Forensic Analysis of Urban Flood using Ensemble Hydrologic Modeling

In the night of 6 to 7 of September 2022, the Tula River in the municipality of Tula de Allende, Mexico, reached its highest level in living memory, flooding the city. More than 31000 peoples were affected and 17 patients at the local hospital died. The Tula river catchment upstream of the city is complex, with four dams, three natural tributaries, and being the outlet of the drainage system of the urban area of Mexico City. Most of those reaches have patchy, inexistent or unreliable hydrometric records, complicating the task of understanding the causes of the flooding.

To circumvent those issues related to hydrometric records, in this study we employ an ensemble hydrologic modeling to reproduce the event and shed light on the relative contribution of each tributary to the flood in Tula de Allende. The considered ensemble will comprise ensembles of the catchment parameters and hydrographs coming from the Valley of Mexico. The aim is to obtain an ensemble of hydrographs, from which those that are closest to observed data will be selected, followed by an uncertainty analysis. This methodology is expected to provide reliable hydrological results to be used as an input of a hydrodynamic model to further the analysis of the event.