FLOOD00830

• County: Larimer
• Community: Estes Park
• Stream Name: Lawn Lake
• Title: Fall River Flood of July 15, 1982
• Date: 7/15/1982
• Prepared By: CWCB
• Floodplain - Doc Type: Flood Documentation Report

upstream reaches of the Big Thompson River, Fall River, and the
entire Fish Creek basin within the corporate limits are largely
undeveloped.

2.3 Principal Flood Problems

The Town of Estes Park has not frequently been subject to damaging
floodflows; however, the flood of 1965 demonstrates the potential
for flooding that does exist, particularly in areas where buildings
encroach upon the riverbanks. Views of the 1965 flood in Estes Park
are shown in Figures 2 through 5. The 1965 flood, which was the
most recent, was the result of a combination of heavy rain and rapid
snowmelt on a warm day in June. Rainfall depth over a 2-day period
was approximately 1.9 inches. The peak in the Big Thompson River
near Lake Estes was approximately double the normal flow. The 1965
peak of 1640 cubic feet per second was the most damaging flow in
recent history; although flows of this magnitude were also recorded
in 1949, 1951, 1953, and 1957. Evidence of flooding from these high
flows is seen in the many flood retaining walls lining the banks of
the Big Thompson and Fall Rivers through town.. Damages from the
1965 event were the result of continued encroachment upon the river
channels and blockage of the Fall River culvert at Elkhorn Avenue
that diverted flows through the center of town.

2.4 Flood Protection Measures

Flood retaining walls have been constructed along much of the stream-
banks through the central business district of town. These retain-
ing walls serve to protect streambanks from erosion and, in areas
where walls extend above the normal bank height, confine floodflows
to the channel.

The Town of Estes Park is also in the process of replacing old
bridges with bridges designed to avoid bridge backwater by perching
the bridge above the channel. Floodflows spill from the. channel
before water rises to the low chord of the bridge. The bridge does
not create a backwater; hence, it does not increase the flood
hazard. Future replacement of inadequate bridges with these perched
bridges will reduce flood potential in some areas.

3.0 ENGINEERING METHODS

For flooding sources studied in detail in the community, standard hydro~
logic and hydraulic study methods were used to determine the flood
hazard data required for this study. Floods having recurrence intervals
of 10, 50, 100, and 500 years have been selected as having special sig-
nificance for flood plain management and for flood insurance premium
rates. The analyses reported here reflect current conditions in the
watersheds of the flooding sources.

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