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Dam breach hydraulics and morphodynamics in overtopped earth dams with chimney filter
Published in Wim Uijttewaal, Mário J. Franca, Daniel Valero, Victor Chavarrias, Clàudia Ylla Arbós, Ralph Schielen, Alessandra Crosato, River Flow 2020, 2020
T. Alvarez, S. Valente, S. Amaral, T. Viseu, R.M.L. Ferreira
Embankment failure by overtopping have been object of several laboratorial studies which have helped characterizing the main modes of erosion and describing the different behavior of non-cohesive and cohesive embankments. The main failure mechanism in the first case (non-cohesive material) is progressive surface erosion and channel enlargement due to bank destabilization (see Singh, 1996; Visser, 1998). For cohesive embankments. headcut erosion, comprising formation and migration of a vertical or nearly vertical canyon on the dam downstream slope, associated with mass detachment episodes of the side walls, often induced by underscouring, are the main modes of erosion (Amaral, et al., 2019; Morris et al., 2009; Zhu, 2006).
The heritage sewer networks of Kolkata (Calcutta) and ascertaining their coping potential under growing urban pressures
Published in ISH Journal of Hydraulic Engineering, 2021
Sunil Kumar Murmu, Nazimul Islam, Dhrubajyoti Sen
The next sewer network to be laid in the city was the ‘Suburban System’ which, as the name suggests, helped to drain the then semi-urban peripheral areas of the city. Covering an area of around 25.7 km2, the conduit network of this catchment terminated at the pumping station marked Y in Figure 2. A head cut channel further conveyed the effluents to the Bidyadhari. This pumping station, commissioned by the late nineteenth century, comprised of around 30 km of main masonry sewer and 35 km of stoneware pipe sewers (Goode 1916). At inception, therefore, the suburban catchment, though spread over a larger area than that of the town, contained shorter mains and fewer branch pipes. Subsequent augmentation of pumps was carried out, keeping pace with the urbanisation taking place in the city over the first quarter of the twentieth century.
Assessment of embankment dams breaching using large scale physical modeling and statistical methods
Published in Water Science, 2018
Muhammad Ashraf, Ahmed Hussein Soliman, Entesar El-Ghorab, Alaa El Zawahry
In the case of sand embankments (test #1 and #2), surface erosion progressed uniformly along the downstream face with a gradual gradient flattening which eventually reaches the bottom of the downstream face. In the case of cohesive soil embankment (test #3 and #4), erosion started at the bottom of the downstream face forming a head cut. Erosion migrated upstream, forming more head cuts towards the crest of the downstream face of the embankment. In test #5, although breaching in the embankment reached an advanced state (the initiation of headcut migration), no complete failure occurred in the embankment. Table 5 shows the comparison between three tests conducted by the HRI for the same setting (reservoir volume) and same embankment dimensions (height, width…etc), which are test #2, 4, and 5. Only the soil composition varied between the three tests leading to a significant variation in the outcome of each test.
Simulation and control of sediment transport due to dam removal
Published in Journal of Applied Water Engineering and Research, 2018
The natural reservoir sediment deposits can be highly graded and stratified, with a wide size distribution, typically a coarse top layer and fine bottom layer, which may form dunes, bars, or Gilbert-type deltas (Kleinhans 2005; Ferrer-Boix et al. 2015). Accelerated river flows in the reservoir after removing a dam will resuspend the deposits, mix with the reservoir waters, and release high-concentration suspended sediments to downstream (Konrad 2009). Dam removal action usually triggers highly dynamic and graded sediment transport processes both upstream and downstream of the dam, such as erosion, deposition, bed material mixing, bank erosion, channel widening, and head-cut (e.g. Doyle & Stanley 2005; Chang 2008).