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to life and p~operty. Wate~ flowing in excess of four feet per second is capable of t~anspo~ting sediment and causing severe erosion of streambanks and fill around bridge abutments. Where velocities drop below two feet per second, debris and silt deposits can build up, extending the flood damages and creating adverse health conditions. The saturation effects of prolonged flooding can weaken bridge abutments, levees and other embankment works so they fail as the floodwaters recede. Prope~ty damage f~om g~eat floods in developed areas Can be ove~whelming. The entire community suffe~s when streets, bridges, sewe:t;"S, and other public utilities are damaged or destroyed. Adding to the phySical haza~ds, a g~eat flood can unleash deadly epidemic diseases, Sanita~y Sewers become pressure lines, blowing ~nhole cove~s to spew raw sewage into the floodwaters; sewage t~eatment plants and feeder lines can be washed out; stockyard waste Can add to the pollution and hazard of an epidemic disease. News~ pape~s sometime 'report a "lighter side of the news" in picturing children at play in the mud and standing water left by a receding flood. Unfortunately, the contamination th~aat to domestic wate~ supplies cannot be illustrated with siNilar aase. floodwate~s become isolated and entrapped in ove~bank areas resulting in depthS greater than those o~own on the ~iqh water prOfile". F~ Inter~tate 25 to t~e Mouth of Hospital Canyon. floodwater elevations for future floods may be expected to be greater in the overbank areas than along the ~ainstem because of the obstructive effects of bridqe~, freeway aCCess ramps, and ro..dbed. In past floods, bridges were washed out which increased channel conveyance and relieved overbank flooding. The areas i~ediately upstream from the mouth of Mcores and Colorado Canyons are subject to severe flOOding in case of floods of less magnitude tr4n the Intermediate Regional Flood. The stream channels are insufficient to carry any but the SMallest flow. The only major development on these flood plains is the trailer park in Moores Canyon. The conduits on fishers Peak ArroyO and Pinon Canyon will not convey floodwatero of Star.dard Project magnitude. Hshers Peak floodwater will leave the channel flowing through buildings and pri~arily do~~ Commercial Street. floodwater on Pinon Canyon will have the chanr.el prio~ to the conduit at Colorado Avenue becaus.. of the ob~tructive effects of the willow Street bridge and insuffi~ cient channel capacity. Flood~aters of Stand~~d Project and Inter~ mediate Regional ~loods will leave the channel at Willow Street and imnlediately below the Kansas Avenue conduit, respectively. Areal dist~ibution for a given flood 1s non-uniforrr, and paths unprL~iotable. Depths of flow for any given stream looation can be estimated from the high water profiles shown On Plates 16 through 38. Plates 39 through 4S show selectad cross sections of the streams that a~e typical of the approximately 145 sections surveyed in th.. study ~eaches; all cross section locations are s'~wn on the profile plates. stream FloooedAreasandFloodDama.ge Trinidad Dam will effectively reduce the frequency of flooding along the Purgatoire .Rive~ in Trinidad f~om storms occu~ring above th.. dam, but flood events may still inundate the historic flood plains. Should a severe sto~m occur ove~ the study area, the trib- utaries will subject mdny a~eas to flooding, and the Purgatoire floodwaters will increase in intensity while proceeding downst~e~~ andcolleotin<.Jfrnmthptrihut"r'l..". Pl"tP?'l""ni1"d"1<n>'I!,f'n,.- the succeeding Plates 3 through 15 which Ohow tho areas along the Purgatoi~e River and tributaries that will be flooded by the Stand- a~d Project Flood, Interm~iate Pegional Flood, and the a~ea flooded by the September 1904 flood or record. Floodwater elevations dete~ined in any particular area are not always ir.dicative of the depths aotually attained. Often characteristios detPrm'ln~ f"-Qm tnP0~,.-~pnic md!,q, ~~,.-f~1 r~~nsr~rhq and valley cross sections Were used to compute and define the flood situation. Velocities, Rates of Pise, and Duration The occurrence of the Intermediate Regional ~r Stand- ard P~oject flood would result in the flood characteristics "ho~~ in Tl;lbl~ S. This data reflocts the avoragcd maxi""um conditions ~'ith " "