Mohammad Javad Amiri; Hamid Jourkesh; Ahmad Nohegar
Abstract
Introduction: Flood is caused by a sudden increase in the water level of a river due to heavy rainfall, in which excess water flows out of the basin and the riverbed and enters adjacent areas, causing extensive damage to the region's ecosystems and infrastructure. In order to determine and implement ...
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Introduction: Flood is caused by a sudden increase in the water level of a river due to heavy rainfall, in which excess water flows out of the basin and the riverbed and enters adjacent areas, causing extensive damage to the region's ecosystems and infrastructure. In order to determine and implement a strategic plan in the direction of crisis management, understanding the mechanism and development of the flood phenomenon and the amount of runoff created as a result is a priority.Material and methods: In this study, three events of flood on 16 February 2017, 26 March, 2019 and 23 January 2020, when the average rainfall in the Shiraz watershed was 100 mm every three days, were selected and interacted with a synoptic approach. Atmospheric conditions and flood patterns were identified. Next, using by HEC-HMS hydrological model, the amount of rainfall to runoff conversion in each of the sub-basins in the Shiraz watershed was simulated.Results and discussion: The results showed that the maximum precipitation occurs in February and the minimum in July. The maximum annual rainfall is 627 mm in the mountainous areas of Qalat and Golestan and the minimum is 245 mm in Maharloo lake. Synoptic results showed that the establishment of low altitude and cold-water trough at the level of 500 hPa in the eastern Mediterranean along with the establishment of dynamic low pressure system in Iran caused surface air instability in Fars province and by injecting moisture from the Persian Gulf to the massif. The weather has caused floods in Shiraz. The results of rainfall-runoff modeling showed that the highest runoff in Sadra and Qalat sub-basins were 5773 and 5076 thousand m3, respectively, and the maximum peak discharge in Sadra and Qalat was 666 and 389 m3/sec, respectively. It happened at 17:00. The highest volume of rainfall penetration in Qalat and Chenar Rahdar was 5423 and 2546 thousand cubic meters, respectively, and the lowest level of penetration in the Quran Gate was 247 thousand m3, the main reason being the high density of residential-commercial use in this sub-basin.Conclusion: Therefore, it is suggested that in order to manage the flood crisis in Shiraz, controlling runoff produced in northern sub-basins such as Qalat, Golestan and Sadra and increasing the level of permeability can be effective in controlling floods.
Farhad Misaghi; Zeinab Bigdeli; Mostafa Razzaghmanesh
Abstract
Introduction: Urbanization is increasing in the world and the world's urban population is becoming denser in cities. One of the effects of urbanization is the increase in the percentage of impervious surfaces in these areas. Today, many important cities in the world pay attention to the concept of sustainable ...
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Introduction: Urbanization is increasing in the world and the world's urban population is becoming denser in cities. One of the effects of urbanization is the increase in the percentage of impervious surfaces in these areas. Today, many important cities in the world pay attention to the concept of sustainable development in order to reduce the effects of their city development on the quality and quantity of runoff and use modern green management technologies, including the best management methods and development methods with minimal side effects. A green roof is a multi-layered system that covers the roof and balcony of a building with vegetation and by absorbing and keeping part of the rain, and by influencing the processes of evaporation and transpiration, purification, the volume and intensity of the peak flow of runoff, the dimensions The drainage system reduces the downstream and improves the quality of air and water, preserves the beauty of the city and prevents the wastage of building energy.Material and methods: This research was conducted as a field experiment in the Faculty of Agriculture of Zanjan University. The test period was from April to August of 2017. In this research, the effect of the use of super absorbent (zeolite) on the amount of water absorption and retention, the maximum and minimum volume of runoff, the volume of runoff, sediment and the start time of the runoff resulting from rainfall in the rain intensity of 35, 45, 55, 65 and 75 mm/h has been investigated on a green roof with a slope of 5%, in a cold dry climate.Results and discussion: Based on this, with the increase in the intensity of rainfall, the volume of runoff also increases, and the volume of runoff in barren soil is more than the rest of the treatments, and its downward trend is soil containing 1% zeolite, soil containing 3% zeolite, and cultivated soil. Be Also, the volume of runoff increased with the increase in rainfall intensity and the highest value of runoff volume belongs to barren soil. The sediment measured in the runoff also increases with the increase in the intensity of precipitation in the treatments, except for the grass treatment.Conclusion: Barren soil has a very high volume of runoff due to the sealing of its surface layers and clogging of pores. Adding zeolite to the soil significantly reduced the volume of runoff and retained more water than barren soil. The rate of erosion in soil with 1% zeolite was high and the rate of erosion was the lowest in grass. In barren soil, because the penetration of water is low, after a short period of time after the rain, the water flows as runoff, but zeolite has the property and characteristic that when added to the soil, the time for the start of runoff is lengthened by 3%.
