Determination of runoff coefficient (C) in catchments based on analysis of precipitation and flow events
Ronalton Evandro Machado, Taís Oliveira Cardoso, Matheus Mortene
Abstract
Runoff coefficient (C) values are tabulated and enshrined in hydrological engineering. These values are considered to be constant although they may not correspond to reality. In the same catchment, they may vary according to intensity, temporal and spatial distribution of precipitation events, humidity conditions, soil and land use. This study aimed to analyze extreme events of precipitation and their corresponding flows to obtain experimental runoff coefficients (C) and compare them with the tabulated values. The study was conducted in five experimental catchments in the state of São Paulo, Brazil, with different land uses. The runoff coefficients (C) were obtained from the analysis of hydrograms and using a digital filter, which made it possible to separate the direct runoff from the total flow. We observed a different variation in runoff coefficient values between catchments compared to those obtained from the tables. The runoff coefficients had a high correlation with land use. In catchments with original vegetation cover, such as Cerrado and forest, they varied little among the events analyzed, unlike the catchments where land use is diversified, with predominantly agricultural and urban occupation.