Modeling urbanization of Istanbul under different scenarios using SLEUTH urban growth model

Urbanization competes with other important land uses such as agriculture and forests and makes ecosystem services and biodiversity sustenance a difficult challenge. It can also induce higher runoff peaks, increase the risk of flooding, and affect water quality. Informed planning and decision making, based on clear understanding of the extent of urbanization over time, can reduce these challenges. This can be achieved by investigating the effects of various scenarios reflecting various land-use policies. In this study, four scenarios were developed and their effects on the urban extent of Istanbul by 2050 were investigated by the slope, land use, exclusion, urban extent, transportation, and hillshade (SLEUTH) urban growth model. For this purpose, historical satellite images were used to develop all the input data using appropriate mapping software. The cell-by-cell matching index, which was found to be 0.773, was used as the performance evaluation criterion of the model. The result showed that the model can be used to predict the urban extent of Istanbul under the various scenarios. Accordingly, the total urban extent of Istanbul is predicted to reach 1,962, 1,188, 1,404, and 1,083 km² under Scenarios 1, 2, 3, and 4, respectively. Based on these results, urbanization under Scenario 1 could be taken as the worst scenario because it affects agricultural and forest land uses. As opposed to this, Scenario 4 is the most desirable for the future urbanization of Istanbul because it limits development in ecologically sensitive areas. However, with the implementation of Project Canal Istanbul, it also results in further urbanization within Ayamama and Tavukcu watersheds. Therefore, studying the potential impacts of urbanization under such scenarios in advance on the rainfall-runoff process and the environment as a whole in these areas is recommended so that appropriate actions could be taken to reduce associated risks.