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

S~tial Concentration - The dry weight of sediment per unit volume of
water-sediment mixiiJre in place or th'l ratio of dry weight of sediment 01' total
weight of water-sediment mixture in a sample or unit volume of the mixture.

.spiU-throu'1h Abutment - A hridge abutment having a fill slope on the
streamward side. The term originally referred to the 'spill-through' or fill at an
open ahutment but is now applied to any abutment having such a slope.

.spread F ootinq - A pier Dr abutment footing that transfers load directly to the
earth.

.?e!lL.-Dike - A permeable Dr impermeable linear structure that project.s into a
channel from the bank t.o alter flow direction, induce deposition, or reduce flow
velocity along the bank.

Stable Channel - A condition that exists when a stream has an appropriate bed
slope and cross-section which allows its channel to transport the water and sediment
delivered from the upstream watershed without aggradation, degradation, or
deposited or streambank erosion.

.?taq~ - Water-surface elevation of a stream with respect to a reference
elevation.

.stone Riprap - Natural cobbles, boulders, or rock dumped or placed on a
streambank or filter as protection against erosion.

Storm Surqe - Oceanic tide like phenomenon resulting from wind and barometric
pressure changes.

Stop -Loqs - Devices used for temporary closure of an opening in a hydraulic
structure.

Stream - A body of water that may range in size from a lan]e river to a small
rill flowing in a channel. By extension, the term is sometimes applied to a natural
channel or drainage eourse formed by flowing water whether it is occupied by water
or not.

Stream bank Failure - Sudden collapse of a bank due to an instability condition
such as removal of the bank by scour.

Stream bank Protection - Any technique used to prevent erosion or failure of a
streambank.

Streambank Erosion - Removal of soil particles or a mass of particles from a
bank surface due primarily to water aetion. Other factors such as weathering, ice
and debris abrasion, chemical reactions, and land use changes may also directly or
indirectly lead to slreambank erosion.

Suspended-Sediment Discharqe - The quantity of suspended sediment by weight
or volume, passing through a stream cross section above the bed layer in a unit of
time.

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