Abstract
Extensive impervious area and the man-made streams are the characteristics of urban areas. In recent years, rapid urbanization has led to change of rural areas into urban areas, and urban runoff will increase as the result of spread and growth of impervious areas. Land use changes, increasing urbanization, unauthorized construction, inefficiency of sewage system and increased impervious surface in urban areas have significant impacts on inundation hazard. Therefore, to manage urban areas and prioritize regions to inundation elimination problems, the area most affected by inundation should be determined. In this study, the Storm Water Management Model (SWMM) is used to simulate the rainfall-runoff in the study area. The simulated runoff in the SWMM model is used as input to the HEC-RAS model and determines inundation hazard zones in 5, 25 and 50 return periods. Then, six factors such as distance from the main channel, slope, land use, drainage density, the main channel slope and elevation were selected to determine inundation hazard map using Analytic Hierarchy Process (AHP). The results showed that the combined model (SWMM and HEC-RAS) was suitable to analyze urban inundation and determine inundation hazard zones on urban areas. Simulated results can be used to develop urban inundation hazard forecasts. In addition, the result of inundation hazard map indicates that 8.2% of the case study is determined as a high hazard zone.
Highlights
Urbanized areas are accompanied by increase in impervious areas such as construction of drainage systems, roads, roofs, destruction of soils structure, and destruction of vegetation due to growth urban area (Hsu et al, 2000; Hung et al, 2018; Kamali et al, 2017; Shuster et al, 2005; Sillanpää & Koivusalo, 2015)
HECRAS is a tow-dimensional (2D) model that developed by Hydrologic Engineering Center (HEC) (Staff, 2008) is one of the most popular model can coupled with storm water management model (SWMM) model
The values of percent of impervious area (%Imperv), width of overland flow (Width) and slope were different in the various subcatchments and can be measured in GIS based on the Digital Elevation Model (DEM) data, land use maps and subcatchment areas
Summary
Urbanized areas are accompanied by increase in impervious areas such as construction of drainage systems, roads, roofs, destruction of soils structure, and destruction of vegetation due to growth urban area (Hsu et al, 2000; Hung et al, 2018; Kamali et al, 2017; Shuster et al, 2005; Sillanpää & Koivusalo, 2015). The HEC-RAS model is frequently used in a river flooding study (Adams III et al, 2018; Gao et al, 2018; Sleiman, 2018), but in the present study, we used and evaluated the HEC-RAS and HEC-Geo RAS extension of ArcGIS10.2 to simulate inundation extents in street and its surface drainage. This hydrological and hydraulic coupled models does not require specific knowledge, nor does it on any commercial modules. Developing hydrological and hydraulic models that provide accurate estimates of urban inundation hazards are important to describe the best strategies for inundation risk mitigation (Ballesteros et al, 2011; de Kok & Grossmann, 2010)
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