ghobad rostamizad; ali salageghe; ali akbar nazari samani; jamal ghodoosi
Abstract
One of the types of water erosion and land degradation which causes imbalance, is the gully erosion phenomenon. Land degradation, a broken ecological balance of the land and landscape and risk of falling at biological resources in these areas, the study of the gully, is inevitable and necessary especially ...
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One of the types of water erosion and land degradation which causes imbalance, is the gully erosion phenomenon. Land degradation, a broken ecological balance of the land and landscape and risk of falling at biological resources in these areas, the study of the gully, is inevitable and necessary especially in the Darrehshahr Township. In this regard, Gully 36 number were selected in Darrehshahr area in the ilam province. To this end, were identified environmental factors, Physical - Chemical Soil properties, cover and hydrological properties of gullies tested using aerial photography, the digital maps and field operations. To determine the extent effect these factors on each of the gully geometry characteristics using fuzzy logic and information theory, the membership function and the weights of the membership function of each of the factors was calculated. Then relationship between the independent and dependent variables was obtained by using multivariate regression. Results of statistical analysis using multiple regression (stepwise method) revealed that length of gully with upstream area of the gully, top and bottom width and cross section of the Gully with basin elongation, deep gully with basin elongation and slope curvature, high of head Gully with local slope of the gully and steep walls of gully with percentage cover have a significant relationship. So could be concluded that characteristics of geometry gully in the study area would be a function of the upstream, basin elongation, curvature slope, Local slope of the gully head and the percentage of canopy cover catchment area of gully.
Jamal Mosaffaie; Davoud Akhzari; Saeed Rashvand; Javad Ataei
Abstract
One of the important parameters in the design of flood control structures is to determine flood peak discharge for various return periods. A primary issue of planners in the face with flood is lack of data or insufficient data. One of the most reliable strategies is generalizing the results from sites ...
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One of the important parameters in the design of flood control structures is to determine flood peak discharge for various return periods. A primary issue of planners in the face with flood is lack of data or insufficient data. One of the most reliable strategies is generalizing the results from sites with observed data to ungauged locations. The main goal of this study is regional flood frequency analysis using multiple regression method for Qazvin province of Iran. 8 out of 23 existing hydrometric station were removed because of the short-term statistics and construction of storage dam at upstream. The results of factor analysis showed that perimeter, equivalent diameter, time of concentration, length of main waterway and area were the main variables affecting flood magnitude. The remaining 15 stations were divided into two homogenous regions using cluster analysis. Homogeneity of these two regions was confirmed using homogeneity and heterogeneity tests of L-moments. Based on the best-fit criteria of Zdist, GNO distribution with the statistic of 0.29 has the best fit for the entire region but for one and two homogeneous regions, GLO and GPA distributions with the statistics equal to 0.09 & 1.56 have the best fit respectively. After calculating parameter values for selected distributions, discharges with different return periods were estimated for all stations. Then, regression relations were obtained between peak discharge and factors affecting flood peak for each return periods at two homogeneous regions. Peak discharges at ungauged locations can be estimated for different recurrence interval using these relationships.
Hojatollah Jalilian; Ghobad Rostamizad; Saleh Arkhi
Abstract
The necessity of using discharge data in hydrological designs and regional programming is an unavoidable matter. Unfortunately, malfunctioning of observation instruments, natural disasters and other problems sometimes result in incomplete or missing data. Having of data related to time series is necessary ...
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The necessity of using discharge data in hydrological designs and regional programming is an unavoidable matter. Unfortunately, malfunctioning of observation instruments, natural disasters and other problems sometimes result in incomplete or missing data. Having of data related to time series is necessary for every investigation about hydrometeorology. Thus missing data should be estimated in a proper way. There are different methods for generation of missing data which estimates the data with regard to particular parameters. In this study, we have used four methods including linear regression, multiple regression, Longbein method and Thomas-Fiering method for reconstruction of hydrometric data including monthly and annual discharge, sediment and water quality data. Results showed that among various methods, in 192 cases of reconstruction of monthly average discharge of 17 stations, Longbein and multiple regression methods in 33% and 27% of the cases have provided the best results, respectively. Two-variable regression in 8 of 17 stations had the best answer and it is suitable for estimating of annual average discharge. Also results indicated that we cannot use of relation between discharge-water quality and discharge-sediment to reconstruct data using above mentioned methods in the Sefidroud basin.
