Journal of Irrigation and Water Engineering
Year:2011 | Volume:2 | Issue:5|Papers Count:7

River confluence is an important element of river system. At this place, because of complex three dimensional flow structure, scour and sedimentation is occur which can damage the surrounding area, change river morphology and can be harmful to navigation. Many variables can effect the sedimentation pattern at river confluence such as bed load coming from the main channel which has not been studied in the past. Therefore it is the main goal of this study to experimentally investigated the effect of bed load. To do so first a general non dimensional relation was developed, then a sediment feeder was designed and calibrated. Afterwards, series of experimental tests were conducted in various hydraulic conditions and sediment discharge. The results indicate that increasing the amount of bed load sediment, reducing the maximum scour depth from up to 35 percent. Also it was observed that bed scour and sedimentation patterns can change when the bed load is presented. Finally, an equation was developed to predict the scour depth in terms of sediment load. The accuracy of the new is within 95 percent. The sensitivity analysis of this equation shows that it is more sensitive to Densimetric Froude. The new relation was compare with Ghobadian and Shafai Bejestan (2007).

Drought is caused decrease by of rainfall, runoff and soil moisture and also increase of air temperature and water table compared to long time average condition. Drought can be divided into four major groups of Meteorological, Hydrological, Agricultural and Social- economical which meteorological drought will be evaluated by rainfall values comparing with its average. In this study, by use of monthly rainfall data of Babolsar, Noushahr and Ramsar synoptic Stations which are related to Mazandaran Meteorological Organization, Drought events was quantified by Standardized Precipitation Index (SPI), Percentage of Normal Index (PNI), Deciles Index (DI), Chinese Z Index (CZI), Modified Chinese Z Index (MCZI) and Z- Score Index and Mohan & Rangacharia method. Results shows that PNI and DI in all stations have similar trends and the Curves of SPI, ZSI and CZI in all stations are well coincide with each other and have a very good fitness but MCZI.In Mohan & Rangacharia method, drought events characteristics consists of commencement, termination, duration and intensity were determined for all stations. Applying this method for preparing iso-duration and iso- intensity maps of drought (Drought zoning) for determination of the drought susceptible area and also forecasting the future condition are recommended.

Soil is one of the most important of natural resources in each country. But soil erosion is threat for human health and welfare which causes inside and outside regional probelems. Gully erosion is one of the erosion advanced and severe type which causes topsoil loss. Therefore, the aim of present study were morphoclimatical and pedological comparison of gullys formed in the two watersheds of Zohreh and Maroon which are located in sensitive Gachsaran and Mishan formations to erosion. This study was done by field operations such as; mapping, marking and sampling of gullys soil at different distance of headcat. Data was analyzed by EXCEL software. The resoults shows that variations of EC, ESP and SAR are more in Gachsaran formation with respect to Dehdasht climate. This difference were caused by the different amount of salt in soil. Therfore, soil erosion in Gachsaran is more than Dehdasht. So that general profile form of gullies in Dehdasht region were linear and palmate forms while in Gachsaran region (Deg-seliman and Drila) are usually unlinear and palmate forms. Headcat profile of gachsaran and Dehdasht regions were were caves and plantcover respectively. The result of soil stability pieces shows that; upper soil horizon of two regions were in class VII (sewelling) and lower soil horizon were in class I (complete despersion).

Most construction materials required for construction projects directly or indirectly supplied from nature. In fact, the resources of construction materials are formed from geological formations or rock units or sediments caused by erosion them in nature. Thus to exploration of construction materials, not only the engineering characteristics and physical properties of geological formations which selected as the mining of construction materials can be estimated from geological data, but also can play an important roles in the region for recognition and determination of the regional resources potential.This paper is a summary of study of the exploration borrow materials resources to use for hydraulic structures in the coastal area of south of IRAN (flood control project for South Pars Energy Zone). In this study, the potentials for various materials have been identified using regional geological information such as lithology of rock units, the description each of them, the conditions of their formation and their depositional environments and the geological structures and phenomena which effect on them. The potentials of region were prioritizing using the above data and other parameters (such as volume, availability...). Also, this knowledge can help to determination of the sampling points and the selection of optimized materials with the lowest risk of considerable. Results this research shows that rock layers with the same litology belonging to different geological formations can have different properties due to various condition of formation. Thus, the regional geological data and geological engineering knowledge can help estimate the engineering characteristics and physical properties of geological formations and determine regional potentials, cost reduction and reduction of duration of studies at various stages of study of the construction materials.

Due to water use increasing, attention to optimal water resources allocation is needed. In Iran, due to lack of rainfall in most watersheds and limitation of water resource, planning is very essential and inevitable to identify facilities and the limitation with the aim of optimum operation. In recent decades, the use of intelligent evolutionary methods for optimization of water allocation was more focused by researchers. Genetic algorithm is one of the new optimization methods which were more applied for complex and nonlinear problems. In this research, Alavian dam and Sufi-chay irrigation and drainage network in downstream of dam was considered. The agricultural lands include four regions with different areas. The results indicated that the difference between the average amount of allocated and optimized water in various regions was equal to 2.1 MCM per year. The average area under cultivation from actual values was 3 percent more than predicted values of water resources. Based on optimal cultivated areas, the benefit from sailing agricultural product has oscillation and does not specific trend.

Design storm estimating is one of the main step in designing and getting the size various structures and hydraulic installations. In some causes by which the capacity of system storage is considerable or returned period of design flood is long such as designing of the spillway of dams using of mathematical model for converting design storm to design flood is usual. In drawing pilgrim method a collection of registered severe rains at studied stations according to 8 base of time (1, 3, 6, 9, 12, 18, 24 and 36) is chosen. Then non-dimensioned cumulative chart is drawn on sheet and cumulative curve of average rain is exploited from each of mentioned continuations. In the Pilgrim method all rains of each continuation are considered and determined being meaningful or meaningless calculated patterns after determining of agreed tables and X2. In half method time distribution of rain is considered in the form of possibly distribution. In this method the shower of specified continuation depends on where the rainfall will be occurred in time-quarter are classified into groups. First shower quarter, second shower quarter, third shower quarter & forth shower quarter. Then the time-distributing of rain in each group is designed by two rainfall curves in from of cumulative rain and continuation of rain. It is represented in the form of 25% from the total time of rain. This methods are done in each of stations, and regional type patterns are gotten by using of all occurred rain. According to the obtained results of pointed possibly patterns, we can say that in the southern regions of province the most rainfalls are in the first quarter rain and in the south and eastern south are in the third quarter rains. The most observed rains in province are in first quarter and third quarter showers. According to the regional patterns, the rain of 1 and 3 hours are in the first quarter, the rain of 6 and 24 hours are in the third quarter and the rain of 9, 12 and 18 are in the forth quarter. The rain of 36 hours is in the first quarter.

Cluster microforms are a type of small scale bedform found in the surface layer of some gravel bed rivers. These bedforms are comprised of discrete, organized groupings of particles that sit above the average elevation of the surrounding bed. As part of the structural organization of the bed, clusters are believed to impact the local dynamics of the fluvial system through the feedback process involving the flow field, entrainable sediment, and stable bed morphology. To investigate the effects of the cluster on average and turbulent characteristics a laboratory model has been used. An acoustic Doppler velocimeter (ADV) has been used to measure average velocities and fluctuations. Results of this study show that compared with nonclusterd bed, clusters have significant effects on flow characteristics. Clusters cause to change the location of maximum RMS (root mean square) and Reynolds shear stress and move it upward. Clusters create a shear layer downstream of it. The results of analysis show that one can distinguish five different areas over a cluster: flow acceleration up the stoss-side of the cluster; recirculation behind the cluster in the wake region; vortex shedding from the pebble crest and shear layer; flow reattachment downstream of the cluster; upwelling of flow downstream of the point of reattachment; and recovery of flow.