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111..11 Another effect on peak flows Is channel ization, by which a clearer, faster and more hydraul ically effecient channel Is cDnstructed in or Dut of the existing channel al ignment. This suble prDcess which has quite ofte~ caused unanticipated results In drainage improvements. The basic concept is that Df an increased translatory wave effect which cascades downstream and overtakes flO',N which was not combined befor'e. As a result, the flow deepens and Increases in velocity, thereby increasing the discharge rate. This increases the flow 34 percent above the future developed conditions for the discharge into Maple Grove Reservoir. This estimate is based on a rough surface, hard-lined channel from the trailer CDurts In Reach 2 to Clear Creek that has a slope approaching existing cDnditions. Below Maple Grove the increase is not significant because of the storage/routing effect of Maple Grove Reservoir. The flo^, increases sharply below Kipling Street because the peak flDws from Basins 7, 8 and 9 cDmbine ",'ith Basin 10 at a more coincident time. On-Stream Storage. Part of any master plan is the investigation of effec- tive on-stream storage and flow regulation measures. Several alternative schemes were investigated to determine which measures would prove the most beneficial. The most obvious alternate was the enlargement of Maple Grove Reservoir by raising the existing dam crest to provide increased storage. Unfortunately, this scheme only relieved the overtopping for the lOO-year frequency event and did not significantly relieve flooding downstream. The problem downstream is one of no significant outfall; that is, flow from Basins 7, 8, and 9 would not be ,;ignlficantly altel'ed by a more con- trolled discharge from Maple Grove Reservoir. The most significant and efficient storage occurs with the first several feet of accumulation in Maple Grove Reservoir. An alternate scheme was an optimj.zat'ion of smal'ler detention reservoirs along the gulch. The best apparent scheme was a larqer' pond below Basin I and one or two other ponds below and possibly amonq the trailer courts. This system of ponds results in a dec;'ease of 80 percent below the trailer court, a decrease of 50 percent of the peak Inf'low to I~aple Grove Reservol r and approximately the same sl ight decrease in f'low in 13asins 8 and 9 as with enlarging Maper Grove Reservoir. This system requires about 100 acre" feet in the upper pond and 150 acre-feet In the lower pond(s). The pecul i- arlty here is that this reduced flow only si'lnificantly benefits the trailer court areas and a few isolated residents. If the trai ler courts had been designed with reasonable channel capacity, only a small detention pond would be necessary for the debris collection and sedimentation basin pur" poses. On-stream detention reservoirs also tend to fncrease major flood hazard due to potential failure. Lar<ler ponds must be evaluated a<Jainst increased hazards during large storm runoff periods.