Drainage Terms A-Z
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impermeable surface
Surface that resists the infiltration of water. Usually a measure of roof and road surfaces in simulation modelling.
industrial discharge
Outflow from an industrial unit, which varies enormously depending on the processes carried out in the factory.
infiltration
(a) the unintended ingress of groundwater into a drainage system ( also termed parasitory flow in some countries).
(b) The introduction of rainwater runoff into the ground.
infiltration (to sewer)
The ingress of groundwater into a drain or sewer system through defects in pipes, joints or manholes.
inflow
Flow which enters the sewer; this can be generated by rainfall or an industrial discharge or other particular connection.
initial loss
In hydrology, rainfall preceding the beginning of surface runoff. It includes interception, surface wetting and infiltration.
inlet
(1) A connection between the catchment area and a drain or sewer for the admission of surface or stormwater.
(2) A structure at the entrance end of a conduit.
(3) The upstream end of any structure through which water may flow.
inspection chamber
A structure that offers access to the drain or sewer for servicing by means of equipment remotely operated from ground level: no personnel access.
intensity-duration-frequency
The relationship between rainfall intensity (amount per unit of time), rainfall duration (total time over which rainfall occurs) and frequency (return interval) at which the intensity-duration relationship is expected to recur.
interception
The process by which rainfall may be prevented from reaching the ground, for example by vegetation.
internal drainage boards
These manage ordinary watercourses in areas know as internal drainage districts.
invert
The floor, bottom or lowest portion of the internal cross-section of a closed conduit. |
