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

Huilan Zhang, Fangzheng Gu, Shaoqin Xia et al.

Understanding how bed roughness modulates hydrodynamic processes around vegetation is critical for predicting soil erosion patterns in sloped landscapes. Through flume experiments with high-frequency particle image velocimetry (PIV), this study quantifies the interactions between bed roughness (ks = 0.009, 0.25, 0.75, 1.55) and horseshoe vortex (HV) dynamics under overland flow conditions (ReD = 2627–3815). Time-averaged flow field analysis, based on vorticity and swirl strength methods, revealed that increasing surface roughness disrupted the HV system by reducing the number of vortices, decreasing the vorticity and swirl strength of the primary HV, and shifting its position closer to the bed. Statistical analysis of the instantaneous velocity components showed the emergence of bimodal probability density functions (PDFs) and joint probability density functions (JPDFs) in the near-wall region upstream of the cylinder, representing the backflow and downflow events. As roughness increased, the bimodal region decreased in size and shifted further from the cylinder. Linear stochastic estimation (LSE) was used to characterize the underlying flow modes, indicating that the backflow event was associated with the backflow mode, while the downflow event was linked to the zero-flow mode. Notably, roughness elements enhanced flow stagnation (zero-flow mode dominance > 60 %), suggesting a potential mechanism for erosion mitigation. These findings provide quantitative linkages between micro-scale hydrodynamics and landscape-scale erosion processes, informing the design of vegetation-based erosion control strategies through targeted roughness manipulation.

Robert H. Moldenhauer, Karl Worthmann, Romain Postoyan et al.

We study closed-loop stability and suboptimality for MPC and infinite-horizon optimal control solved using a surrogate model that differs from the real plant. We employ a unified framework based on quadratic costs to analyze both finite- and infinite-horizon problems, encompassing discounted and undiscounted scenarios alike. Plant-model mismatch bounds proportional to states and controls are assumed, under which the origin remains an equilibrium. Under continuity of the model and cost-controllability, exponential stability of the closed loop can be guaranteed. Furthermore, we give a suboptimality bound for the closed-loop cost recovering the optimal cost of the surrogate. The results reveal a tradeoff between horizon length, discounting and plant-model mismatch. The robustness guarantees are uniform over the horizon length, meaning that larger horizons do not require successively smaller plant-model mismatch.

Nivedita Sairam, Doménica Michelle Jaramillo Sánchez, Lisa Dillenardt et al.

ABSTRACT Effective, timely, and fair evacuation is crucial to mitigate flood impacts. We aim to identify socio‐economic attributes and flood event characteristics influencing evacuation and to quantify the psychological burden of people who experienced evacuation. We implement regression models and matching methods on an empirical dataset (n = 557) collected from the people affected by the 2021 flood in Germany. Homeowners, people with low socioeconomic status, and younger age groups were more likely to be evacuated before/during the flood event. In addition to the severity of the flood experience, high income and insured households were more likely to be evacuated after the event. In instances of evacuation before or during a flood, the psychological burden on those evacuated was found to be 10.3% higher compared to those who were not evacuated. Evacuation did not directly impact the psychological burden of people evacuated after the event. However, the duration of evacuation influenced the psychological burden on the evacuated people. The identification of the drivers of evacuation and quantification of the resulting psychological burden call for improved risk communication, preparedness, and support systems to recognize and address psychological distress in evacuated people.

Darren Lumbroso, Alain Weisgerber, George Woolhouse et al.

ABSTRACT Tourist‐related businesses, which are key to the economies of many small island states in the Caribbean, are often vulnerable to coastal flooding. Nature‐based solutions, such as coral reefs and mangroves, can help to reduce their coastal flood risk. There has been a dearth of work accurately quantifying the risk‐reduction benefits for mangroves and reefs in the Caribbean and what the implications are for developing insurance products. This paper describes the modelling to estimate the expected annual damage (EAD) for buildings in the Caribbean with and without coastal nature‐based solutions in place. Reefs and mangroves have the potential to reduce the EAD. However, in the case of reefs, this effectiveness is related to their health, with unhealthy ones increasing EAD in some cases. One of the limiting factors to developing traditional indemnity insurance products, which take into account coastal nature‐based solutions in the Caribbean, is the accurate quantification of the reductions they have on the EAD. However, to develop indemnity insurance products which take account of reefs and mangroves would require significant updates to existing catastrophe models which are used by the insurance industry, as well as tailoring them for specific locations. Parametric insurance products offer a potential mechanism for restoring damaged reefs and mangroves; however, further research is needed to better align payout triggers with the actual damage these ecosystems sustain.

Egle Saaremäe, Ottar Tamm, Harri Koivusalo et al.

ABSTRACT There is an urgent need to assess the uncertainties in stormwater pipe design owing to the increasing occurrence of urban floods triggered by urbanisation and climate change. The design storm concept involves determining the event duration and corresponding depth. Various design hyetograph methods are available to partition the design storm depth into segments, which raises questions about their impact on stormwater system design. This study analysed an ensemble of eight widely used hyetograph methods, including triangular, linear/exponential, Chicago and alternating block, in industrial and residential urban catchments using the stormwater management model. The modelling results revealed clear disparities between hyetograph methods in terms of catchment hydrological response. Depending on the method used, the simulated outlet peak flow varied by ±30% in both catchments. As a result, outlet pipe sizes varied by one and two increments in the residential and industrial catchments, respectively. Almost no flooding was evident in the manholes using simple single‐point hyetographs, whereas a quarter of the manholes showed flooding with more complex multipoint methods. Results underline the presence of high uncertainty in design flow estimates. Multipoint hyetograph methods should be used for designing critical infrastructure to minimise flooding risk if no local or regional data are available.

Dawei Zhang, Zhongxiang Wang, Huiwen Liu et al.

ABSTRACT A large‐scale experimental model of instantaneous dike‐break induced flow was conducted in this work. Water level variations in the river channel and floodplain, breach discharge, and the surface velocity field at the breach were measured during dike failure. The results show that: (i) The water level in the river rapidly decreased to a minimum (15%–22% of the initial water depth), then began to gradually rise, and finally approached stable. The water level in the floodplain gradually increased and ultimately tended towards stability. (ii) The breach discharge initially increased to a peak, then gradually decreased with a decreasing rate. The peak discharge was not only related to the initial river water level before dike‐break, but also to the river velocity. Under the same conditions, the higher the river water level or the higher the river velocity, the greater the flood peak at the breach. And (iii) During the process of dike‐break, the surface velocity of the breach flow gradually decreased. Other things being equal, a higher river water depth or a higher river velocity led to a larger surface velocity of the breach flow. These findings help better understand the hydrodynamic process and provide data support for models.

Bestami Taşar, Fatih Üneş, Ercan Gemici et al.

ABSTRACT Due to scour problems caused by flooding or high and turbulent flow in the riverbed, river regulation structures are important on the outer meander. Submerged vanes are a new method for meandering open channels and river regulation. In this study, initially, using a flow discharge of 20 L/s, the numerical results of the no‐vane (V0) and three‐array with six submerged vanes (V1) in meandering open channel flows have been calibrated with experimental results. Then, the submerged vane cases with no angle (CV1) and 20° angle (CV2–CV3) were investigated numerically. In the presented numerical models, continuity, momentum, and turbulence model equations were used. The k–ε model was used for turbulence viscosity. The results of the numerical model were compared with the experimental model results. Additionally, flow velocities and depth were analyzed using numerical models. In the outer meander, the three‐array with curved vane structures (CV1, CV2 and CV3) affected the flow velocity by 77%–92% in the region behind the vane. The flow velocities were investigated along with depth using the numerical modeling and found that the mean velocity was reduced by 54%–83% along the depth. As an effective method of reducing flow velocities and directing flows, it is also recommended that submerged vane structures be used.

Jie Song, Yang Bai, Mikhail Svinin et al.

This study presents a control strategy for coordinating multiple unmanned aerial vehicles (UAVs) to monitor unknown flood regions and estimate the extent of inundation. The proposed method adopts a density-driven coverage framework based on Centroidal Voronoi Tessellation (CVT), in which the density function is modeled using a Gaussian Mixture of Density Functions (GMDF). This formulation provides a more accurate characterization of inundated areas compared to conventional axis-aligned Gaussian models. The performance of the two density modeling approaches is systematically evaluated under different UAV fleet sizes (16, 20, and 24), with multiple simulation trials conducted in the ROS/Gazebo environment. The results show that the GMDF-based formulation consistently achieves higher coverage rates, demonstrating its effectiveness in enhancing flood monitoring and improving UAV spatial distribution.

Johannes Köhler, Carlo Scholz, Melanie Zeilinger

We address the design of a model predictive control (MPC) scheme for large-scale linear systems using reduced-order models (ROMs). Our approach uses a ROM, leverages tools from robust control, and integrates them into an MPC framework to achieve computational tractability with robust constraint satisfaction. Our key contribution is a method to obtain guaranteed bounds on the predicted outputs of the full-order system by predicting a (scalar) error-bounding system alongside the ROM. This bound is then used to formulate a robust ROM-based MPC that guarantees constraint satisfaction and robust performance. Our method is developed step-by-step by (i) analysing the error, (ii) bounding the peak-to-peak gain, an (iii) using filtered signals. We demonstrate our method on a 100-dimensional mass-spring-damper system, achieving over four orders of magnitude reduction in conservatism relative to existing approaches.

Hui Yin, Fuqing Bai, Huiming Wu et al.

With the intensification of global warming, droughts and heatwaves occur frequently and widely, which have a serious impact on the healthy growth of vegetation. The challenge is to accurately characterize vegetation vulnerability under compound heat and drought stress using correlation-based methods. This article uses the Haihe River Basin, an ecologically sensitive area known for experiencing droughts nine out of ten years, as an example. Firstly, using daily precipitation and maximum temperature data from 38 meteorological stations in the basin from 1965 to 2019, methods such as univariate linear regression and the Mann–Kendall mutation test were employed to identify the temporal variation patterns of meteorological elements in the basin. Secondly, the Pearson correlation coefficient and other methods were applied to determine the most likely months for compound dry and hot events, and the joint distribution pattern and recurrence period of concurrent high temperature and intense drought events were explored. Finally, a vegetation vulnerability assessment model based on Vine Copula in compound dry and hot climates was constructed to quantify the relationship of the response of watershed vegetation to different extreme events (high temperature, drought, and compound dry and hot climates). The results indicated that the basin’s precipitation keeps decreasing, evaporation rises, and the supply–demand conflict grows more severe. The correlation between the Standardized Precipitation Index (SPI) and Standardized Temperature Index (STI) is strongest at the 3-month scale from June to August. Meanwhile, in most areas of the basin, the Standardized Normalized Difference Vegetation Index (sNDVI) is positively correlated with the SPI and negatively correlated with the STI. Compared to a single drought or high-temperature event, compound dry and hot climates further exacerbate the vegetation vulnerability of the Haihe River Basin. In compound dry and hot climates, the probability of vegetation loss in June, July, and August is as high as 0.45, 0.32, and 0.38, respectively. Moreover, vegetation vulnerability in the southern and northwestern mountainous areas of the basin is higher, and the ecological risk is severe. The research results contribute to an understanding of the vegetation’s response to extreme climate events, aiming to address terrestrial ecosystem risk management in response to climate change.

Pauline Long'or Lokidor, Miho Taka, Craig Lashford et al.

Abstract Africa's population is expected to triple by 2050, owing to rapid urbanisation and overall demographic trends. The combined pressures of urbanisation and climate change impact the ecosystem and the services it provides. As a result, additional dangers such as increased flooding, and environmental disruption have risen. Therefore, devising adaptive solutions to mitigate flood risk impacts while also building community resilience is needed. Evidence suggests that Nature‐based Solutions (NbS) can potentially alleviate floods and mitigate climate change impacts while also delivering other societal benefits. Despite rising NbS popularity following its recognition in the last decade, studies on its recognition in Africa remain limited. For this reason, this paper reviewed NbS studies conducted in East Africa (EA) to evaluate opportunities and barriers surrounding NbS adoption in EA. Academic literature published from January 2012 to May 2022 was reviewed using a comprehensive search of the SCOPUS database. Results show 14 papers have been published during the period, with the majority being post‐2020. In addition, the majority of the articles focused on cities and peri‐urban settlements, while public awareness, clear guidelines on performance monitoring, stakeholder inclusion, and diverse demonstration projects were highlighted as potential success factors for the adoption of NbS in EA.

Samah Abdel Rhman Mohammed Ahmed Tambal, Hanan Mohamed Hassan Elsawahli, Eltayeb Ibrahim Elmadih Ibrahim et al.

Abstract Over the past 30 years, Sudan has experienced several severe floods which have caused loss of life and significant damage to property. The frequency and intensity of floods in Sudan are predicted to increase as a result of climate change. The main objective of this research was to assist policymakers in establishing a mechanism for public participation in Sudan to enable communities to be engaged in improving flood risk management. This paper focuses on Tuti Island, which is located near the confluence of the Blue and White Niles in Khartoum which is severely affected by flooding. The research was based on surveys and interviews with both officials and the public to examine the degree of public participation in mitigating flood risks. The research concluded that Sudan has no policy or official way of engaging the public in disaster risk reduction; however, the traditional method of social mobilization called Nafeer (building together) can play a significant role in increasing communities' flood resilience. Establishing a clear framework for public participation, such as Nafeer, for the various stages of the flood management cycle that coordinates with decision‐makers can help increase the resilience of urban areas in low‐income countries like Sudan.

Maximilian Degner, Raffaele Soloperto, Melanie N. Zeilinger et al.

We present a model predictive control (MPC) formulation to directly optimize economic criteria for linear constrained systems subject to disturbances and uncertain model parameters. The proposed formulation combines a certainty equivalent economic MPC with a simple least-squares parameter adaptation. For the resulting adaptive economic MPC scheme, we derive strong asymptotic and transient performance guarantees. We provide a numerical example involving building temperature control and demonstrate performance benefits of online parameter adaptation.

Md Sadiul Alam Chyon, Subir Biswas, M. Shahjahan Mondal et al.

Abstract In the assessment of flood risk, the future flood hazard due to climate change is often tied to the present socioeconomic conditions. This makes an implicit assumption that the drivers of risk, other than the hazard, remain constant with time. Therefore, such risk assessment does not provide a realistic outlook for devising plausible mitigation strategies and plans. In this study, flood risk was assessed from an integrated perspective by considering both physical hazard, and socioeconomic exposure and vulnerability—all changing with time. The flood hazard in the Arial Khan River floodplain in the southcentral Bangladesh was simulated with a two‐dimensional hydrodynamic model, and the exposure and vulnerability were projected using different statistical techniques. Principal component analysis was conducted to assign weights to the indicators of hazard, exposure, sensitivity, and adaptive capacity. The results show that the flood depth, duration, and extent would increase from the baseline to 2080s under regional concentration pathway (RCP) 2.6 and RCP 8.5 scenarios. The sensitivity and vulnerability would decrease, reflecting an improved adaptive capacity. The low‐risk areas could increase from 62% in the baseline to 85%–91% in 2080s depending on the RCPs. The approach followed can be applied elsewhere in developing countries, particularly in riverine floodplain settings.

Sally Priest

Roman Schotten, Daniel Bachmann

Abstract In flood risk analysis, it is state‐of‐the‐art to determine the direct consequences of flooding for assets and people. Flooding also disrupts critical infrastructure (CI) networks, which are vital in modern society. Cascading effects in a CI network can exceed the hydrological catchment boundaries. The effects of directly impacted CI cascade to other infrastructures, which are thus indirectly affected by a flood. A robust modelling approach of CI networks is a basis for including these effects in flood risk analysis. One challenge is to balance the simplicity of the modelling approach, the reproduction of a CI network's complexity and the decisions made based on potential model outputs. In this article, a topology‐based modelling approach of CI networks for catchment‐wide flood risk analyses is proposed. The basic model elements are points, connectors and polygons, which are utilised to represent a multisectoral and layered CI network. The newly defined approach is implemented as CI network module to the state‐of‐the‐art flood risk analysis framework ProMaIDes. It analyses the CI's direct and cascading impacts as well as the indirect disruption of CI services triggered by flooding scenarios. It quantifies the consequences by determining the number of disrupted CI users or the disruption time. A proof of concept in Accra, Ghana demonstrates the method's capabilities.

Erol Gelenbe, Mohammed Nasereddin

IoT Servers that receive and process packets from IoT devices should meet the QoS needs of incoming packets, and support Attack Detection software that analyzes the incoming traffic to identify and discard packets that may be part of a Cyberattack. Since UDP Flood Attacks can overwhelm IoT Servers by creating congestion that paralyzes their operation and limits their ability to conduct timely Attack Detection, this paper proposes and evaluates a simple architecture to protect a Server that is connected to a Local Area Network, using a Quasi Deterministic Transmission Policy Forwarder (SQF) at its input port. This Forwarder shapes the incoming traffic, sends it to the Server in a manner which does not modify the overall delay of the packets, and avoids congestion inside the Server. The relevant theoretical background is briefly reviewed, and measurements during a UDP Flood Attack are provided to compare the Server performance, with and without the Forwarder. It is seen that during a UDP Flood Attack, the Forwarder protects the Server from congestion allowing it to effectively identify Attack Packets. On the other hand, the resulting Forwarder congestion can also be eliminated at the Forwarder with "drop" commands generated by the Forwarder itself, or sent by the Server to the Forwarder.

Michel Fliess, Cédric Join

Adaptive bitrate streaming (ABR) over the HyperText Transfer Protocol (HTTP), which raises numerous delicate questions, is nowadays almost the only approach to video streaming. This paper presents elementary solutions to three key issues: 1) A straightforward feedforward control strategy for the bitrate and the buffer level via flatness-based control. 2) Closing the loop permits mitigating unavoidable mismatches and disturbances, such as Internet fluctuations. This is adapted from the new HEOL setting, which mixes model-free and flatness-based controls. 3) An easily implementable closed-form estimate of the bandwidth via algebraic identification techniques is derived, perhaps for the first time. It permits handling severe variations in channel capacity. Several computer experiments and metrics for evaluating the Quality of Experience (QoE) are displayed and discussed.

Georgios Mitsopoulos, Michalis Diakakis, Aristeides Bloutsos et al.

We pose the following research question: “what is the effect of flood protection works on flood risk?” To answer this question, we developed a flood risk assessment method that combines the typical hazard assessment via integrated hydrological and hydrodynamic calculations using HEC-HMS and 1D/2D HEC-RAS, respectively, and an original procedure for vulnerability assessment at the building level, which we applied in the town of Mandra in Attica, Greece. We performed calculations for 15 scenarios—combinations of return periods (T = 20, 50, 100, 150, and 200 y) and rain durations (t = 6, 12, and 18 h)—for the conditions of the year 2017, when there were no flood protection works, and today with these works in place. We identified the regions with high flood risk and concluded that the presence of the works caused a decrease in the inundation areas by 53–89%, along with reductions in the maximum water depths, the maximum flow velocities, and the average flood risk in Koropouli Street—the main street of Mandra, which suffered severe damage during the 2017 flood—by 38–62%, 18–52%, and 27–74%, respectively. The effect of the flood protection works increased with the increases in the return period and rain duration, while for the same return period the effect of the rain duration was more pronounced for the smaller return periods.

Shaun A. Maskrey, Nick J. Mount, Colin R. Thorne

Abstract Responsibility for flood risk management (FRM) is increasingly being devolved to a wider set of stakeholders, and effective participation by multiple FRM agencies and communities at risk calls for engagement approaches that supplement and make the best possible use of hydrologic and hydraulic flood modelling. Stakeholder engagement must strike a considered balance between participation ideals and the pragmatic realities of existing mechanisms for FRM decision‐making. This article evaluates the potential for using participatory modelling to facilitate engagement and co‐production of knowledge by FRM modellers, practitioners and other stakeholders. Participatory modelling offers an approach that is flexible and versatile, yet sufficiently structured that it can support meaningful representation of scientific, empirical and local knowledges in producing outcomes that can readily be integrated into existing procedures for shared decision‐making. This article frames the qualities of participatory modelling useful to FRM, as being accessible, transparent, adaptable, evaluative and holistic. These qualities are used as criteria with which to assess the practical utility of three popular participatory techniques: Bayesian networks, system dynamics and fuzzy cognitive mapping. Case studies are used to illustrate how each technique might benefit FRM options appraisal and decision‐making. While each technique has potential, none is ideal, and local contexts will guide selection of which technique is best suited to deliver effective stakeholder participation.