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Suspended sediment dynamics in a tidal channel network under peak river flow
Published in Fernanda Minikowski Achete, Multiple Scales of Suspended Sediment Dynamics in a Complex Geometry Estuary, 2020
To study the influence of the channel network configuration on the deposition patterns we created 4 different networks (Fig 3-2). The average cell size is 100x30 meter for the main rivers decreasing to 20x5m in the creeks. The first grid is of the entire Delta (grid “delta”) and comprises the Sacramento River from Freeport (FPT) and San Joaquin River from Vernalis (VNS) up to Mallard Island (MAL), as well all smaller rivers, channels, creeks and flooded island (Fig 3-1, Fig 3-2a). At FPT and VNS river flow is unidirectional at high discharge, tides are unimportant, and MAL is the Delta seaward limit. The second grid (grid “2 rivers”, Fig 3-2b) keeps the 2 main rivers and the connections between them including the Delta Cross Channel (DCC), Georgiana Slough (GSL) and Threemile Slough (TMS). The third grid (grid “sacra extension”, Fig 3-2c) comprises only the Sacramento River and the north branch that connects with the Yolo Bypass. The Yolo Bypass is a flood bypass to protect Sacramento from flooding; it diverts Sacramento River water at Freemont weir upstream from FPT and connects again with the Sacramento River at Liberty Island. The Yolo is currently a wetland wildlife area. The fourth (grid “sacra”, Fig 3-2d) grid represents only the Sacramento River from FPT to MAL.
Changing Flood Risk – A Re-insurer’s Viewpoint
Published in Zbigniew W. Kundzewicz, Changes in Flood Risk in Europe, 2019
The example of a small town on the upper Danube in southern Germany (Riedlingen) is typical of many similar cases (Fig. 7). In the first decades of the 19th century (1830) people settled at some distance from the river, on higher ground. Subsequently, construction of transport infrastructure (railways and roads) and initial flood protection began. Dikes and a flood bypass were built, and houses sprawled along the road which ran across the valley. These houses were at risk of flood and stood in the path of flood water flowing down the valley on a broad front (1910). In the 20th century, the road was elevated onto a dam, creating a flood-free thoroughfare which also served as a flood barrier (1980). When the dike was breached upstream of the town during a major flood in 1990, the escaping water backed up behind this dam and completely inundated that part of the town which had developed on the plain. The built-up area on the flood plain has not changed much since, and the flood hazard has been reduced by increasing the local discharge capacity and upstream retention measures.
Case studies on prototype scale
Published in G.J.C.M. Hoffmans, H.J. Verheij, Scour Manual, 2021
G.J.C.M. Hoffmans, H.J. Verheij
The flood bypass between Zwolle and Deventer (the Netherlands) alongside the river IJssel was realised in 2017. It conveys water at extreme floods with an estimated frequency of once every 100 years (see Figure 9.31). This reduces upstream flood levels up to 0.7 m. The bypass is part of the Room-for-the-River programme that increases flood protection and environmental conditions along the Rhine branches in the Netherlands. Arcadis acted as a designer in many of the Room-for-the-River projects.
Towards integrated flood management along the lower Rhine and Mississippi Rivers and the international legacy of the 2005 New Orleans Hurricanes Katrina–Rita flood disaster
Published in International Journal of River Basin Management, 2018
In contrast to the lower Rhine, the lower Mississippi is well represented by a ‘pendulum’ model of flood management evolution. This has occurred over about the last 150 years as flood management organizations developed, and is associated with oscillations in flood management alternating between federal- and local-scale organizations. The Great Mississippi Flood of 1927 is the largest flood disaster in US history and its impact on society and science has been thoroughly studied (e.g. McPhee 1989, Berry 1997). From a policy and governmental perspective, the immediate outcome of the 1927 flood was a shift from local and state control to a substantially fortified federal role in flood management with US Congressional passage of the 1928 Mississippi River and Tributaries Project (1928 MR&TP) (US Congress 1928). This resulted in a change from a passive federal role characterized by a ‘no cutoff’ (i.e. ‘levees only’) approach to a strong federal role comprised of four major elements, including (i) repair and construction of 3200 km of dikes, (ii) river channel ‘improvements’, specifically cutoffs of meander bends (e.g. channelization), wing dikes (groynes) for channel alignment, bank stabilization, and dredging, (iii) dam and reservoir construction on upstream tributaries, and (iv) downstream flood crest reduction by routing floodwaters into backwater areas and through flood bypass structures (MRC 2007, Hudson et al. 2008).
Abrasion prediction at Asahi sediment bypass tunnel based on Ishibashi’s formula
Published in Journal of Applied Water Engineering and Research, 2018
Christian Auel, Robert M. Boes, Tetsuya Sumi
Sediment bypass tunnels (SBTs) are one strategy to route sediment load around reservoirs, thereby avoiding accumulation (Vischer et al. 1997; Sumi et al. 2004). Most tunnels are located in mountainous regions, that is, gravel bed rivers at small- to medium-size reservoirs where a considerable amount of coarse material is entrained (Auel and Boes 2011; Boes et al. 2014). Amongst others, ten SBT exist in Switzerland (Egschi, Hintersand, Palagnedra, Pfaffensprung, Rempen, Runcahez, Sera, Solis, Ual da Mulin, and Val d’Ambra) and five in Japan (Asahi, Koshibu, Matsukawa, Miwa, and Nunobiki), others in the USA, China and South Africa, and three are in planning in Taiwan (Nanhua, Shimen, and Zengwen). Additionally, a number of flood bypass tunnels exist in Switzerland involving similar flow characteristics as SBT, namely those on the Rovana River, at the Grindelwald Glacier, and on the Matter Vispa River downstream of Zermatt.