Hasil untuk "River protective works. Regulation. Flood control"

Shanghong Zhang, Hao Jia, Caihong Tang et al.

Aquatic vegetation plays a crucial role in regulating sediment transport and maintaining the stability of aquatic ecosystems. To investigate the turbulence structure and suspended sediment distribution under the influence of natural flexible submerged vegetation, this study selected Vallisneria natans (eelgrass), a representative flexible submerged plant, as the experimental material. Systematic measurements of flow structure and suspended sediment concentration (SSC) were conducted under submerged vegetation conditions. The experimental results demonstrated that the presence of flexible vegetation significantly altered the vertical distribution of flow velocity and turbulence characteristics. Under different vegetation densities, noticeable variations were observed in time-averaged velocity, lateral and vertical Reynolds stresses, and turbulent kinetic energy (TKE), with particularly pronounced changes in the near-bed and canopy regions. Compared to the bare bed condition, SSC in vegetated flows was significantly reduced, and the reduction became more evident with increasing vegetation density. To predict the SSC profiles under flexible vegetation conditions, the vertical distribution of the turbulent diffusion coefficient was calculated. Results showed that the coefficient exhibited a linear distribution within the canopy, reaching a maximum near the canopy top. Based on this distribution pattern, an improved Rouse equation applicable to submerged flexible vegetation conditions was proposed. The modified Rouse model was validated against measured SSC profiles under various vegetation densities and hydraulic conditions, demonstrating its ability to accurately predict the vertical distribution of suspended sediment. This study provides theoretical support for sediment transport modeling, hydrodynamic regulation, and ecological restoration in vegetated riverine and lacustrine environments. It also lays a foundation for advancing the understanding of the coupled interactions among flow, sediment, and vegetation.

Mohamed S. Awaad, Emad H. Habib, Haitham A. Saad

ABSTRACT Flooding in low‐gradient river systems, particularly, within inland‐to‐coastal transitional settings, poses significant risks to both human and natural systems due to complex flow dynamics and the convergence of riverine, tidal, and storm‐driven flooding regimes. Effective flood management strategies in these settings require a careful consideration of the interactions between tributary flows and the main river, as the synchronization of peak flows can intensify flood severity. Using a counterfactual hydrodynamic modeling approach, this study investigates how modifications to magnitudes and timings of tributary inflows, as part of practical flood mitigation interventions, influence flood dynamics and overall flood risk along the Vermilion River in south Louisiana, USA—a representative a case study. Simulations of various tributary desynchronization scenarios showed that, while managing individual tributary flows can lower water levels in the main river, simultaneous manipulation of multiple tributaries can introduce added complexities, since poorly timed tributary interactions could diminish the intended flood mitigation benefits. The analysis also revealed that alterations to tributary hydrographs can modify existing flow exchanges between the river and interconnected large natural storage systems, such as swamps, highlighting the importance of comprehensive flood management strategies that consider different flood dynamics in low‐gradient river systems. Overall, this study offers actionable insights for optimizing flood management strategies in similar systems worldwide, where intricate interdependencies among tributaries, natural storage features, and main rivers can influence flood mitigation outcomes.

Rafia Tasnia Omi, Farzana Raihan, Rajib Shaw et al.

Abstract This study aimed to assess the impact of climate change using the Livelihood Vulnerability Index (LVI) and the adaptation strategies of communities, as measured by the Adaptation Strategy Index (ASI), among 120 households across six villages in Fulchari and Shaghata Upazilas of Gaibandha district in northern Bangladesh. The findings highlight changing climatic patterns and show that while respondents are generally aware of the impacts of climate change, there are notable knowledge gaps. Galna Adarshapara was identified as the most vulnerable village according to the LVI, indicating its high susceptibility in areas such as socio‐demographic profile, food security, health, natural hazards, and climate sensitivity. Factors contributing to this vulnerability include geographical isolation, limited education, underdeveloped infrastructure, inadequate health facilities, and a lack of alternative income sources during extreme events. However, coping mechanisms such as irrigation, crop diversification, and the use of double‐platform tube wells are commonly employed to address these climatic impacts. To enhance resilience, it is crucial to implement policy initiatives and institutional arrangements that support local communities in improving their living conditions and adapting to climate change challenges.

Thomas Wallace, Kaley Crawford‐Flett, Matthew Wilson et al.

ABSTRACT Flood protection assets such as dams are increasingly seen as part of a larger system, but the complexity of dam management, unclear communication, and operational misunderstandings in operational protocols can lead to unnecessary downstream flooding. This paper investigates how human factors, such as dam operators' communication and roles and responsibilities, influence flood flows. Using HEC‐RAS, the study varies initial reservoir volume and pre‐release duration in four New Zealand catchments, with potential for adaptation in other areas. The results found: (i) dams designed to provide flood storage had stronger correlations between the duration of pre‐releases and outflow reductions, (ii) dams with large storage capacities and fewer release mechanisms had stronger correlations between the initial reservoir volume and outflow reductions, (iii) a dam's ability to appropriately control flow is governed by the presence and implementation of clear operating procedures shown by the dam mandated to provide flood storage having the highest consistency in flow reduction and a 6% difference in maximum dam outflow between best and worst‐case operations, and (iv) mismanagement of outflows can increase downstream flooding; in one catchment, the outflow was 38% above the inflow. The results are widely applicable given the increasing importance of flood control mechanisms and operational protocols.

Asid Ur Rehman, Vassilis Glenis, Elizabeth Lewis et al.

ABSTRACT Flood risk managers seek to optimise Blue‐Green Infrastructure (BGI) designs to maximise return on investment. Current systems often use optimisation algorithms and detailed flood models to maximise benefit–cost ratios for single rainstorm return periods. However, the BGI scheme optimised for one return period (e.g., 100 years) may differ significantly from those optimised for others (e.g., 10 or 20 years). This study aims to assess the effectiveness of single return period‐based BGI design across multiple storm magnitudes and introduces a novel multi‐objective optimisation framework that simultaneously incorporates five return periods (T = 10, 20, 30, 50 and 100 years). The framework combines a non‐dominated sorting genetic algorithm II (NSGA‐II) with a fully distributed hydrodynamic model to optimise the spatial placement and combined size of BGI features. For the first time, direct damage cost (DDC) and expected annual damage (EAD), calculated for various building types, are used as risk objective functions, transforming a many‐objective problem into a multi‐objective one. Performance metrics such as Median and Maximum Risk Difference (MedRD, MaxRD) between reference and trial Pareto fronts, capturing characteristic single values from the distribution of risk differences, and the Area Under Pareto Front (AUPF), indicating overall optimisation quality, reveal that a 100‐year optimised BGI design performs poorly when evaluated for other return periods, particularly shorter ones. In contrast, a BGI design optimised using composite return periods enhances performance metrics across all return periods, with the greatest improvements observed in MedRD (22%) and AUPF (73%) for the 20‐year return period, and MaxRD (23%) for the 50‐year return period. Furthermore, climate uplift stress testing confirms the robustness of the proposed design to future rainfall extremes. This study advocates a paradigm shift in flood risk management, moving from single maximum to multiple rainstorms‐based optimised designs to enhance resilience and adaptability to future climate extremes.

Ghasem Farahmand, Behzad Hessari, Hossein Salehi

ABSTRACT This study investigates the impacts of climate change and land‐use changes on peak discharge and runoff behavior in the western watersheds of Lake Urmia, Iran. Employing machine learning algorithms (e.g., SVM), stochastic models (e.g., CA‐MARKOV), ERA5 reanalysis climate data, and the large‐scale hydrological VIC model, we assessed these effects across multiple sub‐basins. Our analysis revealed that a 2°C rise in average minimum winter temperature over the past 50 years has reduced frost days by nearly 80 days, diminished mountain snow volume, and shifted precipitation from snow to a mix of snow, rain, and snowmelt. Consequently, peak discharge timing has advanced from May to March and April, amplifying flood intensity and frequency, with some sub‐basins showing up to 30% higher peak flows. Furthermore, land‐use change assessments indicated that expanding orchards and irrigated and rain‐fed agricultural lands will significantly elevate future peak discharge, with differences exceeding 10 m3/s in sub‐basins like Nazlochay and Barandozchay, driven by reduced infiltration and increased runoff rates. Modeling with these tools confirmed that climate and land‐use changes synergistically alter flood dynamics, a pattern consistent with regional studies. These findings underscore the urgent need to integrate these factors into flood management strategies for this flood‐prone region, offering a robust framework for sub‐basin‐scale hydrological planning.

Mark Wiering, Elizabeth MacAfee, Tara Saharan et al.

Abstract Flood risks can stem from various causes and exhibit distinct characteristics that shape the way they are governed. Depending on flood risk characteristics, specific policies are designed and organisations are involved. In Indonesia, like in other regions, organisational divisions are made for coastal floods, fluvial floods and pluvial floods (resulting from tides, rivers and rain, respectively). The Indonesian cities of Manado and Pontianak both face recurring floods. However, the characteristics of and responses to these floods are different, with consequences for distributive, procedural as well as recognition justice in those cities. In line with Fraser, we define recognition justice in relation to three forms of misrecognition: cultural domination, disrespect, and non‐recognition, with examples from Manado and Pontianak. We show that the misrecognition of certain types of floods overlaps and interacts with the non‐recognition of low‐income informal settlements, disrespect and stereotyping of residents of these areas, and a lack of attentiveness to the culture, livelihoods and practices of people who live alongside rivers. In this way, we examine the landscape of recognition justice in the event of flooding in an urban context, drawing on qualitative interview data gathered from the cities of Manado and Pontianak. The following questions are considered: Who experiences misrecognition? By whom is this misrecognition perpetrated? At which level (institutional frameworks or laws, implementation or social practices) and what are the resulting consequences of this misrecognition? Finally, we explore the interactions between different forms of misrecognition, which create a foundation for further distributional and procedural injustices.

Mandy Paauw, Ann Crabbé, Sofia Guevara Viquez et al.

Abstract Flood risks worldwide are rising and it is increasingly recognised that the impacts of floods are not neutral. Socioeconomic and demographic characteristics determine people's capacity to deal with flood events. These differences in social vulnerability to floods need to be considered in flood risk management (FRM) to prevent the most vulnerable groups from being disproportionately impacted. However, due to a diversification of FRM strategies and the involvement of various policy domains, the experts working on FRM are no longer a homogeneous group. Where FRM was previously dominated by engineers, now various experts are involved that have different disciplinary backgrounds, knowledge bases and approaches to FRM. As a result, they also differ in their recognition of social vulnerability to floods. In this paper, we explore the different types of knowledge and expertise in FRM in three countries (England, Flanders and France), focussing on the strategies of flood defence and flood risk prevention. We characterise the epistemic communities supporting the domains and study to what extent experts differ in their recognition of social vulnerability to floods. We also dive into the mechanisms employed to stimulate integration between experts and consider the extent to which this integration can strengthen recognition justice.

Robert Adler, Guojun Gu, Naijun Zhou et al.

Abstract The application and value of the Global Flood Monitoring System (GFMS) and various remote‐sensing‐based flood products are examined in the context of the severe flood event in Mozambique associated with Cyclone Idai in March 2019. Short‐term forecasts of rainfall and flooding are shown to be useful and validated to some degree by satellite‐based rainfall from the Global Precipitation Monitoring (GPM) Integrated Multi‐satellitE Retrievals for GPM (IMERG) product. However, detailed validation of the satellite‐based rainfall for this event is limited and examination of other similar cases indicates a possible underestimate at high rainfall amounts. GFMS inundation based on the IMERG rainfall and models are compared to Synthetic Aperture Radar (SAR) and other inundation estimates. Results indicate a generally good correspondence, but with the GFMS calculations underestimating the area of broad flooding, but overestimating in smaller streams. The GFMS underestimation compared to a SAR‐based estimate in one particular area seems related to rainfall underestimation. Similar generally good results were found when comparing the GFMS calculations to the FloodScan passive microwave‐based inundation. The various inundation estimates are available at different latencies and likely have different accuracies, indicating a need for integration of these types of information to provide the user community with the best consolidated information and in a timely manner.

Meng Chen, Xinping Zhang, Xiong Xiao et al.

The isotope tracing method provides a novel way to investigate the underlying mechanisms of water balance. This study focused on Taozi Lake in Changsha, a city in the subtropical monsoon region. We conducted continuous monitoring of meteorological factors and stable isotopes in precipitation and lake water samples and further employed the isotope mass balance model to estimate the evaporation to inflow ratio (E/I). The results revealed that the fitted slope of the lake water evaporation line (SLEL) was close to or even greater than the slope of the local meteoric water line (SLMWL) because of the inverse seasonal variations in precipitation isotopes and evaporation intensity. This led to significant depletion of stable isotopes in the water source. Conversely, the theoretical SLEL values derived from the Craig‒Gordon model provided a more accurate depiction of the evaporation enrichment processes of lake water and were more appropriate for identifying lake water sources. The E/I ratios exhibited seasonal variations, with the highest values occurring in autumn and the lowest values occurring in spring, reflecting the interplay between precipitation and evaporation. The interannual variability in the E/I ratios and lake water isotopes further underscored the lake's response to changing hydrometeorological conditions. The uncertainty in the E/I simulations was due primarily to the isotopic compositions of the inflow water and atmospheric vapor, followed by the relative humidity and surface water temperature. This study enhances our understanding of regional hydrological processes, particularly regarding lake water isotopes and simulations of lake water balance, while considering the uncertainties associated with the assumptions and input variables of the E/I ratio.

Leo van Rijn, Marcio Boechat Albernaz, Luitze Perk et al.

This study is focused on the experimental and numerical modelling of sand and mud transport over mud-sand beds with percentages of fines (< 63 μm) up to 50% in conditions with currents, waves and combined currents and waves. Both field and laboratory experiments with mud-sand beds have been performed. Detailed measurements of near-bed hydrodynamic and sediment transport processes have been made in the muddy tidal ferry channel between Holwerd and Ameland in the Dutch part of Wadden Sea. Laboratory flume experiments with currents and waves over a pure fine sand bed show the generation of small-scale sand ripples and strong ripple-induced vortex motions resulting in relatively high sand concentrations close to the bed. The near-bed sediment dynamics of a fine sand bed change drastically when a small amount of cohesive sediments (mud 10%–15%) is added to the sand bed. Bed properties which are changed are the percentage of fines, the dry bulk density (packing) and the cohesivity. The results of exploratory long-bed experiments with various mud-sand mixtures show that the mud particles at the mud-sand surface are washed out and small-scale isolated barchan-type sand ripples develop at the bed surface. The bed ripple heights are suppressed resulting in flatter ripples with less vorticity and as a consequence lower sand concentrations and transport. The critical bed-shear stress (cbs) is not much influenced by cohesive effects if the percentage of fines (< 63 μm) is smaller than about 15%, while for pfines > 15%, the critical bed-shear stress increases for increasing values of pfines. Laboratory results also indicate that the bed ripple development and near-bed sand transport may already be affected for a lower percentage of fines (10%–15%). Various modelling methods are used and discussed, both for the flume and field data.

Ruixun Lai, Junhua Li, Ping Wang et al.

Abstract Flash floods can carry substantial sediment, posing significant sedimentation hazards in hilly cities. The sedimentation hazard map can reproduce the sediment thickness and extent of an extreme events scenario, playing an important role in sediment risk management. However, current research primarily focuses on modeling the inundation area and depth of floods, while studying sedimentation hazard caused by flash floods in urban areas remains insufficient. This paper aims to address this gap by utilizing a numerical model that simulates hyperconcentrated flow in hilly urban areas using the two‐dimensional hydro‐sediment‐morphological model to compile the cumulative sedimentation hazard map. The model, built upon the open‐source TELEMAC‐MASCARET framework, incorporates Zhang Hongwu's formula to simulate sediment‐carrying capacity, particularly suitable for hyper‐sediment concentration near the riverbed. This paper uses the data of extreme flash flood events in the Wuding River basin in 2017 to simulate and compile the cumulative sedimentation hazard map. The hazard map delineates the sedimentation hazard extent and level attributable to overbank floodplain sedimentation. Notably, the sediment thickness is highest in areas near the levees on both sides of the Dali River. Moreover, the map illustrates the extent of channel erosion resulting from hyperconcentrated floods, which could jeopardize bank stability.

Roberto Villalobos Herrera, Stephen Blenkinsop, Selma B. Guerreiro et al.

Abstract The Flood Studies Report (FSR) summer and winter design profiles are a key component of rainfall design guidance in the United Kingdom (UK). We have examined the rainfall profiles of over 70,000 extreme rainfall events with the original FSR profile methodology. This analysis reveals that rainfall profiles change with rainstorm duration but not season, contradicting one of the key assumptions in current UK rainfall design guidance. By using a method that does not artificially generate symmetrical and centred profiles we show that profile shapes are highly variable and strongly related to event duration and magnitude. Short events tend towards front‐loaded profiles, while heavy long‐duration events tend towards centred profile shapes. Finally, manual, automatic and mixed methods of deriving new design profiles for use in the UK were trialled, with consistent results. These could be used to derive new design profiles to supersede the FSR profiles. Notably, peak intensities in observed profiles and trialled summary profiles often exceeded those found in both FSR profiles. We conclude that current design profile guidance for the UK fails to account for the observed variability in event profile shapes and peak intensities and may lead to significant under‐ or over‐design of flood risk management solutions.

Nafiseh Ghasemian Sorboni, Jinfei Wang, Mohammad Reza Najafi

Abstract Flood events can cause extensive damage to physical infrastructure, pose risks to human life, and necessitate the reoccupation and rehabilitation of affected areas. A key parameter for flood vulnerability assessment is the first floor height (FFH), which also plays an important role in setting insurance premiums. Traditional methods for FFH estimation rely on ground surveys and site inspections, yet these approaches are both time‐consuming and labor‐intensive. In this study, we propose an alternative approach based on measurements derived from Google Street View (GSV) images and Deep Learning (DL). We employ the YOLOv5s algorithm, which belongs to a family of compound‐scaled object detection models trained on the COCO dataset, for the detection of crucial building elements such as the Front Door (FD), stairs, and overall building extent. Additionally, we utilized the YOLOv5s algorithm to identify basement windows and assess the existence of basements. To validate our methodology, we conducted tests in both the Greater Toronto Area (GTA) and the state of Virginia in the United States. The results demonstrate an achievement of RMSE and Bias values of 81 cm and −50 cm for GTA, and 95 cm and −20 cm for the Virginia region, respectively.

Pavithra Rathnasiri, Onaopepo Adeniyi, Niraj Thurairajah

Abstract Built environment flood resilience is a critical challenge facing communities worldwide. Amongst various efforts to resilience, the conception towards data utilization becomes popular with enormous technological advancements. Built environment creates varieties of data at larger volumes throughout their life cycle signifying that the importance of these data in the context of flood resilience cannot be ignored. However, despite the power of data, the greatest opportunities that exist for flood resilience enhancement have been mired by numerous and complex unidentified challenges. Thus, identifying these challenges with timely relevant strategies is a significant need. One of the best ways to tackle these challenges is by viewing them through the lens of data life cycle stages. This study, therefore, aimed to identify these challenges in each stage of the data life cycle with strategies to overcome them. Semi‐structured interviews conducted with 12 experts revealed the significant challenges allied with built environment data with potential future strategies. The qualitative content analysis was conducted to analyse the findings. The use of advanced sensing technologies, cloud‐based storage solutions, data governance policies and the development of predictive models are some of the consequential strategies outlined in this study. These findings provide valuable insights and guidance to facilitate built environment data utilization for flood resilience.

Isaac Samuel Greene, Chamila Gunasekara, Weena Lokuge et al.

Abstract The Australian use of the term floodway refers to a trafficable transverse structure designed to facilitate the safe crossing of watercourses. Floodways are also commonly referred to as fords and causeways. This research explores areas of focus through experimental, numerical and survey methods to improve floodway resilience with regard to flood risk management. The industry‐based survey provides a dataset relating to user experiences, deduces the likeliness of floodways to sustain damage, defines several key focus areas, and reveals that the current risk levels are primarily managed without significant investigation into design. A floodway experimental and numerical simulation program was developed to investigate the lateral forces induced through debris impact using scaled models in a soil box and finite element analysis. Qualitatively, crack propagation and displacement correlated closely with the strain concentrations and displacements in the numerical simulation, with failure attributed to tensile strength being exceeded, followed by plastic strain development within the soil elements. It was concluded through this research that floodway failure during flood is complex and can be attributed to several different failure modes including concrete failure, yielding of adjoining soil material, and hydraulically via scour.

Amrei David, Ernesto Ruiz Rodriguez, Britta Schmalz

Abstract In recent years, many two‐dimensional (2D) hydrodynamic models have been extended to include the direct rainfall method (DRM). This allows their application as a hydrological‐hydrodynamic model for the determination of floodplains in one model system. In previous studies on DRM, the role of catchment hydrological processes (CaHyPro) and its interaction with the calibration process was not investigated in detail. In the present, case‐oriented study, the influence of the spatiotemporal distribution of the processes precipitation and runoff formation in combination with the 2D model HEC‐RAS is investigated. In a further step, a conceptual approach for event‐based interflow is integrated. The study is performed on the basis of a single storm event in a small rural catchment (low mountain range, 38 km2) in Hesse (Germany). The model results are evaluated against six quality criteria and compared to a simplified baseline model. Finally, the calibrated improved model is contrasted with a calibrated baseline model. The results show the enhancement of the model results due to the integration of the CaHyPro and highlight its interplay with the calibrated model parameters.

Yunke Xiao, Wan Liu, Yongqiang Wang et al.

Niklas Schwiersch, Torsten Heyer, Jürgen Stamm

Abstract The distributions of soil mechanical parameters required for a comprehensive flood risk assessment are often taken from the scarce literature available. This article therefore presents a method to indirectly obtain the distributions from the results of often conducted classification tests. Empirical correlation terms are used for the transformation of the classification data into stability‐relevant parameters, in particular the void ratio, the soil unit weight, the friction angle and the saturated permeability. The method is applied exemplarily to a data set collected throughout Germany in the immediate vicinity of water bodies and plausible distributions are obtained for 2/3 of the 13 soil classes considered. For the validation of the results, the extension of (inter)national databases by samples of the considered soil mechanical parameters is recommended due to the current poor validation basis.

Zhu Jing, Rongqi Zhang, Hexin Bao et al.

Abstract The flood control ability of cascade reservoirs is affected by many factors, such as the inflow flood form, and flood control scheduling rules. When large cascade reservoirs were built, it is necessary to evaluate the overall flood control ability of the reservoirs and explore the best joint scheduling strategy. In this study, cascade reservoirs in the upper reaches of the Yangtze River in China were selected as the research case. A stochastic model of inflow floods and a dynamic capacity flood regulation model for the Three Gorges Reservoir (TGR) were established, and the most dangerous inflow floods for downstream flood control were generated. Different scheduling strategies for the cascade reservoirs were set to block the TGR inflow flood to explore the flood control risk in the Jingjiang area under joint operation of the TGR and the upstream cascade reservoirs. The research results show that the joint flood control scheduling strategy has a huge impact on the flood control ability of cascade reservoirs, and different scheduling schemes must be adopted according to the inflow flood characteristics of the reservoirs. This study provides a new idea for systematically evaluating the flood control ability of large cascade reservoirs and selecting appropriate scheduling strategies.