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Practical and theoretical issues in channel hydraulics
Published in Donald W. Knight, Caroline Hazlewood, Rob Lamb, Paul G. Samuels, Koji Shiono, Practical Channel Hydraulics, 2018
Donald W. Knight, Caroline Hazlewood, Rob Lamb, Paul G. Samuels, Koji Shiono
For a waterway crossing with multiple openings, the division of flow has to be determined or assumed prior to any analysis. Where there are multiple openings with different invert and drowning characteristics, this will be problematic. As already commented upon, the answer lies in estimating the flow field, by using 2-D depth averaged models that give both the magnitude and the direction of the approaching flow, or by using full 3-D CFD modelling. An example of a single opening culvert with a square headwall with no rounding of the corners is shown in Figure 2.65. A multiple opening culvert, with inverts at different levels is shown in Figure 2.66. Note the tendency for silt to deposit and block the entrance to the right hand side opening.
Infiltration Performance
Published in K. Ferguson Bruce, Stormwater Infiltration, 2017
The comparison of cost in drainage systems is not infiltration vs. nothing; it is infiltration vs. the kind of system one would use if not infiltration—that is, some combination of conveyance and detention. In evaluating infiltration’s cost, it should not be considered an add-on to a conventional runoff conveyance system. Culverts can be eliminated by planning infiltration from the beginning, so that only one primary drainage system—the infiltration one—is paid for, without building two systems side by side. Infiltration surfaces can replace impermeable pavements, eliminating runoff-producing areas. Infiltration basins can replace headwater culverts on a one-to-one basis: wherever there is a drainage inlet, curb cut or headwall that would lead to a culvert for conveyance, it can be replaced with an infiltration basin. Thus there can be a basin at every low point in a road profile, at every street intersection, at every crossing of a driveway over a roadside swale, at intermediate points along a street grade, and perhaps at every downspout discharge.
Science, engineering, and the art of restoration: two case studies in wetland construction
Published in Niall Kirkwood, Manufactured Sites, 2003
The stream enters the system from a pre-existing culvert in a headwall. From this point, carrying run-off from a watershed of 21.7 hectares (55 acres) and a hillside spring, it enters the first basin. Sized at 0.05 hectares (0.13 acres) and designed with a permanent wet pool to trap 50–70 percent of incoming sediment, this first basin provides primary treatment. From its edge, the stream flows to Basin 2, a 0.10 hectares (0.25 acres), heavily vegetated wetland which provides water quality improvement via filtration, biological treatment, and further sedimentation. Soils, fine grading, and plant materials were carefully specified for this pond to maximize fine particle removal, nutrient uptake and hydrocarbon breakdown. Baffles built of natural materials increase surface area for biologic treatment and direct flows to reduce short-circuiting, which would decrease residence time.
Importance of surface drainage management to slope performance
Published in HKIE Transactions, 2018
Ryan W H Lee, Rachel H C Law, Dominic O K Lo
The provision of a trash grille offers benefit in avoiding blockage of downstream drainage services and facilitating maintenance at convenient locations. However, it may also inadvertently create a spot susceptible to blockage and hence overflow, particularly at drainage inlets as in this incident. In lieu of increasing the frequency of unblocking the trash grille, the blockage-induced impact may be averted by judiciously locating and sizing the trash grille as illustrated in the drainage improvement measures implemented following this incident. As part of the measures, the trash grille originally installed at the culvert inlet was set back upstream and a series of trash grilles were installed within the open channel further upstream to increase the solid retention capacity. The top of trash grilles was set to be below the channel sidewalls to confine the flow to overtop within the channel when the grilles were blocked. Other post-incident drainage improvement measures included enlargement of the culvert inlet opening to increase the flow capacity and extension of the headwall surrounding the inlet to provide additional freeboard to attenuate the peak flow. These improvement measures judiciously provided good references in drainage detailing which greatly enhance the flow efficiency and hence minimise the likelihood of overflow onto adjacent ground.
Lithostratigraphy of Paleozoic metasediments in southern Fiordland, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2023
Richard Jongens, Ian M. Turnbull, Andrew H. Allibone
A highly variable succession of biotite, calcic and quartzose psammite, pelitic schist, marble, and quartzite in the Dark Cloud Range (Figure 4E), conformably overlying Long Sound Calc-silicate (Powell 2006), is here named the Prong Lake Formation. This is the structurally uppermost Cameron Group unit preserved. The name Prong Lake Formation replaces the informal Chankly Bore Formation used by Powell (2001, 2006), derived from an informal name for hills west of the lower Long Burn. The type section suggested by Powell (2006) begins near the contact with Long Sound Calc-silicate at the outlet of a tarn at 1128880E 4904120N, and follows a cirque headwall anticlockwise to spot height 1246, southeast of Prong Lake at 1127850E 4904730N (structural top).
Catastrophic ice-debris flow in the Rishiganga River, Chamoli, Uttarakhand (India)
Published in Geomatics, Natural Hazards and Risk, 2022
Vijendra Kumar Pandey, Rajesh Kumar, Rupendra Singh, Rajesh Kumar, Suresh Chand Rai, Ramesh P. Singh, Arun Kumar Tripathi, Vijay Kumar Soni, S. Nawaz Ali, Dakshina Tamang, Syed Umer Latief
The presence of a wedge on the glacier headwall was another reason for the detachment (Figure 6a). The slope's base elevation is 4696 m (asl), and the upper surface elevation is 5542 m, with a mean slope inclination of ∼62° (Figure 6b). The pre-event Sentinel −2 image of 31 January 2021 clearly shows the enlarged scar on the sides of pierced surface (Figure 6c). The maximum width of the rockslide surface is about 755 m, with a length of 1181.2 m covering an area of 0.51 km2. The displaced materials consist of debris, ice, and snow moved downslope in the valley of Raunthi Nala (Figure 6d). This massive debris with ice and snow almost fell to ∼1369 m in the valley (3821 m) from the detached surface, having a mean elevation of 4814 m. The fresh snow melts rapidly due to increased temperature on February 6–7, 2021, and the increased load due to large mass and flow was enhanced due to the steep V-shaped valley. The detached materials are likely to have a large amount of kinetic energy and shock waves that would have accelerated the melting rate. This needs to be verified through numerical calculations. However, it was also observed that marks of dust particles on the side slope and debris plume during the event indicated that it initially moves in the valley as debris flow with the least amount of water. Further, down the valley, the movement of materials increases the melting rate, substantially adding the volume of water. However, this debris flow reached the lower Rishiganga basin adding the live storage of Rishiganga HEP, and a catastrophic flood occurred downstream of Rishiganga and Dhauliganga Rivers that changed the water quality (Meena et al. 2021a, 2021b, 2021c).