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In recent decades, society has paid increased attention to issues related to observed climate change, which also includes recurring extreme hydrological phenomena. Shortterm heavy rainfall and long-term droughts draw attention to the increased need for hydraulic structures, providing protection against floods or creating water supplies in times of water scarcity. Flood control levees are an important part of flood protection measures. We should give them constant attention to prevent them from collapsing, and their safety. Almost 3,000 km of flood control levees were built in Slovakia. Due to their age and importance, in recent years these structures require special attention due to the increased intensity of flood flows, reconstruction, or rehabilitation. The most common is the sealing of the levee bodies or their subsoil. Also, we can increase their crest levels due to changes in hydrological conditions in the last decades. The present article illustrates the results of a study related to increasing the safety of the Nitra levees. It is remarkable here that, despite the engineering research on the unproven occurrence of permeable local leaks, wet areas occur at the foot of the levees during floods. Attention is focused on the probable causes of these phenomena and the possibilities of their solution. [ABSTRACT FROM AUTHOR]

Qiqihar is a significant city on the Nen River in China, which is the main stream of the Songhua River basin. The length of the return period of Qiqihar's flood control design standard is fifty years. If a 100-year flood event happened, Qiqihar would face the risk of a burst levee. To quantitatively evaluate flood risk to the city from a burst levee or proactive flood diversion, a model for analysing flood submergence from a burst levee in the City of Qiqihar is established based on MIKE Flood. The model integrates one- and two-dimensional hydrodynamic models to implement coupled simulation. The terrain data are from city elevation data on a scale of 1:10000. Following local modifications made based on survey data, such as on levees, roads, and buildings, a 20 m × 20 m grid of terrain data was formed as the terrain input of the model. The model simulates the water level of Nen River and the flood path, submerged time/depth/area, and duration in floodplain under three scenarios: baseline, proactive downstream flood diversion, and an upstream levee burst under a flood with a one hundred-year return period. Proactive downstream flood diversion can reduce the maximum water level by 0.068 m and correspondingly decrease peak flood flow by 1120 m 3 s -1. These results provide basic information to support urban flood risk analysis and flood dispatching and management across the whole river basin. [ABSTRACT FROM AUTHOR]

A characteristic feature of streams in the East Slovakian lowland is their considerable fluctuation. On the one hand, this causes dry periods in streams, on the other hand, with periods extremely rich in precipitation -flood periods. One of the most important streams in this area is the Ondava River. One of the essential elements in the protection of the area against floods are hydrotechnical structures along the streams –flood control levees. In terms of construction and also with their parameters, they belong to a group of relatively simple hydraulic structures. First flood control levees (protective backfills) were primitive and did not protect people and their properties enough against floods. Over time they were partly modified but mostly on the same base with the same local materials. Despite this, we encounter many problems in their operation, which are caused mainly by their linear character, the wide variability of geological, morphological and geotechnical conditions, and their short-term hydrodynamic stress. In the present paper, we try to point out the influence of various factors influencing the filtration stability of flood control levees, such as change of the geological composition of the subsoil, morphology of the terrain, the distance of the stream from the flood control levee, the shape of the flood wave, etc. The result of the solution of individual variants is the assessment of the levee's subsoil from the point of view of filtration stability. [ABSTRACT FROM AUTHOR]

The Sacramento-San Joaquin Delta is at the heart of California's water supply system that provides water for irrigation and human consumption. It is also home to subsiding organic soils, decreasing native aquatic species populations, water quality degradation, vulnerable levees (levees are equivalent to dikes) and decreasing agricultural viability. There has been substantial progress in the interdisciplinary understanding and quantification of the nature and effects of subsidence and its mitigation. Because of the need for a drained rootzone, farming of crops such as vegetables, trees, vines, corn and alfalfa, results in an ongoing unsustainable cycle of continuing peat oxidation and deepening of drainage ditches to compensate for elevation loss. Despite substantial evidence for the increasing risks to the State's economy and water supply, the unsustainability of the status quo, and evidence for the benefits of alternatives, there has been limited progress in converting to land uses that can reduce, stop and reverse subsidence. Our overall approach has been to measure land-surface elevation changes; understand, quantify and model subsidence and greenhouse gas emissions from drained organic soil, and evaluate alternate land uses. Subsidence rates vary from less than 0.5 to over 2 cm yr -1 , depending primarily on depth to groundwater and soil organic matter content. The primary cause of subsidence is the oxidation of organic matter, which has resulted in elevations of -3 to -9 m on about 100 000 ha. Using the results from micrometeorological measurements and modelling, we estimate that organic-matter oxidation causes an annual emission of over 2×106 t of CO2 -equivalent which represents about 21 % of the State's plant-based agricultural emissions. Rewetting of the peat soils is emerging as a viable solution. Rice and wetlands stop and (in the case of wetlands) reverse the effects of subsidence and result in a net greenhouse-gas emission reduction benefit. Wetlands accrete about 3 cm of soil per year, can break the unsustainable subsidence/drainage cycle, reverse the trajectory of increasing hydraulic pressures on levees, reduce the probability of levee failure and seepage onto islands (islands are equivalent to polders), and may provide material for biofuels and animal feed. The recent implementation of a methodology for quantification of the GHG benefit is facilitating land use conversion and participation in the carbon market. [ABSTRACT FROM AUTHOR]

For the levee strengthening project Krachtige IJsseldijken Krimpenerwaard (KIJK) a study has been done to examine all buildings along 10 km of levee. These buildings are an important factor in the design stage, because of its sensitivity to deformations due to the natural compaction of the soft deposits (creep) and the potential effects of the levee strengthening. This paper covers the quantification of building settlement due to natural subsidence using InSAR. Research is performed in the city archives to establish the characteristics of the buildings, such as the foundation type. Although the city archive is well organised, it is not complete. The building data density is substantially improved using InSAR information. This enhanced data set is a key factor in establishing an consistent assessment of the risk of damage for the different levee strengthening alternatives. [ABSTRACT FROM AUTHOR]

Earthen levees are commonly used protective structures against seasonal flood activity. Monitoring of the embankments condition is an important issue related to the protection of people's lives, their property, environment and infrastructure. The assessment of the physical condition of the levee can be obtained by comparison of the sensors measurements' localized within the embankment and the changes in parameters values obtained as a result of numerical modelling of flooding process. Uncertainty of the values of material parameters is one of the most important problem encountered in issues related to physical process modelling with geotechnical analysis. The input variable uncertainty and variability propagates through a computational model to its output and affect the modelling results. Sensitivity analysis provides a framework and techniques that can identify important variables in a computational model. In this paper the application of Morris Screening method is proposed to obtain the parameter significance ranking in modelling of water pore pressure and temperature values within flood embankment. Geometry and geomechanical properties of the earthen levee used in numerical calculation were taken from ISMOP project. [ABSTRACT FROM AUTHOR]

Porto Alegre is the capital and largest city in the Brazilian state of Rio Grande do Sul in Southern Brazil with approximately 1.5 million inhabitants. The city lies on the eastern bank of the Guaiba Lake, formed by the convergence of five rivers and leading to the Lagoa dos Patos, a giant freshwater lagoon navigable by even the largest of ships. This river junction has become an important alluvial port as well as a chief industrial and commercial centre. However, this strategic location resulted in severe damage because of its exposure to flooding from the river system, affecting the city in the years 1873, 1928, 1936, 1941 and 1967. In order to reduce flood risk, a complex system of levees and pump stations was implemented during 1960s and 1970s. Since its construction, not a single large flood event occurred. However, in recent years, the levees in the downtown region of Porto Alegre were severally criticized by city planners and population. Several projects have been proposed to demolish the Mauá Wall due to the false perception of lack of flood risk. Similar opinions and reactions against flood infrastructure have been observed in other cities in Brazil, such as Itajaí and Blumenau, with disastrous consequences. This paper illustrates how the perception of flood risk in Porto Alegre has changed over recent years as a result of flood infrastructure, and how such changes in perceptions can influence water management decisions. [ABSTRACT FROM AUTHOR]

Numerical modeling of important stage during planning construction of bridges, levees, tunnels or any others ground and underground building, that may have affect on the neighborhood and human life. Influence of boundary condition on accuracy of numerical calculation is an example of a modeling part, that cannot be omitted. Accuracy and time computing of calculation strongly depend on dimension of analyzed model. Rare computational grids considerably decrease resolution and quality of calculation, whereas big size of numerical computational grids rapidly increase calculation time. One of the method of changing size of model is optimize distance to the edge of model interpreted as boundary conditions. Determination of such distance should be compromise between computational cost and minimize of the influence of the model boundaries on numerical calculation under the levee and its nearest neighborhood. In this paper results of numerical modeling, with different boundary condition offsets are presented in order to find the optimal one. Calculation was conducted using Itasca FLAC v.7.0 2D [ABSTRACT FROM AUTHOR]

In the northwestern Black Sea the Danube deep sea fan has an extent of over 150 km and stretches from several hundred meters water depth down to the abisal plain at 2,200 m water depth. The most recent channel-levee system is connected to the Viteaz Canyon, wich is deeply (500 m) incised into the shelf with the head at about 24 km landward of the shelf edge. Viteaz Canyon is 2.4 to 4 km wide, trending northwest-southeast, with stepped flanks and meandering erosional V-shaped thalveg, slightly sinous and unleeved valley. At about 800 m water depth, the upper slope canyon changes into a large single-leveed channel - Danube submarine channel -- that is feeding a deep water fan. The channel is 2.4 km wide (between the top of the levees) and 270 m deep between the channel floor and the top of the levees, measured at about 1200 m water depth. Below 1400 m water depth, the fan morphology is modified by the bifurcation of this single channel and a new meandering channel on NW-SE direction. In this study we propose to estimate the thickness variation of seismic facies that supports changes in the bifurcation area of the Danube submarine channel. This is possible following the seismic sections proposed for study, defining the main sedimentary facies and get morphological and thickness maps using the software Petrel and applying seismo-stratigraphic method. We will analyze the initiation of new channel NW-SE direction on the seismic sections and thickness and morphologic obtained maps. [ABSTRACT FROM AUTHOR]

The article discusses the study which describes the geotextiles and fibers application in geotechnical engineering industry. It notes that geotextiles and the major advances of polymers have been used to design the critical man-made structures including dams, levees, landfills, and roads. It mentions that early form of geotextile has used the woven cotton fabrics in a series of ground construction. It reveals the availability of 208 different geotextile products in the U.S. which are supplied or produced by 23 different companies for separation, filtration, and erosion control.

A volunteer team of engineers from the American Society of Civil Engineers visited New Orleans shortly after the catastrophic flooding caused by hurricane Katrina on 29 August 2005. Their mission was to make an independent initial assessment of the failed, US Army-engineered levees and floodwalls, as well as to collect perishable data to help provide answers to one of the worst civil engineering disasters in history. This paper reports on their observations and shows that they compared favourably with the findings of later in-depth investigations, to which the team also contributed valuable forensic data. It highlights the vital role engineering institutions can play in helping both the profession and society understand and learn from disasters. [ABSTRACT FROM AUTHOR]

National water programs in the United States centralize decision-making, but they work within the federal system. As a step toward documenting the range of institutional forms likely under federalism, this paper analyzes how the national flood control program developed. In this case, Congress and the Army Corps of Engineers actually resisted taking flood control duties over from the state and local levels. Once advocates from flood-prone valleys managed to get the program created, however, army engineers had to work closely with local contractors, levee districts, and state governments to build levees and weirs. This pattern of organizational articulation is one institutional form that affirms central government authority in distant regions. ..PAT.-Unpublished Manuscript [ABSTRACT FROM AUTHOR]