Flood hazard mapping in Southern Brazil: a combination of flow frequency analysis and the HAND model

Speckhann, Gustavo Andrei; Chaffe, Pedro Luiz Borges; Goerl, Roberto Fabris; Abreu, Janete Josina de; Flores, Juan Antonio Altamirano

doi:10.1080/02626667.2017.1409896

Cited by 47 publications

(29 citation statements)

References 52 publications

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“…Also, one new lateral tunnel was built in each dam to improve the reservoir emptying and its operation capacity during floods. Recent studies have also highlighted the relevance of improving flood risk management in the basin through flood forecasting (Casagrande et al 2017) and flood hazard mapping (Nobre et al 2016;Speckhann et al 2018;Fleischmann et al 2019).…”

Section: Study Area: the Itajaí-açu River Basinmentioning

confidence: 99%

Modeling the role of reservoirs versus floodplains on large-scale river hydrodynamics

et al. 2019

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Large-scale hydrologic-hydrodynamic models are powerful tools for integrated water resources evaluation at the basin scale, especially in the context of flood hazard assessment. However, recent model developments have paid little attention to simulate reservoirs' hydrodynamics within river networks. This study presents an adaptation of the MGB model to simulate reservoirs as an internal boundary condition, enabling the explicit simulation of hydrodynamic processes along reservoirs and their interaction with upstream and downstream floodplains in large basins. A case study is carried out in the Itajaí-Açu River Basin in Brazil, which has periodic flood-related disasters and three flood control dams. The model was calibrated for the 1950-2016 period forced with daily observed precipitation. The adjustment was satisfactory, with Nash-Sutcliffe metrics between 0.54 and 0.84 for the 11 gauges analyzed and with flood frequency curves also well represented. Simulation scenarios with and without floodplains and reservoirs were performed to evaluate the relative role of these factors on flood control basin-wide through evaluation of simulated discharges, water levels and flood extent. Itajaí do Oeste tributary and Itajaí-Açu mainstem present major floodplain attenuation, while in Itajaí do Sul and Itajaí do Norte tributaries the main flood control occurs due to reservoir attenuation. Downstream from the dams, results indicated that the reservoirs reach their maximum discharge reduction capacity for 5-to 10-year floods, decreasing it for larger floods. The developed model may be very useful for operational uses as flood forecasting and coordinated reservoir operation studies, as well as to enhance the comprehension of flood dynamics at basin scale.

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Section: Study Area: the Itajaí-açu River Basinmentioning

confidence: 99%

Modeling the role of reservoirs versus floodplains on large-scale river hydrodynamics

et al. 2019

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“…A digital elevation model (DEM) is a set of digital data describing elevation values of Earth ground surface (or any other surface) which contains additional information about the character of this surface and interpolation algorithm, which is best for approximation (modeling) of the real topography (Szypuła, 2017). A DEM is a complete representation of a land surface, which means that heights are available at each point in the area of interest (Hengl and Evans, 2009).…”

Section: Digital Elevation Model (Dem) Calibrationmentioning

confidence: 99%

Delimitation of flood areas based on a calibrated a DEM and geoprocessing: case study on the Uruguay River, Itaqui, southern Brazil

Araújo

Amaro

Silva

et al. 2019

Nat. Hazards Earth Syst. Sci.

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Abstract. Flooding is a natural disaster which affects thousands of riverside, coastal, and urban communities causing severe damage. River flood mapping is the process of determining inundation extents and depth by comparing historical river water levels with ground surface elevation references. This paper aims to map flood hazard areas under the influence of the Uruguay River, Itaqui (southern Brazil), using a calibration digital elevation model (DEM), historic river level data and geoprocessing techniques. The temporal series of maximum annual level records of the Uruguay River, for the years 1942 to 2017, were linked to the Brazilian Geodetic System using geometric leveling and submitted for descriptive statistical analysis and probability. The DEM was calibrated with ground control points (GCPs) of high vertical accuracy based on post-processed high-precision Global Navigation Satellite System surveys. Using the temporal series statistical analysis results, the spatialization of flood hazard classes on the calibrated DEM was assessed and validated. Finally, the modeling of the simulated flood level was visually compared against the flood area on the satellite image, which were both registered on the same date. The free DEM calibration model indicated high correspondence with GCPs (R2=0.81; p<0.001). The calibrated DEM showed a 68.15 % improvement in vertical accuracy (RMSE = 1.00 m). Five classes of flood hazards were determined: extremely high flood hazard, high flood hazard, moderate flood hazard, low flood hazard, and non-floodable. The flood episodes, with a return time of 100 years, were modeled with a 57.24 m altimetric level. Altimetric levels above 51.66 m have a high potential of causing damage, mainly affecting properties and public facilities in the city's northern and western peripheries. Assessment of the areas that can potentially be flooded can help to reduce the negative impact of flood events by supporting the process of land use planning in areas exposed to flood hazard.

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“…We opted for HAND as it provides a tool for fast grid generation in terms of both data requirements and execution time and is thus well suited for large-scale applications. Besides, HAND was applied for other inundation modelling studies ( Nobre et al, 2016;Speckhann et al, 2018 ) and has only a user-defined upstream area threshold as possible source of uncertainty.…”

Section: Hydrodynamic Discretizationsmentioning

confidence: 99%

Benchmarking flexible meshes and regular grids for large-scale fluvial inundation modelling

Hoch¹,

Beek²,

Bierkens³

et al. 2018

Preprint

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Damage resulting from flood events is increasing world-wide, requiring the implementation of mitigation and adaption measures. To facilitate their implementation, it is essential to correctly model flood hazard at the large scale, yet fine spatial resolution. To reduce the computational load of models, flexible meshes are an efficient means compared to uniform regular grids. Yet, thus far they have been applied only for bespoke small-scale studies requiring a high level of a priori grid preparation. To better understand possible advantages as well as shortcomings of their application for large-scale riverine inundation simulations, three different flexible meshes were derived from Height Above Nearest Drainage (HAND) data and compared with regular grids under identical spatially explicit hydrologic forcing by using GLOFRIM, a framework for integrated hydrologic-hydrodynamic inundation modelling. By means of GLOFRIM, output from the global hydrologic model PCR-GLOBWB was passed to the hydrodynamic model Delft3D Flexible Mesh. Results show that applying flexible meshes can be beneficial depending on the envisaged purpose. For discharge simulations, similar model accuracy was obtained between flexible and regular grids, with the former generally having shorter run times. For inundation extent simulations, however, the coarser gridding of flexible meshes in upstream areas results in a poorer performance if assessed by contingency maps. Moreover, while the ratio between minimum and maximum spatial resolution of flexible meshes has limited impact on discharge simulations, water level estimates may be stronger influenced by the application of larger grid cells. . As this study presents only a small set of possible realizations, additional research needs to unravel how the data and methods used as well as the choices for discretizations influence model performance. Generally, the application and particularly discretization process of flexible meshes involves more options, bringing more responsibilities for the user. Once an a priori decision is made on the model purpose, flexible meshes can be a valuable addition to modelling approaches where short run times are essential, facilitating large-scale flood simulations, ensemble modelling or operational flood forecasting.

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Flood hazard mapping in Southern Brazil: a combination of flow frequency analysis and the HAND model

Cited by 47 publications

References 52 publications

Modeling the role of reservoirs versus floodplains on large-scale river hydrodynamics

Modeling the role of reservoirs versus floodplains on large-scale river hydrodynamics

Delimitation of flood areas based on a calibrated a DEM and geoprocessing: case study on the Uruguay River, Itaqui, southern Brazil

Benchmarking flexible meshes and regular grids for large-scale fluvial inundation modelling

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