Journal of Irrigation and Water Engineering
Year:2011 | Volume:1 | Issue:4|Papers Count:7

In hydrology, although we can not determine the time of flood occurrence, however, by analyzing previous events we can find out the probability of their average occurrences which will be the base for future environmental management programs such as flood control and river marginal planning. In this study several statistical distributions were applied to fit on 7 watershed peak flows at Bohshar province using Analytical Hierarchy (AHP) Process and SMADA software. AHP method and group decision making were used to select the best distribution model. The results indicated 3 parameters lognormal distribution was the best model for 5 watershed including Sarcanat, Jarebala, Sadabad, Ghantareh and Boshigan. The Gumbel and normal distribution was the best model for the watersheds of Kolal and Baghan, respectively. Also, the difference between observed and estimated peak values were lower for the low return periods (<50 years) and the highest differences were for the upper return periods (>50 years).

Kerman province due to special geographic features such as cross the desert and mountainous conditions has specific weather and climate variation and particularly good conditions for cultivation of crops and the garden. Considering the limited threshold of tolerance of plants to meteorological parameters, any abnormalities in these parameters including the occurrence of stress freezing and thaw cycles will be damage to agricultural production. In this research for locating freezing and thaw cycles in the Kerman province, the data of daily minimum and maximum temperatures of 9 synoptic stations was used over 20 statistic years (1989-2008). Also 4 distinct range of temperatures including: the minimum temperatures lesser and equal whit -2 and the maximum temperatures greater and equal whit 2 (A), the minimum temperatures lesser and equal whit -3 and the maximum temperatures greater and equal whit 3 (B), the minimum temperatures lesser and equal whit -4 and the maximum temperatures greater and equal whit 4 (C), the minimum temperatures lesser and equal whit -5 and the maximum temperatures greater and equal whit 5 (D), were presented. After data processing by a computer program into the FORTRAN space, the number of days with this phenomenon for each station was determined as monthly, seasonal and annual, also monthly and seasonal relative frequency are calculated and compared these values with the critical temperature of crops and garden plants, was identified risky areas on province. The investigation of annual graphs showed that Anar station has most days of freezing and thawing cycles during the year. Review of seasonal relative frequency offreezing and thaw cycles show that winter has the most abundance of this phenomenon than other seasons, and two city of Bam and Baft shows higher rate of freezing and thaw in this season. But despite of this topic, because of cold acclimation phenomenon, cold-season cereals and fruit trees have less damage than spring and autumn seasons. Review of monthly results also showed that early planting (in April) fruit trees and crops such as wheat, barley, millet and cotton in the cities including Shahrebabak, Kerman, Kahnuj and Sirjan is risky, while in the cities of Baft, Bam and Jiroft, this plant will not face with damage. Also, since the abundance of this phenomenon in regions such as Shahrebababak, Sirjan and is better be accomplished autumn cultivation (in November and December) of this plants by using of resistant cultivars.

In this experimental study, deferent design methods for baffle sluice gates have been investigated. Baffle modules are considered as a water delivery structure releasing a semi-constant discharge within specific upstream water fluctuations. According to the result of experimental data it was revealed that the performance of this structure is concurred with a desire volumetric water delivery structure and it can be widely used in irrigation channels. Module behavior has been evaluated for both increasing and decreasing of the water depth for deferent design methods. There was no significant effect due to increasing or decreasing of the upstream water depth on the hydraulic performance of the baffle sluice gate. Finally, it was demonstrated that choosing an accurate discharged coefficient can affect the design results significantly. In this regard, the best current design method has been improved based on choosing a suitable discharge coefficient.

This paper studies existing of an empirical equation for the determination of abrasion rate of concrete stilling basins by debris flow sediments’ impact. Mix of friction and impact are modeled by previous researches’ experiments without dividing their share in abrasion and impact. In addition, grains' size were not as big as grains of debris flow in their experiments. Therefore, experimental method is presented for studying the effect of the impact of large grains of the debris flows’ sediment on apron of stilling basins in this paper. According to studied correlation equations between first set of experiments' data, the direct relation between abrasion rate and cumulative potential energy in unite weight of the concrete of the stilling basins is proved. In addition, according to error of linear, power and exponential equations between first set of experiments' data, is verified that the error of power equation is minimum. The equations are verified using second set of experiments. The power equation between abrasion rate and cumulative potential energy in unite weight of concrete stilling basins is recommended. The effect of existing water in stilling basin on reduction of sediment grain's velocity is discussed and it is showed that the reducer effect of water is less than 10% for relative depth smaller than one. In addition, the analysis show that the effect of existing water on reduction of finer sediment of ordinary floods is important and it may reduce the velocity about 90%.

Stepped spillway's are one of hydraulic components of dams that made by straight step's near the spillway's crest to the toe to dissipate energy. In this study to simulate the flow over the stepped spillway, Flow3D software that is analytic flow field was used. The k-e (RNG) model was the turbulence model which had been applied, and to determine the free surface flow profiles VOF model was used. The skimming flow regime was only considered. For this purpose 112 spillway models was designed that from which, 96 models were stepped models and 16 models were smooth models. Stepped models had six configurations, two step sizes and four different slopes (15degrees, 30degrees, 45degrees and 60degrees) below the contact points and also step edges were followed WES profile. Smooth spillways had also corresponding specifications for the slope and crest profiles. The goal of this study was investigating on the effects of discharge, spillway's slope, number of steps, configuration and steps roughness on energy dissipation. It was observed that discharge flowing over the spillway and slope of spillway were among the most effective parameters to achieve the highest energy dissipation on stepped spillways and in higher discharges, the number of steps and its configurations had less effects. Also a mentioned configuration considering the parameters to reach the maximum energy dissipation was introduced.

Scouring will be intensified at the river bend due to the existing of secondary flow in comparison with straight channels so attention to the erosion and its control and mitigation at this part of river is very important. The present paper is aimed to study and design the riprap diameter at bridge abutment in a river bend. In this study first a general non dimensional relationship was developed based on dimensional analysis at the point of incipient motion and incipient failure. Then extensive tests were conducted using three types of riprap with specific gravity of 1.51, 2.05 and 2.65 and sizes of 4.75, 9.52, 12.7 and 19.05 millimeter. Each riprap conducted under four different discharges of 0.017, 0.020, 0.023 and 0.028 m3/s. Each test was started from high flow depth and gradually lowered until the first displacement of rock was observed. The flow characteristics at this point were recorded as incipient motion. Incipient failure defined when all rocks are in motion. Applying the obtained data, formulas were developed to be applicable for design of rock size to control of Scour bridge abutment at river bend. The formulas developed in this research were compared with formulas of earlier studies on riprap at abutment for straight channels and suitable correction coefficients were suggested for these relations to be applicable at river bend.

Rainfall-runoff models are important in the water resource management of river basins. The main aspect of this role is determined through proper use of these models and relies on the quality of their calibration. Mainly, there are two approaches in rainfall-runoff model calibrations. The first one is a simple time consuming trial and error method and is limitedto small problems. The second approach, on the other hand, uses optimization techniques to find proper values of parameters and is capable of handling large scale problems calibrations. This article references an attempted calibration of a precipitation-runoff model using a newly developed heuristic approach called Marriage in Honey Bees Optimization (MBO). The process contains development of simulation-optimization models using the heuristic methods for improving the value of objective function obtained through the simulation of a runoffrainfall Tank model. The results obtained through the application of MBO compares favorably to those of a Genetic Algorithm.