Developing flood mitigation measures for the northern part of Nicosia

This study aims to examine a set of alternatives as remedial measures for the flood management purposes in order to protect the northern part of Nicosia which has been affected by major flooding events in recent years. In this context, at first, in order to obtain the run-off hydrographs at the entrance of reservoirs, the hydrological modelling of the ungauged catchments of Kanlikoy and Gonyeli Reservoirs which are located at the upstream part of the city was performed. In the simulation of these rainfall–run-off processes for different extreme precipitation events, the HEC-HMS software was employed using Soil Conservation Service Unit Hydrograph approach. In hydraulic modelling, the branches of Pedieos (Kanlidere) River and its urbanized floodplain were modelled by coupling the models of one-dimensional (1D) MIKE 11 and two-dimensional (2D) MIKE 21 using MIKE FLOOD tool. The calibration of the coupled hydrodynamic model was carried out by locally modifying the Manning’s roughness coefficients of the floodplains to match with the observed flood inundation extent of 2010 Flood. Consequently, the calibrated model showed nearly 94% similarity in terms of simulating the flood extent areas. Amongst different alternatives, the final proposed solution consisting of implementation of a new nearby upstream reservoir in Kanlikoy, dredging Gonyeli Reservoir and raising the crest elevations of its embankment and spillway, and restoration of possible channels sufficiently contributed to the mitigation of inundation problem and protected the northern part of Nicosia against the flooding events up to 500-year return period.