China
Africa
Explore chapters and articles related to this topic
Effect of wood accumulation on sediment continuity at permeable sediment traps
Published in Wim Uijttewaal, Mário J. Franca, Daniel Valero, Victor Chavarrias, Clàudia Ylla Arbós, Ralph Schielen, Alessandra Crosato, River Flow 2020, 2020
I. Schalko, V. Ruiz-Villanueva, V. Weitbrecht
The role of sediment traps is to retain transported sediment during floods in order to prevent deposition and inundations of downstream areas. However, the prevalent traps also retain sediment during low flows, thereby affecting the sediment transport balance. Schwindt et al. (2018) developed a concept of a semi-permeable sediment trap that enables the retention of sediment during floods as well as sediment continuity during low flows. The concept includes a guiding channel, which passes the retention structure with a given bed slope and allows sediment to be transported downstream for discharges smaller than the bank full discharge Qbf or effective discharge. For mountainous regions, this discharge can correspond to a flood with a return period of up to 50 years (Wohl 2015). However, the design discharge at which sediment retention should take place, has to be defined for each project separately. The retention structure is comprised by a mechanic (inclined bar rack) and a hydraulic barrier (dam with low-level outlet). The governing design parameter for the mechanic barrier is the open spacing between the bottom of the guiding channel and the bar rack.
Erosion
Published in Karlheinz Spitz, John Trudinger, Mining and the Environment, 2019
Karlheinz Spitz, John Trudinger
The basic principle in designing control measures for concentrated water flow leaving disturbed land is to ensure that the viability of ecosystems, aesthetic values, and down-slope areas are not significantly adversely affected. Managed water, whether diverted or leaving the site, usually has an increased flow rate and sediment load. Poorly designed exits from disturbed land can result in off-site erosion near discharge points. Water and sediment retention basins, sediment traps, and constructed wetlands are common erosion control techniques for managing this problem.
Discussions on “water saving and increase in yield of rice crop through on-farm reservoir: a case study” by Deepak Kumar Soni and K.K. Singh
Published in ISH Journal of Hydraulic Engineering, 2021
As regard use of OFR for storing runoff/canal water for reuse, it is a very useful method of improving irrigation efficiency and is widely used in Israel where rainfall is scanty. It is also called service tanks which stores rain/canal water in long distance canals. There are occasions where canal water released from distant reservoir may not be drawn by the farmers due to rainfall or other reasons and the canal water can be diverted to these service tanks. Besides the benefits of OFR pointed out by the author in their paper, OFR helps in conservation of canal/rain water and offers some flexibility of operation by farmers to apply irrigation at their convenience. Their location, storage capacity, inflow and outflow control devices are to be very carefully designed (Zimmerman 1966). Other benefits of such FOR/service tanks are: They act as sediment trap and help in controlling water pollution.They help in fish culture and survival of flora and fauna.They can be used for domestic purposes and for drinking water for animals.They offer recreation opportunities for local/rural people living around the service tanks.
More bed load in rivers. Achieving a sediment balance close to the natural state
Published in Journal of Applied Water Engineering and Research, 2018
M. Pauli, L. Hunzinger, O. Hitz
The above mentioned installations may influence the bed load balance as follows: Hydropower dams: Generally, large dams stop bed load transport completely. In the backwater of small hydropower dams part of the bed load is often deposited, while part of the bed load may be transported through the reservoir. Deposited material must then be removed, e.g. by dredging.Sediment traps: This type of installation reduces sediment delivery from the catchment area. The influence is determined by calculating the expected bed load in a tributary with and without sediment retention by traps.Gravel extraction: Extraction either reduces sediment delivery from the catchment area or it directly reduces bed load rate in the target water course itself.
Wood blockage and sediment transport at inclined bar screens
Published in Journal of Hydraulic Research, 2022
Isabella Schalko, Volker Weitbrecht
Sediment traps are designed to retain sediment during large floods to prevent downstream deposition and inundations. Common sediment traps tend to retain sediment during ordinary floods (i.e. morphologically effective discharge; Schwindt, 2017) and, hence, affect sediment transport continuity during all discharge conditions. Recently, research on sediment traps focused on the design of “semi-permeable structures” that enable sediment retention during large floods and sediment transport continuity during ordinary floods (D’Agostino et al., 2000; Meninno et al., 2019; Piton et al., 2019; Piton & Recking, 2016a, 2016b; Rossi & Armanini, 2019; Roth et al., 2018; Schwindt, 2017). One promising concept was developed by Schwindt et al. (2018). The concept includes a guiding channel that passes the retention structure with a given bed slope and enables sediment to be transported downstream for discharges up to the bankfull discharge of the guiding channel, corresponding to the morphologically effective discharge. For mountainous regions, this effective discharge can correspond to a flood with a return period of up to 50 years (Hassan et al., 2014; Schwindt, 2017). The retention structure consists of a mechanical (inclined bar screen, i.e. a rack structure) and hydraulic barrier (dam with low-level outlet) (Fig. 1a). The governing design parameter for the mechanical barrier to achieve its semi-permeability during ordinary floods is the bottom clearance between the guiding channel and the bar screen, defined as the product of a pre-factor fm and the characteristic grain size diameter d84 (Fig. 1b).