A combined hydrological and hydraulic model is presented for flood prediction in Vietnam. This model is applied to the Huong river basin as a test case study. Observed flood flows and water surface ...levels of the 2002–2005 flood seasons are used for model calibration, and those of the 2006–2007 flood seasons are used for validation of the model. The physically based distributed hydrologic model WetSpa is used for predicting the generation and propagation of flood flows in the mountainous upper sub-basins, and proves to predict flood flows accurately. The Hydrologic Engineering Center River Analysis System (HEC-RAS) hydraulic model is applied to simulate flood flows and inundation levels in the downstream floodplain, and also proves to predict water levels accurately. The predicted water profiles are used for mapping of inundations in the floodplain. The model may be useful in developing flood forecasting and early warning systems to mitigate losses due to flooding in Vietnam.
Urbanization is a significant challenge that catchments face around the world leading to difficulty in implementing stormwater-related engineering solutions. This study aimed at investigating the ...impact of land use/land cover change on hydraulic parameters of a rapidly urbanizing river basin, a case of the Jangwani basin in Dar es Salaam, Tanzania. In this study, the peak discharges were estimated using the SCS-Curve Number Method under the combination of ArcGIS and HEC HMS for three different years (1998, 2009, and 2018). The 100-year rainfall event recorded in 2011 was used to develop the meteorological model in HEC HMS. The steady flow analysis was accomplished using the HEC-RAS software package. To capture the effect of land use/land cover change as well as avoiding variability, the same rainfall dataset was applied for all the three study years. According to the modelling results in HEC RAS, the parameters such as top flow width, average velocity, hydraulic depth, conveyance, shear, stream power as well as the cumulative volume were observed to be increasing with time.
Floods are lethal and destructive natural hazards. The Mediterranean, including Greece, has recently experienced many flood events (e.g., Medicanes Zorbas and Ianos), while climate change results in ...more frequent and intense flood events. Accurate flood mapping in river areas is crucial for flood risk assessment, planning mitigation measures, protecting existing infrastructure, and sustainable planning. The accuracy of results is affected by all simplifying assumptions concerning the conceptual and numerical model implemented and the quality of geospatial data used (Digital Terrain Models—DTMs). The current research investigates flood modelling sensitivity against geospatial data accuracy using the following DTM resolutions in a mountainous river sub-basin of Thessaly’s Water District (Greece): (a) open 5 m and (b) 2 m data from Hellenic Cadastre (HC) and (c) 0.05 m data from an Unmanned Aerial Vehicle (UAV) topographical mission. RAS-Mapper and HEC-RAS are used for 1D (steady state) hydraulic simulation regarding a 1000-year return period. Results include flood maps and cross section-specific flow characteristics. They are analysed in a graphical flood map-based empirical fashion, whereas a statistical analysis based on the correlation matrix and a more sophisticated Machine Learning analysis based on the interpretation of nonlinear relationships between input–output variables support and particularise the conclusions in a quantifiable manner.
This study was conducted to map flood inundation areas along the Manafwa River, Eastern Uganda using HECRAS integrated with the SWAT model. The study mainly sought to evaluate the predictive capacity ...of SWAT by comparisons with streamflow observations and to derive, using HECRAS, the flood inundation maps. Changes in Land-use/cover showed by decrease in forest areas and wetlands, and conversions into farmlands and built-up areas from 1995 to 2017 have resulted in increased annual surface runoff, sediment yield, and water yield. Flood frequency analysis for 100-, 50-, 10-, and 5-year return periods estimated peak flows of 794, 738, 638, and 510 m3/s, respectively, and total inundated areas of 129, 111, 101, and 94 km2, respectively. Hazard classification of flood extent indicated that built-up areas and commercial farmlands are highly vulnerable, subsistence farmlands are moderately to highly vulnerable, and bushland, grassland, tropical high forest, woodland, and wetland areas are very low to moderately vulnerable to flooding. Results demonstrated the usefulness of combined modeling systems in predicting the extent of flood inundation, and the developed flood risk maps will enable the policy makers to mainstream flood hazard assessment in the planning and development process for mitigating flood hazards.
Sediment inflow to the reservoir is a key factor to calculate life of the reservoir. Flushing is a very useful technique in order to enhance the life of reservoir. From the literature review, 14 ...reservoirs were considered where flushing has already been practiced and only 6 reservoirs were found successful in flushing. The others were found partially flushed. In this research, data of three successfully flushed reservoirs namely Baira reservoir (India), Gebidem reservoir (Switzerland), and Gmund reservoir (Austria) were used to run 1-D numerical model HEC-RAS. In the first phase, the longitudinal profiles of delta were modeled and calibrated with observed sediment depositions. In the presence of available data of discharges and respective reservoir levels, the modeled deltas were used for flushing the deltas. With the help of modeled delta and corresponding flushing discharges, sediment deposition and flushing durations were computed. The simulated flushed durations were 31, 102, and 180 h for Baira, Gebidem, and Gmund reservoirs, respectively. The simulated flushed durations were found close to observed durations. Hence, the use of 1-D numerical model HEC-RAS is encouraged for modeling of sediment deposits and flushing operations.
Floods are natural disasters that often impact communities living in low-lying areas in the northern and central parts of Morocco. In this study, our aim was to create a flood susceptibility map ...using three methods; the hierarchy process (AHP) frequency ratio model (FR) and the weights of evidence (WoE) model. We extensively examined the area identified by these approaches using a hydraulic analysis software called HEC-RAS (version 6.3.1). Our analysis focused on the Essaouira watersheds in Morocco, where we identified around 197 flood locations. Out of these, we randomly selected 70% for modeling purposes while the remaining 30% were used for validation. Ten factors that influence floods were considered, such as slope, elevation, proximity to rivers, drainage density, stream order, land use patterns, rainfall data, lithology (permeability level) index (TWI), and curvature. We obtained these factors from data sources. Finally, we generated a flood susceptibility map and evaluated its accuracy by calculating the area under the curve (AUC). The validation results confirmed that all three models were robust and effective with an AUC of 90. Moreover, the research uncovered a trend of vulnerability with the most susceptible area being in close proximity to the city of Essaouira along the Oued Ksob. A detailed analysis using HEC-RAS was conducted at this identified location, pinpointing the village of Diabat as highly exposed. These findings hold significance for flood management, empowering decision makers, scholars, and urban planners to make informed choices and implement strategies that can minimize the impact of floods in susceptible regions while minimizing potential damages.
The research presented herein develops and compares an ADCIRC and ADCIRC/HEC-RAS (1D) paired model for the purpose of compound flood modeling within the Tar River and Pamlico Sound basins of North ...Carolina. Both the ADCIRC and 1D HEC-RAS models are capable of simulating river systems but differ in their underlying numerical formulations. A case-study comparison of each model’s ability to simulate flooding accurately and quickly in a riverine/estuarine system is investigated herein; results may serve as a valuable reference to forecasters and model developers. Individual models of the Tar River and Pamlico Sound area in North Carolina were used, and pairings of these models were devised to determine the benefits and drawbacks of using ADCIRC alone, or ADCIRC + 1D HEC-RAS, to simulate the response of the Tar River and Pamlico Sound during three test events: Hurricane Irene, Hurricane Floyd, and an unnamed April 2003 event. With increased emphasis on predicting total water levels, the results of this study can provide information for the possible development of similarly paired models for coastal river systems across the US and improve the body of knowledge about each model’s relative performance in riverine and estuarine areas.
Kejadian banjir di Kali Juana terjadi setiap musim hujan berlangsung. Beberapa kecamatan seperti Kecamatan Kaliwungu, Undaan dan Mejobo (Kab. Kudus) serta Pati, Margorejo dan Juwana (Kab. Pati) ...selalu menjadi daerah genangan banjir. Beberapa upaya pengendalian banjir sudah dilakukan seperti upaya normalisasi dan perbaikan tanggul. Namun mengingat kompleksnya sistem aliran banir di Kali Juana, upaya tesebut belum memberikan hasil yang memadai. Kajian ini dimaksudkan untuk menganalisis alternatif pengendalian banjir di Kali Juana menggunakan analisis model HEC-RAS. Analisis dilakukan dengan melakukan simulasi terhadap beberapa bentuk upaya pengendalian, guna mengurangi besaran banjir. Hasil analisis menunjukkan bahwa terdapat 6 model alternatif yang muncul dalam pengendalian banjir Kali Juana. Dari beberapa model tersebut, terpilih model simulasi yang meliputi Normalisasi, Tanggul, Waduk logung, 8 kolam Retensi dan Floodway.
The present work deals with the reconstruction of the flood wave that hit Mandra town (Athens, Greece) on 15 November 2017, using the framework of forensic hydrology. The flash flood event was caused ...by a huge storm event with a high level of spatial and temporal variability, which was part of the Medicane Numa-Zenon. The reconstruction included: (a) the post-event collection of 44 maximum water depth traces in the town; and (b) the hydrodynamic simulation employing the HEC-RAS and MIKE FLOOD software. The derived open dataset (which also includes additional data required for hydrodynamic modeling) is shared with the community for possible use as a benchmark case for flood model developers. With regards to the modeling issues, we investigate the calibration strategies in computationally demanding cases, and test whether the calibrated parameters can be blindly transferred to another simulator (informed modeling). Regarding the calibration, it seems that the coupling of an initial screening phase with a simple grid-search algorithm is efficient. On the other hand, the informed modeling concept does not work for our study area: every numerical model has its own dynamics while the parameters are of grey-box nature. As a result, the modeler should always be skeptical about their global use.
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