Urban and municipalities management
M. Eshghizadeh
Abstract
BACKGROUND AND OBJECTIVES: Land use change can directly affect rainfall-runoff relationships. The change in land use is an essential factor in runoff production. This research evaluated the effect of urban development scenarios of land use change on runoff in Gonabad city of Iran. The innovation and ...
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BACKGROUND AND OBJECTIVES: Land use change can directly affect rainfall-runoff relationships. The change in land use is an essential factor in runoff production. This research evaluated the effect of urban development scenarios of land use change on runoff in Gonabad city of Iran. The innovation and importance of this work are to determine which land use changes have the greatest impact on the flood discharge in this urban area. Also, determine how much the minimum development of urban green space is to control and reduce peak flood discharge in this city that is located in a dry area.METHODS: The effect of urban development scenarios on runoff was evaluated by the WinTR-55 model in 5 sub-basins of Gonabad city. The main data required for inputting to the WinTR-55 model are sub-area and reach characteristics, curve number, and storm data. The storm data in TR-55 are 24-hour rainfall amounts in a return period of 2, 5, 10, 25, 50, and 100 years. The changes in the maximum flood discharge and flow hydrograph in each sub-area and return period were calculated by the WinTR-55 model under existing land use conditions and 9 scenarios of urban development.FINDINGS: The greatest increase in runoff production was related to the conversion of abandoned fallow and agricultural lands to residential. Also, the most effective increase or decrease of land cover change in peak flow discharge and total flow volume was at the 2-year return period. The decreased effect of the development of green spaces and urban gardens on peak flow discharge and total flow volume was seen only if their development was more than 50%. The average maximum decrease in peak discharge and total flow volume was 22.7% and 16.1%, respectively. While the average maximum increase in peak discharge and total flow volume was 84.4% and 53.9%, respectively.CONCLUSION: The effect of increasing green spaces and urban gardens on the reduction of peak discharge and volume of runoff was also evident in the study area. Land management and preventing the conversion of permeable land uses such as agricultural, gardening, fallow lands, and rangeland will be much simpler and less costly. Urban land use management to prevent urban floods requires the expansion of permeable surfaces, especially green spaces, and urban gardens. These are the important novelty of this research that can be beneficial for future urban developments of Gonabad city and its flood management activities.
Urban civil engineering and related management issues
Z. Khorsandi Kouhanestani; S. Dehdari; M. Jafarizadeh
Abstract
Urbanism directly affects the hydrological cycle. One of the ways to manage runoffs in urban areas that is considered nowadays is green roof creation. Green roof is mainly created in humid and semi-humid areas, and efficiency of green roofs in arid and semi-arid areas has attracted less attention. In ...
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Urbanism directly affects the hydrological cycle. One of the ways to manage runoffs in urban areas that is considered nowadays is green roof creation. Green roof is mainly created in humid and semi-humid areas, and efficiency of green roofs in arid and semi-arid areas has attracted less attention. In the current study, to evaluate the effect of green roof in arid and semi-arid to reduce runoff, an experimental green roof without vegetation was designed in Behbahan city of Khuzestan province in Iran. The city has an arid and semi-arid climate. Experimental Green roof was studied during 7 months. During the study, the data regarding the height of rainfall, soil moisture in different soil layers of the experimental green roof as well as the amount of output runoff were measured. The results showed that the amount of moisture in the surface layer of soil is severely affected by rainfall. The average surface soil moisture has been about 20.5 % and in the deep and middle layers has been 24.8 and 24.1, respectively. In addition, regarding runoff reduction and delays in creating runoff, the results showed that in the observed rain events, in average, 92.2 percent of volume of rainfall has been kept in soil, and has not been converted into runoff. Due to arid and semi-arid climate of the target area and high-intensity of rainfall, green roof can reduce a considerable percentage of runoff.