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~ L I 19. RAINFALL i; a. During the afternoon of 16 June, unprecedented amounts of rain (estimated up to 14 inches in a few hours at Larkspur, Colorado and 10 inches near Castle Rock, Colorado) fell on the drainage areas of East and West Plum Creeks in the foothills of the Palmer Lake area. The average 6-hour rainfall over 1,000 square miles was 4.8 inches. Again, on' the 17th of June, heavy rains occurred across eastern Colorado. A series of 12- to 14-inch centers were reported in the Falcon, Peyton, and Fords" Colorado area northeast of Colorado Springs. The average 6-hour rainfall over 1,000 square'miles was 7.8 inches. Other centers with total rainfall ,values of 18 inches or more,during this period were reported near Two Buttes, and Holly, Colorado. b. Unsettled weather continued until 26 July 1965, with repeated rainfall and runoff in areas of earlier flooding. During the period 23 to 26 July, the storm pattern also' extended over the foothills areas of.the Bear Creek and Clear Creek watersheds. 20. PATTERNS OF FLOODING a. On the 14th and 15th of June, flood stages on tributary streams in the northern portions of the South ,Platte River basin closed roads and damaged private, property in low-lying areas. The principal streams in flood stage in the lower South Platte River basin were Lone Tree Creek, Crow Creek, Pawnee Creek in Colorado, and Lodgepole Creek in Nebraska. Tornado damage and ,runoff from smaller contributory drainage areas made it difficult to determine the sources and causes of, damage,S in some areas. b. On the afternoon of the 16th of June, storm runoff caused unprecedented discharges an~extensive damages along East and ,West Plum Creeks which combined to cause record flood stages on lower Plum Creek. The flood entered the South Platte River south of Denver at approximately 7 p.m. on the 16th. It destroyed or damaged every- thing in its path through the 44-milereach of metropolitan Denver before spreading out into the agricultural flood plain north and east of Denver. While the Plum Creek flood passed through Denver, heavy runoff from the upper Cherry Creek watershed caused considerable damage above Cherry Creek Reservoir, but additionaldam,age to Denver was prevented when the reservoir impounded the entire flood volume. Because the storm pattern extended over the Sand and Toll Gate Creek watersheds, heavy runoff from these streams destroyed bridges and track facilities in the vicinity of Aurora, Colorado, and contributed additional flood volume to the South Platte River JU'st north of Denver proper. As the flood passed downstream, peavy runoff from the Cache LaPoudre River and the Big Thompson River contributed their.volume to upstream discharges attenuated by valley storage., 11