HYDROLOGICAL MODELING AND SPATIALIZATION OF SUSCEPTIBLE AREAS TO FLOODING IN THE IGREJINHA CITY, RS

Abstract

doi: 10.12957/geouerj.2016.10984

This paper aims to perform a hydrological modeling and flooding susceptibility spatialization applied to extreme precipitation events in Igrejinha City, RS, for different return periods (RPs). The work included seven stages: i) determination of the rainfall scenarios, ii) calculation of the morphometric parameters, iii) application of a rainfallrunoff model in the basins, iv) applying a hydrological model for the propagation of flows in the main rivers, v) hydrological simulation of extreme events with RP 10, 50 and 100 years, through the combination of the two models used, vi) estimation of reached levels in cross-sections of the river Paranhana, vii) flooding susceptibility spatialization for each RP. It was observed a rapid runoff in small streams that flow into the Paranhana River, which favors the occurrence of flash floods, while in the Paranhana River the runoff time is higher, favoring the development of a gradual flood. In the scenario with 10 years of RP the runoff achieves 1,120 m³/s, while in a rainfall with 100 years of RP, we obtained a value of 2.090 m³/s, representing an increase of 86.6%. However, regarding the area reached by the waters, the difference between scenarios with RPs between 10 and 100 years was only 9.4%. This occurred due to the characteristics of the embedded valley where the city is located, where increase of the flow rate is reflected more in changing river level than the flooded area.