Flood Protection Structures Research Articles

Modeling nearshore dynamics of extreme storms in complex environments of Connecticut

Flood hazard planning requires the accurate estimation of total water elevation due to predicted tide, surge, and wave runup to design flood protection structures and improve coastal risk planning for severe storms. The beach geomorphology and nearshore hydrodynamic conditions impact the conclusive flood inundation mapping in complex environments. The conventional approaches of flood modeling are limited due to either i) simple static estimates, ii) the application of a coupled circulation and phase-averaged wave models in coarse resolution, iii) failing to calibrate and validate with in-situ data, or iv) not considering sea-level rise projections in mapping the flood extent. We used a fully nonlinear Boussinesq wave model (FUNWAVE-TVD) on the nearshore area with a high-resolution grid to determine total water elevation on the shores. The model adopted the boundary conditions from coupled circulation and wave model of the Long Island Sound (Liu et al., 2020).We applied the model to Branford, Norwalk, and New Haven, CT to represent the complex topo-bathymetric features and the structural interference in shallow water wave dynamics. We compared the model results with the FEMA base flood elevation, the North Atlantic Coast Comprehensive Study (NACCS), and (Liu et al., 2020)’s Long Island Sound FVCOM-SWAVE model. The FUNWAVE-TVD model is found to model wave processes more accurately in shallow water regions compared to the empirical equation application of FEMA and coupled circulation-phase averaged model application of NACCS and FVCOM-SWAVE. We also examined local sea-level rise predictions of storms with 1% and 10% annual exceedance probability by the year 2050 in Connecticut and found that the flood extent of these two storms showed little to no difference. We suggest the planning approaches should consider the increase in the frequency of the storms in the predicted inundation zones due to sea-level rise.

Heterogeneity in flood risk awareness: A longitudinal, latent class model approach

Insights into the heterogeneity of human behaviours and attitudes toward risk require the understanding of the role played by a plurality of factors, such as risk awareness and trust. However, our knowledge of the interplay of these factors is limited, as is our knowledge of the patterns in risk attitudes and behaviours and their evolution over time. This study explores the interplay between attitudes and behaviours related to flood risk awareness and structural flood protection in two communities in the Eastern Italian Alps, and how they changed over time. To this end, a questionnaire was submitted to a total of 420 residents, in the year 2005 (N = 200) and 2018 (N = 220), and then analysed using Latent Class Analysis. No floods were recorded in the area during this period. The results show that there is a group of residents characterized by low risk awareness and high trust in structural flood protection. Such individuals are likely to live in urban – rather than mountain – communities and are characterized by a lack of or limited experience with floods. They are also prone to believe that such events will not happen in the future. In 2005, this group represented less than half of the sample, but its size substantially increased in 2018. This result has strong implications for local risk managers, because this group of residents is less risk aware than the others and they may deserve special attention and targeted messages in flood risk communication campaigns. This and other results are discussed, including the potential development of generalizable models to provide emergency and risk managers with tools to unveil risk awareness patterns and to tailor risk communication actions to citizens attitudes and behaviours. The paper ends with some considerations about the need not only to better understand but also to address diversity in flood risk awareness.

Environmental Impact Assessment and Hydraulic Modelling of Different Flood Protection Measures

The most appropriate method to protect settlements and economically important sites from flood hazard, is the implementation of flood protection measures in stream catchments and protected localities, which contribute to reduce the peak flow and distribution of the flood wave over a longer period of time. If such measures are not realistic or ineffective, it is necessary to focus on flood protection directly on the area of the protected side or its vicinity. Where the lag time between the flood threat detection and actual flood onset is short, one possible measure is to increase the capacity of the watercourse, very often in combination with other flood mitigation measures in the protected area. The engineering approach to flood protection is the subject of many scientific research studies. Permission for flood protection structures depends on their environmental impact assessment (EIA), according to Law no. 24/2002 Coll. on Environmental Impact Assessment in the Slovak Republic, annex no. 8 (list of activities subject to EIA). Based on the EIA, it is possible to select the best alternative of flood protection, i.e., the alternative with the lowest risk impact on the environment. This paper aims to analyse the flood protection measures along the Lukavica stream (central Slovakia), applying hydraulic models. The best alternative with the lowest impact on the environment, assessed using the risk analysis method, consists of detention reservoir construction. An effective combination of environmental impact assessment and hydraulic modelling contribute to the selection of an effective flood protection measure in the territory.

Remediation of the Solzan Industrial Waste Landfill at the Baikal Pulp and Paper Mill (BPPM)

The main environmental risks in the area of landfills are considered, all aspects of their technological reclamation using waste from the Baikal PPM are discussed. The data on the creation of soil and grounds using lignin-destroying microbiological preparations are presented. The final stage of the remediation of the Solzan landfill is the creation of cadastral maps 8, 9, 10 modern forest nurseries on the site, protected by flood and mudflow protection structures.

Polyelerde Hatalı Arazi Kullanımların Sebep Olduğu Afetlere Bir Örnek: 31 Ocak 2019 Kayaköy Polyesi Taşkını

Kayaköy Polje is a typical karst depression 6 km south of the city of Fethiye, extending for a length of 5 km, with a width of 2 km, and covering an area of 5 km2 at 140 m from the sea level. On January 31, 2019, heavy rainfall occurred in Fethiye, which is on the southwestern coast of Turkey, flooding settlements and agricultural areas on the nearby Kayaköy Polje. Following the process whereby a flood escalates into a disaster, a study was performed to investigate the roles of precipitation, karst processes, and land use, and solutions were proposed. Within the scope of the land surveying work that followed, the spatial information obtained with the help of drones, satellite images, and data collected by meteorological stations were analyzed using geographic information systems to create maps and other outputs. These findings implicated rapid development in the basin, in addition to the strong torrents that accelerated in a very short time, causing flooding in the region. The development activities altered the natural drainage and slope conditions, rendering flood protection structures useless, clogging sinkholes, or turning them into concrete wells. It was concluded that as long as improper land use, which triggered the flood, continued, flood and other disasters were bound to repeat.

The Societal Effects of the Eighteenth- Century Shipworm Epidemic in the Austrian Netherlands (c. 1730-1760)

In the 1730s, the Austrian Netherlands (eighteenth century Belgium) faced the devastating effects of the Great shipworm epidemic. Shipworms are marine wood scavenging molluscs that use their shells to eat their way into submerged wood. Due to the changing environmental conditions (temperature, salinity, …) at that time, the shipworm population exploded along the West-European coast. Within a few years the wooden flood protection structures protecting the low-lying Flemish coastal plain were damaged beyond repair. Adoption of new technologies was successful in safeguarding the embankments, but conflicting interests with the governing elites provoked a political deadlock ultimately resulting in the collapse of the Slyckens locks. The ensuing popular anger - together with other political and economic developments - played an important role in toppling the ruling elites in the county of Flanders in 1754. The following enlightened reforms, backed by Vienna and Brussels, had a decisive and positive impact on both the Flemish waterway and flood protection system. As a consequence of this a new ecosystem emerged which reduced the shipworm’s reproductive capacities.

Modelling a system of intercepting reservoirs distributed on the side tributaries of a river to prevent flooding of agricultural land

One of the areas of engineering protection of lands from flash floods is the use of intercepting waterworks on the side tributaries, which help to reduce the peak of the flood on the main river and redistribute it over time. With an increase in rainfall, flood protection capacity of existing or designed structures may not be enough to transform the river flow. The paper considers a mathematical model of flow control by a system of reservoirs, where a part of the accumulating capacity of the flood protection structure on the side tributary is redistributed into gabion waterworks located upstream of the river. This model allows to clarify the parameters and modes of operation of waterworks and evaluate their functioning, considering current and future economic and environmental conditions.

A new electric streamer for the characterization of river embankments

River embankments are linear earth structures, worldwide diffused, commonly used for flood protection. Their integrity and stability are fundamental prerequisites for the protection efficiency they can offer to the increasing frequency and magnitude of extreme flood events associated to changes in climate. Proper characterization and monitoring are essential to verify the construction requirements of newly built structures and to evaluate the durability of aged ones. Considering their linear extent, the characterization requires not only local geotechnical investigations but also the application of efficient and economically affordable methods. This is even more essential when the investigations are performed after, or in foresee of, significant flood events, when these structures get stressed and timing of the surveys is crucial. In these conditions, new survey methodologies, with the use of mobile systems, are a main research topic. In this paper the application of a new electric streamer, specifically designed for these aims, is presented. The technical solutions adopted for its construction are described and its application to the characterization of three different river embankments is presented. These case studies were chosen in accordance with the Po River Interregional Agency (AIPO), which is the authority deputed to the safety of flood protection structures in North-West Italy, along the hydrographic network of the Po River. The selected embankments are all earth structures, constructed above the natural alluvial soils, but are characterized by different conditions and challenges. The results obtained with the new system were comparable to standard Electric Resistivity Tomography (ERT) methods. The new system has significant advantages in terms of reducing the survey time, improving the efficiency of the surveys and increasing the data coverage. This resulted in a better definition of potentially dangerous anomalies.

The interplay between structural flood protection, population density, and flood mortality along the Jamuna River, Bangladesh

Levees protect floodplain areas from frequent flooding, but they can paradoxically contribute to more severe flood losses. The construction or reinforcement of levees can attract more assets and people in flood-prone area, thereby increasing the potential flood damage when levees eventually fail. Moreover, structural protection measures can generate a sense of complacency, which can reduce preparedness, thereby increasing flood mortality rates. We explore these phenomena in the Jamuna River floodplain in Bangladesh. In this study area, different levels of flood protection have co-existed alongside each other since the 1960s, with a levee being constructed only on the right bank and its maintenance being assured only in certain places. Primary and secondary data on population density, human settlements, and flood fatalities were collected to carry out a comparative analysis of two urban areas and two rural areas with different flood protection levels. We found that the higher the level of flood protection, the higher the increase of population density over the past decades as well as the number of assets exposed to flooding. Our results also show that flood mortality rates associated with the 2017 flooding in Bangladesh were lower in the areas with lower protection level. This empirical analysis of the unintended consequences of structural flood protection is relevant for the making of sustainable policies of disaster risk reduction and adaptation to climate change in rapidly changing environments.

Fish species using the fish passage between Jamuna and Bangali river at Sariakandi, Bogra

Sariakandi fish pass is unique connecting Jamuna and Bangali rivers through an engineered channel. A study was conducted on the fish pass aiming to improve fish diversity in north-west Bangladesh. Sampling at the fish pass, market census, interviewing the locals and focus group discussion were done to collect data from the study area. A total of 69 fish species under 9 orders and 26 families were recorded. Cypriniformes (22 species) was the most dominant order followed by Siluriformes (21 species), Perciformes (13 species), Clupeiformes (4 species), Synbranchiformes (4 species), Osteoglossiformes (2 species), Mugiliformes (1 species), Anguilliformes (1 species) and Tetraodontiformes (1 species). In total 30 threatened species in Bangladesh and globally recognized 9 species were recorded. This fish pass is not working during the dry or winter seasons but helps in the diversified fish migration diversity of Bengali and Jamuna river system during the flood time of Bangladesh. The present study recommends establishing effective fish passages in flood protection structures or dams in Bangladesh to retain the connectivity of fish migration routes and the improving of fish diversity.
 J. Biodivers. Conserv. Bioresour. Manag. 2019, 5(2): 53-62

Monitoring of a Sea-Dike in Northern Germany by Means of ERS-1, ENVISAT/ASAR, and Sentinel-1 SAR Interferometry

Flood events are one of the most severe natural hazards threatening billions of people living in coastal areas. Synthetic aperture radar (SAR) interferometry can contribute significantly to civil security by providing a highly accurate tool for spatially explicit monitoring of flood protection structures. This article analyzes multitemporal SAR interferometry techniques like persistent scatterer interferometry and small baseline subset (SBAS) for C -band radar data in order to show the potential for a precise dike monitoring. These techniques not only achieve accuracies of few millimeters, but they also enable to reconstruct the deformation process in time. Thus, critical deformation processes can be identified timely and precautions can be taken to prevent dike bursts during flood events. In this article, sea dikes located at the North Sea coast in Germany are analyzed in order to show the potential but also the difficulties of this approach, using 34 ERS-1/2, 55 Envisat ASAR, and 44 Sentinel-1 scenes. All results point out that long-term deformation processes can be measured quite well. Due to decorrelation effects, the results on vegetated dikes are ambiguous. Applying SBAS to Sentinel-1 data is very promising to serve as a tool to precisely detect and understand deformation processes of dike bodies on large spatial scales.

Analyzing investments in flood protection structures: A real options approach

The soaring number of natural hazards in recent years due largely to climate change has resulted in an even higher level of investment in flood protection structures. However, such investments tend to be made in the aftermath of disasters. Very little is known about the proactive planning of flood protection investments that account for uncertainties associated with flooding events. Understanding the uncertainties such as “when” to invest on these structures to achieve the most optimal cost-saving amount is outmost important. This study fills this large knowledge gap by developing an investment decision-making assessment framework that determines an optimal timing of flood protection investment options. It combines real options with a net present value analysis to examine managerial flexibility in various investment timing options. Historical data that contain information about river water discharges were leveraged as a random variable in the modeling framework because it may help investors better understand the probability of extreme events, and particularly, flooding uncertainties. A lattice model was then used to investigate potential alternatives of investment timing and to evaluate the benefits of delaying investments in each case. The efficacy of the proposed framework was demonstrated by an illustrative example of flood protection investment. The framework will be used to help better inform decision makers.

Morphological Evolution of an Intertidal Area Following a Set-Back Scheme: A Case Study From the Perkpolder Basin (Netherlands)

IIn the present context of sea-level rise, the reconstruction of previously reclaimed intertidal areas represents an opportunity to build dynamic coastal defences, to decrease flooding under storm conditions by the dissipation of wave and surge energy across the vegetated domain. In Europe, this approach started in the late 1990s along the coast of eastern and southern England but it is becoming common to many European countries around the North Sea margin. The process of salt-marsh restoration normally develops around the opening or removal of flood protection structures and gradual flooding of the hinterland. If the intertidal zone starts to experience vertical accretion, vegetation will colonize the area and a saltmarsh will develop. This paper presents the morphological evolution and sediment distribution in the Perkpolder basin, SW Netherlands (NL), following the conversion of a reclaimed area into a tidal flat, after the opening of an inlet in the flood defence structures in June 2015. The main focus of this study is the description of the evolution of the tidal flat since the opening of the inlet and the identification of spatio-temporal conditions for the evolution of a salt marsh. To reach this objective, several topographic surveys were undertaken, together with sediment surface sampling. Sedimentation rates at fixed sampling stations were assessed during the transition between neap and spring tides over a period of 1 month and 2 weeks. The morphological analysis of the inlet evolution proved that 6 - 8 months after the opening the inlet reached an equilibrium state. The average accretion rate across the whole study area was about 6 - 7 cm year-¹. The average deposited sediment was about 100 g m-² per day. Considering the sedimentation rates in the most elevated regions, 80-110 cm above NAP (Normaal Amsterdams Peil), and assuming that the sedimentation rate will remain constant in time, the conditions for the on-set of salt-marsh formation will not be reached before 8-10 years. Projections indicate that the area located at +50 cm above NAP will not become a mature marsh before 50 years.

Future Trends in the Interdependence Between Flood Peaks and Volumes: Hydro‐Climatological Drivers and Uncertainty

AbstractReliable flood estimates are needed for designing safe and cost‐effective flood protection structures. Classical flood estimation methods applied for deriving such estimates focus on peak discharge and neglect other important flood characteristics such as flood volume and the interdependence among different flood characteristics. Furthermore, they do not account for potential nonstationarities in hydrological time series due to climate change. The consideration of both the interdependence between peak discharge and flood volume and its nonstationarity might help us derive more reliable flood estimates. A few studies have looked at changes in the general dependence of peak discharge and flood volume for small sets of catchments and explored ways of modeling such changes. However, spatial analyses of trends in this dependence or in their climatological drivers have not been carried out. The aim of this study was to help close this knowledge gap by first quantifying trends in the general dependence between peak discharge and flood volume as described by Kendall's tau on a spatially comprehensive data set of 307 catchments in Switzerland. Second, potential climatological drivers for changes in the dependence between peak discharge and flood volume were identified. Our results show that the dependence between peak discharge and flood volume and its trends are spatially heterogeneous. This pattern cannot be explained by one driver only but by an interplay of changes in precipitation, snowmelt, and soil moisture. Both the trends and the links between drivers and trends depend on the climate model chain considered and are therefore uncertain.

Application of Remote Sensing and GIS in Sinuosity and River Migration Analysis of the Lower Parts of River Niger in the Niger Delta

This research is financed by the African Union in collaboration with Pan African University Life and Earth Sciences (including health and Agriculture), Ibadan, Nigeria and University of Ibadan, Ibadan Nigeria. Abstract Sinuosity and river migration analysis of the lower parts of the River Niger in Niger Delta from Onitsha to the coast has been done using various Landsat images during 1985 to 2015. The transect method was used for the river shifting measurement. The study area consists of a stretch characterized by uneven meandering and migration. Consequently, the adjacent areas are susceptible to flooding that causes significant losses of crops, property, livestock, and human lives. During the study period, the channel pattern moved from a sinuous-straight to straight-sinuous pattern with sinuosity reducing in the upper portions of the channel. It was found that in the upper portions of River Niger, the west bank of the channel was subjected to more erosion and that the river is migrating towards the west. In the lower portions of the River Niger, the east bank is subjected to more erosion and thus the channel is migrating towards the east. The width of the meander belt ranged from less than 1km to 4.9 km with an average of about 2km. Based on the findings of this study, it is suggested that the flood protection structures are crucial for the west bank in the upper reaches and the east bank in the lower portions of the channel in the study area. It is further suggested that these structures be constructed outside the meander belt of the river. Keywords : Sinuosity. Channel migration. Meander belt. Channel pattern. GIS. Landsat images. DOI : 10.7176/JEES/9-4-08 Publication date : April 30 th 2019

Flooding, channel dynamics and transverse infrastructure: a challenge for Middle Ebro river management

ABSTRACT This study documents the impacts of engineering works on flood risk and channel dynamics of the maximum geomorphic flow reach of the Middle Ebro River (Spain) over the last ninety years. The map reveals how the construction of transversal transport lines and their ineffective design and maintenance has contributed to an elevated risk of flooding and channel avulsion at this location. In addition, the development of flood protection structures has restricted the natural dynamics of the river. These modifications have restricted the passage of flood waters, ultimately increasing flood hazards, by changing the area and depth of inundation and extending the flood hydrograph. The map allows for the interpretation of key processes, forecasting of flood hazards, and the evaluation of possible mitigating actions. These findings reconfirm that reducing space for the mobility of a river is not a good management solution and further aggravates the current situation.

Dependence of flood peaks and volumes in modeled discharge time series: Effect of different uncertainty sources

Flood estimates needed for designing efficient and cost-effective flood protection structures are usually derived using observed peak discharges. This approach neglects, firstly, that floods are characterized not only by peak discharge but also by flood volume, and, secondly, that these characteristics are subject to modifications under climate and land use changes. Bivariate flood frequency analysis based on simulated discharge time series makes it possible to consider both flood peak and flood volume in design flood estimation. Further, this approach considers changes in discharge characteristics by using discharge series generated from climate time series used as an input for a hydrological model. Such series are usually not available at an hourly resolution but at a certain aggregation level (e.g. 24 h) and might not perfectly represent observed precipitation distributions. In this study, we therefore investigate how the aggregation and distribution of precipitation series and discharge distribution affect flood peaks and volumes and their dependence. We propose a framework for assessing the uncertainty in bivariate design flood estimates that is caused by different factors in the modeling chain, which consists of precipitation-discharge modeling, flood event sampling, and bivariate flood frequency analysis. The uncertainty sources addressed are precipitation aggregation and distribution, parameter and model uncertainty, and discharge resolution. Our results show that all of these uncertainty sources are relevant for design flood estimation and that the importance of the individual uncertainty sources is catchment dependent. Our results also demonstrate that substantial uncertainty is introduced already in the first step of the model chain because commonly used calibration procedures do not take into account the reproduction of flood volumes. Researchers should be aware of such deficiencies when performing bivariate flood frequency analysis on modeled discharge time series and should aim to tailor model calibration procedures to the problem at hand.

Is Bangkok becoming more resilient to flooding? A framing analysis of Bangkok's flood resilience policy combining insights from both insiders and outsiders

The rapidly urbanizing cities in Southeast Asia experience increasing flood impacts due to the consequences of climate change. In these cities, policy efforts to build flood resilience are gaining momentum. The aim of this paper is to understand and assess flood resilience policy development, particularly in cities in developing countries. Bangkok is one of the cities that participates in the 100 Resilient Cities Programme (100RC) - the international policy platform for building resilient cities. In 2017, the Bangkok Metropolitan Administration (BMA) launched the ‘Bangkok Resilience Strategy’ to translate the resilience concept to its urban context. A framing perspective is adopted to reconstruct the strategy, process and anticipated outcome of Bangkok's flood resilience policy. We studied data obtained from ‘insiders’ (involved policy makers, experts and consultants) and ‘outsiders’ (local communities, civil society organizations and news media). Findings indicate that the economic growth frame is prevailing in the development of Bangkok's flood resilience policy, prioritizing structural flood protection with little attention for flood adaptation measures and related social impacts among vulnerable communities. The role of local communities and civil society in the formulation of Bangkok's flood resilience policy is limited. This paper therefore recommends cities in developing countries and cities in the 100RC Programme to organize a more inclusive resilience building process for addressing social problems regarding urban poor communities along with increasing flood safety and protection.

Characterization of Hydraulic Heterogeneity of Alluvial Aquifer Using Natural Stimuli: A Field Experience of Northern Italy

This study investigates the hydraulic heterogeneity of the alluvial aquifer underneath the dam and the stilling basin of a flood protection structure in Northern Italy. The knowledge of the interactions between the water in the reservoir upstream of the dam and the groundwater levels is relevant for the stability of the structure. A Bayesian Geostatistical Approach (BGA) combined with a groundwater flow model developed in MODFLOW 2005 has been used to estimate the hydraulic conductivity (HK) field in a context of a highly parameterized inversion. The transient hydraulic heads collected in 14 monitoring points represent the calibration dataset; these observations are the results of the hydraulic stresses induced by the variations of the lake stage upstream of the dam (natural stimuli). The geostatistical inversion was performed by means of a computer code, bgaPEST, developed according to the free PEST software concept. The results of the inversion show a moderate degree of heterogeneity of the estimated HK field, consistent with the alluvial nature of the aquifer and the other information available. The calibrated groundwater model is useful for simulating the interactions between the reservoir and the studied aquifer under different flood scenarios and for forecasting the hydraulic head levels due to strong flood events. The use of natural stimuli is useful for obtaining information for aquifer heterogeneity characterization.

A hazai árvízvédelmi stratégia főbb irányai

Formulation of a country’s flood protection s trategy in every case depends on the technical-socio-economic conditions of the given country. The flood safety requirements are highly influenced by the country’s performance and financial situation. On the Hungarian rivers, flood safety is based on the 100-year return period maximum flood events and the flood safety requirements must be developed accordingly. The state must guarantee the success of the flood protection up to this flood safety level. The water management sector has also formed the Hungarian flood protection strategy to this flood safety level as an operator of primary flood protection structures. In the past decades, due the changes in socio-economic conditions and the rise of extremities caused by climate change have caused that flood protection strategy had to be changed several times. In my article I show the changes and the effects of changes on the operational flood protection activities and preventive flood protection strategy.