Abstract
Rapid and uncontrolled changes in land use patterns due to urbanization negatively affect urban rainfall-runoff processes and flood hazard. In this study, a method that included different sustainable drainage solutions, such as green infrastructure (GI) usage for flood hazard mitigation with various scenarios on a geographic information system (GIS) platform within a 1653 ha catchment of the Kağıthane Stream in İstanbul, Turkey is presented. Developed scenarios are as follows: scenario one (SN1) is the current situation; scenario two (SN2) used green roof application for buildings and a permeable surface for roads; scenario three (SN3) used only green roof application for buildings; scenario four (SN4) used a rainwater barrel for collecting roof water, a swale canal for collecting road water, and added additional structures to open areas to observe urbanization; scenario five (SN5) considered multiple GI implementations; and scenario six (SN6) considered full urbanization. The results indicate that greener infrastructure implementation provides benefits in reducing both the runoff coefficient and the peak flowrate, and the flood inundation area and number of structures affected by flood risk were decreased. The integrated evaluation system, which consisted of the geographic information system and the assessment of the 1D HEC-RAS hydrologic model, was applied to evaluate the GI usage and flood mitigation.
Highlights
Global urbanization is proceeding rapidly and has increased in recent years [1]
The aim of this study was to show how flooding, which will occur with increasing urbanization, can be reduced by applying green infrastructure instead of gray infrastructure using the geographic information system (GIS) platform
In Scenario 2 (SN2), the GI solution was applied to buildings and roads and the current flood risk area was reduced by 18.93%
Summary
According to the United Nations, half of the world’s current population live in urban areas, and this rate is expected to increase to 68% by 2050. According to World Bank data, Turkey’s urban growth rate was 31.5% in 1960 and rose to 75.1% in 2018. This rate is well above the world average of 55.2% [3]. The rapid increase in the urban population brings unplanned urbanization, climate change, environmental degradation, and natural disasters such as floods. Flooding can be exacerbated by increased amounts of impervious surfaces produced by urbanization or by natural hazards that reduce the supply of vegetation that can absorb rainfall [5]
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