Drainage Glossary E-R


The wearing away of the land surface by water, wind, ice, gravity, or other geological agents.

Excess Rainfall

The amount of rainfall that runs directly off an area.

Farm or Field Tile

A small diameter clay pipe installed in an agricultural area to allow drainage or farmland.

Filter Strip

Usually a long, relatively narrow area (usually 20-75 feet wide) of undisturbed or planted vegetation used to retard or collect sediment for the protection of watercourses, reservoirs, or adjacent properties.


A device that allows liquids to flow in only one direction in a pipe. Backflow preventers are used on outlet pipes to prevent a reverse flow during flooding situations.


Land immediately adjoining a stream which is inundated when the discharge exceeds the conveyance of the normal channel. The channel proper and the areas adjoining the channel which have been or hereafter may be covered by the regulatory or 100-year flood. Any normally dry land area that is susceptible to being inundated by water from any natural source. The floodplain includes both the floodway and the floodway fringe districts.


The channel of a river or stream and those portions of the flood plains adjoining the channel which are reasonably required to efficiently carry and discharge the peak flow of the regulatory flood of any river or stream.


A constructed channel lined with erosion-resistant materials used to convey water on the steep grades without erosion.

Foundation Drain

A pipe or series of pipes that collects groundwater from the foundation or footing of structures to improve stability.


A wire mesh cage, usually rectangular, filled with rock and used to protect channel banks and other sloping areas form erosion.


The distribution of the various sized particles that constitute a sediment, soil, or other material, such as rip-rap.


  • The slope of a road, a channel, or natural ground.
  • The finished surface of a canal bed, roadbed, top of embankment, or bottom of excavation; any surface prepared to a design elevation for the support of construction, such as paving or the laying of a conduit.
  • To finish the surface of a canal bed, roadbed, top of embankment, or bottom of excavation, or other land area to a smooth, even condition.


A change of elevation, velocity, pressure, or other characteristics per unit length. Slope.


The source of a stream. The water upstream from a structure or point on a stream.


A graph showing for a given point on a stream the discharge, stage (depth), velocity, or other property of water with respect to time.


Not allowing infiltration.


Passage or movement of water into the soil.

Intermittent Stream

A stream that ceases to flow in very dry periods.


The inside bottom of a culvert or other conduit.

Land Surveyor

A person licensed under the laws of the State of Indiana to practice land surveying.

Land Use Controls

Methods of regulating the uses to which a given land area may be put, including such things as zoning, subdivision regulation, and floodplain regulation.

Non-Point Source Pollution

Pollution that enters a water body from diffuse origins on the watershed and does not result from discernible, confined, or discrete conveyances.

Open Drain

A natural watercourse or constructed open channel that conveys drainage water.


The point, location, or structure where wastewater or drainage discharges from a pipe or open drain to a receiving body of water.


The point of water disposal from a stream, river, lake, tidewater, or artificial drain.

Outlet Channel

A waterway constructed or altered primarily to carry water from man-made structures, such as smaller channels, tile lines, and diversions.

Peak Discharge

The maximum instantaneous flow from a given storm condition at a specific location.


The movement of water through soil.

Percolation Rate

The rate, usually expressed as inches per hour or inches per day, at which water moves through soil.

Perennial Stream

A stream that maintains water in its channel throughout the year.


A numerical measure of hydrogen ion activity, the neutral point being 7.0. All pH values below 7.0 are acid, and all above 7.0 are alkaline.

Point Source Pollution

Any discernible, confined, and discrete conveyance including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged.

Private Drain

A drain that: 1. Is located on land owned by one person or by two or more persons jointly; 2. Was not established under or made subject to any drainage statute.

Professional Engineer

A person licensed under the laws of the State of Indiana to practice professional engineering.

PVC Pipe

Polyvinyl Chloride Pipe.

Receiving Stream

The body of water into which runoff or effluent is discharged.

Regulated Drain

A drain, either open channel or closed tile/sewer, subject to the provisions of the Indiana Drainage code, IC 36 9, 2027.


A natural or artificially created pond, lake or other space used for storage, regulation or control of water. May be permanent or temporary.


The storage of storm water to prevent it from leaving the development site. May be permanent or temporary.

Retention Facility

A facility designed to completely retain a specified amount of storm water runoff without release except by means of evaporation, infiltration or pumping.


A small intermittent watercourse with steep sides, usually only a few inches deep.


Of, on, or pertaining to the banks of a stream, river, or pond.

Riparian Rights

A principle of common law requiring that any user of waters adjoining or flowing through his lands must use and protect them in a manner that will enable his neighbor to utilize the same waters undiminished in quantity and undefiled in quality.


Broken rock, cobble, or boulders placed on earth surfaces, such as the face of a dam or the bank of a stream, for protection against the action of water (waves).


The inlet portions of a drop inlet spillway that extend vertically from the pipe conduit barrel to the water surface.


That portion of precipitation that flows from a drainage area on the land surface, in open channels, or storm water conveyance systems.