Modeling peak discharge on the Siret River (Romania)

The purpose of this study is to identify potentially flood-prone areas in the section between the Siret hydrometric station and the confluence of the Siret River with the Suceava River.Data related to water flow and specific flow parameters were incorporated into a dedicated hydrodynamic modeling program, in accordance with its requirements (DHI). The construction of the model focused on reproducing the field’s reality as faithfully as possible. Flow parameters were individually configured for each calculation section, taking into account their specific characteristics. Roughness values were determined non-uniformly based on the areas traversed by each cross-sectional profile.Great emphasis was placed on model calibration, using monitored data from the Zvoriștea and Huțani hydrometric stations as reference points. A time series spanning 15 years, including two of the largest floods recorded in the sector, was used. Following the simulation of two scenarios, Q1% and Q0.1%, three types of files were generated, describing the flood boundary, water depth at each point on the boundary surface and water velocity at each point within the flood boundary. Localities and types of potentially flood-prone surfaces were identified on a map using GIS techniques. Furthermore, flood boundary limits from different scenarios were overlaid to quantify areas at risk of flooding. Although the scenarios were simulated on a previously calibrated model, the fact that the simulated flows exceeded the observed flows required several post-calibration steps. In the case of the first scenario, the simulation did not show significant errors, precisely because the Q1% flow is close in value to the maximum flows observed during the calibration period. In the case of the second scenario, the fact that the flow extended to non-specific areas even during historical maximum flows, resulted in stability errors or non-conforming results obtained by the program, inconsistent with research and studies in the field.