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<br /> <br />GLOSSARY <br /> <br />[References in "Glossary" are listed under "Selected References" in Part BJ <br /> <br />Aggradation. The deposition of sediment by a stream of water. <br />Alluvium. Sediment including clay, silt, sand, and gravel in transit andlor) deposited by a <br />stream. Excludes detritus deposited in standing water such as lakes or oceans. <br />Altimeter setting. The pressure required to make an altimeter indicate zero altitude at an ele- <br />vation of 10 feet above mean sea level. <br />Cirrus anvil. High clouds which spread outward from the tops of thunderstorms. <br />Colluvium. A deposit of unconsolidated detritus or earthy material that has been carried <br />downslope chiefly by gravity, as opposed to running water. Generally is heterogeneous. poor. <br />ly sorted, and poorly bedded. Includes but is not limited to talus, soil creep, landslides, <br />avalanche deposits, and sheetwash. <br />Colorado Piedmont. A section of the Great Plains. The part of the Great Plains lying between <br />the Southern Rocky Mountains and the High Plains. In the Big Thompson region it is the <br />area east of the hogback belt at the foot of the Front Range. The name "High Plains" is <br />sometimes used erroneously for this section. <br />Convection. Vertical motions and mixing resulting when the atmosphere becomes thermody- <br />namically unstable. <br />Cubic feet per second Ids or ftJ/sl. A rate of discharge. One cubic foot per second is equal to <br />the discharge of a stream of rectangular cross section 1 foot wide and 1 foot deep flowing at <br />an average velocity of 1 foot per second. <br />dBZ. A measure of the relative power (in decibels I of returned energy to transmitted energy. <br />Debris avalanche. In the Big Thompson Canyon area, term is applied to a very heterogeneous <br />mixture of water-saturated bouldery debris flowing very rapidly down a long, narrow steep <br />channel and leaving behind a conspicuous linear scar on the mountainside. Similar to a debris <br />flow but moving at a higher velocity down a steeper gradient lfig. A). <br /> <br />~~-~ <br />~ A(~\' 1- (- '\ <br />~\ill f tt~ <br />\~ ~~\\ <br />~~\ '\ \\ \/~ <br />\ \ \-~ <br />\ \. _-------"'''RJ;. <br />______ 10'<') <br />~ . <br /> <br /> <br />FIGURE A.-Debris avalanche deposit and scar. <br /> <br />iii <br />