Rainfall-Runoff Model for Flood Risk Management (Case Study: Haraz District)

Hamzeh Ahmadi, Abbasali Dadashi-Roudbari

Abstract


BACKGROUND: Today, due to climate changes, climate risks are the most important challenges and threats to mankind, among which flood is one of the most common hazards. In Iran, due to its geographical location and climatic conditions, this hazard causes loss of lives and enormous financial damages to agricultural land, infrastructure, and settlements of the country every year. Haraz region, as one of the most populous areas in the north of Iran, within the two provinces of Mazandaran and Tehran, Iran, with one of the major transportation arteries, is faced with a flood incident each year. Therefore, this study was conducted with the aim to develop a rainfall-runoff model for flood risk management in the main road in Haraz.

METHODS: The research method was statistical documentary. Due to the purpose and content of the study, the research was based on climatic data, geographic information, and satellite imagery of Haraz region. The numerical model of the Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS) was used for flood modeling. With this model, the hydrograph of each rainfall incident could be produced. The topographical features and hydro-geomorphological of the study area, as quantitative data and in the form of a raster, were defined as topographic profiles. Then, 29 sub-regions were identified. With the completion of the required information, the med-term and long-term return period, and flood hydrograph, the flood plan for the area was determined. Antisense method was used to evaluate the status of regional changes in precipitation.

RESULTS: Increasing trend in precipitation of the area, changes in precipitation time until the end of the season, especially in winter and summer, irregularities in the regional climate system, and the effect of global climate changes and global warming were observed. Based on the model results, in the mid-term and long-term return periods, Tiran and Andvar areas (Iran) were the most susceptible to flooding in Haraz region. The large flood area in the Haraz River was about 300 meters and the small river beds were 20-35 meters. The river flood active zone was about 100 to 150 meters and parts of this area can be flooded periodically. Areas in the southern part of the Haraz region, due to their lack of vegetation and a covering of snow, were more prone to massive runoff and floods than other areas. Due to the existence of such circumstances, comprehensive watershed studies and flood control systems, and establishment and equipping of pre-hospital care stations for times of crisis are necessary.

CONCLUSION: By integrating a geographic information system (GIS) and hydrological models, the interaction effects of physiographic factors and the climate can be studied on the flooding potential of the watersheds. The prioritization of flood potential high risk areas could be performed better through considering the possibility of peak flow, important residential and communication areas, and the role of flood routing in waterways. Considering that the infrastructure of crisis management is prevention, analysis of flood prone areas could be effective in the flood prevention plan. Results of this study were important in the implementation of the flood risk management plans before the crisis.


Keywords


Flood Modeling; Rainfall-Runoff Models; Risk Management; Iran

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