The city of Villahermosa, a logistical center in the State of Tabasco’s economy, is affected by recurrent river floods. In this study, we analyzed the impact of two factors that are the most probable causes of this increase in flood hazard: changes in land use in the hydrological catchments upstream of the city, and the uncontrolled urbanization of the floodplains adjacent to the main river channels. Flood discharges for different return periods were evaluated, considering land uses of the catchments, both as they were in 1992 and as they are today. These flood discharges were then used in a 2D shallow water model to estimate the increase of water depths in the city from 1992 to the present day. To evaluate the influence of urban expansion on inundation levels, three future urbanization scenarios were proposed on the basis of the urban growth rate forecast for 2050. Results confirm that the change in land use in the hydrological catchments is the main factor that explains the increase in inundation events observed over recent years. This study also provides useful insights for future city planning that might help to minimize the flood impact on Villahermosa.

No abstract

On 3 July 2019, Stromboli volcanic island experienced a paroxysmal explosion that triggered wildfires on vegetated areas in the south, southwestern, and eastern part of the island. This study analyzes the runoff and the transport of sediment originating from rainfall, to verify whether the vegetation loss due to wildfire changed the hydrogeological structure of the affected area and the flooding hazard. A preliminary hydrological study was conducted to analyze the superficial runoff due to rainfall. According to local planning, the hydrogeological study and flood risk assessment were carried out for the return periods corresponding to 50, 100, and 300 years. The flooding levels were calculated using the hydrodynamic module of the IBER software. The IBER sediment transport module was applied in a non-stationary regime for erosion and sedimentation analysis. The results showed that the fire caused an increase of the water discharge rates between 0.06 and 0.16 m2/s, for the 50 year return period, in the Ginostra inhabited area. The great differences of the flood levels between pre- and post-eruptive scenarios, for the highest return periods, were recognized. The analysis of sediment transport showed that rains could exert an erosion and re-sedimentation effect that would transport from 0.1 m to more than 1 m of re-mobilized material in the Ginostra area, which could cause inconvenience in the inhabited area of the island.

In recent decades, the Tulancingo municipality (Mexico), has been affected by numerous extreme weather phenomena that caused heavy flooding events with severe damage to property and people. Most of the weather phenomena placed several dams under hydrologic risk. The hurricane ‘Dean’, in 2007, led to the overflow of the dam ‘La Esperanza’, generating inundations that reached levels of 1 m in Tulancingo. Mexico does not have a specific regulation that establishes critical thresholds for the construction of flooding hazard maps. With the aim to provide a tool for the flooding hazard assessment, we performed a numerical study of inundation waterdepths by means of the IBER software. The study is based on the construction of different inundation scenarios that are based on the hydrologic study of ‘La Esperanza’ dam's basin, associated to regional precipitation and different return periods. Inundation waterdepths, flow velocity, and land use were used to construct flooding hazard maps. We calculated the occurrence probability of the considered inundation events. The hazard maps presented here and the evaluation of the flooding likelihood can support long‐term planning that would help minimise the impact of such events in Tulancingo.