Glossary of Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

average recurrence interval (ARI)

The average interval in years between the occurrence of a flow, discharge or rainfall greater than or equal to a specified amount.

Top of page

batter

A uniform slope.

berm

A horizontal ledge at the top of an earth bank.

Top of page

channel

An open waterway.

conduit

Any channel or pipe for flowing water.

contraction

A reduction in waterway area.

culvert

A covered channel or pipe for carrying a watercourse below ground level, usually under a road or railway.

Top of page

id.

Top of page

Diameter of the drain.

discharge

The volume of fluid per unit time flowing along a pipe or channel.

Top of page

easement

Acquired right or privilege held by a person or public authority, including Melbourne Water, to make specific use of land owned privately or by another authority.

encumbrance

Anything within the scope of Melbourne Water activities affecting a property that would not be disclosed by a search at the Titles Office.

entry point

The point at which a branch drain joins the main drain.

entry shock loss

The energy lost at an entry point due to turbulence.

expansion

An increase in waterway area.

Top of page

floodway

A channel designed to carry flows in excess of the underground drain capacity.

freeboard

The vertical distance of a defined point or feature above the design water level.

Top of page

grade

The gradient of sloping features. This is expressed as 1:5 (vertical:horizontal) for batters and `1 in 200' for drains and slopes.

Top of page

head

The potential energy per unit weight of fluid above a certain point. This point is usually the height of the free water level.

head loss

The loss of head between two points in a pipe or channel.

hydraulic grade line (HGL)

A line along a pipeline which shows the levels to which the water would rise in open pipes leading up from the pipeline.

Top of page

inlet

The point at which a branch drain discharges into the main drain.

invert

The floor of the drain.

Top of page

live load

A load which may be moved onto or off a structure.

load

The weight carried by a structure.

Top of page

manhole

An access hole to the drain to allow a person to enter.

Manning's roughness coefficient

A value that expresses the friction or resistance to flow due to the surface texture of the channel or pipe.

Top of page

obvert

The top of the inside of the drain.

outlet

The point at which the underground drain discharges into an open watercourse.

Top of page

pipe jacking

A pipeline construction technique which pushes the pipes through the ground using hydraulic rams.

pool and riffle

Ponded water flowing over and down the face of a small natural or raised section of stream bed.

Top of page

sacrificial concrete

Concrete that can be eroded without affecting the structural integrity of a structure.

splay pipes

Pipes with non-parallel end faces.

Top of page

transition

The junction of two drains with different waterway area and/or shape.

Top of page

velocity head

The energy per unit weight of water due to its velocity. It is also the vertical distance the fluid must fall freely under gravity to reach its velocity.

wetted perimeter

The length of the channel surface in contact with the water, measured on a channel cross section.