Critical analysis of the Geomorphological Instantaneous Unit Hydrograph (GIUH). A flood study application in four Chilean basins.

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Jose Vargas, Sergio Vilches

Tuesday 30 june 2015

17:57 - 18:00h at North America (level 0)

Themes: (T) Extreme events, natural variability and climate change, (ST) Hydrological extremes: floods and droughts, Poster pitches

Parallel session: Poster pitches: 7I. Extreme - Flood Drought

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The flood study has been an important topic in applied hydrology for about a century. The problem is even greater in areas without fluviométric information. In this sense, one of the most important challenges in basins not controlled is validate reliable methods for calculating flood associated with a given return period. In recent years, taking advantage of the potential of geographic information systems (GIS), we have used the geomorphological unit hydrograph (GUH) to estimate storm flood in river uninformed. The theme of this research focuses on a comprehensive analysis of this model in four Chilean river basins. The conceptual basis of the model assumes that the effective rainfall can be traced through the drainage network with a probabilistic approach by adopting the hierarchical system of Horton and Strahler. They assume a linear hydrological response, Rodriguez-Iturbe and Valdes derived the most important features of GUH, parameterized in terms of the reasons for Horton. To test the geomorphological model was used predictive design approach , using rainfall and discharge associated with a given average occurrence interval. With this type of work, a triangular unit hydrograph approach was used, as they defined their authors. In this case, the hydrogram only described the peak flow rate, time to peak and time base. The other main hypothesis was to specify a storm design with intensity and constant duration equal to the critical time of concentration (tc). The study was limited in Itata River watershed, which is part of the Biobío Region in southern Chile, which comprises an area of approximately 11,294 km2. To study watersheds, the model presented the lowest average percentage error with respect to frequency analysis of maximum flow, with values between 2% and 11%. By sensitivity analysis, it was found that the ratio of length is the lattice parameter of hydrographic best explains variations in time and flow, and found that the reasons for bifurcation and area have a minor effect on the results.