The deposition of sediment by a stream of water. Alluvium.Sediment including clay, silt, sand, and gravel in transit and(or) deposited by a stream. Excludes detritus deposited in standing water such as lakes or oceans. Altimeter setting.The pressure required to make an altimeter indicate zero altitude at an ele vation of 10 feet above mean sea level. Cirrus anvil.High clouds which spread outward from the tops of thunderstorms. Colluvium.A deposit of unconsolidated detritus or earthy material that has been carried downslope chiefly by gravity, as opposed to running water. Generally is heterogeneous, poor ly sorted, and poorly bedded. Includes but is not limited to talus, soil creep, landslides, avalanche deposits, and sheetwash. Colorado Piedmont.A section of the Great Plains. The part of the Great Plains lying between the Southern Rocky Mountains and the High Plains. In the Big Thompson region it is the area east of the hogback belt at the foot of the Front Range. The name "High Plains" is sometimes used erroneously for this section. Convection.Vertical motions and mixing resulting when the atmosphere becomes thermodynamically unstable. Cubic feet per second (cfs or ft3/s).A rate of discharge. One cubic foot per second is equal to the discharge of a stream of rectangular cross section 1 foot wide and 1 foot deep flowing at an average velocity of 1 foot per second. dBZ.A measure of the relative power (in decibels) of returned energy to transmitted energy. Debris avalanche.In the Big Thompson Canyon area, term is applied to a very heterogeneous mixture of water-saturated bouldery debris flowing very rapidly down a long, narrow steep channel and leaving behind a conspicuous linear scar on the mountainside. Similar to a debris flow but moving at a higher velocity down a steeper gradient (fig. A). FIGURE A.-Debris avalanche deposit and scar. GLOSSARY Debris fan.A fanlike or conelike subaerial accumulation of sand, gravel, cobbles, boulders, and more or less organic trash deposited where the velocity of a stream is abruptly checked by a change of gradient, as at the mouth of a gulch. Deposit is generally poorly sorted and poorly stratified. Generally, a product of torrential runoff. The fanlike form results from the shifting of the channel as the stream blocks and diverts itself repeatedly with its own debris (fig. B). FIGURE B.-Debris fan. Debris flow.A very heterogeneous mixture of water-saturated debris flowing slowly to very rapidly down a ravine and discharging onto a debris fan. In the Big Thompson Canyon area, many debris flows contained abundant woody trash, such as logs and brush. Some debris flows evidently discharged directly into the Big Thompson River and were swept away by the flood. Similar to a debris avalanche but flowing down a flatter gradient at lesser velocity. Debris slide.The most common type of landslide set off by the Big Thompson storm. In the Big Thompson area, a moist stony heterogeneous landslide that moved downward and out ward without backward rotation. Motion may have been slow to rapid....

A comprehensive plan is presented for researching methods of flood-data analysis and information transfer for foothill areas, and for establishing a hydrologic data-collection network in the foothill areas of Colorado. The research will concentrate on three areas: 1. Developing methods to analyze flood peaks in foothill areas by using gaging-station records to obtain annual arrays of snowmelt and rainfall peaks. 2. Investigating techniques for flood information transfer, using physical and climatic characteristics. 3. Testing and, if required, verifying hydrologic models. The available gaging-station data consists of records from 81 active and ^3 discontinued gaging stations. The National Weather Service operates 53 recording and 70 nonrecording precipitation gages, and has kj& storm observers within the project boundaries. The Soil Conservation Service is installing a network (SNOTEL) of ^6 automated snowpack monitors. A data-collection network will be established in areas of data deficiencies, consisting of streamflow stations, crest-stage gages, and precipitation stations.

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Large quantities of ground water and surface water are available in Washington County. Major sources of ground water are the Gosport Sand and Lisbon Formation undifferentiated, the Oligocene Series undifferentiated, the Miocene Series undifferentiated, and alluvium and low terrace deposits. The Miocene, the most productive source of ground water, will yield 0.5 to 1.0 mgd (million gallons per day) per well and is a potential source of larger supplies in most of the county. The quantity of potable water available is governed largely by geologic structures.

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