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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 constructed in or out of the existing channel al ignment. This suble process which has quite ofte~ caused unanticipated results in drainage improvements. The basic concept is that of an increased translatory wave effect which cascades downstream and overtakes flO',,, 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 cond'tlons for the discharge into Maple Grove Reservoir. This estimate is based on a rough surface, hard-lined channel from the trailer courts in Reach 2 to Clear Creek that has a slope approaching existing conditions. Below Maple Grove the increase is not significant because of the storagelrouting effect of Maple Grove Reservoir. The flo^, increases sharply below Kipling Street because the peak flows from Basins 7, 8 and 9 combine ",'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 rei ieved the overtopping for the 100-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 ,;ignificantly alte,-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 optimi;zat'ion of smal'ler detention reservoi rs along the gulch. The best apparent scheme was a lar'ler. pond below Basin I and one or two other ponds belo," and possibly amon<) the trailer courts. This system of ponds results in a dec;-ease of 80 percent below the trai ler court, a decrease of 50 percent of the peak inf'low to I~aple Grove Reservoi 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- arity here is that this reduced flow only si'lnificantly benefits the trailer court areas and a few isolated re5idents. If the trai ler courts had been designed with reasonable channel capacity, only a smal I 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 aqainst increased hazards during larqe storm runoff periods.