Applying 2D MIKE+ hydraulic model for fluvial and pluvial flood inundation modeling: Evidence from a case study in Slovakia

The study aims to simulate the extent and depth of fluvial and pluvial flooding under different scenarios using the 2D hydraulic MIKE+ model in combination with geographic information systems (GIS). As for the fluvial floods, we used steady-state flow conditions for three flood scenarios (Q10, Q100, and Q1000). The modeled flood maps were compared to official flood maps created under the second cycle of EU Floods Directive (2007). Regarding the pluvial flooding, we used the rain-on-grid method, where the rainfall input was set to three constant intensities (20, 40, and 60 mm/hour) under two scenarios: fully saturated soils and infiltration losses. Study area was the Teplica River section (3.68 km) in western Slovakia. Based on the results, the flood extent difference against the official flood maps was 0.009, 0.075, and 0.123 km2 for Q10, Q100, and Q1000, respectively. In case of 20, 40, and 60 mm/hour rainfall scenarios and fully saturated soils, 13.5, 22.1, and 29.2% of the domain, respectively, had flow depths between 0.005-0.1 m while 2.0, 4.2, and 6.1% of the domain had flow depths above 0.1 m. In case of 20, 40, and 60 mm/hour rainfall scenarios with infiltration losses, 6.0, 14.6, and 22.7% of the domain, respectively, had flow depths between 0.005-0.1 m while 0.4, 2.5, and 4.5% of the domain had flow depths above 0.1 m. When the infiltration rates of land cover classes are applied, pluvial flood extent decreases by 58.2%, 34.4%, and 23.2% for the 20, 40, and 60 mm/hour rainfall scenario, respectively.