Channel roughness is a sensitive parameter in development of hydraulic model for flood forecasting and flood inundation mapping. The requirement of multiple channel roughness coefficient Mannnig’s ‘n’ values along ...Channel roughness is a sensitive parameter in development of hydraulic model for flood forecasting and flood inundation mapping. The requirement of multiple channel roughness coefficient Mannnig’s ‘n’ values along the river has been spelled out through simulation of floods, using HEC-RAS, for years 1998 and 2003, supported with the photographs of river reaches collected during the field visit of the lower Tapi River. The calibrated model, in terms of channel roughness, has been used to simulate the flood for year 2006 in the river. The performance of the calibrated HEC-RAS based model has been accessed by capturing the flood peaks of observed and simulated floods;and computation of root mean squared error (RMSE) for the intermediated gauging stations on the lower Tapi River.展开更多
Channel roughness is considered as the most sensitive parameter in development of hydraulic models for flood forecasting and flood inundation mapping. Hence, it is essential to calibrate the channel roughness coeffici...Channel roughness is considered as the most sensitive parameter in development of hydraulic models for flood forecasting and flood inundation mapping. Hence, it is essential to calibrate the channel roughness coefficient (Mannnig’s “n” value) for various river reaches through simulation of floods. In the present study it is attempted to calibrate and validate Mannnig’s “n” value using HEC-RAS for Mahanadi Riverin Odisha (India). For calibration of Mannnig’s “n” value, the floods for the years 2001 and 2003 have been considered. The calibrated model, in terms of channel roughness, has been used to simulate the flood for year2006 inthe same river reach. The performance of the calibrated and validated HEC-RAS based model has been tested using Nash and Sutcliffe efficiency. It is concluded from the simulation study that optimum Mannnig’s “n” value that can be used effectively for Khairmal to Barmul reach of Mahanadi Riveris 0.029. It is also verified that the peak flood discharge and time to reach peak value computed using Mannnig’s “n” of 0.029 showed only an error of 5.42% as compared with the observed flood data of year 2006.展开更多
The Sahelian regions have experienced a drought that has made them vulnerable to hydro-climatic conditions. Strategies have been developed to re</span><span style="font-family:Verdana;">duce this...The Sahelian regions have experienced a drought that has made them vulnerable to hydro-climatic conditions. Strategies have been developed to re</span><span style="font-family:Verdana;">duce this vulnerability. The governments of Senegal, Mauritania, Mali and Guinea</span><span style="font-family:Verdana;"> have created the Organization for the development of the Senegal River (OMVS in french) with the aim of realizing large hydraulic installations. This resulted in the construction of the Diama and Manantali dams in the Senegal River Basin. The first aims to stop the saline intrusion, the second to regulate the flow of the river, to allow the irrigation of agricultural perimeters, and to produce electrical energy. The impoundment of the Diama dam has modified the hydraulic behavior of the estuary. The purpose of this study is to carry out </span><span style="font-family:Verdana;">the hydraulic modeling of the estuary of Senegal river downstream of the Diama Dam in transient mode by the HEC-RAS software. Two geometric models were </span><span style="font-family:Verdana;">constructed on the basis of a digital terrain model (DTM) using the Arc-GIS and HEC GeoRAS soft wares after processing the collected topographic data. The first geometric model, of which the areas of Senegal river downstream Diama Dam have been represented by cross-section, is one-dimensional. The </span><span style="font-family:Verdana;">second one is also one dimensional;in this model, the area of the Senegal River </span><span style="font-family:Verdana;">estuary downstream Diama Dam is introduced as water storage zones. The components of these models are the stream sections, lateral links, and storage areas. The flood hydrograph downstream Diama Dam is introduced as conditions at the upstream limits of the models while the tidal is introduced as a downstream condition. After the stability and calibration, the results given by HEC-RAS simulations are the variations of the water levels, the temporal variations of the flow rates for each section, the maximum flow velocities and the propagation times of the flood waves. The analysis and comparisons of these results strongly suggest using HEC-RAS issues as a decision-making tool helping to manage floods during times of crisis.展开更多
Channel roughness is the most sensitive parameter in development of hydraulic model for flood forecasting and flood plane mapping. Hence, in the present study it is attempted to calibrate the channel roughness coeffic...Channel roughness is the most sensitive parameter in development of hydraulic model for flood forecasting and flood plane mapping. Hence, in the present study it is attempted to calibrate the channel roughness coefficient (Manning’s “n” value) along the river Mahanadi, Odisha through simulation of floods using HEC-RAS. For calibration of Manning’s “n” value the flood of year 2003 has been considered. The calibrated model, in terms of channel roughness, has been used to simulate the flood for year 2006 in the same river reach. The performance of the calibrated and validated HEC-RAS based model is tested using Nash and Sutcliffe efficiency. It is concluded from the simulation study that Mannnig’s “n” value of 0.032 gives best result for Khairmal to Munduli reach of Mahanadi River.展开更多
<span style="font-family:Verdana;">Flooding regimes in arid regions are heavily influenced by climate change, water shortage, water regulations, and increased water demands. The low amount of annual pr...<span style="font-family:Verdana;">Flooding regimes in arid regions are heavily influenced by climate change, water shortage, water regulations, and increased water demands. The low amount of annual precipitation due to the desert climate may lead to false estimations of flooding hazards. This study analyzed flash floods caused by short-intense rainstorms. The objective of this study was to determine flood risk related to identified precipitation depths. The project quantized the runoff corresponding to different design storms and used hydraulics and geospatial data to determine flood elevations. The study constructed hydrologic and hydraulic models to quantify flood hazards in the adjacent area of Wadi Abu Nashayfah. Peak discharges for the wadi were computed by using observed rainfall data, and the output of this process was applied to compute water surface elevations within the flow channel. At upstream, there is </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">high potential of flooding when Wadi Abu Nashayfah receives </span><span style="font-family:Verdana;">a </span><span style="font-family:""><span style="font-family:Verdana;">minimum of 25 mm of rain which generates 40.60 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">/s of peak discharge, thus, at this point the stream will overtop its banks and risking the adjacent area. In </span></span><span style="font-family:Verdana;">the </span><span style="font-family:""><span style="font-family:Verdana;">second case, flow will overtop its banks when the channel receives at least 35 mm of rain and peak discharge level to 67.20 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">/s. While flow will reach bank full point if wadi Abu Nashayfah receives 10.00 mm of rain and generates 14.80 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">/s of streams downstream. The depth of precipitation at which the channel was overtopped was determined in several locations. The predicted overtopping was compared to historic events with good agreement.展开更多
This paper describes a model of a 3.06km long river reach between two small reservoirs under both open flow and ice covering conditions for different operational settings of the stoplogs in the downstream reservoir. T...This paper describes a model of a 3.06km long river reach between two small reservoirs under both open flow and ice covering conditions for different operational settings of the stoplogs in the downstream reservoir. The HEC-RAS model developed by the Hydrological Engineering Center of US Army Corps of Engineers was used to compare different approaches in terms of flow velocity, water level and the Froude number. The impacts of heavily vegetated main channel and floodplain on ice accumulations were investigated. And it is shown that this vegetation plays a significant role in the formation of river ice jam during winter period and thus the vegetated channel has strong influence on ice flooding. In addition, the paper explores the impact bouh of the operation of the stoplogs during the winter period and the presence of the downstream dam on the accumulation of ice jam along this river reach.展开更多
Accurate and reliable river flow information is critical to planning and management for sustainable water resources utilization. Most of engineering activities related to hydrologic designs, flood, drought, reservoirs...Accurate and reliable river flow information is critical to planning and management for sustainable water resources utilization. Most of engineering activities related to hydrologic designs, flood, drought, reservoirs and their operations are heavily dependent on the river flow information derived from river rating curve. The rating curve for a given river section is normally developed from a set of direct stage-discharge measurements for different periods. This involves considerable labour, risk and resources, and presupposes a complex and extensive measuring survey. Extrapolating the rating curve beyond the measured range, as common in many cases, is fraught with errors and uncertainties, due to the complex hydraulic behaviour of the surface water profile in transition from section, channel, downstream and flood plain controls which are often poorly understood with direct measurements. Hydraulic modeling has recently emerged as one of the more promising methods to efficiently develop accurate rating curves for a river section with simple or complex hydraulic structures and conditions. This paper explores the use of a Hydraulic Engineering Center-River Analysis System (HEC-RAS) model to review and develop river rating curves for three hydrometric stations on two rivers in Kwale, coastal Kenya. The HEC-RAS models were set up based on topographical (cross section and longitudinal) survey data for the reaches and engineering drawings for the hydraulic structures commonly used as section controls for flow measurement. The model was calibrated under unsteady state conditions against measured stage-discharge data which were captured using a Velocity Current Meter (Valeport) and an Acoustic Doppler Current Profiler (ADCP) for both low and high flow. The rating curves were extracted from model results and the uncertainty associated with each rating curve analyzed. The results obtained by the HEC-RAS model were satisfactory and deemed acceptable for predicting discharge across the stage range at each river section.展开更多
文摘Channel roughness is a sensitive parameter in development of hydraulic model for flood forecasting and flood inundation mapping. The requirement of multiple channel roughness coefficient Mannnig’s ‘n’ values along the river has been spelled out through simulation of floods, using HEC-RAS, for years 1998 and 2003, supported with the photographs of river reaches collected during the field visit of the lower Tapi River. The calibrated model, in terms of channel roughness, has been used to simulate the flood for year 2006 in the river. The performance of the calibrated HEC-RAS based model has been accessed by capturing the flood peaks of observed and simulated floods;and computation of root mean squared error (RMSE) for the intermediated gauging stations on the lower Tapi River.
文摘Channel roughness is considered as the most sensitive parameter in development of hydraulic models for flood forecasting and flood inundation mapping. Hence, it is essential to calibrate the channel roughness coefficient (Mannnig’s “n” value) for various river reaches through simulation of floods. In the present study it is attempted to calibrate and validate Mannnig’s “n” value using HEC-RAS for Mahanadi Riverin Odisha (India). For calibration of Mannnig’s “n” value, the floods for the years 2001 and 2003 have been considered. The calibrated model, in terms of channel roughness, has been used to simulate the flood for year2006 inthe same river reach. The performance of the calibrated and validated HEC-RAS based model has been tested using Nash and Sutcliffe efficiency. It is concluded from the simulation study that optimum Mannnig’s “n” value that can be used effectively for Khairmal to Barmul reach of Mahanadi Riveris 0.029. It is also verified that the peak flood discharge and time to reach peak value computed using Mannnig’s “n” of 0.029 showed only an error of 5.42% as compared with the observed flood data of year 2006.
文摘The Sahelian regions have experienced a drought that has made them vulnerable to hydro-climatic conditions. Strategies have been developed to re</span><span style="font-family:Verdana;">duce this vulnerability. The governments of Senegal, Mauritania, Mali and Guinea</span><span style="font-family:Verdana;"> have created the Organization for the development of the Senegal River (OMVS in french) with the aim of realizing large hydraulic installations. This resulted in the construction of the Diama and Manantali dams in the Senegal River Basin. The first aims to stop the saline intrusion, the second to regulate the flow of the river, to allow the irrigation of agricultural perimeters, and to produce electrical energy. The impoundment of the Diama dam has modified the hydraulic behavior of the estuary. The purpose of this study is to carry out </span><span style="font-family:Verdana;">the hydraulic modeling of the estuary of Senegal river downstream of the Diama Dam in transient mode by the HEC-RAS software. Two geometric models were </span><span style="font-family:Verdana;">constructed on the basis of a digital terrain model (DTM) using the Arc-GIS and HEC GeoRAS soft wares after processing the collected topographic data. The first geometric model, of which the areas of Senegal river downstream Diama Dam have been represented by cross-section, is one-dimensional. The </span><span style="font-family:Verdana;">second one is also one dimensional;in this model, the area of the Senegal River </span><span style="font-family:Verdana;">estuary downstream Diama Dam is introduced as water storage zones. The components of these models are the stream sections, lateral links, and storage areas. The flood hydrograph downstream Diama Dam is introduced as conditions at the upstream limits of the models while the tidal is introduced as a downstream condition. After the stability and calibration, the results given by HEC-RAS simulations are the variations of the water levels, the temporal variations of the flow rates for each section, the maximum flow velocities and the propagation times of the flood waves. The analysis and comparisons of these results strongly suggest using HEC-RAS issues as a decision-making tool helping to manage floods during times of crisis.
文摘Channel roughness is the most sensitive parameter in development of hydraulic model for flood forecasting and flood plane mapping. Hence, in the present study it is attempted to calibrate the channel roughness coefficient (Manning’s “n” value) along the river Mahanadi, Odisha through simulation of floods using HEC-RAS. For calibration of Manning’s “n” value the flood of year 2003 has been considered. The calibrated model, in terms of channel roughness, has been used to simulate the flood for year 2006 in the same river reach. The performance of the calibrated and validated HEC-RAS based model is tested using Nash and Sutcliffe efficiency. It is concluded from the simulation study that Mannnig’s “n” value of 0.032 gives best result for Khairmal to Munduli reach of Mahanadi River.
文摘<span style="font-family:Verdana;">Flooding regimes in arid regions are heavily influenced by climate change, water shortage, water regulations, and increased water demands. The low amount of annual precipitation due to the desert climate may lead to false estimations of flooding hazards. This study analyzed flash floods caused by short-intense rainstorms. The objective of this study was to determine flood risk related to identified precipitation depths. The project quantized the runoff corresponding to different design storms and used hydraulics and geospatial data to determine flood elevations. The study constructed hydrologic and hydraulic models to quantify flood hazards in the adjacent area of Wadi Abu Nashayfah. Peak discharges for the wadi were computed by using observed rainfall data, and the output of this process was applied to compute water surface elevations within the flow channel. At upstream, there is </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">high potential of flooding when Wadi Abu Nashayfah receives </span><span style="font-family:Verdana;">a </span><span style="font-family:""><span style="font-family:Verdana;">minimum of 25 mm of rain which generates 40.60 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">/s of peak discharge, thus, at this point the stream will overtop its banks and risking the adjacent area. In </span></span><span style="font-family:Verdana;">the </span><span style="font-family:""><span style="font-family:Verdana;">second case, flow will overtop its banks when the channel receives at least 35 mm of rain and peak discharge level to 67.20 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">/s. While flow will reach bank full point if wadi Abu Nashayfah receives 10.00 mm of rain and generates 14.80 m</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;">/s of streams downstream. The depth of precipitation at which the channel was overtopped was determined in several locations. The predicted overtopping was compared to historic events with good agreement.
文摘This paper describes a model of a 3.06km long river reach between two small reservoirs under both open flow and ice covering conditions for different operational settings of the stoplogs in the downstream reservoir. The HEC-RAS model developed by the Hydrological Engineering Center of US Army Corps of Engineers was used to compare different approaches in terms of flow velocity, water level and the Froude number. The impacts of heavily vegetated main channel and floodplain on ice accumulations were investigated. And it is shown that this vegetation plays a significant role in the formation of river ice jam during winter period and thus the vegetated channel has strong influence on ice flooding. In addition, the paper explores the impact bouh of the operation of the stoplogs during the winter period and the presence of the downstream dam on the accumulation of ice jam along this river reach.
文摘Accurate and reliable river flow information is critical to planning and management for sustainable water resources utilization. Most of engineering activities related to hydrologic designs, flood, drought, reservoirs and their operations are heavily dependent on the river flow information derived from river rating curve. The rating curve for a given river section is normally developed from a set of direct stage-discharge measurements for different periods. This involves considerable labour, risk and resources, and presupposes a complex and extensive measuring survey. Extrapolating the rating curve beyond the measured range, as common in many cases, is fraught with errors and uncertainties, due to the complex hydraulic behaviour of the surface water profile in transition from section, channel, downstream and flood plain controls which are often poorly understood with direct measurements. Hydraulic modeling has recently emerged as one of the more promising methods to efficiently develop accurate rating curves for a river section with simple or complex hydraulic structures and conditions. This paper explores the use of a Hydraulic Engineering Center-River Analysis System (HEC-RAS) model to review and develop river rating curves for three hydrometric stations on two rivers in Kwale, coastal Kenya. The HEC-RAS models were set up based on topographical (cross section and longitudinal) survey data for the reaches and engineering drawings for the hydraulic structures commonly used as section controls for flow measurement. The model was calibrated under unsteady state conditions against measured stage-discharge data which were captured using a Velocity Current Meter (Valeport) and an Acoustic Doppler Current Profiler (ADCP) for both low and high flow. The rating curves were extracted from model results and the uncertainty associated with each rating curve analyzed. The results obtained by the HEC-RAS model were satisfactory and deemed acceptable for predicting discharge across the stage range at each river section.
