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Process-based approach on tidal inlet evolution – Part 1
Published in C. Marjolein Dohmen-Janssen, Suzanne J.M.H. Hulscher, River, Coastal and Estuarine Morphodynamics: RCEM 2007, 2019
D.M.P.K. Dissanayake, J.A. Roelvink
In terms of the influence of root systems on bank geomorphology, it is important to identify the influence of roots on bank sediment properties in terms of stability/erodibility. In an eroding environment, the erosion threshold is the key to examine the erodibility of bank sediments, at a particle scale. At a larger scale, the bulk properties, e.g. erosion rate and shear strength, are the important factors controlling bank stability. Root systems have been shown to enhance bank stability, although the mechanism is unclear. In this study, it is assumed that the fine roots: (a) acts as obstacles to the surface erosion process to enhance the erosion threshold; (b) they add organic matter into the sediment, to improve particle stability; and (c) increase shear strength, which is related to root density and structure. Relationships between root properties and sediment characteristics are investigated, to examine the influence of root systems on the bank sediments.
Alternative revetments
Published in Krystiaim W. Pilarczyk, Dikes Aimd Revetments, 2017
Mark Klein Breteler, Krystian W. Pilarczyk
Gabions are used throughout the world to protect river banks, dikes and other slopes against the erosive forces of currents and waves. The gabions are made of rectangular baskets of wire mesh, which are filled with stones (Figure 16).
Using combined slots as a new approach for optimizing erodible bed changes around the spur dikes in series
Published in International Journal of River Basin Management, 2022
Mehran Kheirkhahan, Shahab Nayyer, Khosrow Hosseini, Sayed-Farhad Mousavi
Bank erosion and bed changes in rivers have always been of interest to engineers. Various methods and structures exist, such as spur dikes to control bank erosion and bed river changes. Spur dikes could be implemented with Simple, L –shaped, T-shaped, triangular, and other forms with different angles concerning the flow direction. Scouring around spur dikes is produced by down-flow and initial vortices at the upstream corner of the spur dike. In addition, secondary eddies and wakes are in the middle and their downstream corner (Barbhuiya & Dey, 2004; Coleman et al., 2003). Therefore, different methods are proposed to reduce scouring and prevent undesirable effects on the stability of the structure, such as changing the flow pattern and decreasing its intensity. The use of collars, vanes, a combination of spur dikes in series, and slots are part of the leading solutions for changing the flow pattern (Chiew, 1992; Nayyer et al., 2019).
Buckling analogy for 2D deformation of placed ripraps exposed to overtopping
Published in Journal of Hydraulic Research, 2021
Ganesh H. R. Ravindra, Fjola G. Sigtryggsdottir, Leif Lia
Riprap is one of the most widely used erosion protection measure for various in-stream hydraulic structures such as embankment dams, spillways, streambeds, river banks, bridge piers and abutments (e.g. Abt et al., 2013; Hiller et al., 2018a; Khan & Ahmad, 2011; Siebel, 2007; Thornton et al., 2014). Ripraps are also used in coastal protection structures such as dikes, embankments and jetties against wave action (Kobayashi & Jacobs, 1985). Ripraps can be broadly classified into two categories based on the method of construction: dumped ripraps comprise randomly placed stones while placed ripraps are characterized by stones arranged in a specific interlocking pattern. Although dumped ripraps could be considered as a more viable alternative from an economic standpoint, placed ripraps have been found to offer a significantly higher degree of stability against overtopping in comparison with dumped ripraps (Hiller et al., 2018a). This is attributed to the formation of a bearing structure due to interlocking of stones, which results in increased stability compared to randomly dumped stones. In this article, primary emphasis is laid on placed ripraps constructed on steep slopes subjected to overtopping flows.
Field and model tests of riprap on steep slopes exposed to overtopping
Published in Journal of Applied Water Engineering and Research, 2019
Priska H. Hiller, Leif Lia, Jochen Aberle
Riprap consisting of large natural rocks or artificial elements is widely used to protect river banks, streambeds, bridge piers and abutments, dams, shorelines and other hydraulic structures against the impact of currents and waves (e.g. Abt and Johnson 1991; CIRIA et al. 2007; Abt et al. 2013; Chanson 2015; Jafarnejad et al. 2016). There exist two general riprap types, dumped and placed, which are constructed by either dumping the riprap elements or placing them in an interlocking pattern. The construction of placed riprap is more cost- and labour-intensive than simply dumping elements (Peirson et al. 2008), but placed riprap can withstand higher discharges than dumped riprap constructed with the same stone size (Larsen et al. 1986; Peirson et al. 2008; Hiller et al. 2017), especially on steep slopes (Dornack 2001).