# Evaluation of Different Simulation Methods for Analyzing Flood Scenarios in the Danube Delta
## 1 Introduction
Depending on their magnitude, they proportionally affect a certain part of the Delta surface, and especially the settlements along the main branches of the river [12]. The Danube Delta is a very dynamic area, whose main direction of evolution is horizontal and vertical growth. The character of the water level variations in the Danube Delta presents a series of particularities specific to the discharge area of the Danube into the Black Sea. Of course, the variation of the water levels in the Delta is, first of all, closely related to the variation of the water supply at the entry point at the Chilia Coastal, and to the variation in the wind where the water flows into the Black Sea [13; 14]. General practice has shown that floods cannot be prevented. Still, they can be managed, and their effects can be reduced through a systematic process that leads to a series of measures and actions designed to help reduce the hazards associated with these phenomena [15]. The capacity of flood reservoirs is influenced by the scale of each type of river flooding. Similar river flooding, in terms of maximum water level reached and duration, can find the inside area of the delta in different stages of initial accumulation, which contributes to emphasizing the complexity of the flooding phenomenon. Therefore, due to the varied relief and the particularities of the flow regime of each flood, the flooding process across the entire delta becomes particularly complex [16]. Floods in the Danube Delta become natural disasters when they affect human settlements. The vast majority of localities in the Danube Delta are situated in floodable areas, especially those distributed along the main branches of the Danube, presenting a high hazard of flooding [17]. The hazard is determined by the failure of the dams to defend the localities, due to severe river flooding on the Danube and its extended duration. The pressure of the flood exerted on the dyke causes it to give in, especially in vulnerable areas (a breach/rupture is created in a section of the dam), endangering homes and households [18]. For a wetland with a variety of ecosystems and biodiversity, such as the Danube Delta, one of the most important conditions is the water circulation system [19]. Different land use modifications over time of some important territories, by disregarding the effect of the floods, have caused a decrease of the storage capacity of the Delta by approximately 34%, and at the same time, modified the environmental and social characteristics [20]. This area is of great interest for flood analysis because the settlements in the Danube Delta have a long history of destructive events. A good amount of Danube water is taken by the main branches and distributed to the mouths at the Black Sea [21]. In the Danube Delta there is a danger of spillage for dammed areas in places where the dam tamping phenomena (dam falling) has occurred, and even the major danger of infiltration due to the very long duration of river flooding on the Danube [22]. At the same time, there is the permanent danger of erosion, sometimes accompanied by landslides, that endanger homes and households. Identifying the scenarios in which river flooding can occur on the Danube is central in the broader flood scenarios analysis. Once the context of the specific flood problem to be addressed has been established, the hazard of flooding must be identified and analyzed [23]. This involves hydrological and hydraulic analyses using specialized software that models flood phenomena. [24] Some of the key elements resulting from the flood scenarios analysis are flood extension maps, as well as tables and graphs showing the state of play during the unfolding of these phenomena [25]. The first problem that arises when elaborating flood maps is the choice of hydrological situation when the water levels on the main branches are high, and this must be considered and analyzed [26].