Behrooz Mohseni; Benyamin Matinnia; Hadi Razzaghian
Abstract
Determining the precise location of sub-watersheds in flood production is very important. In some cases, it is time consuming and costly to do this by conducting field studies and mapping topographic maps. Today, the new and growing technology of LIDAR active sensor data is used to collect data from ...
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Determining the precise location of sub-watersheds in flood production is very important. In some cases, it is time consuming and costly to do this by conducting field studies and mapping topographic maps. Today, the new and growing technology of LIDAR active sensor data is used to collect data from the ground surface, which operate based on measuring the distance of the laser. In this research, Gorgan Shast-Kalateh forest basin was selected due to various data. In order to prepare sub-watersheds and their characteristics, it is necessary to have a digital elevation model. In the above model, LIDAR and radar data and other sensors were used with spatial resolutions of 1, 12.5 and 30 m, respectively to control the ground data. The streams were extracted using the appropriate model in each method and all types of watershed characteristics were obtained through Arc-Hydro and IDRISI software. The distance index of each stream from others and ground reality were investigated. Comparison of analyses was done in SPSS software. The sig-value for comparing altitudes along the streams for LIDAR with a pairwise t test was 0.13, which shows no significant difference. Comparison of the streams of different digital models between the land 12.5th m and 30th m and LIDAR, the sig-value of 0.002 in Wilcoxon test, shows significant difference. Also, based on the overall conclusion, it was observed that there is a significant difference at 95% probability level, between the methods used. Eventually, LIDAR data had the highest accuracy with ground reality.
Behrouz Mohseni; Hadi Razzaghian; Abdollah Darzi-Naftchali; Esmaeel Nikzad
Abstract
Runoff as one of the water balance components of a basin, is of great importance in watershed and water resources management. Suitable estimation of runoff is requires to determination of runoff coefficient. In this study, runoff coefficient was estimated for return periods of 25 and 50 years using rational, ...
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Runoff as one of the water balance components of a basin, is of great importance in watershed and water resources management. Suitable estimation of runoff is requires to determination of runoff coefficient. In this study, runoff coefficient was estimated for return periods of 25 and 50 years using rational, SCS and Cypress-Creek methods for basins up to 50 square kilometers. GIS software was used to overlay layers and basin analysis. Chow, s table was used to correspondence different methods. Due to the lack of compliance with Chow, s table and estimating lower runoff coefficients than reality in most of the study area, Rational Method did not provide suitable results. Cypress-Creek method was also effective in some basins due to it similarity with the SCS method. Average equivalent runoff coefficient of C25=0.37 and C50=0.41 demonstrated high accuracy of SCS method compared with two other methods. According to the soil conservation service method, minimum and maximum runoff coefficients of 25- year return period were related to Chalakrud 1 (0.06) and Safarood 4 (0.61) watersheds, respectively. Also, the minimum and maximum runoff coefficients of 50- year return were 0.1 (for Chalakrud 1) and 0.65 (for Safarood 4), respectively. According to the results of three methods, the lowest runoff coefficients were obtained for watersheds with the highest area and the lowest rainfall intensity.
