Fluvial Flood Inundation Modeling: a Comparative Assessment of 1D and 2D Hydraulic Approach Using MIKE+

Abstract Fluvial floods are one of the most frequent types of floods worldwide. Fluvial flood inundation modeling focuses on determination of at least flood extent and flows depths in studied domain. In our case, the study area was represented by a short upstream reach of the Gidra River, which is located in western Slovakia. The aim of this study was to compare 1D and 2D hydraulic approaches for fluvial flood modeling of three flood scenarios (Q 1000 , Q 100 , Q 10 ) using the MIKE + model and geographic information systems (GIS). The hydrologic input was represented by the officially determined flood discharges. Hydraulic input data were maintained the same for comparison purposes. Both hydraulic approaches were also compared to 2D benchmark (official) flood hazard maps. To quantify the differences between 1D and 2D flood extents and as respect to the benchmark flood maps, we applied five pixel-to-pixel cross-evaluation metrics. The results showed that 1D hydraulic model did not provide sufficiently reliable and comparable results to 2D hydraulic model as well as to 2D benchmark flood maps. Compared to the flood extent of 2D benchmark flood maps for Q 1000 , Q 100 , and Q 10 , the 1D modeled flood extent was lower by 5.59%, 49.63%, and 56.23%, respectively while in case of the 2D model, it was higher by 22.31% for Q 1000 , lower by 0.71% for Q 100 , and lower by 33.58% for Q 10 . We concluded that 1D model is not suitable for producing fluvial flood inundation maps in similar study areas/geomorphological settings and 2D approach should be used instead for practical purposes.