Methodologies for generation of hazard indicator maps and flood prone areas: municipality of Ipojuca/PE.

ABSTRACT Studies focusing on urban vulnerabilities due to river floods need the construction of hazard maps and definition of potential flood areas. The objective of this article is to describe the development of a methodology for hazard mapping of river floods and to map areas susceptible to inundation on a municipal scale. The study area is the municipality of Ipojuca – Pernambuco State with area of 527.11 km2 and population of 80,637 inhabitants. The first methodology uses the hydrologic-hydraulic simulation for the lower course of the Ipojuca River using the HEC-HMS and HEC-RAS models. The streamflow calculated in the rainfall-runoff model is used as input for the hydraulic model, to simulate the water surface profile in the river. This makes it possible to calculate the water depth and flow velocity, the key elements for the definition of hazard indicators. The results of the hydraulic model were used to generate the hazard indicators: water depth, flow velocity, combination of depth and velocity, energy head, flow force and intensity (flow velocity x water depth). The other methodology seeks to identify areas with potential for inundation considering the entire territory of the municipality. Topographic index of the region and a distance cost matrix (which uses slope and drainage) are the auxiliary variables for determination of this map. Both variables use the digital terrain model. Analysis of risk is essential for planning and intervention in areas susceptible to inundation. Both characterizations of hazard and vulnerability are needed to evaluate risk. The results of the study in Ipojuca can be used for hazard characterization.