FLOOD06421

• County: Statewide
• Basin: Statewide
• Title: Highways in the River Environment
• Date: 2/1/1990
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

!'Jonalluvial Channel - A channel whose boundary is completely in bedrock.

!'Jorrnal Staqe - The water stage prevailing during the greater part of the yeaL

Qrqanic Mixtures and Mulches - Any of a number of agents (e.g. petrochemicals
or vegetative matter) used to stahilize a strearnbank against erosion by providing
protection and nutrients while vegetation becomes established. These agents, which
may be in the Form of liquids, emulsions, or slurries, are normally applied by
mechanical means.

Overbank Flow - Water movement over top bank either due to a rising stream
stage or to inland surFace water runoff.

!]xbow - T he abandoned bow -shaped or horseshoe -shaped reach of a former
meander loop that is left when the stream cuts a new shorter channel across the
narrow neck between closely approaching bends of the meander.

pavement - Streamhank surFace covering, usually impermeable, desi9nt~d to
serve as protection against erosion. Common pavements used on streamhanks are
concrete, compacted asphalt, and soil-cement.

paving - Covering of stones on a channel bed or bank (used in the Manual with
reference to natural covering).

Peaked Stone Dike - Riprap placed parallel to the toe of a streambank (at the
natural angle of repose of the stone) to prevent erosion of the toe and induce
sediment deposition behind the dike.

Perennial Stream - A stream or reach of a stream that Flows continuously for
a II or most of the year.

Phreatic Line - T he upper boundary of the seepage water surface landward of a
stream bank.

Pile - An elongated member, usually made of timber, concrete, or steel, t.hat
serves as a structural component of a river - training structure.

pile Bin (or Pile Pier) - A pier composed of piles capped or decked with a
timber grillage or with a reinforced-concrete slab forming the bridge foundation.

Pier Shaft - The main part of a pier above the footing dr foundation.

pipinq - Removal of soil material through subsurface flow of seepage water
that develops channels or 'pipes' within the soil bank.

Point Bar - An alluvial deposit of sand or gravel lacking permanent vegetal
cover occurring in a channel at the inside of a meander loop usually somewhat
downstream from the apex of the loop.

Pressure Ridqes - Ridges on an ice-sheet over a body of water caused by
expansion and consequent upheaval of the ice.

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