Mohsen Armin; mohammadrasul Rajabi; Fatemeh Barzegari Banadkooki
Abstract
we study the loss of fertility by analyzing the sediments retained behind check dams which was designed to control erosion and fixation of longitudinal profiles in the Safarood watershed of Ramsar during the years 1373 to 1388. For this purpose, soil losses were determined by determining the physicochemical ...
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we study the loss of fertility by analyzing the sediments retained behind check dams which was designed to control erosion and fixation of longitudinal profiles in the Safarood watershed of Ramsar during the years 1373 to 1388. For this purpose, soil losses were determined by determining the physicochemical properties of sediments deposited behind the selected check dams and comparing them with the same soil characteristics. In the analysis of physicochemical properties of soil, the results showed that most of the studied soils are of sandy, non-saline, neutral, calcareous and non-sodium. Based on the classification of organic matter, approximately 60% of the studied soils have poor structure and little structural stability and are often in the moderate class of erodibility. In the soil fertility loss section, the results showed that erosion leads not only to the loss of solid mineral components from the soil but also to the loss of organic matter and chemical nutrients. Changes in the properties of a soil due to erosion affect the level of fertility, basically as a result of a reduction of the effective depth. There is a significant reduction in the carbon and nitrogen contents and all macro and micronutrients. The losses of carbon, nitrogen, phosphorus, potassium, sodium, and total calcium and magnesium content in the study area were 6588.26, 1921.78, 19.71, 53.6, 19.89 and 503.13 g/ha/year respectively, which this level of loss is a serious threat to processes and activities related to soil fertility, including vegetation development in the region.
Bita Shiravi; Ali Golkarian; Ali Abotalebi pirnaeemi
Abstract
Check dams, are small dams in the watershed. These dams are constructed in susceptible areas to erosion due to reduce of flow velocity and erosion, control of sediment and flood in upstream of reservoir dams. These structures are made using wood, stone and cement, and Gabion. These structures change ...
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Check dams, are small dams in the watershed. These dams are constructed in susceptible areas to erosion due to reduce of flow velocity and erosion, control of sediment and flood in upstream of reservoir dams. These structures are made using wood, stone and cement, and Gabion. These structures change the hydrological response of the watershed by reducing flow velocity, the channel slope and storage of flow.
Analyzed the effects of these dams before making can be deciding on the correct and efficient implementation of the project as well as better management in order to achieve various objectives effectively. Since the constructions of these dams are effective on flood behavior, this research aims to impact of check dams on time of concentration and reduction of flood peak discharge in the Gash watershed. In this research are used from Puls method for flood routing in reservoir and Muskingum method for flood routing in river due to evaluate the impact of dams, and also flood hydrograph with 25 to 100 year return period was simulated the situation before and after construction of dams. The results showed that the proposed check dams are reduced peak of flow between 75 to 97 percent and flood volume from 73 to 98 percent that shows the positive effects of the construction of these dams in reducing the peak of flow and flood volume. In addition, in different return period with increasing peak of flow and flood volume, reservoir role in reducing peak of flood discharge and flood volume will be decreased. Also time of concentration will be increased between 0.26 to 0.98 hours by Construction of check dams.