Flood Zoning Simulation by HEC-RAS Model (Case Study: Johor River-Kota Tinggi Region)

Flooding of rivers has caused many human and financial losses. Hence, studies and research on the nature of the river is inevitable.However, the behavior of rivers hasmany complexities and in this respect, computer models are efficient tools in order to study and simulate the behavior of rivers with the least possible cost. In this paper, one-dimensional model HEC-RAS was used to simulate the flood zoning in the Kota Tinggi district in Johor state. Implementation processes of the zoning on catchment for return periods of 2, 25, 50 and 100 years were applied with different roughness coefficients. In order to improve the results of flood zoning from the obtained results, it is better to include the items for changing hydraulic platform as a different scenario's problem.The sensitivity of HEC-RAS model to the roughness coefficient, the coefficient of narrowing and opening, and energy slope were examined and observed. The most sensitive on water surface profile is created by the changes in the roughness coefficient. The volume and upstream surface runoff area and stream or flood conditions and physical characteristics of the area (surface morphology, etc.) can be named as the most significant factors that can affect the severity and recurrence of floods in every region.