FLOOD06904

• County: Larimer
• Basin: South Platte
• Title: Hydrology, Geomorphology, and Dam-Break Modeling of the July 15, 1982 Lawn Lake Dam and Cascade Lake Dam Failures, Larimer County
• Date: 1/1/1986
• Prepared For: Larimer County
• Prepared By: USGS
• Floodplain - Doc Type: Flood Documentation Report

FIGURE 55-70.

TABLE

CONTENTS

Graphs showing:
55. Lawn Lake dam embankment cross section on the Roaring River at river mile 0.0
56. Lawn Lake dam cross section of breach (right side) on Roaring River at river mile 0.0 . . . . .
57. Lawn Lake dam cross section of breach (left side) on the Roaring River at river mile 0.0
58. Roaring River cross section at river mile 0.55 . . . . . . . . . . . . .
59. Roaring River cross section at river mile 1.50 ... . . . . . . . . . . . . . . . . . . . .
60. Roaring River cross section at river mile 3.83 ... . . . . . . . . . . . . . . . . . .
61. Fall River cross section at river mile 5.36 . . . . . .
62. Fall River cross section at river mile 5.78 .. . . .. .........
63. Fall River cross section at river mile 6.50 (site 1)
64. Cascade Lake dam croes sections on the Fall River at river mile 6.67 (site 2)
65. Fall River cross section at river mile 7.68 (site 3)
66. Fall River cross section at river mile 7.74 .. ... . . . . .... .... ,
67. Fall River cross section at river mile 8.78 .. _ . . . .
68. Fall River cross section at river mile 10.28 (site 4) ........... . . . . . . . . . . . . . . . .
69. Fall River cross section at river mile 11.45 (site 5) ..........
70. Big Thompson River cross section at river mile 12.5 (site 6) .... . . . . . . . . .

TABLES

1. Geotechnical characteristics of the Lawn Lake dam earthfill . . . . . . . . . , . . . . . . . . . . . .
2. Flood stages and discharges in Larimer County for the flood of July 15, 1982, and during previous maximum
floods.. ............. ................. ........ ........
Storage capacity and other pertinent information for Lawn Lake and Cascade Lake . . . . .
Peak flow data at selected cross sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Discharge-frequency swnmary for the Roaring River at mouth and the Big Thompson River at Estes Park . . .
Time of flooding from the failures of Lawn Lake dam and Cascade Lake dam, July 15. 1982 .....
Channel conditions, Roaring River . . . . . . . . ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Field~selected and calibrated model-composite Manning' s n~values . . . . . . . . . . .
Summary of dam-break model simulation.... .... .................... .. . ... ... ..
Comparison of model results of a hypothetical breach width of 25 feet to the actual breach width of 55 feet
Comparison of model results of a hypothetical breach width of 200 feet to the actual breach width of 55 feet . .
Comparison of model results with and without the failure of Cascade Lake dam . . . . . . . . . .
Damage estimates for the July 15, 1982, flood . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .

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