Overland flow generation mechanisms in the Concórdia River basin, in southern Brazil

Abstract

Overland flow in watersheds is responsible for the occurrence of various environmental problems, including flood formation, erosion and the transportation of sediment, and the addition of pollutants to the soil. Additionally, understanding this hydrological process is fundamental to improving knowledge regarding individual interest factors in a region, since it interferes with agricultural productivity and water supply for both the population and industry, among other contributions. Two principal theorists have described the overland flow generation processes: Horton (1933) and Dunne (1978). The TOPMODEL (a topography-based hydrological model) approach represents the overland flow by variable contribution areas, which develop along the watercourses following the concept of Dunne's overland flow. Thus, this study aimed to evaluate the mechanisms of overland flow generated in the Concórdia River basin based on the application of the TOPMODEL, using measured hydrological data obtained from a high frequency installed monitoring network. Discharge data series were performed for three sub-basins: SF3 (29.74 km ). In these sub-basins, the flood hydrograph were separated and its response conditions were verified in the TOPMODEL. Rainfall, discharge, and potential evapotranspiration data were used in an hourly scale for the three sub-basins. In general, the model showed adequate efficiency for the SF3 sub-basin; however, the SF2 and SF1 sub-basins showed distortion in its parameters, thereby delaying the simulated hydrograph in terms of time. Accordingly, the results corroborate the more frequent appearance of Dunnian overland flow in the SF3 sub-basin, where the topography is smoother and features large areas with a low slope, which serve as variable saturation areas. The SF2 and SF1 sub-basins present characteristics that strongly reflect Hortonian overland flow, with slopes in the topography that do not allow the frequent formation of variable contribution areas.Keywords: Hydrological processes in watersheds; Variable contribution area; Hydrologic model of physical based. RESUMOEm uma bacia hidrográfica o escoamento superficial é responsável pela ocorrência de diversos problemas ambientais, como formação de ondas de cheias, erosão e transporte de sedimentos e de poluentes nas vertentes. Além disto, entender este processo hidrológico é de fundamental importância para aprimorar o conhecimento sobre fatores de interesse próprios de determinada região, pois interfere na produtividade agrícola e abastecimento de água para população e indústria, entre outras contribuições. Dois conceitos têm sido utilizados para descrever os processos de geração de escoamento superficial: (i) Horton (1933); e (ii) Dunne (1978). O modelo TOPMODEL representa o escoamento superficial pelas áreas de contribuição variável, que se desenvolvem ao longo dos cursos de água, seguindo o conceito de escoamento superficial de Dunne. Assim, este trabalho visou à avaliação dos mecanismos de geração de escoamento superficial da bacia do ribeirão C...

The uncertainties of synthetic unit hydrographs applied for basins with different runoff generation processes

“…The higher drainage area, lower slope, low flow, and high storage capacity of soils (Schechi et al, 2013), suggest the Dunnian surface flow (Loewen & Pinheiro, 2017) is dominant in the Pequeno river, resulting in the worst agreement between measurements and simulations. The SUH is based on Hortonian overland generation Figure 8 shows the estimation ratio of peak flow considering the SUH simulation with the excess rainfall computed from measured data (see Pedroso ( 2019)) for details in obtaining excess rainfall computed from flowrate measurements).…”

“…As with most hydrological rainfall-runoff models (Loewen & Pinheiro, 2017), SUH are indicated for areas with fast runoff generation in which flow generation processes are based on Hortonian concept. It is important to know and discuss the possible additional errors in cases where the principles of SUH are disregarded (Schulz et al, 2018), even though this hydrological process may not be known previously.…”