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Dynamic Flood Analysis and Determination of Flood-Prone Areas for Different Return Periods Using Hydraulic Modeling in the Azar Shahr Chai Drainage Basin
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Mohammad Hossein Rezaei Moghaddam *1   , Davood Mokhtari2 , Tohid Rahimpour2 , Vahideh Taghizadeh Teimourloei2 |
1- University of Tabriz & Iranian Hazardology Association
2- University of Tabriz |
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Abstract: (59 Views) |
Introduction
Today, global warming has led to rising sea levels and increasing heavy rainfall. The impact of global warming on the process of intensifying the hydrological cycle has become an undeniable fact. Many studies have shown that flood risk in response to global warming often appears as an increasing pattern in both occurrence and magnitude at a regional scale. In fact, floods are one of the most common and destructive phenomena observed worldwide and are caused by excessive rainfall, which can take the form of incessant rain that exceeds the carrying capacity of the riverbed, causing water to overflow the river banks and adjacent areas. Floods threaten a large area of fertile land along the river banks, making them one of the worst natural disasters when they occur. To deal with the devastating consequences of floods, a mechanism for flood forecasting, flood warning and risk assessment must be established. In fact, flood prediction and river flood modeling is an urgent need in the present time which has always been a great challenge for researchers in helping administrative authorities in flood management. The present study attempted to identify flood-prone areas around the Gonbarchay and Almaludash rivers in the Azarshahrchay watershed using HEC-RAS software to provide effective solutions for risk reduction and crisis management of this natural hazard.
Materials and Methods
In this study, HEC-RAS was selected to investigate the floodplains of the Gonbarchay and Almaludash rivers located in the Azarshahrchay basin and simulate floods with different return periods for the management of the banks and floodplain; however, due to the lack of access to elevation data for all of the aforementioned rivers with a resolution of 2 meters, only ranges of the rivers in the catchment area, which included 451.9 km of Gonbarchay with coordinates '43 and 37 ° to '44 and 37 ° North latitude and '3 and 46 ° to '7 and 46 ° East longitude, and 571.7 km of Almaludash with coordinates in '40 and 37 ° to '24 and 37 ° North latitude and '3 and 46 ° to '6 and 46 ° East longitude, were modeled. First, the geometric characteristics of the rivers, including the main centerlines, banks, flow paths, floodplains, right and left floodplains, and cross sections with 100-meter intervals, were reconstructed using ArcGIS software and the HEC-GeoRAS extension, and then the prepared layers were transferred to the HEC-RAS software environment for simulation in different return periods. In order to estimate the distribution of flood frequency, the maximum daily discharge statistics of the Germezgigol hydrometric station (Regional Water Organization of East Azerbaijan Province) were used, and flood zones were prepared for return periods of 2, 5, 10, 25, 50, 100, 200, and 500 years, and roughness coefficients for the bed and banks of both rivers were determined using the Coven table and field studies.
Results and Discussion
The results of the study of flood risk affected areas and the area of each of them for different return periods for the Gonbarchay River showed that floods with 2 and 5-year return periods will not pose any threat to the lands adjacent to the river and flooding will only occur in the riverbed. In floods with a 10-year return period, gardens with an area of 15 hectares are known as the largest areas with flood potential in this return period. In the 25-year return period, gardens, pastures, irrigated agriculture and agriculture-gardens are the areas with the highest flood risk potential, which are 16.8, 11.8, 3.7 and 0.36 hectares, respectively. In the 50-year return period, 18.45 hectares of gardens, 12.7 hectares of pastures, 3.87 hectares of irrigated agriculture and 0.45 hectares of agriculture-gardens are at risk of flooding. In a flood with a 100-year return period, 19.30 hectares of orchard land, 13.4 hectares of pasture land, 3.96 hectares of irrigated agricultural land, and 0.45 hectares of agriculture-garden are at risk of flooding. In the 200-year return period of the flood in the study area, 20.3 hectares of orchard land, 13.7 hectares of pasture land, 4 hectares of irrigated agriculture, and 0.54 hectares of agriculture-garden land are at serious risk in the event of flooding. In the 500-year return period, as in the aforementioned return periods, areas of orchard land, pasture land, irrigated agriculture, and agriculture-garden land are at risk of flooding with areas of 21.9, 14.9, 4.14, and 0.63, respectively. Like the Gonbarchay River, in the Almaludash River, there is a flood state within the riverbed during the 2 and 5 year return periods, and no water flows outside the river banks. In the 10 to 500 year return periods, according to the results, the highest flood potential is observed in lands used for pastures, irrigated agriculture, rainfed agriculture, and gardens, which, if flooded, will cause extensive environmental damage to these areas.
Conclusion
Flooding, as one of the natural hazards, has significant impacts on human life and environmental infrastructure. In this regard, the aim of the present study was to identify areas with flood risk potential and determine flood behaviors during different return periods using HEC-RAS in parts of the Gonbarchay and Almalodash rivers in the Azarshahrchay (Silchay) watershed. In the study area of the Gonbarchay River, in the 10- to 500-year return period, the most susceptible areas to flooding were identified as gardens. In the second stage, the lands used for pasture have a high potential for flooding. The third and fourth ranks belong to the lands used for irrigated agriculture and orchards in terms of flood potential. In the study area of Almalodash, the lands used for pastures were identified as the most susceptible areas to flooding, and the irrigated, dryland, and orchards were identified as the next most vulnerable areas to flooding, respectively.
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Article number: 4 |
| Keywords: Almaloodash, Azarshahr chay watershed, Gonbarchay, flood, HEC-RAS |
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Full-Text [PDF 2102 kb]
(48 Downloads)
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Type of Study: Research |
Subject:
Special
Received: 2025/11/10 | Accepted: 2026/04/26 | Published: 2026/04/26
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Rezaei Moghaddam M H, Mokhtari D, Rahimpour T, Taghizadeh Teimourloei V. Dynamic Flood Analysis and Determination of Flood-Prone Areas for Different Return Periods Using Hydraulic Modeling in the Azar Shahr Chai Drainage Basin. جغرافیایی 2026; 25 (92) : 4 URL: http://geographical-space.iau-ahar.ac.ir/article-1-4204-en.html
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