An Extensive Italian Database of River Embankment Breaches and Damages

Failure of (floodplain) river embankments is mainly due to internal erosion phenomena, hydraulic heave, mechanical instability triggered by seepage forces. In order to minimize the risk of internal erosion (piping) or hydraulic heave, the use of plastic diaphragm or sheet piles is recommended. The main advantage of sheet piles is the structural resistance of this type of barrier which contributes to the mechanical resistance of the embankment and provides a hydraulic barrier even in the case that overtopping of the embankment has caused the erosion of the bank itself on the country side. On the other hand, sheet piles are very expensive and subject to possible corrosion or thickness reduction because of aggressive water and parasite currents into the soil. Plastic diaphragms are less expensive than sheet piles and can be installed quickly without compromising the serviceability of the embankment. This last advantage is also typical of sheet piles. The (dry) deep—mixing technology for the construction of plastic diaphragms is shortly illustrated and the advantages of such a method are pointed out. Eventually the effectiveness of a trial diaphragm, that have been constructed inside an existing (floodplain) river embankment at the Bottacci site (Province of Lucca, Northern Tuscany, Italy), is shown after the occurrence of repeated floods. Direct controls of the diaphragm and the information obtained by a monitoring system installed inside the embankment have been used for such a purpose. The geotechnical characterization of the embankment and the monitoring system are illustrated in a companion paper.

Abstract. Internal erosion is the cause of a significant percentage of failure and incidents involving both dams and river embankments in many countries. In the past 20 years the use of fibre-optic Distributed Temperature Sensing (DTS) in dams has proved to be an effective tool for the detection of leakages and internal erosion. This work investigates the effectiveness of DTS for dike monitoring, focusing on the early detection of backward erosion piping, a mechanism that affects the foundation layer of structures resting on permeable, sandy soils. The paper presents data from a piping test performed on a large-scale experimental dike equipped with a DTS system together with a large number of accompanying sensors. The effect of seepage and piping on the temperature field is analysed, eventually identifying the processes that cause the onset of thermal anomalies around piping channels and thus enable their early detection. Making use of dimensional analysis, the factors that influence this thermal response of a dike foundation are identified. Finally some tools are provided that can be helpful for the design of monitoring systems and for the interpretation of temperature data.

In slopes where a mixture of coarse and fine particles is present, the infiltration of rainfall can cause the migration of fine particles. This migration alters the hydraulic properties of the soil and has implications for slope stability. In this study, the slope under investigation is a tailings dam composed of loosely consolidated soil with a wide particle size distribution. Due to rainfall infiltration, fine particles tend to migrate within the voids of the coarse particle framework, leading to changes in hydraulic properties and inducing slope instability. The classical internal erosion constitutive model, known as the Cividini and Gioda erosion criterion, is commonly used to predict the behavior and effects of fine particle erosion in geotechnical engineering. However, certain parameters in this erosion criterion equation, such as long-term density, are challenging to obtain through experiments. To investigate the coupled evolution of seepage and erosion within landfill slopes under the influence of rainfall infiltration and to understand the mechanisms of slope instability, this research assumes the erosion of fine particle suspension and adopts the Worman and Olafsdottir erosion criterion to establish a coupled model of unsaturated seepage and internal erosion. The developed model simulates the coupled response of seepage and erosion in unsaturated landfill slopes under three different rainfall intensities. It is then combined with the infinite slope model to quantitatively analyze the impact of fine particle migration on soil permeability and slope stability. The numerical simulations provide the following findings: The Worman and Olafsdottir erosion criterion, unlike the Cividini and Gioda erosion criterion, only requires the determination of the soil’s gradation curve to estimate the erosion rate. Internal erosion primarily occurs within the leading edge of moisture penetration, accelerating the advancement of the wetting front and reducing slope stability. When the rainfall intensity is lower than the saturated permeability coefficient, the influence of internal erosion can be disregarded. However, under rainfall intensities equal to or greater than the saturated permeability coefficient, considering internal erosion results in a difference in the depth of the wetting front of up to 34.2 cm after 6 h in the R2 scenario. The safety factor without considering internal erosion is 1.12, whereas considering internal erosion yields safety factors between 1.08 and 1.09. In the R3 scenario, the difference in the depth of the wetting front reaches 53.8 cm after 6 h, with a safety factor of 1.12 without considering internal erosion and safety factors between 1.06 and 1.07 when considering internal erosion.

The catastrophic floods in Poland in previous years and the current one in 2024 have highlighted the importance of slope stability in the design, maintenance, and operation of levees, which are crucial for flood protection. While the causes of this year's flood have not been determined yet, as experts are still working on assessing the reasons for the failure of various structures, it is evident that many have failed due to multiple factors, such as overtopping, internal erosion, and slope instability. The article highlights the importance of the observational method, which, during the operation of hydraulic structures often in use for decades, enables data collection on potential seepage through the levee and on adverse filtration phenomena. Such information allows revising previous safety calculations for the structure, adjustments of geotechnical parameters adopted during the design phase, and consideration of factors like the presence of water on the downstream side. Evaluating slope stability under these conditions reflects the actual working environment of the structure and facilitates decision-making regarding potential modernization initiatives. The article analyses the stability of the levee slope before and after its modernization. A transient seepage analysis through the levee was carried out in the selected cross-section for various water levels, and the stability of the embankment in such conditions was also assessed. Next, the modernization of the embankment was briefly described, with particular emphasis on the sealing system. Stability was evaluated under the new filtration conditions through the levee. Based on this, it was concluded that the sealing system plays a crucial role in improving the safety and stability of the slope. The analysis revealed that remedial actions alone—such as soil compaction and raising the levee crest—without the installation of sealing systems would have virtually no significant impact on the structure safety. After implementing the remedial measures, the levee safety factor can be considered safe, and the numerical analysis of water filtration through the levee indicates that future water seepage on the downstream side during river flooding should not occur.

Between 1928 and 1971, a total of 10 barrages including river embankments with a height of up to approx. 10 m were erected on the Upper Rhine between Basel and Karlsruhe. The river embankments were constructed using local building materials : the shells consists of sandy gravel, and the cores of a silty material (alluvial loam).The in-situ sandy gravels in the Upper Rhine region show a pronounced grain-size gap for coarse-grained sand and fine gravel which is why they are not resistant to suffosion. This lack of suffosion resistance affects both the ground below the river embankments and their shells. Furthermore, the filter stability of the silty soil material used in the cores is not sufficient to filter the sandy gravels of the ground below the embankments and/or their shells. Immediately after flooding of the impoundments, the exit of seepage water was observed on the downstream embankment slopes. Due to the embankment material’s lack of suffosion resistance and filter stability this caused a loss of soil in certain areas.To improve the situation, and working from the crest downwards, cut-off walls (diaphragm walls, injection walls and sheet pile walls) were subsequently driven into the river embankments over long stretches. These increase the length of the seepage path, thus reducing the hydraulic gradients in the embankment and the ground. The resulting reductionof the seepage forces reduces the risk of internal erosion. The efficiency of the cut-off walls embedded in the embankments subject to seepage depends on the overall ground situation and the groundwater flow characteristics on the one hand, and on the walls’ resistance to geohydraulic load on the other hand.

Human settlements have historically concentrated near rivers due to their transportation benefits and fertile lands, despite the inherent flood risks. To mitigate these flood risks, societies have implemented various interventions, including flood control structures such as embankments. Although these structures can reduce the frequency of small or moderate floodplain inundation, which can support economic growth, they also create a false sense of security, leading to increased settlement in floodplains. This, in turn, can exacerbate the impact of high flood events that exceed the design capacity of flood protection structures. The increasing frequency of flood hazards, driven by changing climatic conditions and changes in land use, raises critical questions about whether these flood control structures alone can serve as long-term sustainable solutions for flood mitigation. In this context, this research investigates how flood control embankments and sediment transport affect river morphology, channel capacity, and flood inundation by simulating various extreme flood scenarios in Himalayan river reaches in Nepal. The results show that river embankments can reduce the extent of floods for low-flow or high-frequency floods, up to the designed discharge. However, in rivers with moderate to high sediment transport rates, the construction of embankments and channel confinement can significantly alter sediment mobility, potentially increasing downstream flood risks and compromising embankment stability during extreme events. This research highlights the importance of evaluating multiple aspects of river embankments, particularly their impact on river morphology, sediment mobility, and flood risk management in sediment-rich rivers undergoing rapid urbanisation and climate change. In these contexts, sediment transport effects should be considered in embankment design and floodplain planning.Keywords: River embankments, Sediment transport, Flooding, River morphology, Himalayan Rivers

Jakarta is prone to pluvial, fluvial, and coastal flooding due to its geographical location and topography. In response to this problem, the Indonesian government has implemented several master plans, including the National Capital Integrated Coastal Development (NCICD). This ongoing program encompasses the construction of coastal and river embankment that stretch all over the coast of Jakarta. Since many coastal areas in Jakarta are residential or industrial, evaluating this performance of embankment has become crucial for effective flood management. The findings of this research can also support the development of other locations where NCICD embankment plan and enhance coastal resilience. Therefore, this research assessed the effectiveness of coastal and river embankment at Cengkareng Drain, a vital floodway in Jakarta, during extreme events that occur simultaneously. To simulate flooding events, two-dimensional HEC-RAS features were used to numerically calculate the area and depth of inundation. The simulation required geometry, terrain, land cover, and unsteady flow data. For the flow boundary conditions, a 100-year design rainfall, HHWL (Highest High Water Level), and 100-year design wave were considered to represent estuary conditions accurately. The simulation result showed that the maximum water level influenced by these factors was +3.145 mMSL, while the planned embankment top elevation was +3.40 mMSL. Furthermore, without the NCICD embankment, the simulation showed an inundation area of 1212.37 ha, which was reduced to 1111.22 ha after their implementation, leading to a decrease of 101.15 ha. This reduction significantly decreases potential damage to property and infrastructure, particularly in densely populated areas. The simulation also showed a reduction of 86.49 hectares or 66.22% in the inundation area with a depth exceeding 1 meter. These findings demonstrate the effectiveness of embankment in reducing the inundation area without any overtopping incidents.

A levee failure occurred along the Secchia River, Northern Italy, on 19 January 2014, resulting in flood damage in excess of $500 million. In response to this failure, immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring Panaro River, where rapid mitigation efforts were successful in averting a full levee failure. The paired breach events that occurred along the Secchia and Panaro Rivers provided an excellent window on an emerging levee failure mechanism. In the Secchia River, by combining the information content of photographs taken from helicopters in the early stage of breach development and 10 cm resolution aerial photographs taken in 2010 and 2012, animal burrows were found to exist in the precise levee location where the breach originated. In the Panaro River, internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top. This paper uses detailed numerical modeling of rainfall, river flow, and variably saturated flow in the levee to explore the hydraulic and geotechnical mechanisms that were triggered along the Secchia and Panaro Rivers by activities of burrowing animals leading to levee failures. As habitats become more fragmented and constrained along river corridors, it is possible that this failure mechanism could become more prevalent and, therefore, will demand greater attention in both the design and maintenance of earthen hydraulic structures as well as in wildlife management.

Rainfall-induced slope failures in natural terrains are destructive natural disasters. Transport of fine particles may be induced by the rainwater seepage in a natural terrain slope comprising mixed coarse and fine particles. In this study, the interaction of internal erosion and infiltration in a soil slope is investigated. A coupled model of unsaturated flow and internal erosion is established. The effects of internal erosion on pore water pressure profiles and slope stability are studied. Parametric studies on erosion parameters and hydraulic parameters are conducted. The results of the numerical example show that internal erosion occurs mainly in the zone within the wetting front, which accelerates the advance of the wetting front and decreases the slope stability. The coefficient of erosion flux rate, βer of the erosion law, is the main factor that affects the internal erosion. The effect of erosion on the wetting front movement is more significant with large values of βer. The effects of parameters i* and αer are less significant when compared with βer. When the rainfall flux is equal or greater than the saturated coefficient of permeability, the influence of internal erosion on water infiltration and slope stability is significant. The effect of internal erosion can be neglected as long as the rainfall flux is less than the saturated coefficient of permeability. When the air-entry value of the soil is greater, the influence of internal erosion on infiltration and slope stability becomes less significant.

The characterization of earthen and concrete river embankments plays a pivotal role in the hydrogeological risk assessment and is typically carried out with techniques that provide only punctual information (e.g., visual inspection, geotechnical soundings, etc.) In order to improve the extension and the completeness of the characterization procedure, applied geophysics provides several methods that, moreover, are also non-invasive, cost-effective and rather quick to use. In this work, we consider a 100-meter long river embankment located in the Veneto region (north-eastern Italy), reconstructed after its collapse due to an extreme rain event in 2010. This artificial levee consists of a bouldering structure hosting a jet-grouting wall in the central part that still does not assure an appropriate embankment waterproofing. Therefore we combined electrical resistivity tomography, multi-channel analysis of surface waves, and ground penetrating radar to investigate the heterogeneities of both the reconstructed and the natural parts, as well as the mechanical properties of the grouting wall. The results show this inner septum as a relatively conductive mean with evident discontinuities, which can be related to the infiltration phenomena taking place. Finally, our outcomes are validated thanks to several geotechnical soundings.

A new electric streamer for the characterization of river embankments

Problem statement: Embankment failure and riverbank erosion are common problem in Bangladesh. Almost every year earthen embankments and riverbanks are facing problems like erosion, breaching or retirements. Among many reasons the major causes are considered due to the use of geotechnically unstable materials, improper method of construction, seepage and sliding. In this study the problem is considered geotechnical point of view where the geotechnical properties of failed Jamuna river embankment material and Padma riverbank material were investigated. Moreover, stability analysis technique of embankment has been reviewed through a case study of Manu river embankement. Approach: Sample materials were collected during field investigation and tested at laboratory according to Japanese Industrial Standard (JIS). Limit equilibrium stability analysis and steady state seepage analysis was conducted for Manu river embankment to review the existing design procedure of embankment. Results: Study results reveal that the soil of Jamuna river embankment is not well graded sand and the permeability is found minimum of 1.29×10-5 cm sec−1 (at w = 24%) which increases rapidly in submerge condition. The maximum strength is found 51.8 kN m−2 which is not preferable as embankment material. Moreover, the slope is not well protected that makes the embankment vulnerable to erosion. In contrast, the soil of Padma riverbank contains mostly sand with 25% clay content. Both permeability and strength of bank material decrease rapidly with the increase of water content. Nevertheless, tension crack and toe erosion also accelerate the mass failure mechanism of riverbank. From case study the Factor of Safety (FS) is found overestimated of about 22-24% in stability analysis of embankment in usual practice. Conclusion: Embankment soil needs to be improved geotechnically to minimize mass failure. Geo-bags, cement composites with reinforcement could be used for slope protection. To obtain reliable factor of safety seepage analysis is recommended in designing stable embankment.

Understanding the internal structure and material properties of landslide dams is essential for evaluating their potential failure mechanisms, especially by seepage and piping. Recent research has shown that the behaviour of landslide dams depends on the internal composition of the impoundment. We here present an experimental investigation of the hydromechanical constraints of landslide dam failure by piping. Experiments were conducted in a 2 m × 0.45 × 0.45 m flume, with a flume bed slope of 5°. Uniform dams of height 0.25 m were built with either mixed or homogeneous silica sands. Uniform-sized pebbles encased in a plastic mesh were used to initiate internal erosion. Two laser displacement sensors were used to monitor the behaviour of the dams during the internal erosion process while a linear displacement transducer and a water-level probe were deployed to monitor the onset of internal erosion and the hydrological trend of the upstream lake. Five major phases of the breach evolution process were observed: pipe evolution, pipe enlargement, crest settlement, hydraulic fracturing and progressive sloughing. Two major failure modes were observed: seepage and piping-induced collapse. Majority of the dams composed of homogeneous material failed by seepage and downstream slope saturation, whereas dams built with mixed material failed by piping. We found that an increase in soil density and homogeneity of the dam materials reduced the potential to form a continuous piping hole through the dams. Furthermore, the potential for piping and progression of the piping hole through the dams increased with an increase in the percentage of fines and a decrease in hydraulic conductivity. The rate of pipe enlargement is related to the erodibility of the soil, which itself is inversely proportional to the soil density. This study provides new insights into the governing conditions and breach evolution mechanisms of landslide dams, as triggered by seepage and piping.

Erosion, deposition and breach evolution of landslide dams composed of various dam material types based on flume tests

River embankments are designed to face hydraulic actions produced by river level fluctuations. Breach occurrence on these earth structures could be driven by various factors, all possibly concurring in the collapse during an extreme event. Among the possible mechanisms that may lead the structure to failure, the onset and progression of erosion phenomena are certainly relevant for the performance of the embankment. When erosion occurs in a sandy aquifer underlying a water-retaining structure during a sufficiently high and persistent hydrometric peak, and an outflow area on the landside is close enough to the river, backward erosion piping (BEP) could produce the removal and transport of sand particles from the aquifer. As pipes start to be created, the safety conditions of the river embankment are threatened. The experimental strategies reproducing this phenomenon at the laboratory scale are already rather established. A newly designed physical modelling approach is currently under development at the Bologna University geotechnical laboratory. The main aim of the model is to investigate the effect of innovative and sustainable countermeasures against BEP. The experimental activities described in this paper rely, in particular, on the use of a small-scale model for the development of a suitable procedure to effectively reproduce BEP. The design schemes and the preliminary results so far obtained are presented to validate the devised physical modelling strategy and the reliability of the adopted monitoring tools.