfd6fca2808009947de4ffe25ac5987.pdf
dx.doi.org/10.30482/jhyd.2014.6414
Depth-averaged Velocity Distribution in Compound Channel with Vegetated Floodplains
مرضیه
محسنی
دانشجوی دکتری سازههای آبی، دانشکده کشاورزی، دانشگاه تربیت مدرس
author
جمال
محمد ولی سامانی
استاد گروه سازههای آبی، دانشکده کشاورزی، دانشگاه تربیت مدرس
author
سید علی
ایوب زاده
دانشیار گروه سازههای آبی، دانشکده کشاورزی، دانشگاه تربیت مدرس
author
text
article
2013
per
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, , 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 ( ) 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.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
8
v.
3
no.
2013
63
75
https://jhyd.iha.ir/article_6415_7a4b2b05eabc32ca2a994d6661d00e6b.pdf
dx.doi.org/10.30482/jhyd.2014.6415
Optimum Design of Levees Considering Hydrologic, Hydraulic and Economic Uncertainties by Monte Carlo Method
معصومه
بهروز
دانشجوی کارشناسی ارشد، دانشکده عمران و محیط زیست، پردیس فنی-مهندسی عباسپور، دانشگاه شهید بهشتی
author
سعید
علیمحمدی
استادیار دانشکده عمران و محیط زیست، پردیس فنی-مهندسی عباسپور، دانشگاه شهید بهشتی
author
جلال
عطاری
استادیار دانشکده عمران و محیط زیست، پردیس فنی-مهندسی عباسپور، دانشگاه شهید بهشتی
author
text
article
2013
per
Design, analysis and operation of flood control systems are subjected to several uncertainties due to inherent behavior of flooding and random errors associated with measurements. One of these issues is, the design of levees that collaborated with hydrologic, hydraulic and economic uncertainties. In this paper, for the design of levees considering these uncertainties a stochastic optimization model based on Monte Carlo simulation has been developed. The resulted model is a nonlinear stochastic model that has been solved by LINGO-13 software. A reach in the Moali-abad river in the north of Shiraz city, has been considered as case study. Obtained results are compared with results of deterministic model. According to the results of the of model, a 20-year return period flood like deterministic model had highest annual net benefit and was selected as the design flood. Unlike the deterministic model, that every output (design parameters) is single valued, stochastic model gives a range for each parameter. Thus the statistical distributions of these parameters are also obtained.
Journal of Hydraulics
Iranian Hydraulic Association
2345-4237
8
v.
3
no.
2013
77
93
https://jhyd.iha.ir/article_6416_9db07db45e6f0e2ab43dd8e6a0dc3bc3.pdf
dx.doi.org/10.30482/jhyd.2014.6416