2 



sma I I river - A river with a drainage area less than 100 km and a mean 



annual flow channel top width of less than 15 m. 



split river — A river having numerous islands dividing the flow into two 

 channels. The islands and banks are usually heavily vegetated and 

 stable. The channels tend to be narrower and deeper and the f I oodp I a i n 

 narrower than for a braided system. 



stage — The elevation of a water surface above or below an established 

 datum or reference. 



standing crop — The abundance or total weight of organisms existing In an 

 area at a given time. 



straight river — The thalweg of a straight river typically winds back and 

 forth within the channel. Gravel bars form opposite where the thalweg 

 approaches the side of the channel. These gravel bars may not be ex- 

 posed during low flow. Banks of straight systems typically are stable 

 and f loodplains are usual ly narrow. These river systems are considered 

 to be an unusual configuration in transition to some other configura- 

 tion. 



subarctic — The boreal forest region. 



suspended load — The portion of stream load moving in suspension and made 



up of particles having such density of grain size as to permit movement 

 far above and for a long distance out of contact with the stream bed. 

 The particles are held in suspension by the upward components of turbu- 

 lent currents or by colloidal suspension. 



talik — A zone of unfrozen material within an area of permafrost. 



terrace — An abandoned floodplain formed as a result of stream degradation 

 and that is expected to be inundated only by infrequent flood events. 



thalweg — The line following the lowest part of a valley, whether under 

 water or not; also usually the line following the deepest part or 

 middle of the bed or channel of a river or stream. 



thermokarst — Landforms that appear as depressions in the ground surface 

 or cavities beneath the ground surface which result from the thaw of 

 ice-rich permafrost material. 



top width — The width of the effective area of flow across a stream chan- 

 ne I . 



velocity — The time rate of motion; the distance traveled divided by the 

 time required to travel that distance. 



wash load — In a stream system, the relatively fine material in near-perman- 

 ent suspension, which is transported entirely through the system, 

 without deposition. That part of the sediment load of a stream which is 

 composed of particle sizes smaller than those found in appreciable 

 quantities in the shifting portions of the stream bed. 



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