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PRECIPITATION AND FLOODS . The BellI';' and Clear Creek basin! are characterized by vide ranges 1n elevations "'bieh rell~t in verletlonB in climatic cond,ition9. In the ~pper elevations the climate is a~bhumld, with long cold winters and frequent acc~ullltion of heavy Snows. Melting of this BOO'" produces the annual late spring rises 1n the streams. In the Denver area, which 16 loclIted at a lower elevation, the climate 1s lIeml-erld with little accumulation of BnOW co~r. During the s~r months both basins are subject to BUdden and intense thunder storms Which generally cover small aress ond produce flash. type tlooda of soortduratlon. .. Damaged car and debria, Mt. Vernon Cree~ in Morrlson, September 1938 flOOD CONTROL IMPROVEMENTS Some Incldentlll channel work haa been accomplished 1n connection \11th high\lsy illlprovements and extendoos of urban development. This \lork prOVides a 10\1 degree of flood protection for the adjacent lands. The Corps of Engineera, aa part of its authorized South Platte River investiga- tion, is considering potential upstreo~ storage reoervoirs and local channel and levee \lork along Bear and Clear Creeks. . FLOOD PROBLEMS Historic flooding in the Bear and Clear Creek baSins has been relatively infrequent. F10odsgenerallyresu1tt"rOlllintensethunderatol'lllsinthe mountainous portions of the badn. Occaaional1ya moderate rainhll combined with rapid enovmelt also causea flooding. '!he upper reaches of the etreams are undeveloped, and much of the sDOllme1tsnd rdnf'all infiltrates into the ground and ie re~oved froRl flood t"lO\1s. As development of the flood plains increases, however, lees area will be available for 1.nfiltration, and runoff will be Dlorepronounced. Streem chennels unable to conte1.n flood flows undere:xistillg conditions lIil1 become further taxed, and more frequent flooding lIi11 result. Urbanization on Bear Creek is presently confin~d to the 1011er t"our miles ot" the stream and the town of ~orrison. Current urbanization on Clear Creek io limited to the suburbs of Arvada, Lakewood and Wheatridge and the to'Jn at GOlden. Development which \1111 further arrect the flood plain haa begun at several other locations in both basins. Thesbllitycfa ch.::.nnc1tocollveyrloodflO'olsdependatoa1argt: extent upon its size and condition. Streams are often used as dumps tor trash. In time of high \later this debris collects st bridges, culverts snd other structures forming obstr~ction8 which force the wster onto sdjscent lands. Moreover, chsnne1 capscities are often reduced by encroachment resulting from edjacent develo~ent. Failure to keep the channel free reduces the capacity and increasea the flood hazard. In addition to the flood prOblem, high veiocities on these stresms ca~sc serious bank erosion at many locetions and endsnger adjscent structures.