مجله مهندسی آبیاری و آب ایران
پیاپی 19 (بهار 1394)

Estimating of bridge piers scouring is essential for engineers. Since many empirical formulas to predict the scour depth is presented and this formula used various dimensionless and dimensional parameters. In this study, two series dimensional and dimensionless parameters that are expected to be effective on pier scour were selected. Then, parameters affecting the scour were selected using three different gamma test (GT), principal component analysis (PCA) and stepwise regression (FS). Findings indicated that using GT critical velocity and pier length to width ratio are most important dimensional and dimensionless parameters respectively and pier shape is less effective. Furthermore, 360 amounts of training data are required to ensure robust model estimation. Finally, we examine the use of support vector machines (SVMs) for estimating the scour depth using selected input parameters by three methods. The results showed that the accuracy of dimensionless parameters set by all three methods is low, but SVM technique was estimate the scour depth using dimensional parameters successfully. The coefficient of determination of the GT, PCA and FS parameters in test phase is 0.76, 0.69 and 0.73 respectively and RMSE is 0.63, 0.55 and 0.50 respectively. In this study, in order to increase accuracy, two different combinations of input parameters to estimate the scour depths were determined. The performances of SVM and empirical formula for scour depth prediction were compared and results showed that SVM model can be used for predicting scour depth more accurately compared to empirical formula using dimensional parameters.

Note that the border village’s expansion of Khabr’s River of Baft located in Kerman and incursion into river’s sides in recent years, flood damages to rural areas, agricultural Lands and its around gardens a lot. Bed’s slope, existence of river’s meanders, high velocity of water flow, incursion by agricultures into river’s sides induced under cutting and degradation of farms, and in some area caused of overflow and entrance of water into the marginal farms and gardens. The river’s behavior is simulated by HEC-RAS model and succeeding results used for presenting of Khabr river’s flood control scheme. Among the different methods for modification and training of river’s path, At first, building of training wall at river’s watersides was investigated. The model which yields such results, increases foundation depth and water scour depth causing cost will increase. Results of model illustrates that using of two parallel methods i.e. waterside walls and successive dams was investigated in order to decrease the costs. Constructing these Dams results in the total cost is significantly decreased. In order to evaluate the performance of these constructions, specifications of proposed constructions was imported to HEC-RAS model, and constructions’ influence on improvement of conditions was evaluated and confirmed by means of further execution of the model.

Flood forecasting is of great importance in hydrologic planning, hydraulic structure design, water resources management and flood control. Nash’s Instantaneous Unit Hydrograph (IUH) is frequently used for simulating hydrological response in natural watersheds. Rapid development of urban areas affect the hydrologic process of the watershed by decrease in soil permeability, flood base flow, lag time and increase in flood volume, peak of the hydrograph, flood frequency and surface runoff. In this study the influence of land use like urbanization on the significant parameters of the Nash model have been investigated. These parameters calculated using three popular methods i.e. moment, root mean square error and random sampling data generation, in two sub-watersheds with different land uses in the city of Sierra Vista, Arizona. The results showed that in all three methods the lag time of the watershed, which is product of K by n, in natural watershed is greater than urban one, which means more storage in natural watershed. The median of three mentioned method in calibration events were used in remain events for verification. The results showed that all the three method have acceptable accuracy in hydrograph simulation. Some specific upper and lower percentile values of the median of the generated parameters (i.e. 10, 20, 30 and 40 %) were analyzed to future investigates the derived parameters. There is a wider range in parameter values in urban sub-watershed than the natural one in which the efficiency has an acceptable value. It might be due to less uncertainty in urban watersheds where runoff to rainfall ratios are much larger than in the natural sub-watershed.

It is so called inception motion of sediments when sediment particles begin to move in a flow. So far numerous studies have been performed about the determination of inception motion of uniform non-cohesive sediments in the open channels with the positive slope and relations or graphs in this topic have been presented however, there are a few studies about inception motion of non-uniform non-cohesive sediments in the channels with the negative slope. In this research, conditions of inception motion of non-uniform non-cohesive sediments were investigated by using a laboratory flume and dimensional analysis. The 9 samples of non-uniform non-cohesive sediments with different size and uniformity coefficient at three positive slopes 0/0005, 0/001, 0/002 and three negative slopes, 0.0005, 0.001, 0.002 were examined in this experiment. Results showed that by increasing the positive slope, the stability parameter of particle reduces and by increasing negative slope, the stability parameter of particle increases. Moreover, results showed that by increasing particle size parameter, particle stability parameter reduces and by increasing the uniformity coefficient of sediments, particle stability parameter increases.

Drought charachteristics including severity, duration and magnitude and the associated spatio-temporal variability in Karkheh basin was investigated using Standardized precipitation index (SPI) for the period 1965-2000. The results showed that the time variability of SPI series strongly co-vary accros the basin resulting in simultaniusely occurring dry and wet spells in the considered stations though the they may differ regarding to drought severity. Regarding to SPI on 3 month time scale it was found that most of the stations has experienced dry spells in 1966-67, 1970-71, 1973, 1977-78, 1984, 1991, 1995 and 1998-2000 which were very important for the basin regarding agricultural point of view. Though the short dry spells most often occur simultaneously in all stations when shorter SPI time scales are considered, but they are less concordance regarding the initiation and termination of drought when SPI time scale increased. The results also indicate that the basin has experienced between 20 and 23 dry spells among which some last between 9 and 11 months. A survey on SPI series at 12 month time scale also showed that the basin experienced between 7 to 10 long lasting drought events. The most frequent drought events in October (between 11 and 14 cases) were occurred in southeastern and wetern parts of the basin. In November, the northern, northwestern and southern parts of the basin are the regions that frequently hitted by drought ranging between 20 and 24 events. In April and May the northern part of the basin has experienced the most frequent drought events. Overall, it can be concluded that the northen and southern parts of the basin are the more prone areas to frequent drought events.

Rivers are important because they are one of the major sources of water supply for various uses including agriculture, industry and drinking. Considering to importance of this tract and droughts in recent years, protect of these resources is very important. In this study, to survey the chemical quality and trend of water quality parameters was used 37 years of data for Golestan Gorganrood River in Nodeh station that these data are belong to this station. For this purpose, the river's water quality condition is determined using graphics method and annual general trend and different season of the years are specified and determined. Considering to this fact that all observed series were abnormal, we used from nonparametric test of man - Kendall to determine the trends of data. The results of Qualitative analysis showed that considering to Piper diagram of water, Gorganroud river is one of the brackish water types and the base of total hardness, is from hard type. According to the Schuler chart, this region is in acceptable range from aspect of drinking water and the Vylkvks graph results showed that it is can be used for agriculture. The results of trend showed that the most significant parameters in Nodeh station have been rising and significant trend in long-term. In general, considering declining trend of flow discharge in different seasons of year and rising trend of existing salinity in the water, will cause reduction the chemical quality of water for various uses.

Iran is one of dry region in the world. Except the Caspian sea borders and the range and the elevations of Alborz and Zagros, this country often have a dry climate with a little precipitation. The collect rainwater method for different purposes has been used for the long time in Iran. This research has been done for Kalat basin, and conduct to check the appropriate way to determine the location for collecting rainwater. At the first step, the basin was divided to smaller sub basins by GIS software. Then for a period of 18 years (1991-2010) the need of water plant was calculated by Cropwat software. The assumption was that the cropping pattern of all of sub basin was the same pattern with basin area. Then due to lack of rain station, to calculate runoff in the spring, the curve number method was used (SCS). After estimating the runoff created in upstream of any sub basin, by comparing the net irrigation needs in downstream lands with the runoff created in upstream, a convenient location to collect rainwater, was suggested. Eventually, it became clear that it is possible to add 46 percent to irrigation lands.

In this study the SSIIM numerical model has been verified by the experimentally model also the bed topography and three-dimensional velocity components have been compared together. For this purpose the simulation carried out based on experimentally channel model that included the installation of non-submerged T-shape spur dike vertically (with equal ratio of wing to web length) in movable channel bend, that located in outer bank of 90 degree bend at 45 degree of bend. The verifications were done in relative curvature equal to 4 and the results compared in longitudinal, cross and vertical sections that express the capable of SSIIM model in determinations of range and maximum scour and sedimentation amounts and also the value of longitudinal and resultant velocities in channel bend or meandering channel. The second scour hole for numerical model formed in downstream of channel in the output of bend and for experimentally model observed in the range between the spur dike and the output of bend. In case of a rigid bed, due to less complexity of flow and non-movable bed, the transverse velocities are much more consistent with the experimentally model compared to the moving bed.

Sprinkler droplet diameter is one of the affecting factors on the application radius, wind drift and evaporation losses, soil compaction and generally it is sprinkler quality indicator. Determination of the proper drop diameter helps the efficient sprinkler selection to meet technical and design goals. In this research, the intelligent Gene Expression Programing (GEP) method was applied for modeling of mean drop diameter emitted from impact sprinklers. Model input data were included nozzle diameter, operation pressure and distance from sprinkler; and model output was mean drop drop diameter landed at the certain distance from sprinkler. For preparing model inputs, experiments were conducted for 22 nozzle size and operation pressure combinations and considering 9 to 14 spatial steps of 1.5 m intervals. Using digital photographic method and analyzing the photos, the drops drop diameter data were obtained under all experimental conditions. In addition, sprinklers application radii were measured in the experiments. Consequently, by classification of nozzle sizes, operation pressures, measuring distances on one hand and mean drop drop diameters on the other hand and application of GEP method, a model was developed to predict mean drop size in the different distances from sprinkler. Comparisons between model results and observation data showed high accuracy of the proposed model with R2=0.91 and RMSE= 0.402. In addition the simultaneous effects of pressure and nozzle diameter on drop drop diameter were investigated in this research.

Due to newly-installation of drainage systems in the northern Iran paddy fields and special conditions of soils in these areas, performance evaluation of different drainage envelopes has a great importance. In this study, effect of two types of drain envelopes (mineral and geotextile) on the quantity and quality of drainage water of subsurface drains and water table depth was studied in the consolidated paddy fields of Sari Agricultural Sciences and Natural Resources University. During four successive growing successive seasons of rice and canola, from July 2011 to May 2013, discharge and water table depth in midway between of drain lines and the concentration of EC, pH, Na and Cl of drainage water were measured. Average of drain discharge volume with mineral and geotextile envelopes per day was 2381 lit and 2961 lit, respectively. Comparison of amounts of SEW30 (Sum of Excessive Water) in two growing canola seasons showed that geotextile envelope was more effective in lowering of water table depth than mineral envelope. Also, the minimum and maximum of EC were 1280 and 2190 for drains with mineral envelope and 1190 μs/m and 2026 μs/m for drains with geotextile envelope, respectively. Assessment of amounts of SEI (Salt Export Indicator) of soil showed the leaching during growing seasons. According to the results, geotextile envelope was more effective than mineral envelope in draining surplus water and controlling water table in the study area.