DETERMINISTIC HYDROLOGICAL MODELING AND GRID SIZE SENSITIVITY ANALYSIS FOR FLOOD RISK ASSESSMENT OF MEXICO CITY

Mexico City is facing problems of flooding in some areas at certain times of the year, causing important losses and damages on properties and residents including some casualties. Therefore, it is important to carry out a flood risk assessment in the catchment of Mexico City and estimate damages of probable flood events. However, limited data of observed discharges and water depths in the main rivers of the city are available. The premise of this study is that with the limited data and resources available, the catchment can be represented with an acceptable degree by the construction of a deterministic hydrological model of the Mexico City basin using the MIKE SHE software; and the resulting discharges in the rivers can be used to carry out a flood hazard assessment. The discharges in 7 rivers, and the water level downstream, were input in MIKE 21 as boundaries for the model. Furthermore, these results were used in the MIKE 21 model for assessing the extent of the areas of flood risk and the flood depth in Mexico City. In addition, the effect of changing the resolution of topographic data was studied to determine the impact of DEM accuracy and case studies on the effect of resolution of topographic data are discussed in Section 2.3. DEMs with larger grid sizes have less detailed information as they have one elevation value for a larger area. DEMs with high resolution or smaller grid sizes represent elevations of smaller areas and can better represent the smaller topographic details., and a grid size sensitivity analysis was carried out for the topography in MIKE 21. Grid sizes of 50 m, 30 m and 20 m were used in MIKE 21 to create flood maps and analyze the differences in the results of flood extents and depths.