Estimating areas vulnerable to flooding in urban zones: Morelia, Michoacan, Mexico

We determined areas of Morelia, Michoacan, that are vulnerable to flooding caused by the river Rio Grande de Morelia, which crosses the city. A hydrological model in the river's basin and another hydraulic model on the stretch of river that goes through the city were applied. The hydrological model was carried out with HEC-HMS considering the characteristics of the sub-basins such as area, lag time and number of runoff curves. The precipitations were incorporated with hyetographs for September 2013. The model was calibrated based on a gauged hydrograph at the outlet of the basin and adjusting the values of the runoff curve number until an acceptable fit was obtained between the hydrograph calculated by the model and that gauged at the basin's exit. The fit was evaluated with the criteria Nash-Sutcliffe, RMSE and Coefficient of Determination. With the calibrated hydrological model, an event lasting 24 hours was identified and the precipitations for hyetographs were substituted by those associated with 100- and 500-year return periods estimated with the Gumbel Probability Distribution. Both events were modeled, and hydrographs were obtained. Hydraulic modeling of the section of the Rio Grande River that crosses the city was carried out with IBER, using the hydrographs for each return period, channel topography and Manning roughness coefficients. The results of this last modeling allowed identification of the areas vulnerable to flooding produced by rises associated with the return periods considered.