MODELING OF URBAN FLOODING AND WATERFALL EFFECT ON STEPPED STREETS IN ISTANBUL, TURKEY

Year 2021, Volume: 22 Issue: 2, 148 - 159, 29.06.2021

Oğuzhan Murat Halat , İlke Ciritci , Gül Yücel

https://doi.org/10.18038/estubtda.811503

Abstract

Flood is one of the most common and deadly natural disasters. Most of the cities are under the threat of flash floods due to precipitation regime changes with global climate change. The existing infrastructure and the stepped streets that were not previously risky in the city create a waterfall effect in heavy rain and reduce street safety. Today, there are more than a hundred stepped streets in the settlement as by topography conditions such as Beyoglu, Sisli and Uskudar, with different type of stepped streets that form a short path in the transportation network. Many researchers studied to calculate discharges through spillways or dam break flows using numerical models. In the study, different step streets related vertically with Meclis-i Mebusan Street in Istanbul are examined in terms of flooding after heavy rains. The data was obtained through on-site observation. Physical properties such as stair length, width, slope, stair shape and railing were taken into consideration during the on-site examination. The step street as staircase models was analyzed with FLOW 3D software according to the selected flood height. In the numerical models examined by CFD method, the maximum speed zones occurring on the staircase during the flood were determined and the critical zones were specified. In this way, it is possible to comment on the impact assessment of stairs by considering water heights and speeds in critical areas. Some precautions are suggested to be taken in line with the data against the flash floods.

Keywords

Disaster, Urban Flooding, Step Streets, Water Effect, CFD Method, Istanbul

References

• https://www.wri.org/blog/2015/03/world-s-15-countries-most-people-exposed-river-floods (last accessed: 27.07.2020)
• [2] Jonkman SN. Global Perspectives on Loss of Human Life Caused by Floods, Natural Hazards, 2005; 34, 151-175.
• [3] Nguyen VT. 3D Numerical Simulation of Free Surface Flows Over Hydraulic Structures In Natural Channels And Rivers’, Applied Mathematical Modelling, 2014; 39(20), 6285-6306.
• [4] Savage BM, Johnson MC, Flow Over Ogee Spillway: Physical and Numerical Model Case Study, Journal of Hydraulic Engineering, 2001; 127 (8).
• [5] Yakun G, Xianyun W, Chigong W, Duo F. Numerical Modelling of Spillway Flow with Free Drop and Initially Unknown Discharge, Journal of Hydraulic Research, 1998; 36 (5), 785-801.
• [6] Song CCS, Zhou F. Simulation of Free Surface Flow Over Spillway, Journal of Hydraulic Engineering, 1999; 125 (9).
• [7] Olsen NRB, Kjellesvig HM. Three-Dimensional Numerical Flow Modelling for Estimation of Spillway Capacity, Journal of Hydraulic Research, 1998; 36 (5), 775-784.
• [8] Kang S, Sotiropoulos F. Numerical Modeling of 3D Turbulent Free Surface Flow In Natural Waterways, Advances in Water Resources, 2012; 40, 23-36.
• [9] Husain SM, Muhammed JR, Karunarathna HU, Reeve DE. Investigation of Pressure Variations Over Stepped Spillways using Smooth Particle Hydrodynamics 2014, Advances in Water Resources, 66, 52-69.
• [10] Aydin MC, Emiroglu ME. Numerical Analysis of Subcritical Flow Over Two-Cycle Trapezoidal Labyrinth Side Weir, Flow Measurement and Instrumentation, 2016; 48, 20-28.
• [11] Ghaderi A, Abbasi S, Abraham J, Azamathulla HM. Efficiency of Trapezoidal Labyrinth Shaped Stepped Spillways, Flow Measurement and Instrumentation, 2020; 72.
• [12] Irzooki RH, Mohammed R.J, Ameen SA. Computational Fluid Dynamics Modeling of Flow over Stepped Spillway, Tikrit Journal of Engineering Sciences, 2016; 23 (3),1-11.
• [13] Rad NI, Teimouri M. An Investigation of Flow Energy Dissipation in Simple Stepped Spillways by Numerical Model, European Journal of Scientific Research, 2010; 47(4), 544-553.
• [14] Eghbalzadeh A, Javan M. Comparison of Mixture and VOF Models for Numerical Simulation Of Air-Entrainment In Skimming Flow Over Stepped Spillways’, Procedia Engineering, 2012; 28, 657-660.
• [15] Lopes P, Leandro J, Carvalho RF. Numerical Procedure for Free-Surface Detection Using A Volume-of-Fluid Model, Journal of Hydro-Environment Research, 2018; 21, 43-51.
• [16] Zhang G, Valero D, Bung DB, Chanson H. On The Estimation of Free-Surface Turbulence using Ultrasonic Sensors, Flow Measurement and Instrumentation, 2018; 60, 171-184.
• [17] Xia J, Falconer RA, Lin B, Tan G. Modelling Flash Flood Risk In Urban Areas, Proceedings of the Institution of Civil Engineers: Water Management, 2011; 164 (6), 267-282.
• [18] Orman ve Su İşleri Bakanlığı (2018) Araştırma Dairesi Başkanlığı Meteorolojik Afetler Şube Müdürlüğü, Meteorolojik Karakterli Doğal Afetler 2017 Yılı Değerlendirmesi, https://www.mgm.gov.tr/FILES/genel/kitaplar/2017MeteorolojikAfetlerDegerlendirmesi.pdf (last accessed : 27.07.2020)
• [19] TS 12576. (2012) TS 12576. Şehir içi yollar - Kaldırım ve yaya geçitlerinde ulaşılabilirlik için yapısal önlemler ve işaretlemelerin tasarım kuralları, Ankara, Türk Standartları Enstitüsü. http://www.erisebilirim.com/Images/ts-12576.pdf (last accessed: 27.07.2020).