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 km 2 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.

The present study aimed to investigate the use of mobile applications on smartphones, specifically the Hidromapp application, as a technical support tool for flood data collection, as well as its use in flood mapping. To this end, information about a flood event of May 2017 was collected in the municipality of Jaqueira-Pernambuco, using smartphones and the Hidromapp application. Information was later used as input data for modeling and floodplain reconstitution. The study used geoprocessing techniques and a high-resolution Digital Terrain Model (Pernambuco Tridimensional - PE3D). For result evaluation, the reconstituted floodplain was compared with hydrodynamic modeling results using statistical indicators (RMSE and Critical Success Index - C). The app presented a good performance as a support tool for field collection of floodmark data. The applied method allowed a partially adequate estimation of the reconstituted event, in which the flooded area (extension) showed a high degree of similarity with the compared model, but with caveats for water surface elevations, where considerable discrepancies were detected in some points of the study area.

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There are still gaps in defining values and category classifications of exposed items in quantitative damage analysis. This paper proposes a framework that refines the development of flood risk analysis at a local scale. This study first performs a quantitative risk analysis, based mainly on secondary data; it then attempts to communicate the results graphically, aiming to reduce the financial and human resources required. We propose an easily standardized database in a GIS environment, analyzing the influence of a reservoir for flood control and the construction of replicable local-scale risk curves. Hydrological (HEC-HMS) and 2D hydrodynamic (HEC-RAS) models were used to simulate hydrographs considering different return periods. For damage estimation, the processing included vectorization of lots, building use definition with Google Street View, classification of standard designs, and a field survey to validate those classes. In monetary value, this study calculated the effect of the construction of a reservoir for damage reduction, showing the potential to determine the effectiveness of measures adopted to mitigate flood impacts. In addition, for each simulated return period, exposure, hazard, and damage maps can be established, making it possible to perform a complete risk analysis.

Worldwide floods stand out as some of the most recurrent and potentially destructive phenomena. Risk reduction management must consider dynamics involving structural risk elements called indicators. The objective of this paper was to simulate an extreme flood event in the Pirapama river basin, Pernambuco State, Northeastern Brazil, and to analyze some risk components, focusing on the application of damage models in the Brazilian scenario. The hydrological model HEC-HMS (Hydrological Modeling System) was calibrated in order to generate streamflow for ungauged areas. The model was able to identify the highest flood peaks and the statistic criteria were consistent with daily simulation. The parameters calibrated for the HEC-HMS model allowed us to generate results used as input flow in HEC-RAS (River Analysis System). The hydrodynamic model HEC-RAS performed steady flow simulations for the peak flow that occurred in 2010. Remote sensing products with high spatial resolution were used successfully to identify and calculate dwellings surface in the municipality of Cabo de Santo Agostinho. Flood damage estimates were performed through transferred depth-damage curves which is a methodological option verified in the literature. The two main Brazilian studies on this field were selected. The difference between the functions is just over BRL$72 per square meter, and around BRL$85 million for the entire area in the 2010 event (BRL$234.58 and BRL$149.11 million). Those values were adjusted for inflation until 2019. A combination of different methodologies is a way to try to overcome the lack of information, but much remains to be done to validate damage analysis, especially in what concerns to prevention.