Calibration process is usually time demanding and as much streamflow information as possible in rainfall-runoff models. Nevertheless, from a practical point of view, the available information is measurement of water level, which is essential to design rating curves. This manuscript proposes a set of joint calibration of hydrological model parameters with a range of rating curves, developed for the main channel of the catchment in a crowded urban area. As an alternative of free calibration, the simulations were carried out based on a list of proficient parameters. Four streamflow gauging stations were analysed and used to subdivide the basin. The hourly lumped rainfall-runoff model GR4H was applied to four critical flash flood events to create a rank of Nash-Sutcliffe efficiency criteria (NSE) applying the best set of parameters. The results indicated that the hydrological model errors were compensated by hydraulics errors and they presented an equifinality in the process. RESUMONos modelos chuva-vazão, a etapa de calibração geralmente exige tempo e grande quantidade de informação das vazões. No entanto, do ponto de vista prático, a informação usualmente disponível é o nível d'água medido, este, por sua vez, utilizado na construção das curvas-chave. Este artigo propõe uma calibração conjunta dos parâmetros de um modelo hidrológico com uma gama de curvas-chave, as quais foram desenvolvidas para o canal principal da bacia em estudo em uma área altamente ocupada e urbanizada. Como alternativa a uma calibração livre, as simulações foram realizadas com base em uma lista de parâmetros previamente testados. Quatro estações linimétricas foram analisadas e utilizadas para subdividir a área da bacia. O modelo concentrado horário de chuva-vazão GR4H foi utilizado com quatro eventos críticos de inundações bruscas com o intuito de criar uma classificação de critérios de eficiência de Nash-Sutcliffe aplicando o melhor conjunto de parâmetros. Os resultados indicam que os erros do modelo hidrológico foram compensados pelos erros hidráulicos e apresentaram uma equifinalidade no processo. Palavras-chave:Modelo chuva-vazão; Inundações bruscas; Curvas-chave; Hidrologia urbana; Modelagem hidrológica e ambiental. RBRH, Porto Alegre, v. 24, e24, 2019 Joint calibration of a hydrological model and rating curve parameters for simulation of flash flood in urban areas 2/15
A definição do risco associado à eventual ruptura de uma barragem constitui um problema corrente na engenharia. As barragens têm um papel importante na sociedade e o colapso de tais estruturas traz consigo desastres de grandes dimensões. A presente pesquisa procurou sistematizar uma técnica de simulação numérica de análise de risco,conhecida como Simulação de Monte Carlo, para avaliar a probabilidade de galgamento de uma barragem, causado por eventos de naturezas hidráulicas e hidrológicas, e aplicá-la em estudo de caso. A simulação foi utilizada com o intuito de avaliar a probabilidade de galgamento da barragem da PCH Cajuru, situada em Minas Gerais, em decorrência de uma cheia de determinado tempo de retorno, considerando as incertezas presentes na análise local de frequência de vazões máximas anuais. O método de Monte Carlo, ao ter em conta as incertezas das estimativas de eventos de dado tempo de retorno, demonstrou ser de muita utilidade na avaliação completa da probabilidade de galgamento. No caso em estudo, a simulação mostrou que a barragem de Cajuru apresenta grau não desprezível de vulnerabilidade a eventos de grandes magnitudes. Além das cheias, também foram analisadas as incidências do vento sobre o paramento de montante da barragem, provocando ondas e consequentes reduções da borda livre existente, entre o NA máximo-maximorum e a crista do referido barramento.
Since the 1940s, the number of people living in Brazilian cities doubled, however, the process of cities growth has occurred in a disordered manner, resulting in several socio-environmental problems, mainly during the rainy season, when the events of floods and landslides are more frequent. João Monlevade is a municipality in Minas Gerais that has a history of disasters. Thus, this study aims to analyze the flooding events recorded in the Carneirinhos sub-basin, located in João Monlevade, Minas Gerais state, their impacts, as well as the meteorological systems acting in the occurrence period. Firstly, the study area was delimited and characterized, data collection related to the historical series of flood events that occurred in the hydrographic sub-basin of the Carneirinhos stream, during the period from 1969 to 2020, was carried out. Secondly, the meteorological systems acting on the event data were identified. From the results obtained, it is possible to verify that Carneirinhos stream recorded 14 flood events according to the management organizations of the municipality. These events are mainly associated with the South Atlantic Convergence Zone or with Humidity Convergence Zones. Some possible factors that may justify an occurrence of these events are changes in hydrological patterns due to climate change, the stream’s canalization, possible flaws in the design of the basin drainage system design, and / or a combination of all these factors. Finally, it is recommended that studies be carried out on the current drainage system in the municipality, addressing the dimensioning of the existent galleries to face future changes, since some studies point to an increase in the frequency of flood events.
Devido à ausência de sistemas de drenagem eficientes e aos altos índices pluviométricos em determinados períodos do ano, eventos de inundação no mundo e no Brasil, e, principalmente, em Belo Horizonte-MG, têm sido observados com muita frequência. À vista disso, este trabalho teve como objetivo desenvolver a modelagem hidráulica de um canal em meio urbano visando a discussão sobre a sua capacidade de drenagem e minimização de incertezas, relacionadas ao escoamento de água no canal em eventos extremos. Para a elaboração dos mapas e delineamento do canal foi utilizado o software ArcGIS, com suas extensões ArcHydro e HEC-GeoRAS. Além disso, para aplicação dos dados geométricos e hidráulicos das seções, e simulações hidráulicas, foi empregado o software HEC-RAS. Como resultado do estudo, teve-se a comprovação, quantitativa, da influência do coeficiente de Manning no escoamento do canal e pôde-se também, determinar, por meio de um conjunto de vazões críticas, trechos do curso d’água mais susceptíveis à inundação. Observou-se que, quanto menores os valores dos coeficientes de Manning das seções, maiores são suas vazões críticas, ou seja, para corpos hídricos canalizados por obras com revestimento e com acabamento, as vazões necessárias para as seções inundar possuem valores mais altos, justamente, pelo menor atrito do material de revestimento com o fluxo de água; enquanto que, para canais naturais, as vazões determinantes para a ocorrência de inundação da seção, são menores, pela maior potencialidade da vegetação e do solo em resistir ao escoamento. Flooding Area Simulation through Hydraulic Modeling in the Urban Channel: Case Study Jatobá Stream, in Belo Horizonte, Minas GeraisA B S T R A C TDue to the absence of efficient drainage systems and high rainfall rates at certain times of the year, flood events in the world and in Brazil, and especially in Belo Horizonte, Minas Gerais, have been observed very frequently. In view of this, this work aimed to develop the hydraulic modeling of an urban canal in order to discuss its drainage capacity and minimize uncertainties related to water runoff in extreme events.For the maps elaboration and the channel drawing was used the ArcGIS software with its extensions ArcHydro and HEC-GeoRAS. The HEC-RAS software was used to apply the geometric and hydraulic sections data and for hydraulic simulations. As a result of the study, the influence of the Manning coefficient on the flow of a channel was quantitatively verified. Through a set of critical flows, it was also possible to determine the most susceptible to flooding watercourse stretches. In this case, it was observed that the smaller the values of the Manning coefficients of the sections, the higher their critical flow rates, that is, for water bodies piped by coated and finished works, the flow rates needed to flood the sections have higher values high due to the lower friction of the coating material with water flow; whereas, for natural channels, the water volumes per unit of time, which are determinant for the sections flooding, were smallers, precisely because of the greater capacity of the vegetation and soil to resist runoff.Keywords: hidraulic modelling, HEC-RAS, urban floods.
Floods are a recurring natural phenomenon during the rainy season in many Brazilian municipalities. Nevertheless, shifts in weather patterns have contributed to an increased incidence of these events in urban areas, where their impact can be amplified by the way the surrounding catchment is occupied. Hence, the present study sought to evaluate the susceptibility of the urban drainage infrastructure in João Monlevade, Brazil, to the effects of climate change by undertaking a comprehensive assessment of the Carneirinhos catchment, including its morphometric characteristics. For this purpose, we employed a hydrological model driven by regional rainfall projections from a high-resolution climate model (HadGEM2-ES downscaled to 5 km resolution) under the Representative Concentration Pathways (RCP8.5) scenario. Several combinations of rainfall occurrence were simulated, incorporating temporal aspects (different durations and return times), as well as spatial aspects (concentrated and distributed rainfall within the catchment). The results showed that the area of exposed soil in the Carneirinhos catchment experienced an increase of more than 140% from 2016 to 2019, favoring runoff surface and evaporation, which contributed to the increase in the number of flood events in the region. In addition, only 1 of the 56 heavy rainfall event simulations performed did not exceed the capacity of the macro drainage gallery.
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