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The main objective of the research reflects the great need to generate hazard maps and calculate risk in the basin Huahuatay Rosarito in Baja California Sur, Mexico. For the topography in the study area, it is associated with a basin with fast response to rainfall - runoff relationship, because of that is considered necessary to establish the cell size of 50 m side and a time increment of 0.65 seconds. The estimate of the flow of water on the surface from the rain was based on the characterization of soils and vegetation cover, through the called number of the runoff curve proposed by the Soil Conservation Service. Flood areas calculated with a mathematical model of two-dimensional hydraulically from rain (FLUBIDI); they are sensitive to the quality of the input data. Thus, a digital terrain model with good resolution is undoubtedly necessary, and it depends on the path of the runoff. A good estimate of the effective rainfall, in time and space allows for a volume of runoff, flood areas and depths according to the hydraulic conditions of the study area. The size of the elements of the mesh used in the calculations generally is higher than the resolution of digital terrain models available, so that processing time would be suitable and which are related to cell size. The results successfully represent runoff within the watershed. Appropriate selection of the value of the friction coefficient of the Manning formula influences, largely, in the magnitudes of the velocities and depths of flow. Maps maximum depths, maximum speed and severity parameter (or multiplication deep drag velocity) for return periods of two, 5, 10, 50 and 100 years for river floods and storm were obtained. The maximum values that appear in the maps refer to the largest amount came to present at a certain point in each of the cells in the spreadsheet grid. Maps where the expected damage is presented annually were also developed. The damages were estimated at 60,250 homes and be led risk analysis for return periods from 2 to 100 years. Not necessarily, the works are constructed to reduce flood damages. Sometimes the water that temporarily occupied an area of land can be shifted to other areas where it could cause further injury; it is therefore advisable to make comprehensive basin-wide studies to evaluate the goodness of the proposed works, usually with simulation models embracing the basin where the floodplains are located…

Analysing some aspects of water management in urban areas affected by flooding, an event that occurred in September 2010 by overflows Cotaxtla Jamapa and rivers in western Mexico along with the rain event for five consecutive days. In this area, near the Gulf of Mexico, the elevations are less than three meters elevation. Floods are common in cities like Veracruz, in this article the flood risk calculated by means of a hydraulic model of rainfall-runoff dimensional type developed at the Institute of Engineering of the National Autonomous University of Mexico. Data digital terrain elevation models of LIDAR were used, records hourly rainfall levels and channels of some hydrometric stations of the National Water Commission. The location of housing and services in a metropolitan area considered to calculate the depths of flooding in them. To estimate the damage, shall take into account the hydrodynamic behaviour of the flows. Since houses remain flooded for several days, was the reason to use precipitation level for more than seven days. in the mathematical modelling of flows water with a regular grid made up of cells 10 m by side with the boundary condition downstream, corresponding to the predicted change in the average sea level.