Development of River Flood Maps in GIS Environment Prof. Dr. Andrej Šoltész Dr.Ammar H.Kamel Slovak University of Technology-College of Civil Eng. Al-Anbar University- College of Eng. soltesza@svf.stuba.sk dr.ammar1972@hotmail.com Abstract The paper was focused on 1) the development of an accurate and workable digital terrain model of the study area (The study area applied to the model is the Latorica River located in the Eastern part of Slovakia.); 2) the development of a MIKE 11 model based on surveyed, stream cross-section data; 3) draw maps of the resulting floodplain in ArcView GIS; and 4) Make the frequency analysis for the study area to draw flood map for recurrence period (1,5,25, and 50) years to determine the hazard of the flood and determine the probability of extension flooded area. The stream geometry was based on surveyed data, which did not extent over the full width of the inundated floodplain. A digital terrain model is synthesized from MIKE11 cross-sectional coordinate data and a digital elevation model of the study area. The resulting surface model provides a good representation of the general landscape and contains additional detail within the stream channel. The flood maps provide a good indicative picture of flood risk to be used as a strategic flood management tool and in relation to land use planning. Keywords: unsteady flow, flood map, MIKE11 Introduction: The desire to build and live along rivers creates the necessity for accurate calculation of water level and flow rates and provides the impetus to develop complex flow routing models. The computation of flood water level is needed because this level delineates the floodplain and determines the required height of structures such as bridges and levees; the computation of flood flow rate is also important; first, because the flow rate determines the water level, and second, because the design of any flood storage structure such as a detention pond or reservoir requires an estimate of its inflow hydrograph. In case of flood, knowledge of the flood, the occurrence (temporally) and the magnitude of flood inundation (spatial extent) is necessary to minimize the damage. Hydrologic/hydraulic modelling can play an important role in obtaining these characteristics. The ability to model potential flood inundation and map actual extent of inundation, timing, and intensity under different conditions depends upon the type of model being used. Progress in hydrologic/hydraulic modelling over the last decade has led to considerable improvements in our ability to simulate river flooding problems. The impetus for this progress has come from a number of fields and incorporates improvements in process understanding, mathematical and numerical developments and available computational power [3]. Developments in fully dynamic, unsteady models have provided engineers with highly accurate hydraulic modelling methods that result in graphical two- and three-dimensional visualizations for the purpose of analysis [2]. The key to graphical visualizations in dynamic modelling is the inclusion of time-series data within a spatial interface, like a Geographic Information System (GIS). The Danish Hydraulic Institute (DHI) is one of the world-leading software developers for incorporating water resources related time-series data into modelling. DHI’s MIKE 11 hydrodynamic model uses 1-D implicit, dynamic wave routing based on the Saint-Venant equations for unsteady flow. Additionally, DHI’s MIKE 11 GIS extension to ESRI’s Arcview GIS interface allows the user to import MIKE 11 model simulations in a time-series format into the Arcview GIS spatial environment. Two-dimensional models, compared with 1-D models, require a significant amount of additional data (especially topographic data) and time to set up and run. Any change in topography like addition of dike or road will require a change in topographic data and incorporating such changes, in general, is more time consuming compared to 1-D modelling [1].