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Volume 18, Issue 64 (5-2024) |
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Investigating the Effect of Check Dams on Flood Hydrograph in an Ungauged Watershed (Case study: Kander Abdolreza, Fars province)
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Ali Reza Nafarzadegan *   , Mohamad Kazemi , Masoud Samiee |
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Abstract: (183 Views) |
Introduction
Flooding is one of the environmental hazards that causes a lot of repeated damage to water and soil resources in different regions of Iran and around the world. Check dams as a mechanical practice have been built in many watershed areas of the country to control peak discharge and prevent soil erosion. Therefore, it is essential to examine the role of these mechanical practices in flood control at the level of watersheds. The current study aims to investigate the effect of the construction of three proposed structures (two masonry check dams and one embankment dam), with spillway heights of 9, 6, and 8 meters, on flood characteristics in Kander Abdolreza watershed, Fars province, Iran. In other words, this study examines whether the construction of these three consecutive structures fulfills the goal of the operation, which is flood control through a significant reduction in peak discharge and flood volume in the study area. Therefore, the most important variables in this study is the flood volume and the volume of reservoirs proposed for flood control. The amount of flood volume is extracted from the flood hydrograph, and the volume of reservoirs is obtained using a contour map and storage-height curves. It is obvious that if the volume of the reservoir is more than the volume of the flood, all the flood will be attenuated by the structure and the runoff would not pass through the spillway of the dam.
Materials and Methods
In this study, the HEC-HMS model was used to simulate the rainfall-runoff process and the reservoir effect of each of the three proposed consecutive check dams on flood characteristics. The study area, Kander Abdul Reza watershed, is located about 27 kilometers southeast of Lamerd city, Fars province, Iran. According to the division of watersheds in the country, it is part of the Kol-Mehran basin which is a subbasin of the major basin of the Persian Gulf and Oman Sea. In this regard, after preparing the required data, including properties related to topography, rainfall, soil hydrologic group, and designed structures, the peak discharge and volume of flood under different return periods were estimated using the HEC-HMS model. Ghahreman-Abkhezr method was also used to estimate the intensity of rainstorms. The characteristics of the flood in the downstream were investigated in the absence of three proposed structures (two masonry check dams and one embankment dam) and in the next step, the effect of these reservoirs/dams on the hydrograph of the flood was analyzed. Due to the fact that the proposed structures are located upstream of the residential area and the highway, the basis of the design of the structures was the flood discharge with a return period of 100 years. Finally, using the obtained results, the percentage of reduction in the peak discharge of the flood under the influence of the construction of each of the reservoirs/dams was determined and compared.
Results and Discussion
The outcomes of SCS unit hydrograph for Kander Abdolreza watershed showed that the flood peak discharge in the return period of 2, 5, 10, 25, 50, and 100 years is equal to 7, 32, 46, 72, 91, and 116 m3.s-1, respectively; so that the time base of the hydrograph varies from 6.5 hours in the 2-year return period to nearly 9 hours in the 100-year return period. Meanwhile, the volume of runoff varies from 1.73 m3 in the return period of 2 years to 1053 m3 in the return period of 100 years. The results also showed that if the three proposed three consecutive structures were built, with a total reservoir volume of 614367 m3, the peak flood discharge would fall from 116 m3.s-1 to 32 m3.s-1 over a 100-year return period. In addition, the outcomes of the simulation of the rainfall-runoff process in the study watershed indicated that the reduction in the peak discharge and volume of the flood after the implementation of the proposed structural measures for the 50-year return period was 84% and 73%, respectively; and for the 100-year return period it was reduced by 72% and 57%, respectively. Thus, according to the results of the simulation of the effect of the designed structures, it can be claimed that the proposed structures for the study watershed would have the ability to mitigate and control floods.
Conclusion
The implementation of the proposed structural measures for the Kander Abdolreza watershed, including two masonry check dams and one embankment dam, in addition to reducing the peak discharge and the volume of flood flows, can stabilize the longitudinal profile of the stream channels, which is useful for the conservation of soil and water resources in the study area. At different return periods (2, 5, 10, 25, 50, and 100 years), the three proposed structures have the required capacity to store runoff and reduce the peak discharge in the study watershed; however, as the return period increases, the role of these reservoirs/dams in controlling the flood and reducing the peak flow decreases. Moreover, the effect of the proposed consecutive structures system on peak flow reduction is greater than the effect of these structures on flood volume reduction.
In general, to increase the effectiveness of the watershed studies plans, it is recomended to include the study of the impact of the implementation of structural measures on the characteristics of flood flows in the service description worksheet of these projects so that the decision to carry out or not to carry out for structural operations in each basin or sub-basin is made based on the simulation results and with more detailed information. In addition, to better evaluate the proposed structural measures for flood control, it is suggested to prioritize the installation of hydrometric stations in ungauged watersheds that are prone to flood generation. |
Article number: 6 |
| Keywords: Hydrologic model, Flood control, Flood mitigation, Peak discharge, Structural measures |
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Full-Text [PDF 1774 kb]
(86 Downloads)
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Type of Study: Research |
Subject:
Special
Received: 2024/01/26 | Accepted: 2024/03/16 | Published: 2024/06/6
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Nafarzadegan A R, Kazemi M, Samiee M. Investigating the Effect of Check Dams on Flood Hydrograph in an Ungauged Watershed (Case study: Kander Abdolreza, Fars province). jwmseir 2024; 18 (64) : 6 URL: http://jwmsei.ir/article-1-1154-en.html
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