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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 upstrea~ storage reaervoirs 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. Occaaiona11ya moderate rainhll combined with rapid enovme1t fIlso csusea flooding. '!he upper reaches of the atreams are undeveloped, Bnd much of the snolIme1tand 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 infiltration, and runoff will be Dlorepronounced. Streem chennels unable to conte1n flood flows undere:xisting conditions lIil1 become further taxed, and more frequent flooding lIi11 res~t. Urbanization on Bear Creek is presently confin~d to the 1011er t"our miles ot" the stream and the tOlln of ~orrison. Current urbanizatioll on Clear Creek ia limited to the suburbs of Arvada, Lakewood and Wheatridge and the to'Jn of GOlden. Development which \lil1 t"urther arrect the flood plain haa begun at several other locations in both basins. Thesbilityofa ch.::.nnc1 to convey t"lood rlO'olsdependatoa 1argt: extent upon its size and condition. Streams are often ueed ae dumpe t"or trash. In time of high \later this debris collects st bridgea, culverts snd other struct~res t"orming obstr~ction8 which force the wster onto sdjscent lands. Moreover, Channel capscitiea are often reduced by encroachment resulting t"rom adjacent develo~ent. Failure to keep the chsooe1 t"ree reducea the capacity and increases the flood hazard. In addition to the t"100d problem, high veiocities on theae streams ca~sc serioua bank erosion at many locstions and endanger adjacent structures.