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(elevations) because of changes in meteorologic conditions. Flood- plain management, including the design of a flood-warning syetem needs an accurate assessment of the magnitude and frequency of ~looding. The concentration of population along these foothill streame, coupled with the nature of flaeh floode, dictates sound scientific mPthods be employed in flood-plain management (including flood-warning ~ystems). Consequently flood-plain management seeks an optimal baAance of identifying the true flood potential. PALEOFLOOD TECHNIeUES Because of the relatively few floods in the streamflow records in the foothills in this area, conventional hydrologic analyses does not provide the moet accurate aeseesment of the magnitude and frequency of floode. Paleohydrologic studies can assese the magni~ude and frequency of flooding and can be used to enhance conventional hydrologic techniques. Paleoflood hydrology is the study of the movement of water and sediment in channela. Historic and prphistoric floods in streams are recorded as diatinctive deposits and landforme in and along channels. The interpretation of these deposits and landforme provides supplemental information about the apatial occurrence, magnitude, and frequency of large floods. Large floods leave distinctive erosional and depc~aitional features that remain in the ch.annel until a larger flood reworks the deposite. Theee features arP~ easily recognizable and long lasting (multi-thousande of years). In this type of study, lack of flood evidence is aa relevant ae tangible flood evidence (it indicates that floods above a given magnitude have not occurred for many tho~sands of yeare ) . A brief overview of paleohy~drologic techniques uaed in tk~e onsite investigations follows. Intense rain causes rill and gully ero'sion on s~eep unvegetated surface. Occurrence or lack of occurrence of rills and gullies ie indicative of whether intense rain occura. During a flood the fluicf stress exceeds a critical value which results in streambed and bank erosion. The greater the fluid etress the more material eroded anc[ the higher the rate of sediment transport. It has been shown (Jarrett, 1987) that for steep, small, tributary basins such as those in thie study area, streamflow greater than about 200 to 300 cubic feet per second will leave eaeily recognizable fTood features in channels. This range in streamflow is termed the eroeion threshold discharge. Following floods erosional features include sc~rred and raw banke and channels often removing much of the vegatation (Figure 2A). Uprooted trees or debris-ecarred treea and buehes are located in the floodplain. Flood debris is very common and is lodged along the stream bank and upstream from obstructione, such ~s trees and boulders (in Colorado'a semiarid climate ~hie flood debrie remains for 50 to 100 yeare). Steep mountain channels sub~ect to ~loode typically are scoured ~o bedrock and take many hundreds to thousands of years to recover to preflood conditione. During a flood moss and l~.chen are abraided from the bedrock and boulders in the channels up to the level of the flood. The regrowth Z.