HEC-RAS 2D Research Articles

Redesign of an Intake Fish Pass Structure

Abstract The article describes the process of redesigning the intake structure of the fish pass at the Žilina water structure in Slovakia. The existing intake structure does not meet the passability requirements for the target species of migratory fish. A design utilizing intake windows at various levels that cover fluctuations in the water level in the reservoir, which has been successfully used for other water structures, has been proposed. The new design was subjected to hydraulic calculations and simulations in the HECRAS 2D, 2D numerical model in order to achieve the required parameters such as the discharges, depths, and velocities within the limits for the specified fish zone.

Flood Inundation Modelling in Greater Colombo Region Using HEC-RAS 2D

"ENGINEER", established in 1973 by The Institution of Engineers, is a Journal for dissemination of Engineering knowledge, published quarterly.If you are interested in contributing an Original Technical Paper based on research by the author(s) (intended for Section I) or an Original Article of Professional or Technical interest related to Engineering. (Section II) to this journal please go through the publication checklist which can be downloaded from here.Cover DescriptionCover images show a few views of the Maduru Oya reservoir and construction of right bank canal. The Institution of Engineers, Sri Lanka, acknowledges Eng. L.D. Amila Sanjeewa of the Department of Irrigation for providing images and related information of the project.

Detecting and mapping flood inundation areas in Fogera-Dera Floodplain, Ethiopia during an extreme wet season using Sentinel-1 data

The study area, Fogera-Dera Floodplain, has experienced frequent flooding events in the past several decades related to the topography of the region, mainly during the rainy season. In this study, Four Sentinel-1A Synthetic Aperture Radar (SAR) data was utilized to detect, map, and analyze flood water inundations in the 2020 extreme wet season. Besides this, HEC-RAS 2D (Hydrologic Engineering Center-River Analysis System) hydrodynamic model was utilized for result validation and comparison. Doing so, Sentinel- 1A VV polarized SAR data sets were selected, and histogram-based thresholding method was applied to extract flood and non-flood inundated areas. The result showed that flood inundated area was about 32.02 km2 on July 04, 2020, 79.96 km2 on July 28, 2020, 127.48 km2 on August 09, 2020, and 83.89 km2 on August 21, 2020. Flood water expansion was linearly increased from 04 July up to 09 August, which was about 95.46 km2and reached its peak stage on August 09, 2020. Afterward, from the period of 09–August 21, 2020, the flood was receded and decreased by 43.59 km2. In contrast, the Hydrodynamic model was used to simulate flood inundations based on Ribe and the Gumara River time-series discharge data. The model simulation determines the flooding extent of the study area on August 09, 2020, and the result shows an inundation area of 135 km2, which is similar to flood inundations extracted by SAR imagery. Generally, floodwater was expanded towards Ribe and Gumara river courses, on wetlands, depression areas, and along Lake Tana shoreline, where the elevation was extremely low. Therefore, a Time-based flood inundation map extracted from SAR images can give valuable information for the analysis of flood propagation and flood risk management.

Hypothetical failure of the Khassa Chai dam and flood risk analysis for Kirkuk, Iraq

Many of Iraqi's high-hazard dams lack an Emergency Action Plan, which should include a flood inundation map to show which downstream areas would be flooded if the dams were to fail. This article presents the results of the simulation of a hypothetical 2D dam break for the 58 m high Khassa Chai dam in Kirkuk, Iraq, using HEC-RAS 2D 5.0.7 software. The Khassa Chai dam is situated 7.4 km north of Kirkuk. The simulations revealed that the dam-break flood will affect eight major bridges and the majority of Kirkuk city's metropolitan neighborhoods. Within an hour, the floodwaters will reach the city's center. The flood hazard map revealed that if the Khassa Chai dam fails, many people, vehicles, and structures will be at danger. The findings of this paper can be used to identify evacuation routes and refuge sites as well as build suitable warning systems in order to limit the risk for fatalities if the Khassa Chai dam fails. Moreover, as the effect of modeling bridges downstream of failed dams has not been explored yet, to the knowledge of the authors, eight bridges have been modeled. It was concluded that ignoring bridges in such a large dam break model will not affect the results significantly, which saves the time of data collection and model development.

A practical probabilistic approach for simulating life loss in an urban area associated with a dam-break flood

Dam safety simulation is crucial to design and improve emergency plans to mitigate the flood disaster risk associated with break events, particularly in the areas located downstream. Applying deterministic estimation of the peak flow has some limitations for deciding in terms of uncertainty. In this study, we proposed an integrated approach based on Monte Carlo Simulation (MCS), HEC-RAS 2D, and HEC-LifeSim models to simulate dam break to deal with the flood risk with probability rather than analyzing a few dam break scenarios. This approach was applied to simulate a dam break event and its impact on Life Loss (LL) according to 12 alternatives in Sidi Yahya Zaer town, in Morocco. The results showed that for dam-break peak flows associated with Exceedance probabilities of 1%, 5%, 10%, 50%, 90%, and 95% the mean of the simulated LL are ranging from 2 to 334 people at night time and from 2 to 173 people at day time. They exponentially depend on dam-break peak flows. Furthermore, the comparison of the LL results with those of the historic events showed that a fatality of 125 people that was occurred by the Buffalo Creek dam break in the USA (1972) is possible in SYZ town with a probability of 9.2%. Globally, the proposed methodology is valuable to evaluate the dam-break consequences associated with a probability. Also, it can be reproduced to evaluate the vulnerability of the future urbanized areas not only to flood disasters but to other natural and industrial disasters.

Development of a risk-based optimization approach to improve the performance of urban drainage systems

ABSTRACT Considering the great deal of rainfall uncertainty in urban drainage system (UDS) design/rehabilitation, a copula-based design approach is developed within a Monte Carlo simulation (MCS) to improve system performance. Firstly, inundation zones are determined using HEC-RAS 2D and GIS tools. Then, inundation zones of flood scenarios are integrated with damage–depth functions in GIS to obtain the associated damage costs. Accordingly, a mapping is made between the flood volume (calculated by EPA-SWMM) and its related damage. This information is used in a coupled EPA-SWMM and differential evolution (DE) search algorithm to determine the best rehabilitation strategies. The approach is applied to a catchment in Tehran and its results are compared with the return-period method. Results show that the risk-based design approach could provide a 92% reduction in expected annual flood damage (EAD) and presents optimal designs with benefit-to-cost ratios up to 11, according to budget level. This approach yields more robust designs/strategies relative to the return-period method.

Flash Flood Water Depth Estimation Using SAR Images, Digital Elevation Models, and Machine Learning Algorithms

In this article, the local spatial correlation of multiple remote sensing datasets, such as those from Sentinel-1, Sentinel-2, and digital surface models (DSMs), are linked to machine learning (ML) regression algorithms for flash floodwater depth retrieval. Edge detection filters are applied to remote sensing images to extract features that are used as independent features by ML algorithms to estimate flood depths. Data of dependent variables were obtained from the Hydrologic Engineering Center’s River Analysis System (HEC-RAS 2D) simulation model, as applied to the New Cairo, Egypt, post-flash flood event from 24–26 April 2018. Gradient boosting regression (GBR), random forest regression (RFR), linear regression (LR), extreme gradient boosting regression (XGBR), multilayer perceptron neural network regression (MLPR), k-nearest neighbors regression (KNR), and support vector regression (SVR) were used to estimate floodwater depths; their outputs were compared and evaluated for accuracy using the root-mean-square error (RMSE). The RMSE accuracy for all ML algorithms was 0.18–0.22 m for depths less than 1 m (96% of all test data), indicating that ML models are relatively portable and capable of computing floodwater depths using remote sensing data as an input.

Toward improved river boundary conditioning for simulation of extreme floods

Hydrodynamic modeling is a common approach for flood inundation mapping. These models use conservation of mass and momentum to simulate the river hydrodynamics during flood events. To simulate floods and estimate the spatio-temporal distribution of extreme water levels, the upstream and downstream flows are used as the minimum required boundary conditions (BCs) in a hydrodynamic model. In this study, we show that such approach does not provide a realistic estimate of fluxes at boundaries and so poses uncertainty to estimated flood inundation, especially during extreme floods. To overcome these limitations, we propose a new BC approach that demonstrates the significance of two additional BC components, namely lateral flows and vertical fluxes, applied to the channel, and incorporates hydrologic bias impacts into the hydrodynamic model setup. The basis for applying these BC modifications is to conserve the water mass flux into the river systems during extreme flood events. We utilize two well-known hydrodynamic flood inundation models, LISFLOOD-FP and HEC-RAS 2D, to simulate a flash flood in 2016 as well as an extreme flood during Hurricane Harvey in fully-gauged and semi-gauged river systems, respectively. Results from both case studies confirm that modeling with only upstream and downstream BCs underestimates the flood hydrographs and inundation areas while using the proposed BC approach can significantly improve the modeling performance.

Indian Oil lets contract for new units at Barauni refinery

Rain-on-Grid (RoG) modelling is an increasingly popular approach within the storm risk management, in which the hydrological and hydrodynamic flood processes are modelled entirely within the 2D hydrodynamic model. Contrarily to what was done in the context of flood propagation in rivers, at the present time no systematic benchmarking study of the software packages implementing this approach is available in the literature. The need of benchmarking studies related to the RoG approach is becoming ever more important for HEC-RAS 2D (HR2D), the use of which has been rapidly increasing in the last few years, as further testified by very recent papers explicitly focussed on this research issue. However, there is still a lack of studies that clearly show the suitability of this software package as a reliable fully integrated hydrologic-hydrodynamic model. Therefore, the novelty introduced by this paper is the benchmarking of HR2D for RoG simulations, analysing several situations representing most of the applications related to “storm-event” hazard assessment. Specifically, after the analysis of ideal cases, which gave the opportunity to carefully assess the accuracy of the numerical schemes for RoG simulations, practical applications were considered to face some challenging issues related to the analysis of rainfall/runoff in urbanized areas and actual basins, including the numerical treatment of buildings and the computation of infiltration losses within hydrodynamic computations. The HR2D results were compared to analytical solutions, when available, experimental data and numerical solutions of a numerical code developed by the authors. The results shown in the paper highlight the potential but also the limitations of this software package, providing evidence to scientists and technicians about those situations for which reliable results are expected but also indications on specific aspects that need improvements so as to increase the model accuracy.

Is HEC-RAS 2D accurate enough for storm-event hazard assessment? Lessons learnt from a benchmarking study based on rain-on-grid modelling

Rain-on-Grid (RoG) modelling is an increasingly popular approach within the storm risk management, in which the hydrological and hydrodynamic flood processes are modelled entirely within the 2D hydrodynamic model. Contrarily to what was done in the context of flood propagation in rivers, at the present time no systematic benchmarking study of the software packages implementing this approach is available in the literature. The need of benchmarking studies related to the RoG approach is becoming ever more important for HEC-RAS 2D (HR2D), the use of which has been rapidly increasing in the last few years, as further testified by very recent papers explicitly focussed on this research issue. However, there is still a lack of studies that clearly show the suitability of this software package as a reliable fully integrated hydrologic-hydrodynamic model. Therefore, the novelty introduced by this paper is the benchmarking of HR2D for RoG simulations, analysing several situations representing most of the applications related to “storm-event” hazard assessment. Specifically, after the analysis of ideal cases, which gave the opportunity to carefully assess the accuracy of the numerical schemes for RoG simulations, practical applications were considered to face some challenging issues related to the analysis of rainfall/runoff in urbanized areas and actual basins, including the numerical treatment of buildings and the computation of infiltration losses within hydrodynamic computations. The HR2D results were compared to analytical solutions, when available, experimental data and numerical solutions of a numerical code developed by the authors. The results shown in the paper highlight the potential but also the limitations of this software package, providing evidence to scientists and technicians about those situations for which reliable results are expected but also indications on specific aspects that need improvements so as to increase the model accuracy.

RELIABILITY OF 2D HYDRODYNAMIC MODEL ON FLOOD INUNDATION ANALYSIS

This paper presents a flood inundation analysis to determine the possibility of flooding in urban areas. Many studies have conducted flood simulations to generate inundation problems due to river overflow. Urban flood problems commonly occur because of rainfall in subcatchments that do not enter the channel effectively. Therefore, it is necessary to analyze the inundation that occurs owing to overland flow. This study investigates the usefulness of rain-on-grid boundary conditions compared to flow hydrographs to represent the overland flow. The 2D shallow water equation was applied using the HEC RAS 2D model to select suitable boundary conditions to describe watershed problems. The rain-on-grid boundary condition gives a direct rainfall–runoff calculation in the simulation. The flow hydrograph was calculated separately using the rainfallrunoff analysis based on the storm-water-management model. Although rain-on-grid represents the real physical condition, it is difficult for the 2D hydrodynamic model to assess the drainage channel. However, the flow hydrograph boundary condition shows good results compared qualitatively with historical data based on on-site observations obtained from the Department of Public Works, Highways, and Drainage Management. Furthermore, this research provides the capability of flow hydrographs and rain-on-grid boundary conditions for flood simulation in urban areas. The results can be used to conduct an appropriate future simulation of urban drainage planning

Normalizing the river of Cisangkuy to reduce the flood risk in the future

The rapid population growth has made residential land more widespread. causing the surface water runoff getting bigger and coupled with the narrowing of the river cross-section by sediment so that the river’s capacity is no longer able to accommodate the existing flood discharge. This study aims to reduce the risk of flooding in the Cisangkuy river. Modeling was carried out using HEC-RAS 2D. Modeling results in the existing conditions show that water has flowed into the residential area. Handling in the form of normalization of the Cisangkuy River as an appropriate alternative for reducing flood risk. After normalization, there was a decrease in the water level in the upper reaches of the Cisangkuy river from an altitude of 672.13 masl to 667.85 masl and in the middle of the Cisangkuy river it fell + 3.3 meters. which was originally from an altitude of 668.57 masl to 665.21 masl. The improvement of the Cisangkuy River has had a significant impact on the flow of the Cisangkuy tributary and the urban drainage system around the area. So that the Cisangkuy River can accommodate the discharge and the risk of urban flooding can be reduced. With this risk reduction, flooding that has an impact on the social, economic, and health sectors can be controlled and can be focused on future urban problems.

An interactive Web-GIS fluvial flood forecast and alert system in operation in Portugal

Floods are one of the natural disasters not preventable, affecting people and causing significant damage to economic activities and infrastructures. Thus, it is of foremost importance to, within a disaster risk-reduction strategy, develop a useful flood forecast and alert system to prevent people from suffering flood disasters and mitigate its consequences. This article presents the Flood Forecast and Alert System in operational mode since 2019 for the Águeda river basin located in Portugal’s centre region. This system is technologically advanced, differing from others since it uses a coupled real-time hydrologic and 2D hydrodynamic modelling supported on numerical weather prediction and a high-resolution digital terrain surface model. The system components are automatically activated and linked: i) a rainfall forecasting model (WRF), ii) a hydrological model (HEC-HMS), iii) a hydraulic model (HEC-RAS 2D), and a iv) Web-GIS platform. The hydrological model is forced with forecast precipitation for the next three days and updated every 6 h, which is crucial to generate pre-flood hazard maps. It also includes a Web GIS service for flood hazard dissemination available for civil authorities and citizens. A flood forecast and alert system is highly relevant to the community since, by enhancing knowledge, it provides the authorities responsible for assessing and managing the flood risk, responsiveness to disasters and timely decision-making, which is even more evident in the context of climate change.

Urban flood risk analysis of buildings using HEC-RAS 2D in climate change framework

AbstractThe present study aims to assess flood depth, building risk analysis, and the effectiveness of various flood adaptation strategies to attenuate building risk caused by urban floods in climate change scenarios. A framework is proposed where a hydraulic model, Hydrologic Engineering Center's-River Analysis System 2D (HEC-RAS 2D), is applied for 2-dimensional flood modeling to estimate (a) submerged areas, (b) flood depth, and (c) building risk for extreme events corresponding to two representative concentration pathways (RCPs), 6.0 and 8.5. Greater Hyderabad Municipal Corporation (GHMC), India, is chosen for demonstration. Percentages of buildings in GHMC under high, medium, and low risks for RCP 6.0 are 38.19, 9.91, and 51.9% in the respective order, and these are 40.82, 10.55, and 48.63% for RCP 8.5. Six flood proofing (FP) strategies (S1–S6) are proposed for attenuating building risk along with the required capital cost. The capital investment required for FP to achieve the ideal situation of no risk for all buildings (strategy S6) works out to Rs. 3,740 × 107 and Rs. 3,800 × 107 for RCPs 6.0 and 8.5. It is observed that the effect of adaptation strategies is significant.

Simulation Of Flood Mapping in Amasing Kali Village Using HEC-RAS 2D

This study aims to map the distribution of floods that occurred due to the overflow of the Amasing Kali River on Bacan Island, South Halmahera. The magnitude of the flood as an input in the Watershed (DAS) system was analyzed using the Nakayasu unit synthetic hydrograph (HSS) method, while the morphometric characteristics of the watershed were analyzed by extracting digital elevation model data (Digital Elevation Model, DEM) using a Geographic Information System (GIS) application. The simulation of flood distribution with return periods of 2, 5, 10 and 25 years was carried out by applying the HecRAS 2D application. The mapping of the analysis and simulation results of this study shows that the potential flood-affected areas are on the north and south sides of Amasing Kali village with inundation heights varying between 0.50 m – 1.50 m.

Integrating Reservoir Operations and Flood Modeling with HEC-RAS 2D

Current free to use models developed by the United States Army Corps of Engineers (USACE) perform unique functions (e.g., hydrology, hydraulics, reservoir operations, and flood impact analysis) that are widely used in numerous studies and applications. These models are commonly set up in a framework that is limited to point source connections, which is problematic in regions with flat topography and complex hydrodynamics. The separate models need to be integrally linked and jointly considered for accurate risk communication and decision-making, especially during major storm events. Recently, Hurricane Harvey (2017) exposed the shortcomings of the existing framework in West Harris County, TX, where an insufficient understanding of potential flood risk and impacts contributed to the extensive flood damages sustained in the region. This work illustrates the possibility of using a single hydraulic model, HEC-RAS 2D, to perform all hydrologic, hydraulic, and reservoir operations modeling necessary for accurate flood impact assessments. Implications of this study include a simplification of the entire flood impact analysis, which could help future flood risk communication and emergency planning.

Dam-Break Wave Propagation in Alpine Valley with HEC-RAS 2D: Experimental Cancano Test Case

AbstractFlood modeling by numerical solution of the two-dimensional (2D) shallow-water equations is ordinary practice. HEC-RAS 2D was recently released along with a suite of test cases showing the ...

Hydrodynamic Modelling of Juwana River Flooding Using HEC-RAS 2D

On the equator, Indonesia had very complex geographical, geological, hydrological conditions. It was also traversed by three large plates namely the Eurasian plate, the Indo-Australian plate, and the Pacific plate. Because of the colliding meeting of the three plates, the territory of Indonesia had a variety of topography ranging from hills, mountains, plateaus, lowlands, and basins. The basin found in the Juwana watershed caused frequent flooding every year due to the overflow of Juwana River. The river passed through Kudus and Pati. In the last ten years there had been 179 floods in Juwana River. This study aimed to examine the discharge and distribution of floods based on the return period of floods 2, 5, 10, 25, 50 and 100 years. The research method used was frequency analysis, snyder synthetic unit hydrograph analysis, and hydrodynamic modelling using HEC-RAS 5.0.6 2D (two dimention) with unsteady flow. The findings indicated that on the return period of floods 2, 5, 10, 25, 50, and 100 years, the discharge and distribution of floods were 1169.2 m3/with the inundated area of 22898.54 Ha, 1401.7 m3/with the inundated area of 25558.51 Ha, 1541 m3/with the inundated area of 26916.42 Ha, 1704.9 m3/with the inundated area of 28411.52 Ha, 1819.9 m3/with the inundated area of 29905.85 Ha, and 1930 m3/with the inundated area of 30785 Ha respectively.

SIMULASI KERUNTUHAN BENDUNGAN BILI-BILI KABUPATEN GOWA PROVINSI SULAWESI SELATAN

The extreme weather that occurred on January 22-24, 2019 in the Makassar city and surrounding areas caused massive flooding in the downstream area of ​​the Bili-Bili DAM which covered 5 districts and cities, namely Gowa Regency, Makassar City, Jeneponto Regency, Maros Regency, and Selayar Regency. There 6757 people were displaced and tens of hectares of rice fields and housing were inundated. As a form of evaluation in the context of disaster mitigation efforts if similar or larger events occur in the future, it is very important to do a floods simulation to mapping which areas will be affected by flood inundation if the Bili-Bili DAM collapses. The software used to simulate flooding in this study is HEC-RAS 2D. The object of research is focused in the city of Makassar which is a densely populated city center and other vital objects. The parameters analyzed are the distribution of flood inundation area and the depth of flood inundation. Simulation results that have been calibrated will be used as a reference for disaster mitigation planning.

Assessment of inundation risk in urban floods using HEC RAS 2D

Flood is the most common natural disaster upsetting the highest population of the world. In recent times, severe floods in urban areas are occurring more frequently owing to uncontrolled urbanization and climate change and it will continue to grow in upcoming years. Prevention of such events is not possible but with advancement of technology, flood-vulnerable areas can be identified through 2-D modeling of critical rainfall events. The difficulty associated with urban floods is unpredictable flow conditions in urban environment due to rapid alterations in topography and unavailability of extensive raw dataset. Thus, modeling of urban floods becomes a complex process. A vast number of numerical models have evolved over the past few years which are capable of flood mapping; most of them are commercial, rigorous and need extensive dataset to generate precise results. This paper presents a simple sophisticated approach to analyze extreme rainfall events based on past critical events and synthetic hyetographs developed from IDF curves for a part of Hyderabad, India. HEC-RAS, a freely available 2-D hydraulic model with integration to GIS is used to generate depth of flood inundation over underlying terrain and risk maps of flood inundation are developed for different rainfall scenarios. The model results identify 17% of total area is liable to floods out of which 9% area indicates high risk, 52% area shows medium risk and remaining 35% area falls under low risk of flooding.