Guidelines and Technical Information
Design runs
(a) General Design in DRAINS involves the determination of the characteristics of the components in a drainage system. This can be by trial and error, or by use of an automatic pipe system, such as that provided in DRAINS. The design is than checked ...
Design and analysis procedures
Different design and analysis methods are recommended by the 1987 and 2019 editions of Australian Rainfall and Runoff. The 1987 Procedure The 1987 procedure simulates the conversion of (a) rainfall intensities to peak flowrates, using the rational ...
Culvert hydraulics
While culverts are simple in concept, consisting of a pipe, an entrance and an outlet, their hydraulics can be quite complicated. Many combinations of flows can occur, depending on the headwater and tailwater levels, whether flows inside the culvert ...
Cross-section
This is a transverse view of part of a pipe or channel system that shows the shape of the conduit. This can be prismatic, with a fixed shape such as a trapezoid, or irregular, with a complex shape and/or sections with different slopes. With ...
Critical flow (Critical depth)
In open channel flows, flow conditions can occur where the velocity is the same as that of a shallow water wave. These critical conditions are influenced by the channel’s cross-sectional shape and the flowrate. Flows with velocities slower than this ...
Cover depth
This is the depth from the surface to the top (of the outer surface) of a pipe. In cases where paving or a pavement is applied to a surface, the cover might apply to the underside of this overlay, rather than the finished surface. Minimum cover ...
Controls
This is a hydraulic term for a feature in a pipe or channel system that controls flows through the system, acting as a 'bottleneck'. In open channel hydraulics, a control is some feature that obstructs flow to the extent that it produces subcritical ...
Colebrook-White equation
This pipe friction equation is generally considered to be the most accurate available for determining head losses and flowrates. The following equation can be used to obtain velocities: Where g is gravitational acceleration (9.80 m/s2 in Australia), ...
Closed Conduit
A conduit is a carrier or conveyance for some material, such as water. In stormwater drainage it can be a pipe with a roof or enclosed shape so that it can operate under pressure when the hydraulic grade line rises higher than the obvert and the ...
Catchments
A catchment is an area of land or other type of surface draining to a point in a drainage system, defined by its topography and the catchment boundaries or divides. For most hydrological applications, catchments are horizontal projections of the ...
Backwater
Along flowing open channels the depth of water will vary due to (a) the boundary conditions at the beginning and end of the channel, (b) changes to the channel geometry (longitudinal- and cross-sections) and (c) the presence of structures such as ...
Australian Rainfall and Runoff
This is the most widely-used hydrological manual in Australia, originally produced by the Institution of Engineers, Australia. There have been four editions, released in 1958, 1977, 1987 (reissued 1998) and 2019. Some parts of the 1987 edition, ...
Australian practice (in urban stormwater management)
Urban stormwater management in Australia is quite advanced, due to the high level of development and infrastructure standards. The level of knowledge of designers is good, and there is extensive technical support in the form of education, manuals and ...
Average recurrence interval (ARI)
Also known as the return period, this is the mean time between occurrences of some event, such as a flood. It is used as the foundation of many design procedures based on acceptable frequencies of occurrence. For urban stormwater drainage design the ...
Annual exceedance probability (AEP)
This is the probability of an event occurring in a year. It has been adopted by the Australian Bureau of Meteorology (BOM) and Australian Rainfall and Runoff (2019) as the preferred terminology for rainfall and flood magnitudes, superseding average ...