Inundation Risk Index as an Urban Planning Supportive Tool
Urban densification and severe housing deficit of the low and middle-income population have been worsening as the urbanization process grew. It is not uncommon that lower income population finds some shelter irregularly occupying riverine areas. Today, flood risk processes associated with river dynamics generate significant expenses and concerns for public management. In view of this, the main objective of this work is to develop a flood risk supporting tool, which deals with some of the current urban planning drawbacks, being simple and accessible even to cities with little technical and investment capacities. This tool results from a multi-criteria analysis, and it is represented by a quantitative index, called the Inundation Risk Index, varying from 0 to 100. This new index is capable of combining factors related to both the natural characteristics of the watershed, which respond to the physical susceptibility to flooding, simulating the hazard, and to socioeconomic characteristics of the population and of the region affected, representing the vulnerability. Once normalized, each of the factors that compose the index is operated, in a relatively simple formulation, composed of weighted sums and weighted products. The Inundation Risk Index was applied to a case study in the Bacanga river basin, in the municipality of São Luís–Maranhão State/Brazil. In this work, was used a hydrodynamic model to validate the hazard component of the index. The results obtained by the mathematical modeling are consistent with the situation measured by Inundation Risk Index, which are also consistent with real practical observations and historical reports.