Hazard Analysis on the Rainwater Runoff in Tulcea City, Romania

Abstract

Floods are natural processes. Urbanization and increasing population density, as well as a concentration of economic values in flood prone areas have increased the risks in many regions. Natural flood plains all over the world are being urbanised or used for industrial purposes. Perception of the flood hazard and the associated risks in many cases is low, if not inexistent, particularly in such areas considered to be safe, e.g. behind dams or levees. New spatial planning approaches, though, try to cope with these developments and create suitable flood protection concepts. In this process, the delineation of flood-prone areas is a very important first step. The torrential rains of very high intensity and large amounts of water (Flash Flood), generated in a short period of time, are the main cause of floods in the city of Tulcea. The most useful and comprehensive way to understand the runoff of the rainwater is to use maps from the hydraulic modeling results. This type of results gives a clear impression of the runoff in time and space. For viewing, ArcMap (GIS Software) is used, where the results of running over the same geographic data are loaded. The main results of this type are records that can track the evolution of flows or levels over time. Flood hazard maps of runoff of the rainwater shows that the evolution of the rainwater runoff is natural, taking into account the digital terrain model of the city (as the geographic support of the relief of Tulcea), as well as the state and construction of the rainwater sewage system (the collector size calculations were not made at the current precipitation level). Above all, climate change, that brings more and more extreme hazard events with flows above historical values is another determinant factor in producing the current effects of runoff floods in the studied area.

Keywords

• Floods
• flood hazard maps
• runoff
• rainwater drainage system