FLOOD02077

• County: Larimer
• Community: Larimer County
• Stream Name: Lawn Lake Dam
• Title: Hydrology, Geomorphology, and Dam-Break Modelling of the July 15, 1982 Lawn Lake Dam and Cascade Lake Dam Failures
• Date: 1/1/1983
• Prepared For: State of Colorado
• Prepared By: USGS
• Floodplain - Doc Type: Flood Documentation Report

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~ Photographs
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51A.
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55-70.
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CONTENTS

Page

45-54,--Continued:
The Ponderosa Lodge, which was destroyed by the flood, at
river mile 9.9 on the Fall River--------------------------- 82
The Ponderosa Lodge as rebuilt after the flood, from the
same perspective as figure 51A----------------------------- 82
Debris jam on the upstream side of Elkhorn Avenue at river
mile 11.8 along the Fall River in Estes Park--------------- 83
High-water lines on buildings along the Fall River at Estes
Park------------------------------------------------------- 83
View upstream from Olympus dam and Lake Estes, containing
the floodwaters (aerial)----------------------------------- 84
Graphs showing:
Lawn Lake dam embankment cross section on the Roaring River
at river mile 0,0------------------------------------------ 94
Lawn Lake dam cross section of breach (right side) on the
Roaring River at river mile 0.0---------------------------- 95
Lawn Lake dam cross section of breach (left side) on the
Roaring River at river mile 0,0---------------------------- 96
Roaring River cross section at river mile 0,55--------------- 97
Roaring River cross section at river mile 1.50--------------- 98
Roaring River cross section at river mile 3.83--------------- 99
Fall River cross section at river mile 5.36------------------ 100
Fall River cross section at river mile 5,78------------------ 101
Fall River cross section at river mile 6.50 (site 1)--------- 102
Cascade Lake dam cross sections on the Fall River at river
mile 6.67 (site 2)----------------------------------------- 103
Fall River cross section at river mile 7.68 (site 3)--------- 104
Fall River cross section at river mile 7.74------------------ 105
Fall River cross section at river mile 8,78------------------ 106
Fall River cross section at river mile 10,28 (site 4)-------- 107
Fall River cross section at river mile 11.45 (site 5)-------- 108
Big Thompson River cross section at river mile 12,5 (site 6)- 109

TABLES

Page

Geotechnical characteristics of the Lawn Lake dam earthfill---- 11
Flood stages and discharges in Larimer County for the flood
of July 15, 1982, and during previous maximum floods--------- 22
Storage capacity and other pertinent information for Lawn Lake
and Cascade Lake--------------------------------------------- 24
Peak flow data at selected cross sections---------------------- 27
Discharge-frequency summary for the Roaring River at mouth and
the Big Thompson River at Estes Park------------------------- 28
Time of flooding from the failures of Lawn Lake dam and
Cascade Lake dam, July 15, 1982------------------------------ 32
Channel conditions, Roaring River------------------------------ 50
Field-selected and calibrated model-composite Manning's n-
values------------------------------------------------------- 70
Summary of dam-break model simulation-------------------------- 71
Comparison of model results of a hypothetical breach width of
25 feet to the actual breach width of 55 feet---------------- 75

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