Scour Potential Research Articles

Cold Region River Flood Mapping and Scour Potential Prediction: Insights from Hydraulic Model Using Advanced Autonomous Surface Vehicles

This study aimed to map the 2022 flood with a 16.5-year return period near a bridge on the Red River, close to Grafton City, North Dakota, and evaluate the scour potential around the bridge. The Red River Basin (RRB) near Grand Forks, ND, and Emerson, ND, is a cold region river vulnerable to floods. Local scouring around bridge piers during floods can lead to hydraulic structure failure. An Autonomous Surface Vehicle (ASV) equipped with LiDAR DEM data from the ND DWR’s LiDAR dataset was used to collect comprehensive bathymetry and discharge data, including the 2022 flood. The HEC-RAS model was used to create flood maps, and the Colorado State University (CSU) methodology was employed to assess local scour around the bridge pier. The study area recorded maximum velocities of 1.71 m/s, 1.87 m/s, and 1.56 m/s for discharge values of 368 m3/s, 784 m3/s, and 1335 m3/s, respectively, with higher velocities recorded upstream of the bridge. The maximum water depth reached 13.14 m during the peak discharge of 1335 m3/s. Higher discharge resulted in increased Froude number and contraction scour depth, with the latter continuing to increase even when the Froude number decreased as water reached the bridge deck. The study highlights the effectiveness of integrating ASVs, bathymetry, and LiDAR data to comprehensively understand flood dynamics and bridge scour in cold region rivers, offering the way for the development of effective flood control measures and strategies to safeguard critical infrastructure.

ArchIMEDES: Computer Vision Tracking of the Inherent Changes to Structural Stability of Masonry Arch Bridges Resulting from Increased Bed Scour.

Scour-induced failure of masonry arch bridges is a common cause of bridge collapse, especially during extreme flood events. Over recent years there has been a significant increase in the numbers of documented scour induced failures of this bridge stock across Europe and the USA. The extent of the scour can erode the supporting soil or sediment around the bridge piers or abutments, leading to a loss of support for the structure. As the foundation becomes unstable, it can result in settlement or tilting of the bridge, potentially causing structural damage, while the ongoing nature of scour can result in the progressive deterioration of the bridge’s ability to safely transfer load. Traditional hydraulic adjustments, such as streamlining abutments with wing walls and using cutwaters on piers, do not significantly reduce scour depth for masonry arch bridges. This paper presents initial findings of an investigation that links the changes of response in load carrying capacity to the easement of support at the bridge foundation due to scour. Scale experiments on the FlexiArchTM under loading with realistic scour conditions is contributing to the development of an algorithm based on the relationship between the structural response of the FlexiArchTM and prevailing scour conditions. The computer vision-based monitoring package ArchIMEDES, developed as part of the research, will use this algorithm to predict current bridge scour conditions at any given time. This will allow for potential scour development to be identified and investigated before the bridge collapses, ensuring the security and safety of these vital pieces of infrastructure.

Advanced Hydrodynamic Modelling of Flow at a River Bridge: Insights from 3D Computational Fluid Dynamics

Failure of river bridges is often due to hydraulic reasons, such as the development of severe scouring around piers and abutments. In many cases, the presence of bridge structures produces complex flow fields, which are difficult to predict using standard hydraulic models. This entails difficulties in estimating the hydrodynamic actions on the structure and the potential scour on the riverbed. A three-dimensional Computational Fluid Dynamics (3D CFD) model is used to analyze the flow field and the bed shear stresses at an existing bridge. The Volume of Fluid (VoF) method allows resolving the deformable free-surface, and the Detached Eddy Simulation (DES) approach allows resolving the dynamics of the energetically important turbulent eddies in the flow. The analysis deals with modeling the flow around a realistic, full-scale, multi-pier bridge in the Po River. Simulations considered different hydrodynamic regimes, i.e., the free-surface flow regime and the hypothetical pressure-flow regime which would occur when water levels are higher than the low chord of the bridge deck. The numerical application highlights the potential of the DES technique for analyzing the hydrodynamics of flow at bridges in natural river channels. Besides the turbulent flow fields and the description of the vortical structures, relevant results include the time-varying spatial distribution of the hydrodynamic forces acting on the different parts of the bridge and the time-varying distribution of the shear stress on the bed. This aspect is of particular interest because i) the estimation of drag forces on the structure components may be oversimplified using canonical, averaged formulas, and ii) the fluctuations in time of the bed shear stresses play a key role in determining the removal of sediments from the bed and the scour hole close to the bridge piers.

CORPUS CHRISTI SHIP CHANNEL DEEPENING PROJECT: OVERVIEW and MODELING APPROACH TO ASSESS ENVIRONMENTAL IMPACTS

The Corpus Christi Ship Channel in Texas connects the Port of Corpus Christi to the Gulf of Mexico. The Port is seeking to deepen the Corpus Christi Ship Channel to 22.9m (75ft) nominal depth in order to allow fully loaded very large crude carriers (VLCC’s) to access proposed terminals within the port complex. As a part of the environmental coordination requirements of the National Environmental Policy Act (NEPA) the Port Authority prepared a number of studies to assess the potential environmental impacts of the proposed channel deepening. These included assessing changes in hydrodynamics, salinity, storm surge, and sedimentation patterns including sediment movement generated by vessel generated currents. The channel design was also verified through vessel maneuvering studies which were conducted using modeled currents, dynamic underkeel clearance assessment, and propeller scour potential determination. The fate of proposed beneficial use of dredged materials to construct a submerged beach berm and perform beach nourishment was also assessed.

Toward a Complete Kinematic Description of Hydraulic Plucking of Fractured Rock

Scour by hydraulic plucking is a fundamental process in landscape evolution in which large, competent rock blocks are eroded from a fractured rock mass by flowing water. This process also affects engineered structures interacting with water, such as dams and bridges, and often leads to operational and safety concerns because erosion of large volumes of material can compromise structure foundations and serviceability. To assess potential scour at a site, present methods either are empirically derived, assume a specific failure mode, or significantly simplify the geometry of potentially eroding rock particles. This limits the broader applicability of these methods and their ability to offer actionable insight into scour risk. Therefore, the discrete-element method coupled with the lattice Boltzmann method was applied to assess hydraulic plucking of fractured rock. In this approach, the three-dimensional shape of rock particles was considered explicitly, including how each particle interacts dynamically with fluid. Additionally, the highly turbulent flow conditions at which plucking often occurs were modeled using large-eddy simulation. The results show that this modeling methodology was able to capture the correct kinematic failure mode in block removal in two example scenarios without restricting the potential failure mechanism, and naturally captures the governing response. This capability makes this scour assessment technique broadly applicable since site-specific characteristics can be input directly into scour risk assessments to understand the influence of local features on the plucking process.

Investigation of using mangrove-inspired skirt pile group as a scour countermeasure

Mangrove forests are able to protect the coastline because their dense prop root system reduces the flow velocity and stabilizes sediments against erosion. Inspired by this unique character of the mangrove root structure, a ring of skirt piles is proposed as a measure to mitigate local scour around monopile foundations. Numerical simulations using computational fluid dynamics (CFD) modeling as well as laboratory flume experiments were conducted to evaluate the scour mitigation effect in clear water current. The simulation results reveal that the presence of skirt piles reduces the near-bed tangential velocity and affects the vertical flow field around the monopile. The experimental results indicate that if all other parameters are held constant, the scour depth and volume increase with skirt pile spacing, decreases with the number of skirt pile rings. With a single ring of skirt piles, the scour potential reaches the lowest with an intermediate critical submerged height of the skirt piles; the scour depth and volume increase when the submerged height deviates from the critical value. The comparison between the numerical and experimental results implies that the installation of the skirt piles has not only hydraulic but also geotechnical benefits for scour mitigation.

MODIFIKASI KOLAM OLAK TIPE AMBANG BERGIGI DALAM RANGKA REHABILITASI KERUSAKAN BENDUNG CIKEUSIK DI JAWA BARAT

The presence of hydraulic jumps downstream of the weir structure is a natural occurrence that indicates a change in supercritical to subcritical flow characteristics. Hydraulic jump is one indicator of the dissipation of energy in the stilling basin. Therefore, the absence of a hydraulic jump can be a problem for some weirs, as happened in the Cikeusik Weir, which experienced damage to the stilling pool floor so that the energy dissipation did not function optimally. This paper will discuss the potential causes of damage to the Cikeusik weir and alternative designs for its countermeasures. A physical model test was carried out in the laboratory with a scale of 1: 40 to obtain an appropriate alternative to the stilling pond design for the Cikeusik weir. The tests were carried out with variations in the discharge Q2 years, Q25 years, and Q100 years, respectively. Three model tests were conducted, namely the existing and two modified designs. Based on the model testing results, extending stilling basin floor length with a dentated end sill and adding downstream riprap is the most optimal alternative because it has an energy reduction effectiveness of up to 80% and the lowest downstream scour potential compared to other options. The results of this test are expected not only to be used as an alternative to mitigate the damage to the Cikeusik weir but also to other locations that have similar problems. Keywords : Cikeusik Weir, stilling basin, Froude number, local scour, physical model

Evaluation: Screening, Analysis, and Countermeasures for Bridge Scour for AL-Manshia Bridge

This paper aims to study scouring and the recommended countermeasures for Al Manshiya Bridge, which is located in the Blue Nile in Khartoum city. The bridge was constructed in the year 2006, but in 2015; the east embankment approach of the bridge was exposed to scour causing failure of the approach deck slab. The paper follows the general procedure outlined by the Federal Highway Administration (FHWA) for stream stability, evaluating scour at bridges and countermeasures in order to have hydraulically safe bridge. Geomorphic and hydraulic factors affect the stream were studied; a scour analysis was made using Hydrologic Engineering Center - River Analysis System (HEC-RAS) software. To account for long-term, contraction, and local scour potential for the Peak flow event, HEC RAS model was used to construct quasi- unsteady sediment model. In order to protect the bridge, countermeasures for the bridge east abutment and channel adjacent to the bridge are studied, riprap around abutment and spur dikes were considered as the most suitable countermeasures.

Methods to detect and measure scour around bridge foundations

Bridges are indispensable structures vital to the operation of road and rail transportation networks. Crossing rivers and artificial waterways, however, presents a risk to their foundations due to scour actions. Scour is the number one cause for bridge failures and may occur beneath any bridge, large or small, with supports located within the waterway. This paper provides a summary of present scour detection and measurement equipment and associated assessment methodologies. In this regard, particular emphasis is placed on structural health monitoring better to evaluate the presence and influence of potential scour. A Sensitivity Analysis on a newly introduced monitoring system is also assumed. Furthermore, much research has been undertaken to create a technology that can instantly identify and detect bridge scour, improving survey reliability through prior inspection and prompt intervention. This research will explore and evaluate bridge scour detection methods employed and suggest a possible path for developing the detection system to identify scour depth effectively and efficiently. Finally, our key aim is to minimize human effort in identifying and bridge scour by using a quick, easy-to-use, cost-effective process, resulting in fewer injuries and economic savings.

Numerical Study on the Effect of Bank Vegetation on the Hydrodynamics of the American River under Flood Conditions

Vegetation can have an appreciable impact on the hydrodynamics and scour potential in natural rivers, but this effect is generally unaccounted for in high-fidelity computational fluid dynamic models. In this study, we have incorporated trees into the flow domain using two different approaches to study the hydrodynamics of the American River in Northern California under flood conditions. In the first approach, we resolved numerous trees as discrete objects. The second method incorporated a vegetation model into our in-house numerical model to treat the vegetation as a momentum sink along the banks. The flood flow of both cases was modeled using the large-eddy simulation. The computed hydrodynamics results of the cases were compared with a baseline case, which did not include any trees. Although both the tree-resolving and vegetation model approaches compared well with one another with respect to the flow field, they significantly altered the computed river flow dynamics and bed shear stress near the banks and the midwidth of the river compared with that of the no-tree case. Both methods that accounted for the resistance of the trees obtained lower and higher bed shear stresses and velocities along the banks and the midwidth of the river, respectively, than that of the baseline case. This research identified the important role that vegetation plays in natural rivers and provided researchers and engineers with the conceptual tools needed to incorporate vegetation into numerical models to improve the accuracy of the model results.

Flow Characteristics and Scour Depth in Lenticular Shaped Pier: Case Study at Ciujung Bridge, Banten

Pier is part of the structure under the bridge. The existence of a pier in the river flow causes changes in river flow patterns. Changes in the flow pattern will result in local scouring around the pier. This study aims to determine the effect of the shape of the pier on the potential for local scour that occurs around the pier, and the flow characteristics around the pier. This studymodelled the existing conditions of the Ciujung Bridge, where the Ciujung Bridge uses an oblong pier shape, and the shape will be replaced with a lenticular model pier. FLOW-3D (CFD) software will be used to modelled flow characteristics and the depth of scour that occurs.

Bridge pier geometry effects on local scour potential: A comparative study

Scour, or the localized loss of soil around the foundation, is a dominant factor contributing to failure. Scour at bridge piers, columns of elevated buildings, and wind turbines with monopile foundations can cause damage after flooding and natural hazards. However, due to the lack of sophisticated modeling, scour is not fully understood. This study utilizes computational fluid dynamic (CFD) simulations to understand the performance of different flow countermeasures in reducing the scour potential. We look at altering the flow around the pier and thereby alleviating the horseshoe vortices and downflow issues. CFD models are developed and validated with available experimental data. The recommended models, with turbulence closures, are employed to predict the bed shear stress for different pier configurations: streamlined shape, tapered sheath, delta vane, and guide wall with slanting vanes. Reductions in the maximum bed shear stress are 30% for both the angled plate and the delta vane, 20% for the tapered sheath, and 15% for the guide wall with slanting vanes. By reducing the bed shear stress, these countermeasures demonstrate their capability to mitigate scour. The proposed solutions have a potential to minimize the accelerated deterioration and protect bridges, elevated buildings, wind turbines, and coastal and offshore infrastructure against scour-induced failures.

Steep Creek Risk Assessment for Pipeline Design : A Case Study From British Columbia, Canada

ABSTRACT Pipelines in mountainous terrain often cross alluvial fans formed by steep creek processes of debris flows and debris floods and are thus exposed to their associated hazards. The design of new pipeline infrastructure and maintenance of existing pipelines necessitates steep creek risk assessments and appropriate mitigation design. We present methodology for assessing steep creek risk along pipeline routes that evaluates the probability of such processes causing a pipeline loss of containment or disruption in service. The methodology consists of estimating event frequency, scour potential, and the vulnerability of the pipeline to break if impacted by boulders. The approach can be adapted to other landslide geohazards so that different geohazard locations can be evaluated with a common metric. Steep creek process frequency is estimated based on field observations and review of documented events, historical air photo records, and terrain mapping based on LiDAR-generated topography. Scour potential is estimated based on channel morphology, presence of bedrock, and grain size distribution of channel bed material. Vulnerability is estimated based on flow width and velocity and can be modified for different pipe diameters and wall thicknesses. Mitigation options for buried pipelines include those intended to decrease the likelihood of the pipeline being exposed and to increase the resiliency of the pipeline to boulder or organic debris impacts, if exposed. The methodology presented is embedded in risk-informed decision making where pipeline owners and regulators can define probability thresholds to pipeline exposure or rupture, and pipeline designers can demonstrate that proposed mitigation measures achieve these threshold criteria.

Numerical Simulation of Effects of River Reconstruction on Flooding: A Case Study of the Ba River, China

The local reconstruction of river channels may pose obstacles of flood flow, local eddy currents, or high flow velocity which pose potential threats to human life and infrastructures nearby. In the design of such projects, the effects of local reconstruction of the river channel on flooding are often evaluated by the one‐dimensional method, which is based on the formula of one‐dimensional nonuniform flow. In this study, a two‐dimensional hydrodynamic model based on shallow water equations is employed to investigate the impacts of river reconstruction on flooding in the Ba River, China. The finite volume method and an unstructured triangular mesh are used to solve the governing equations numerically. The numerical model is validated by comparison with the results of a physical model of 1 : 120 scale. The backwater effects and impacts of flood flow fields under two flood frequencies are analyzed by comparing the numerical results before and after local reconstruction. The results show that the backwater length under both 10‐year and 100‐year floods can be reached up to the upstream boundary of the computational domain. However, the maximum water level rises are limited, and the levees in this river channel are safe enough. The flow velocity fields under both floods are changed obviously after local reconstruction in the Ba River. Areas with the potential for scour and deposition of the river bed are also pointed out. The findings of this study are helpful for the evaluation of flood risks of the river.

Dynamic morphology in a bridge-contracted compound channel during extreme floods: Effects of abutments, bed-forms and scour countermeasures

Fluvial morphology in compound river channels usually undergoes drastic variation during extreme floods due to scour and erosion processes. Those processes can be highly dynamic consisting of multiple elements (e.g. bed-form migration, bank erosion, riprap break-down, etc) that are inter-dependent. The existence of bridge abutments and embankments that lead to flow contraction on the floodplain brings more complexity and uncertainty. The present study investigated flood-related processes around bridge sites in a compound channel with different abutment/embankment configurations. Results show that a longer abutment/embankment pushes the high-shearing zone on the floodplain (around abutment toe) further towards the bank slope and causes a higher risk of undercutting at the toe area, while vertical flow pressurization had a more significant effect on enhancing general bed shearing. The main channel bank tends to retain a constant slope (2:1) as scour progresses gradually during floods. The channel bed scour is closely related to the unit discharge contraction ratio determined by both lateral and vertical flow contractions. Regarding the interaction between dynamic processes, migrating bed-forms enhanced sediment erosion by cyclic “embedment–winnowing” processes when they met destabilized loose riprap rocks. Thus, rocks sliding into the main channel may cause a higher risk of bed subsidence and then embankment failure. In total, four bed-form migration types (i.e. interaction types) are observed for different abutment/embankment lengths and flow intensities. In general, the observed processes provide a clear picture of how channel morphology is altered dynamically by multiple factors during extreme floods. Additionally, the findings in this study are integrated under a framework to evaluate the potential scour and erosion hazards in a real river section. It is found that those hazards may go beyond individual sites, affecting each other and then the morphological evolution at a catchment scale. A more comprehensive study in the future will enable this framework to performed more quantitative analysis.

STORM-DRIVEN WAVE IMPACT LOADS AND SCOUR AT A BEACH SEAWALL

The Grande-Motte port and seafront development project on the French Mediterranean coastline entailed evaluating wave impact loads (pressures and forces) on the new beach seawall and comparing the resulting scour potential at the base of the existing and new seawall. A physical model was built at ARTELIA's hydraulics laboratory in Grenoble (France) to provide insight into: wave and setup at the beach, the evolution of scour over time at the front of the wall, quasi-static and impulsive wave force intensity and distribution on the wall, and water and sand overtopping discharges over the wall. Light-weight sediment physical model and pressure and force measurements were performed with scale 1:18. The paper will discuss the pros and cons of a physical model versus numerical/ empirical modelsRecorded Presentation from the vICCE (YouTube Link): https://youtu.be/AeW3SPwDtVg

Probabilistic seismic response analysis of coastal highway bridges under scour and liquefaction conditions: does the hydrodynamic effect matter?

Coastal highway bridges are usually supported by pile foundations that are submerged in water and embedded into saturated soils. Such sites have been reported susceptible to scour hazard and probably liquefied under strong earthquakes. Existing studies on seismic response analyses of such bridges often ignore the influence of water-induced hydrodynamic effect. This study assesses quantitative impacts of the hydrodynamic effect on seismic responses of coastal highway bridges under scour and liquefaction potential in a probabilistic manner. A coupled soil-bridge finite element model that represents typical coastal highway bridges is excited by two sets of ground motion records that represent two seismic design levels (i.e., low versus high in terms of 10%-50 years versus 2%-50 years). Modeled by the added mass method, the hydrodynamic effect on responses of bridge key components including the bearing deformation, column curvature, and pile curvature is systematically quantified for scenarios with and without liquefaction across different scour depths. It is found that the influence of hydrodynamic effect becomes more noticeable with the increase of scour depths. Nevertheless, it has minor influence on the bearing deformation and column curvature (i.e., percentage changes of the responses are within 5%), regardless of the liquefiable or nonliquefiable scenario under the low or high seismic design level. As for the pile curvature, the hydrodynamic effect under the low seismic design level may remarkably increase the response by as large as 15%–20%, whereas under the high seismic design level, it has ignorable influence on the pile curvature.

Assessment of dam appurtenant structures under multiple flow discharge scenarios

This study investigates the capacities of chute spillway and stilling basin under multiple flow discharge scenarios. Thirteen cases, categorised as low, medium, and high flow discharges were experimentally conducted, with a 100% increase of Probable Maximum Flood (PMF) as the modified maximum flow. An analysis is extended to flood and scour potential at the Type II and III stilling basin. Low and medium discharge scenarios have no significant impact on the spillway but posed insufficient capacity to confine efficiently the hydraulic jump within the stilling basin. Types II and III basins reduced the length of hydraulic jump up to 50% and 73%, respectively at PMF. Similarly, potential of severe scour particularly at the spillway exit increases to 5 times more than the cases for low discharge. Similarly, potential of severe scour at PMF, particularly at the spillway exit increases to 5 times more than the cases for low discharge. High discharge not only compromises the spillway integrity due to overflow but also increases flood and scour potential at the stilling basin. An up-to-date evaluation of the existing dam appurtenances capacities to withstand the future flow pattern is crucial to ensure smooth dam operations and avoiding catastrophic events such as dam breach, jeopardising the river environmental flow and water resources.

Seismic Behavior of Pile-Group-Supported Bridges in Liquefiable Soils with Crusts Subjected to Potential Scour: Insights from Shake-Table Tests

One-g shake-table tests were conducted to characterize seismic demands and reveal failure mechanisms of pile-supported bridges in liquefiable soils with crusts subjected to different scour scenarios, namely no scour, partial scour, and complete scour of the crusts. To this end, reinforced concrete bridge models, each consisting of a single pier supported by a 2×2 pile group, were constructed and embedded into liquefiable soil profiles with a full crust or with a partial crust or without crusts to represent the studied three scour scenarios. Physical observations and characteristic soil and structural responses are interpreted first, followed by the primary focus on seismic failure mechanisms and kinematic and inertial effects on pile responses. Test results indicate that scour tends to strongly affect failure mechanisms of the studied bridges via shifting damage positions from pier bottoms to pile heads and from piles at crust-sand interfaces to pile heads. This tendency is against the current capacity design principle that piers should fail before pile foundations. Special attention should be paid to future seismic design of bridges undergoing scour and liquefaction. Furthermore, the kinematic effect is found more prominent before scour, whereas the inertial effect itself becomes more influential after scour.

Pier scouring reduction using a Strip Guide Flow Panel device

A set of laboratory experiments were conducted to study the effect of using a Strip Guide Flow Panel device to reduce scour process effects around a bridge pier. Three cylindrical piers of different diameter values and three different Strip Guide Flow Panel devices were used. Every Strip Guide Flow Panel device is simulated by two arms connected together at one of their edges at a right angle. The length of every arm is selected in a way to cover the pier diameter. Every Strip Guide Flow Panel was mounted on the upstream face of the corresponding cylindrical pier diameter at elevation adjacent to the flume bed. A uniform sized sediment were used as a bed material. Based on the experimental data, an acceptable range of scour reduction efficiency (35.71-66.67%) and high hydraulic safety factors were obtained when using Strip Guide Flow Panel. Also it is found that the scour depth when using Strip Guide Flow Panel is small comparing with corresponding potential and maximum scour depth values. So it can be concluded that the Strip Guide Flow Panel device can work like a turbulence kinetic energy dissipater to reduce the risk of scour around the pier during the serviceability life of bridge structure.