Application of MIKE 21 in a multi-purpose floodway zoning along the lower Hungarian Drava section

Floodway delineation, zoning and hydrodynamic modelling for a section of the Drava River was carried out with MIKE 21 software at a one-time input flood pulse of 3000 m3s-1 discharge. The objective of the current study was the delineation and mapping of floodway zones in the form of a set of georeferenced GIS data for the section between Őrtilos (river kilometer 236 km) and Drávaszabolcs (70.2 km). Zonation was based on water velocities. Four zones were delineated upstream Barcs, and three between Barcs and Drávaszabolcs, where, due to the confined floodplain downstream Barcs, no stagnant water area was identified. Specific velocities ranged between 0.089 and 3.476 m2s-1 and 0.075 and 2.01 m2s-1 upstream and downstream Barcs, respectively, markedly lower than stated in the Government Decree (0.2 to 6.0 m2s-1). The primary and secondary conveyance zones covered a combined area of about 40% of the entire floodplain, while the remaining 60% included both the transitional and stagnant water zones upstream Barcs and solely the transitional zone downstream Barcs. Our analyses help to mitigate the effects of flood peaks and provide information for decision makers and local stakeholders on flood management tasks.