Abstract
ABSTRACT In urban areas, rainfall-runoff modeling provides large uncertainties due to the difficulty in representing the spatial distribution of rainfall events. In this context, the this work aims to evaluate the effect of temporal and spatial of rainfall data (weather radar and distributed rainfall gauges network) on runoff estimation in a urban basin. The Reginaldo basin, inserted in the urban area of the Maceió city, capital of state of Alagoas (Brazil), has a reasonable availability of rainfall datal covered with a high number and spatial distribution of rain gauges and weather radar, which was used as input of a hydrological model The EPA Storm Water Management Model (SWMM) has been used with 3 analysis rainfall scenarios: (i) considering uniform rainfall distribution based on measured average rainfall, (ii) considering distributed rainfall using catchment discretization, and (iii) considering distributed rainfall using radar cell discretization. In order to evaluate the model outcomes, we analyzed four hydrological output variables: (i) the peak flow; (ii) the peak time; (iii) the volume flowed and (iv) the volume losses. Based on this criterion, it was clear that, considering he analyzed scenarios, the effect of spatial distribution of rainfall data on hydrological response in small urban basins, with high impervious coverage, was not divergent for the analyzed scenarios and that the radar data showed significantly higher data resolution than rainfall gauges.
Highlights
The uncertainties generated from the rainfall-runoff representation in urban basins are linked to the models and simplifications adopted, the difficulties of estimating the physiographic parameters of the basin, and, mainly, the precipitation estimation
Even presenting relatively high differences, it can be justified by the difference between the models used, which according to Souza (2017) the representation of the same event in different hydrological models can present variations of up to 100%
This study used three scenarios for hydrograph analysis based on different sources of precipitation as an input of a hydrological model coupled with a hydrodynamic model applied to the Reginaldo river basin, which is fully inserted in the urban area of the municipality of Maceió - AL
Summary
The uncertainties generated from the rainfall-runoff representation in urban basins are linked to the models and simplifications adopted, the difficulties of estimating the physiographic parameters of the basin, and, mainly, the precipitation estimation. Rainfall gauge measurements and remote sensing observations show that precipitation fields may largely vary on a spatial scale from a few meters to hundreds of kilometers. Retrieval of spatial distribution of rainfall can lead to large uncertainties considering the methods used for this purpose. In the case of rainfall gauges, retrieval of the average spatial distribution is performed through spatial methods (Adilson Moreira et al, 2007; Cabral et al, 2017). On the other hand, mau improve spatial rainfall resolution, despite the interference of various media and bodies that hinder the use of the product generated as an accurate estimate of rainfall
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