V . International Scientific Conference on Water, Climate and Environment

1. V. International Scientific Conference on Water, Climate and Environment BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 Impact of Extreme Urbanization on WaterResources and Flood Risk in Sazlıdere Watershed, Istanbul Sezar GÜLBAZ Cevza Melek KAZEZYILMAZ-ALHAN • Department of Civil Engineering, Istanbul University, Istanbul, Turkey

2. CONTENT • Introduction • Objectives • Methodology • Case Study Description • Computer modeling • Results • Conclusions

3. IntroductionObjectives Methodology Case Study Description Hydrodynamic ModelingResults Conclusions Sazlıdere Watershed is an important drinking watershed in Istanbul • Provides 55 million m3 of water • There is a new dam (Sazlıdere Dam) at the outlet of the catchment Sazlıdere Watershed encounters some risks due to: • Domestic and industrial wastewater • Lack of sewer system • Lack of landfill • Rapid population growth • Uncontrolled settlements • Rapid and uncontrolled extreme urbanization • Extreme impervious landuse change

4. IntroductionObjectivesMethodologyCaseStudyDescriptionHydrodynamic ModelingResultsConclusions The aims of this study: Develop a calibrated hydrodynamic model by using EPA SWMM Investigate the impact of extreme urbanization on surface runoff and flood in Sazlıdere Watershed Suggestseveral stream restoration options to prevent floodand water loss

5. IntroductionObjectivesMethodologyCaseStudyDescriptionHydrodynamic ModelingResultsConclusions EPA Storm Water Management Model (SWMM) EPA SWMM is a dynamic rainfall-runoff simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality Continuity Equation Momentum Equation Green-Ampt Method

6. IntroductionObjectives Methodology Case Study Description Hydrodynamic ModellingResultsConclusions SAZLIDERE WATERSHED Istanbul

7. IntroductionObjectives Methodology Case Study Description Hydrodynamic ModelingResultsConclusions

8. Introduction Objectives Methodology Case Study Description Hydrodynamic ModelingResults Conclusions Rain Gauge • Conduit: 173 15 km Main Stream • Subcatchment:177 40 km2 • Junction: 171 • Green-AmptMethod • Diffusion Wave Model

9. Introduction Objectives Methodology Case Study Description Hydrodynamic ModelingResults Conclusions Calibration

10. Introduction Objectives Methodology Case Study Description Hydrodynamic ModelingResultsConclusions ExtremeUrbanization

11. Introduction Objectives Methodology Case Study Description Hydrodynamic ModelingResultsConclusions * Percentage of increase in amount of total water and flood is compared with 10% urbanization

12. Introduction Objectives Methodology Case Study Description Hydrodynamic ModelingResultsConclusions ExtremeStormEvent

13. Introduction Objectives Methodology Case Study Description Hydrodynamic Modeling Results Conclusions Conclusions A calibrated hydrodynamic model is developed for Sazlıdere Watershed. The current stream sections of Türkköse Stream are insufficient to carry the flowrate under typical and extreme rainfall events. A notable increase in the amount of water and flood is observed due to the urbanization in Sazlıdere Watershed.  Unbounded and unexpended extreme population increase and thus extreme urbanization result in an extreme increase in water quantity and flood events. Stream restoration may be a viable solution in preventing such extreme flood events.

14. THANK YOU FOR YOUR ATTENTION