Nadergholi Ebrahimi; Alireza Eslami; Fourod Sharifi
Abstract
Climatic conditions in arid and semi-arid regions, poor vegetation cover and mountainous conditions of watersheds concentrates surface water as floodwater and cause vital and financial damages in industrial, urban and rural areas. Runoff threshold is one of most important factors in accurately estimation ...
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Climatic conditions in arid and semi-arid regions, poor vegetation cover and mountainous conditions of watersheds concentrates surface water as floodwater and cause vital and financial damages in industrial, urban and rural areas. Runoff threshold is one of most important factors in accurately estimation of flood volume and intensity for designing and securing constructive projects which saves expenses and leads to optimum dimensions of structures. In this research, rainfall simulator was used to investigate the effective factors on runoff threshold. Rainfall intensities of eight to 40 mm/h in periods of 15, 30, 60 and 120 minutes were simulated and runoff thresholds were measured. Acceptable methods for estimation of runoff threshold were introduced based on rainfall characteristics and pedology and geology parameters using measured data and multivariable linear and nonlinear regression methods. Results demonstrated that the rainfall volume and intensity as climatic factors, vegetation cover and slope as terrain factors and soil texture as pedologic factors are the most effective ones in runoff threshold. The relation of independent factors and their partnership in runoff threshold is statistically acceptable for the research area. The results showed a significant correlation (R2=0.98) between estimated and viewed runoff threshold.
Alireza Eslami; Jahangir Porhemmat; Nadergholi Ebrahimi
Abstract
Quantitative analysis of runoff and estimates of stream flow in gauged basins and its transferring to ungauged sites has special importance for water resources planning, watershed and agricultural lands management, as the layout and optimal design of diversion structures and flow control need runoff ...
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Quantitative analysis of runoff and estimates of stream flow in gauged basins and its transferring to ungauged sites has special importance for water resources planning, watershed and agricultural lands management, as the layout and optimal design of diversion structures and flow control need runoff information with different probability levels. In this research, runoff information of hydrometric stations which located in river catchments of Isfahan, Markazi, Qom, Tehran, Hamadan and Qazvin provinces was collected and investigated. In this regard, such stations which included data with the appropriate quality and quantity were selected in a common period of time. In this case study, results of cluster analysis concluded three homogeneous regions of watershed based on independent variables. According to mean annual runoff probability analysis; the best statistical distribution was fitted and runoff values were determined with return periods of 2 to 100 year. Also, regional runoff models based on hydrological and morphometric parameters were extracted with different return periods for each homogeneous region. In each homogeneous region, evaluation of regression models obtained was carried out using a number of hydrometric stations control. In this case study, area, average slope, main river slope, length and gravilus coefficient of watershed were detected as the most influential parameters in estimation of runoff. Root Mean Square Error (RMSE) for models represented minimum values of 1.2, 5, 7.6 with two years return period and maximum values of 14.4, 32.8 and 18 with 100 years return period in the first, second and third homogeneous groups , respectively.
