CRITICAL ANALYSIS OF THE GEOMORPHOLOGICAL INSTANTANEOUS UNIT HYDROGRAPH (GIUH) A FLOOD STUDY APPLICATION IN FOUR CHILEAN BASINS

摘要

Based on Geographic Information Systems (GIS), an assessment of the Geomorphologic Instantaneous Unit Hydrograph (GIUH) is presented in the context of a flood study. First, the governing equations are defined and then the model is used to calculate peak flows with different return periods in four catchments of the Itata River basin. Methodology includes the selection of rain and flood information, as well as basins morphological characterization with the employ of a Digital Elevation Model (DEM). Predictions are compared with frequency analysis of the historical information and with the results of typical flood estimation Chilean procedures. GIUH's results are the most consistent ones, with average percentage errors between 2% and 11%. Finally, regional expressions are proposed to compute peak flows and times of runoff events at Itata's basin and a sensitivity analysis is done to the drainage networks generated in ArcGIS and to the formulations terms with the major source of uncertainty. Conclusions show that design equations are not substantially sensitive to governing variables changes and it's demonstrated that the length reason is the hortonian number that has more influence in the rainfall-runoff process.