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Drainage gradient (DG) is a term in road design, defined as the combined slope due to road surface cross slope (CS) and longitudinal slope (hilliness). Although the term may not be used, the concept is also used in roof design and landscape architecture. If the drainage gradient is too low, rain and melt water drainage will be insufficient.
the design drain spacing (L) can be found from the equation in dependence of the drain depth (Dd) and drain radius (r). Drainage criteria One would not want the water table to be too shallow to avoid crop yield depression nor too deep to avoid drought conditions. This is a subject of drainage research.
It is a very important safety factor. Cross slope is provided to provide a drainage gradient so that water will run off the surface to a drainage system such as a street gutter or ditch. Inadequate cross slope will contribute to aquaplaning.
The runoff curve number is based on the area's hydrologic soil group, land use, treatment and hydrologic condition.References, such as from USDA [1] indicate the runoff curve numbers for characteristic land cover descriptions and a hydrologic soil group.
Drainage density is a quantity used to describe physical parameters of a drainage basin. First described by Robert E. Horton , drainage density is defined as the total length of channel in a drainage basin divided by the total area, represented by the following equation:
i = hydraulic gradient (dimensionless), A = flow cross-section area (m 2), θ = transmissivity (m 2 /s), W = width (m), and t = thickness (m). As seen in the equation, q/W and θ carry the same units and are directly related to one another by means of the hydraulic gradient i. At a hydraulic gradient of 1.0, they are numerically identical.
The method consists of filling the flow area with stream and equipotential lines, which are everywhere perpendicular to each other, making a curvilinear grid.Typically there are two surfaces (boundaries) which are at constant values of potential or hydraulic head (upstream and downstream ends), and the other surfaces are no-flow boundaries (i.e., impermeable; for example the bottom of the dam ...
The Hjulström curve. The Hjulström curve, named after Filip Hjulström (1902–1982), is a graph used by hydrologists and geologists to determine whether a river will erode, transport, or deposit sediment.