Hydrological modeling using Geographical Information Systems

Natural phenomena are very difficult to be accurately simulated, as our knowledge of the physical laws that govern these phenomena is not complete and the available data on the current situation are inadequate. Therefore, the models that are created for these processes are conceptual and their accuracy depends on the values of the parameters. This thesis develops two distributed conceptual models in G.I.S. environment using the ArcGIS software. The first model simulates the hydrological phenomena that take place during rainfall - runoff and calculates the required time for each section of the basin to be fully drained. The model can calculate the curves representing equal timing conditions for the runoff of each region, given the Digital Terrain Model, and produces the corresponding runoff hydrograph resulting from the synthetic unit hydrograph of the basin. The main objective of the model is to estimate the peak of the flood discharge and the corresponding time. This model was derived by modifying existing models of rainfall – runoff, introducing new techniques (new empirical formulas) and updating the whole process to make the results more accurate in the minimum possible time. The second model provides estimates of the discharge at the outlet of the basin, taking as input the measured values of rainfall in specified measuring stations or a surface distribution of a given rainfall. The purpose of this model is the creation of the flood hydrographs for a basin with different conditions of rainfall (intensity, duration and spatial distribution). These models were applied in the Sperhios river basin, upstream of the junction with Gorgopotamos river by varying numerous parameters. The models were used to investigate the spatial distribution of rainfall in the produced flood hydrograph of the basin by applying different rainfall conditions in the region and to estimate the design flood hydrograph with 50-year return period.