Jamal Mosaffaie; Amin Salehpour Jam
Abstract
Evaluation of the impacts of past watershed projects provides useful insights for future projects. In this study, the hydrology and water resources status of Akujan Catchment of Qazvin Province has been the object of the study in which the effects of various measures of watershed managements were evaluated. ...
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Evaluation of the impacts of past watershed projects provides useful insights for future projects. In this study, the hydrology and water resources status of Akujan Catchment of Qazvin Province has been the object of the study in which the effects of various measures of watershed managements were evaluated. For this purpose, the changes of water resources discharge, increased infiltration, water storage, peaks and volumes of catchment floods, were compared before and after the implementation of watershed management projects. Results showed that 114000 m3 more runoff storage has been carried out by watershed management operations that 20.1% of this volume was related to the structural operations and 79.9% of it was due to biological and biomechanical projects of the catchment. Results of the flood analysis indicated that the role of structural measures in the change of time of concentration is low and even negative. Therefore the reduction of the peak flow and flood volume at the outlet of the catchment is due to the implementation of biological and biomechanical measures which reduces the peak flows by 42.7, 25.4, 20.8, 17.1, 15.3 and 13.8% and flood volumes by 41.8, 24.8, 20.2, 16.5, 14.8 and 13.3% respectively for the return periods of two, five, 10, 25, 50 and 100 years. Another observation is that the effect of watershed management practices on the reduction of flood peak and volume decreases when the return period of flood is increased.
Behnoush Farrokhzadeh; Sepideh Choobeh; Hamid Nouri; Massoud Goodarzi
Abstract
In addition to climate change, the land use changes as an ancillary factor affects flooding. Thus evaluation of impacts of climate change and land use change (together) on flood situation in the coming decades will open a new way to deal with this phenomenon. In this research, to study the effects of ...
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In addition to climate change, the land use changes as an ancillary factor affects flooding. Thus evaluation of impacts of climate change and land use change (together) on flood situation in the coming decades will open a new way to deal with this phenomenon. In this research, to study the effects of climate change on 2020s in Balighloo Chai Watershed, HadCM3 under A2 and B1 senarios was downscaled with LARS-WG. Results showed an increase between 8.78 to 12.86 percent in average of annual rainfall in 2020s. Average annual temperture increases 0.66 °C in 2020s. After examining past hanges in land use, two scenarios were developed to predict the impact of land use changes on the runoff in the coming decades: the first scenario assumes a constant in current land use and the second scenario assumes continuation of changes rate during past decades in the future. Results showed a decrease between nine percent in rangelands and five percent increase in agricultural lands area respectively in 2020s. In order to simulate the hydrologic system in the coming decades, HEC-HMS model was calibrated and validated using data of past period, and was used with new curve number, impersive area and hytograph estimated for the future decades. Then the coming decades predicted hydrographs were compared to the past ones. Results showed an increase in peak flow and flood volume in April while they will decrease in March, May and June. If land use change occures with climate change, this increase will be intensified.
Seyed Aliasghar Hashemi; Sargis Ghazariyan
Abstract
In this research, two small sub-basins were selected in Darjazin Watershed of Semnan to evaluate the effect of ruck check dams on peak and volume of flood in small watersheds. Two watersheds were chosen as study area in a part of southern Alborz Mountain with arid and semi-arid climate. These watersheds ...
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In this research, two small sub-basins were selected in Darjazin Watershed of Semnan to evaluate the effect of ruck check dams on peak and volume of flood in small watersheds. Two watersheds were chosen as study area in a part of southern Alborz Mountain with arid and semi-arid climate. These watersheds are located in upland of Mahdishahr city and many check dams are constructed for flood control in past few years. All check dams were examined during field operation and their sedimentation were assessed. Results showed that all check dam reservoirs were filled by sediment. In this research, the peak and volume of floods were assessed in three scenarios of 1) watersheds with no check dams 2) watersheds with empty of sediment check dam reservoirs and 3) watersheds with full of sediment check dam reservoirs. HEC-HMS model was used for rainfall-runoff simulation. . Mean comparison test by paired method for all three scenarios showed that flood peak and volume have significant difference at α=1% level. But, flood peak and volume in scenario 2 are computed less than that of scenario 1 and in scenario 3 are computed more than that of scenario 2. On the other hand, flood peak and volume in the scenario 3 slightly decreased by 4.8 and 5.7 percent respectively compared to scenario 1 where is not significant based on the objectives of project.
