Influence of different sources of topographic data on flood mapping: urban area São Vendelino municipality, southern Brazil

Zambrano, Fernando Campo; Kobiyama, Masato; Pereira, Marco Alésio Figueiredo; Michel, Gean Paulo; Fan, Fernando Mainardi

doi:10.1590/2318-0331.252020190108

Cited by 3 publications

(1 citation statement)

References 39 publications

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“…Essa velocidade multiplicada pela profundidade, resulta em um índice de perigo de 0,75 m 2 .s -1 que, segundo a classificação de Stephenson (2002), pode expor as pessoas ao perigo quando estiverem dentro do rio. Segundo Zambrano et al (2020) e Monteiro et al (2021), esse valor de índice de perigo deve ser utilizado para identificação de risco no momento de enchente e inundação. Com base nos critérios de perigo estabelecidos desses autores, os valores da Tabela 3 indicam que a medição de velocidade de campo foi executada no máximo possível, ou seja, não foi possível realizar a medição de velocidade no momento em que a profundidade era maior.…”

Section: Resultsunclassified

Avaliação de velocidade de rios em bacias montanhosas, região sul de Santa Catarina

Szymasnki

Kobiyama

Giehl

et al. 2022

Rev. Bras. Geog. Fis.

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O presente estudo teve por objetivo avaliar a velocidade de dois rios, Malacara e Molha Coco, de bacias montanhosas no sul do Brasil. As velocidades foram avaliadas com três métodos: (a) medição direta da velocidade em campo; (b) equações de Manning e de Jarret, usando dados geomorfológicos medidos em campo; (c) simulação com HEC-RAS 2D. Para verificar a coerência das velocidades calculadas e simuladas com os coeficientes de Manning (n) de 0,03, 0,05 e 0,07, comparou-se com as velocidades medidas em campo, onde existe uma estação fluviométrica que mede o nível de água com intervalo de 10 min. As velocidades que mais se aproximaram aos dados medidos foram as calculadas pela equação de Jarrett, sendo a diferença média entre elas de 12%. As velocidades calculadas por Manning com n=0,05, também apresentaram velocidades próximas aos dados medidos. Porém, com n=0,03 a diferença aumentou significativamente. Já com o HEC-RAS 2D ocorreu o inverso de Manning, ou seja, com n=0,03 as diferenças foram menores em relação aos dados medidos. Comparando os métodos de Manning e HEC-RAS 2D com o método de Jarrett, as velocidades que mais se aproximaram foram estimadas com n=0,05 e 0,07. As equações de Manning e de Jarrett e a modelagem com HEC-RAS 2D mostraram-se adequadas para estimar a velocidade dos rios Malacara e Molha Coco. Porém, Manning e HEC-RAS 2D dependem da escolha do valor de n adequado, que é sensível à variação do fluxo na seção de medição e ao longo do canal.Palavras-chave: velocidade. bacias montanhosas. equações empíricas. HEC-RAS 2D Velocity assessment of rivers in mountainous watershed, southern of Santa Catarina A B S T R A C TThis study aimed to evaluate the velocity of two rivers, Malacara and Molha Coco, in mountain watershed located in southern Brazil. Velocities were assessed with three methods: (a) direct velocity-measurement in field; (b) Manning's and Jarrett´s equations with geomorphological data measured in the field; (c) simulation with HEC-RAS 2D. To check the coherence of the calculated and simulated velocities with the Manning coefficients (n) of 0.03, 0.05 and 0.07, the present study compared velocities measured in the field, where there is a discharge station that measures the water level with 10 min interval. The velocities that were closest to the measured data were those calculated with Jarrett equation, where the mean difference between them was 12%. The velocities calculated by Manning equation with n=0.05 were also close to the measured data. However, with n = 0.03, the difference increased significantly. With the HEC-RAS 2D, the inverse of Manning occurred, i.e., with n = 0.03 the differences were smaller in relation to the measured data. Comparing the Manning and HEC-RAS 2D methods with the Jarrett method, the velocities that came closest were estimated with n=0.05 and 0.07. The present study showed a good performance of the Manning and Jarret equations and the HEC-RAS 2D modeling to estimate the velocity of the Malacara and Molha Coco rivers. However, with Manning equation and HEC-RAS 2D depended on the choice of the appropriate value of n which is sensitive to the flow variation at the measurement section and along the channel.Keywords: velocity. mountain watershed. empirical equations. HEC-RAS 2D

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Section: Resultsunclassified

Avaliação de velocidade de rios em bacias montanhosas, região sul de Santa Catarina

Szymasnki

Kobiyama

Giehl

et al. 2022

Rev. Bras. Geog. Fis.

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Hydrological and Hydraulic Modeling Applied to Flash Flood Events in a Small Urban Stream

et al. 2022

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In flood area mapping studies, hydrological-hydraulic modeling has been successfully applied around the world. However, the object of study of most of the research developed in Brazil is medium to large channels that use topographical and hydrometeorological data of coarse spatial and temporal resolution. Thus, the aim of this study is to investigate coupled modeling in a small urban channel, using high-resolution data, in the simulation of flood events in a small urban channel, located in Campo Grande, Mato Grosso do Sul. In this study, we used the HEC-HMS and HEC-RAS programs, where topographic information, land use, land cover, and observed data from rain gauges, water level, and flow sensors from 2015 to 2018 were used as input data. To calibrate and validate the hydrological model, four events were used that occurred during the monitoring period, while in the hydraulic model we chose a historical event that caused great disturbances. We then generated flood scenarios with representative synthetic rainfall for a basin, with return times of 5, 10, 50, and 100 years. We observed a good fit in the calibration and validation of the HEC-HMS, with values of R2 = 0.93, RMSE = 1.29, and NSE = 0.92. In HEC-RAS, we obtained values of R2 = 0.93, RMSE = 1.29, and NSE = 0.92 for the calibration, and in the validation, real images of the event prove the computed flood spot sources. We observed that rain with a return time of less than five years provides areas of flooding in several regions of the channel, and in critical channeled sections, the elevation and speed of the flow reach 5 m and 3 m·s−1, respectively. Our results indicate that the channel already has a natural tendency towards flooding in certain stretches, which become more compromised due to land use and coverage and local conditions. We conclude that the high-resolution coupled modeling generated information that represents local conditions as well, showing how potential failures of drainage in extreme scenarios are possible, thus enabling the planning of adaptations and protection measures against floods.

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Use of HAND terrain descriptor for estimating flood-prone areas in river basins

Dantas

Paz

2021

Rev. Bras. Ciênc. Ambient.

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The flood hazard mapping in a river basin is crucial for flooding risk management, mitigation strategies, and flood forecasting and warning systems, among other benefits. One approach for this mapping is based on the HAND (Height Above Nearest Drainage) terrain descriptor, directly derived from the Digital Elevation Model (DEM), in which each pixel represents the elevation difference of this point in relation to the river drainage network to which it is connected. Considering the Mamanguape river basin (3,522.7 km²; state of Paraíba, Brazil) as the study location, the present research applied this method and verified it as for five aspects: consideration of a spatially variable minimum drainage area for denoting the river drainage initiation; the impact of considering a depressionless DEM; evaluation of hydrostatic condition; effect of incorporating an existing river vector network; and comparative analysis of basin morphology regarding longitudinal river profiles. According to the results, adopting a uniform minimum drainage area for the river network initiation is a simplification that should be avoided, using a spatially variable approach, which influences the amount and spatial distribution of flooded areas. Additionally, considering the depressionless DEM leads to higher values of HAND and to a smaller flooded area (difference ranging between 3% and 99%), when compared with the use of DEM with depression, despite 3.1% of the pixels representing depressions. The use of the depressionless DEM is recommended, whereas the DEM pre-processing by incorporating a vector network (stream burning) generates dubious results regarding the relation between HAND and the morphological pattern presented in the DEM. Moreover, the estimation of flooded areas based on HAND does not guarantee the hydrostatic condition, but this disagreement comprises a negligible area for practical purposes.

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Influence of different sources of topographic data on flood mapping: urban area São Vendelino municipality, southern Brazil

Cited by 3 publications

References 39 publications

Avaliação de velocidade de rios em bacias montanhosas, região sul de Santa Catarina

Avaliação de velocidade de rios em bacias montanhosas, região sul de Santa Catarina

Hydrological and Hydraulic Modeling Applied to Flash Flood Events in a Small Urban Stream

Use of HAND terrain descriptor for estimating flood-prone areas in river basins

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