Flood Protection Structures Research Articles

Geo-Referenced Databases and SWOT Analysis for Assessing Flood Protection Structures, Measures, and Works at a River Basin Scale

This research aims to evaluate the operational effectiveness of current flood protection infrastructure and measures in a flood-prone area using geo-referenced information systems and SWOT analysis. To achieve this, all existing flood protection measures and works in the case study basin, namely Strymonas River basin in Greece, were mapped and recorded. These data, along with water-related spatial information, were stored in a geo-referenced database created within an open-source GIS environment. Additionally, the system was populated with the basin’s recorded historic floods, derived from the European Union’s Floods Directive implementation process. The outputs of the research, which include a spatial comparison of flood protection measures and works with flood event occurrences as well as analyses of the figures, density, and locations of flood protection works, were evaluated as an integrated system and further processed using SWOT analysis. The latter was informed by questionnaire results, and the identified strengths and weaknesses of the flood protection infrastructure were used to explore potential opportunities and threats, which could respectively reinforce or jeopardize the basin’s capacity to effectively respond to future floods. The research framework can be applied to any river basin and could provide important assets in flood protection planning at a basin scale.

Assessing the impact of climate change on high return levels of peak flows in Bavaria applying the CRCM5 large ensemble

Abstract. ​​​​​​​Severe floods with extreme return periods of 100 years and beyond have been observed in several large rivers in Bavaria in the last 3 decades. Flood protection structures are typically designed based on a 100-year event, relying on statistical extrapolations of relatively short observation time series while ignoring potential temporal non-stationarity. However, future precipitation projections indicate an increase in the frequency and intensity of extreme rainfall events, as well as a shift in seasonality. This study aims to examine the impact of climate change on the 100-year flood (HF100) events of 98 hydrometric gauges within hydrological Bavaria. A hydrological climate change impact (CCI) modeling chain consisting of a regional Single Model Initial-condition Large Ensemble (SMILE) and a single hydrological model was created. The 50 equally probable members of the Canadian Regional Climate Model version 5 large ensemble (CRCM5-LE) were used to drive the hydrological model WaSiM (Water balance Simulation Model) to create a hydro-SMILE. As a result, a database of 1500 model years (50 members × 30 years) per investigated time period was established for extreme value analysis (EVA) to illustrate the benefit of the hydro-SMILE approach for a robust estimation of HF100 based on annual maxima (AM) and to examine the CCI on the frequency and magnitude of HF100 in different discharge regimes under a strong-emission scenario (RCP8.5). The results demonstrate that the hydro-SMILE approach provides a clear advantage for a robust estimation of HF100 using the empirical probability of 1500 AM compared to its estimation using the generalized extreme value (GEV) distribution of 1000 samples of typically available time series sizes of 30, 100, and 200 years. Thereby, by applying the hydro-SMILE framework, the uncertainty from statistical estimation can be reduced. The study highlights the added value of using hydrological SMILEs to project future flood return levels. The CCI of HF100 varies for different flow regimes, with snowmelt-driven catchments experiencing severe increases in frequency and magnitude, leading to unseen extremes that impact the distribution. Pluvial regimes show a lower intensification or even decline. The dynamics of HF100 driving mechanisms depict a decline in snowmelt-driven events in favor of rainfall-driven events, an increase in events driven by convective rainfall, and almost no change in the ratio between single-driver and compound events towards the end of the century.

Managing residual flood risk: Lessons learned from experiences in Taiwan

Flood risk has dramatically increased over the decades and is complicated by climate change. Nevertheless, the residual risk of flooding remains scarcely addressed in practice and theory. This paper is to document the lessons learned from managing residual risk in Taiwan. Through a semi-structured interview process, fourteen stakeholders from the flood management in academia, government, and local communities shared their perspectives on residual risk covering various aspects, including flood risk mapping, social representations, and some management strategies. Land use regulation and community-based disaster prevention were highlighted as preparedness measures and recognized for their effectiveness to mitigate flood residual risk. However, there is still an insufficient consideration of flood maps as public communication tools rather than mere decision-informing documents. Besides, all the interviewed stakeholders agreed that marginal flood risk awareness limits the recognition and discussion of residual risk as a problem of its own. Misconceptions and the lack of communication between stakeholders were identified as the main barriers too. Interviewees pointed out that citizens are unaware of risks mainly either due to their inexperience or over-trust in the safety of flood protection structures. Overall, this work may inform residual flood risk management for Taiwan and elsewhere enduring similar extreme floods.

Review on Lightweight Mobile Flood Wall Barrier: Way Forward for Malaysia

Flooding is a persisting challenge in Malaysia. Combating flood risk has become a main priority for sustainable development in this country. The application of sophisticated engineering in hard structure approaches and flood control systems are often incongruous to the public. Therefore, there is a need to integrate the soft engineering approaches and the best practises of flood management to mitigate flood risk. There is also a need to integrate the concept of sustainable development into its planning policies towards flood hazard reduction. Mobile flood protection measures are useful as an alternative solution in flood protection and mitigation purposes. Mobile protective systems can be used for temporarily increasing the height of permanent flood protection structures during extreme events and can be utilised as emergency measure against flooding in unprotected low-lying areas. As the available mobile systems differ in the type of material, method of installation and available protection height, a description of their features, and potential application were examined including their respective opportunities and drawbacks. This article presents a review on different types of lightweight mobile flood wall barrier (MFWB) that were implemented to cope with floods in Malaysia with examples of application in other countries such as United Kingdom, Slovakia, and Netherlands. The MFWB products are reviewed and compared to each other according to the types, characteristics, mechanisms, drawbacks and how these measures are integrated into spatial planning. Based on the findings, several suggestions are given on how to improve the flood risk management in flood-prone areas and way forward for Malaysia.

Temporal Variations in Chemical Proprieties of Waterbodies within Coastal Polders: Forecast Modeling for Optimizing Water Management Decisions

In polder-type land, water dynamics are heavily influenced by the artificial maintenance of water levels. Polders are low-lying areas of land that have been reclaimed from the sea or from freshwater bodies and are protected from flooding by dikes or other types of flood-protection structures. The water regime in polders is typically managed using a system of canals, pumps, and sluices to control the flow of water in and out of the area. In this study, the temporal changes in water salinity in the polder-type agricultural floodplain within the Neretva River Delta (NRD), Croatia, were analyzed by applying multivariate statistics and forecast modelling. The main aim of the study was to test the model that can be used in practice to forecast, primarily, water suitability for irrigation in a coastal low-lying agricultural catchment. The specific aim of this study was to use hydrochemistry data series to explain processes in water salinity dynamics and to test the model which may provide accurate salinity prediction, or finally select the conditions in which the model can be applied. We considered the accuracy of the model, and it was validated using independent data sets. To describe different patterns of chemical changes in different water classes due to their complex hydrological connectivity, multivariate statistics (PCA) were coupled with time-series analysis and Vector Autoregression (VAR) model forecasting. The multivariate statistics applied here did not indicate a clear connection between water salinity of the surface-water bodies and groundwater. The lack of correlation lies in the complex hydrological dynamics and interconnectivity of the water bodies highly affected by the artificial maintenance of the groundwater level within the polder area, as well as interventions in the temporal release of freshwater into the drainage canal network. Not all individual water classes contributed equally to the dominant patterns of ionic species identified by PCA. Apparently, land use and agricultural management practices in the different polders lead to uneven water chemistry and the predominant contributions of specific ions, especially nutrients. After applying the Granger causality test to reveal the causal information and explain hidden relationships among the variables, only two surface-water and two groundwater monitoring locations displayed a strong causal relationship between water electrical conductivity (ECw) as an effect and sea level as a possible cause. The developed models can be used to evaluate and emphasize the unique characteristics and phenomena of low-lying land and to communicate their importance and influence to management authorities and agricultural producers in managing and planning irrigation management in the wider Mediterranean area.

Quantification of Groundwater Hazards Related to Fluvial Floods via Groundwater Flow Modelling: A Review

Flood-related issues include the impact of groundwater on flood protection measures and other subsurface structures in a protected area. At the same time, subsurface elements of flood protection structures may significantly influence the natural groundwater regime and affect existing structures during non-flood periods. The paper provides an overview of hazardous factors linked to groundwater and specifies variables for the quantification of related hazards. Appropriate hydraulic groundwater flow models are presented and discussed, and their suitability for the modelling of individual typical problems and for hazard quantification is specified. The use of models and the application of CAD and GIS tools for data pre- and post-processing is mentioned in brief and demonstrated on examples of typical practical situations.

How Can Nature Protect People Against Sea-Level Rise?

Almost one third of people on Earth live near the coast where they are at risk from floods. Coastal areas are often protected from flooding by human-built flood-protection structures, like dikes and seawalls. Now that Earth’s climate is changing, sea-level rise and storms are becoming more intense and frequent, which increases the risk of flooding. Therefore, we need to develop bigger flood-defense structures to stay safe from flooding. However, this is very expensive. Is there an alternative? It may sound surprising, but nature can help us out. Around the world, ecosystems like mangrove forests, salt marshes, and coral reefs can help to protect our coasts from flooding. They can contribute to greener, more natural, biodiverse coasts, and make living along Earth’s coastlines safer and more sustainable. Using these natural systems is called nature-based flood defense. In this article, we explain how it works.

Flood frequency and flood intensity changes in the post embankment period in the Kosi sub-basin India: Impact of location, caste, and class on the flood vulnerability of the marginal communities

The overall precipitation in the state of Bihar, India is showing a decreasing trend both annually and seasonally, and yet extreme flood events are on the rise. The Kosi river embankments built to safeguard communities against flood risk are a product of socio-political and historical events in the past, but have resulted in differential impacts on those living inside and outside these embankments. The geomorphology of the river Kosi also makes it highly susceptible to recurring floods because it forms one of the largest inland deltas in North Bihar. Flood protection structures such as embankments exacerbate the magnitude of floods by jacketing the heavy sediment load and thus raising the riverbeds and exacerbating the intensity and duration of floods. Our paper employs an interdisciplinary approach to analysing both the biophysical and socio-institutional causalities of increasing flood events. From the quantitative analysis of rainfall data, we find that the daily, as well as monthly rainfall alone are not responsible for extreme flood events. The extreme rainfall events in the summer monsoon also do not increase the odds of flooding. Therefore, we conclude that precipitation alone is not the main factor affecting community's vulnerabilities but, a combination of socio-institutional factors including spatial location with respect to the embankment, class and caste of these communities. Our statistical analysis correlating daily and monthly gridded rainfall to the occurrences of flooding at the district level suggest that there are fewer flood events in the presence of the embankments across all years. However, primary data from household interviews and field observations confirm that the frequency and intensity of floods have increased in the post-embankment period. We found that the breaching of the river embankments is one of the major factors responsible for floods outside of the embankments. Kosi's marginalized communities perceive that they have become more vulnerable to flood risk in the post-embankment period with a declining standard of living in the Kosi villages caused by lack of proper roads, economic opportunities, educational institutions, public utilities and healthcare facilities, especially in areas with embankments.

Development and research of basalt plastic material for the flood protection structures

Due to the increasing number of catastrophic floods around the world, creation of an effective system to protect against natural disasters became particularly relevant. The paper investigates introduction of the basalt fiber to reinforce the composite sheet piles. Influence of the reinforcing fiber interlacing type on the nature of plastics destruction was established. Results of the work prove that basalt plastic (BP) exhibits higher climatic resistance than the fiberglass plastic (FGP). After post-curing, strength characteristics relative to the second year were decreasing by 15% with BP and by 22% with FGP in extension, and the strength limit in bending was decreasing by 12% with BP and by 47% with FGP. It was experimentally shown that under a long-term stationary thermal and humidity effect of 23°C/68RH, diffusion was observed on the basalt and fiberglass plastics consisting of two stages. The first stage had a satisfactory statistical error and was adequately approximated by the Fick’s diffusion model and the relaxation model. The second stage had an unsatisfactory statistical error for approximation and was of the spasmodic nature, while the jump in FGP was the largest indicating that the FGP was more susceptible to destruction exposed to the influence of long-term temperature and humidity regime of 23○С/68 RH, than the BP.

Near surface roughness estimation: A parameterization derived from artificial rainfall experiments and two-dimensional hydrodynamic modelling for multiple vegetation coverages

Roughness is the key parameter for surface runoff simulations. This study aims to determine robust Manning resistance coefficients (n) on the basis of consecutive artificial rainfall experiments on natural hillslopes available in literature, obtained at 22 different sites with different degrees of vegetation cover and type. The Manning resistance coefficient is particularly important in the context of two-dimensional (2D) hydraulic heavy rainfall simulations. Since there is a wide range of possible resistance values available leading to significantly different results regarding the accumulation of surface runoff, especially for shallow water depths. The planning of flood protection structures is directly affected by these uncertainties. This work also improves the knowledge between roughness and the shape of the hydrograph allowing a better calibration of infiltration models. As flow velocity, water depth, and infiltration rate were not observed during the rainfall experiments, only the outflow of the test field and rain intensity are known. For this purpose, a framework was developed to parameterize shallow water depth (<1 cm) -dependent roughness coefficients. To test the robustness of the framework, three different formulations of depth-dependent roughness and a constant Manning coefficient are used by comparing the measured discharge under different rainfall intensities with simulations in a 2D-hydraulic model. We identified a strong dependency of Manning’s n on the degree of vegetation cover and -type as well as an influence of consecutive rainfall events. This finally leads to a more robust parameterization of near surface roughness for hydrodynamic modelling, which is particularly important for the simulation of heavy rainfall events.

State of the practice and engineering framework for using emergent vegetation in coastal infrastructure

Natural and Nature-Based Features (NNBF) are promoted as alternatives to structural flood protection measures. Progress has been made in understanding the physics and engineering of these systems; however, engineering, ecological, and social barriers to implementation remain. This paper identifies these barriers using the results of a literature review and summary of expert opinion; contrasts the state of the practice of NNBF with traditional structures; and details the main engineering challenges to NNBF implementation, including the uncertainty in current calculation techniques and lack of engineering design guidelines. We suggest that emergent vegetation systems can be designed with the current body of information, and an example framework is proposed for assessing these systems for their wave attenuation performance. The framework is discussed in the context of risk, and future research priorities are presented.

Large-scale dynamic flood monitoring in an arid-zone floodplain using SAR data and hybrid machine-learning models

• Three novel hybridized models were used to describe spatio-temporal flood dynamic based on SAR data. • SVM-GWO model yielded the highest accuracy with an overall accuracy of 93.39%. • Temporal oxbow-lakes significantly affect flood inundation duration in the Kuzestan plain. • The proposed method provides insights into identifying suitable sites for flood protection structures. Although the growing number of synthetic aperture radar (SAR) satellites has increased their application in flood-extent mapping, predictive models for the analysis of flood dynamics that are independent of sensor characteristics must be developed to fully extract information from SAR images for flood mitigation. This study aimed to develop hybrid machine-learning models for flood mapping in the Ahvaz region, Iran, based on SAR data. Each hybrid model consists of a support vector machine (SVM) algorithm coupled with one of the following metaheuristic optimization procedures: grey wolf optimization (GWO), differential evolution, and the imperialist competitive algorithm. Sentinel-1 acquired SAR images before and during flooding between 20 March and 26 May of 2019. The goodness-of-fit level and predictive capability of each model were scrutinized using overall accuracy, producer accuracy, and user accuracy. The SVM-GWO approach yielded the highest accuracy with overall accuracies of 96.07% and 93.39% in the training and validation steps, respectively. Furthermore, this hybrid model provided the most accurate classification of water-inundation class based on producer accuracy (96.67%) and user accuracy (95.05%). The results highlight that wetland is the last land-use/land-cover type to return to normal conditions due to the many previously dry oxbow lakes that could trap water for a long time. Furthermore, the nine most suitable sites for flood-protection structures (e.g., embankments and levees) were identified based on floodwater distribution analysis. This work describes a robust, data-parsimonious approach that will benefit flood mitigation studies seeking to identify the most suitable locations for embankments based on spatio-temporal flood dynamics.

Spatially explicit agent-based approach for human–flood interaction modeling under external support

Two-way feedback between humans and flood systems is important for a better understanding of flood resilience and how flood risk evolves over time through human adaptation. However, most studies on this subject have assumed human traits and actions to be uniform, overlooking the diversity of human responses to floods. Furthermore, in many developing countries, the flood protection infrastructure is co-managed and co-maintained through the involvement of local communities as well as external or governmental support. However, the influences of differing levels of external intervention on the long-term outcome of co-management and on community behavior remain underexplored. In this study, we aimed to overcome this issue by considering a community as a heterogeneous group under flood risk via geographically explicit agent-based modeling. This method allowed us to computationally experiment on how human–flood interactions are conditioned by variations in household-level attributes and governmental support. Specifically, our study considered the community-based flood protection system in the Ganges-Brahmaputra River basin in Bangladesh. Our results suggest that heterogeneities in the geographic location, income, and flood damage have significant effects on the outcome of human–flood interactions, specifically cooperative efforts toward minimizing flood damage and maintaining flood protection structures. Our results also highlight that a moderate level of governmental support (i.e., assisting with only a part of the required labor) is necessary to maintain the infrastructure built to promote cooperative action in a community-scale flood protection system. Overall, we believe our agent-based model provides a potential for investigating the community dynamics from modeling individual-level human–flood interactions, ultimately provide a guidance for planning future governmental support for self-managed flood protection system.

Redress of damages inflicted by a due and proper exercise of water law permit for flood protection structures (issued in accordance with the applicable legal norms)

The exercise ofrights specified in the water law permit may result in damage to property owned by third parties, in particular individuals carrying on business in the vicinity. The category of cases in which legal action is temporarily inadmissible includes cases for damages, but only those “referred to in the provisions of the Act”. The purpose of this paper is to analyseof the issues of redress of damage inflicted by due and proper exercise of water law permit for flood protection structures (issued in accordance with the applicable legal norms). It presents the historical context of regulatory changes to the indemnification mechanism in the field of water law in Poland. It also discusses the most significant elements of this procedure with particular emphasis on administrative and civil aspects. The temporary inadmissibility of legal action resulting from statutorily designated administrative proceedings specific to these claims has been subject to criticism in this article.

Stability investigation of the flood protection structure at Nava Nakorn industrial estate, Thailand

A flood protection structure was built around the industrial area of Nava Nakorn in Pathum Thani Province, Thailand to ensure the safety of the industrial estate. Three types of flood protection walls were constructed and completed in 2012, which were prestress corrugated concrete sheet pile and reinforced concrete retaining wall. A large-scale experiment using a large navy watercraft for generating the water pressure on the flood protection structure was performed. Finite element analysis for simulation the flooding over 4 months was also performed. Factor of safety (FS) against external and internal failures decreased with increasing the flooding levels; however, all FS values were higher than the typical requirement for geotechnical design. All bending moments and shear stress in the flood protection walls were found to be lower than the required design values. The knowledge gained from this research can be applied to other flood walls, in similar soft clay deposits.

Bivariate Nonstationary Extreme Flood Risk Estimation Using Mixture Distribution and Copula Function for the Longmen Reservoir, North China

Recently, the homogenous flood generating mechanism assumption has become questionable due to changes in the underlying surface. In addition, flood is a multifaced natural phenomenon and should be characterized by both peak discharge and flood volume, especially for flood protection structures. Hence, in this study, data relating to the 55-year reservoir inflow, annual maximum flood peak (AMFP), and annual maximum flood volume (AMFV) for the Longmen Reservoir in North China have been utilized. The 1-day AMFV exhibits a significant correlation with AMFP. The extreme flood peak-volume pairs are then used to detect the heterogeneity and to perform nonstationary flood risk assessment using mixture distribution as the univariate marginal distribution. Moreover, a copula-based bivariate nonstationary flood frequency analysis is developed to investigate environmental effects on the dependence of flood peak and volume. The results indicate that the univariate nonstationary return period is between the joint OR and the AND return periods. The conditional probabilities of 1-day AMFV, when AMFP exceeds a certain threshold, are likely to be high, and the design flood values estimated by joint distribution are larger than the ones in the univariate nonstationary context. This study can provide useful information for engineers and decision-makers to improve reservoir flood control operations.

Comparative Analysis of Developed Rainfall Intensity–Duration–Frequency Curves for Erbil with Other Iraqi Urban Areas

Rainfall Intensity–Duration–Frequency (IDF) relationships are widely used in water infrastructure design and construction. IDF curves represent the relationship between rainfall intensity, duration, and frequency, and are obtained by analyzing observed data. These relationships are critical for the safe design of flood protection structures, storm sewers, culverts, bridges, etc. In this study, the IDF curves and empirical IDF formulas for the city of Erbil were developed for the first time by employing the annual maximum rainfall data for a period of 39 years (1980–2018), which is the only available recorded data. Statistical techniques such as Gumbel and Log-Pearson Type III (LPT III) were utilized to determine the IDF curves and empirical equations from daily rainfall data for several standard durations and return periods. The correlation between the rainfall intensities obtained from IDF curves and the empirical formula presented a reliable match, with a coefficient of determination of (R2 = 1). The results were compared to previously developed IDF curves and empirical formulas in Iraqi cities to show their reliability. Moreover, the results can be an initial step for authorities to establish required guidelines in the studied area, and in the design process of the storm water infrastructure of urban basins in the future.

Assessment of climate change impact on probable maximum floods in a tropical catchment

The increases in extreme rainfall could increase the probable maximum flood (PMF) and pose a severe threat to the critical hydraulic infrastructure such as dams and flood protection structures. This study is conducted to assess the impact of climate change on PMF in a tropical catchment. Climate and inflow data of the Tenmengor reservoir, located in the state of Perak in Malaysia, have been used to calibrate and validate the hydrological model. The projected rainfall from regional climate model is used to generate probable maximum precipitation (PMP) for future periods. A hydrological model was used to simulate PMF from PMP estimated for the historical and two future periods, early (2031 − 2045) and late (2060 − 2075). The results revealed good performance of the hydrological model with Nash–Sutcliffe efficiency, 0.74, and the relative standard error, 0.51, during validation. The estimated rainfall depths were 89.5 mm, 106.3 mm, and 143.3 mm, respectively, for 5, 10, and 50 years of the return period. The study indicated an increase in PMP by 162% to 507% and 259% to 487% during early and late periods for different return periods ranging from 5 to 1000 years. This would cause an increase in PMF by 48.9% and 122.6% during early and late periods. A large increase in PMF indicates the possibility of devastating floods in the future in his tropical catchment due to climate change.

Utilization of Risk Analysis of Hydraulic Structures for Efficient Allocation of Means

Efficient allocation of available means presuppose detailed knowledge about risks, costs and benefits within the area of interest. The societal demand for increased safety of hydraulic structures, as components of the critical infrastructure, requires considerable investment. To evaluate the effectiveness of potential measures in an environment influenced by epistemic and aleatory uncertainties, risk analysis and cost-benefit analysis are used in practice. The above described approach is now fully implemented when considering natural floods and structural flood protection measures, and also presented in the paper. For potential failures of dams and other important hydraulic structures however the procedure becomes rather more complex to comprehend the effect of designed measures on different failure modes. After introducing governing theoretical principles used for the natural flood vs structural measures analysis, the paper presents examples of application of combination of cost-benefit and risk analysis in the framework of the authors’ work as Strategic Expert of the Ministry of Agriculture of the Czech Republic for the different stages of the flood prevention program. The last part of the paper focuses on dam safety and the application of risk analysis as a support tool for decision making processes. It describes the practice applied in the Czech Republic and comments on the advantages and disadvantages of the current approach while suggesting further possible improvement.

Fragility Curves for Slope Stability of Geogrid Reinforced River Levees

When constructing flood protection structures such as river levees, oftentimes due to various factors engineers must design composite structures, i.e., reinforced earthen structures which comply with all the stability criteria. The most common way of reinforcing such structures is the usage of geosynthetics, or mostly geogrids when talking about stability. Since geosynthetics are man-made materials produced in a controlled environment and go through quality control measures, their characteristics contain a negligible amount of uncertainty compared to natural soils. However, geosynthetic handling, their installation in the levee, and their long-term degradation can all have significant effects of variable magnitude on geosynthetic characteristics. These effects and their variability can be considered as random variables, which can then be used in probabilistic analyses together with soil properties. To investigate the effects of the geogrid’s resistance variability on slope stability compared to soil properties variability, probabilistic analyses are conducted on a river levee in northern Croatia. It is found that the geogrid’s variability generally has very little effect on the total uncertainty compared to the friction angle’s variability, but out of the three geogrid layers used the top grid has the most influence.