FLOOD09213

• County: Jefferson
• Community: Edgewater
• Basin: South Platte
• Title: Flood Insurance Study - City of Edgewater
• Date: 8/15/1989
• Prepared For: Jefferson County
• Prepared By: FEMA
• Floodplain - Doc Type: Historic FEMA Regulatory Floodplain Information

remaining 60 percent of the precipitation occurs as
small amounts of water in the air are accompanied
percentage of sunshine and sizable temperature changes
night.

snow. The
by a large
from day to

Winters in the study area are long and cold, with mean daily
temperatures of approximately 30oF. Summers are hot and mild with
mean daily temperatures near the mid 70s (References 4 and 5). The
soils in the area are generally deep, well-drained, clayey soils
that are neutral or mildly alkaline (Reference 6).

2.3 Principal Flood Problems

Flood problems within the Sloans Lake subbasin in the City of
Edgewater are due to overflow from the drainageway between Ingalls
Street and 20th Avenue to the eastern corporate limi ts at Depew
Street. Upstream of Ingalls Street and 20th Avenue to the western
corporate limits, overflow is split between a storm sewer and the
streets. Flooding in this area is caused in part by thunderstorms
during the spring, perpetuated by antecedent ground moisture and
melting snow.

2.4 Flood Protection Measures

The City of Edgewater, in conjunction with the City of Lakewood and
City and County of Denver, permitted the Denver Urban Drainage and
Flood Control District (UD&FCD) to plan and implement channel and
culvert improvements in 1977. The UD&FCD constructed the West 18th
Avenue extension channel from Depew Street to Sheridan Boulevard.
To improve the efficiency of bridge culverts at Depew Street and
Sheridan Boulevard, the UD&FCD installed twin 12- by 5-feet
culverts at Depew Street and four 7- by 5-feet precast-concrete
boxes at Sheridan Boulevard. All construction was completed by
early 1983. The newly installed culverts relieve bottleneck
conditions caused by inundation. In 1987, channel improvements
between Ingalls Street and 20th Avenue to Depew Street were
completed. A detention pond outside the corporate limits at 25th
Avenue and Wadsworth Street reduces sheet flow east of Pierce
Street.

3.0 ENGINEERING METHODS

For the flooding sources studied by detailed methods in the community,
standard hydrologic and hydraulic study methods were used to determine
the flood hazard data required for this study. The flood event of a
magnitude which is expected to be equaled or exceeded once on the
average during any 100-year period (recurrence interval) has been
selected as having special significance for floodplain management and
for flood insurance rates. The event, commonly termed the 100-year
flood, has a I-percent chance of being equaled or exceeded during any
year. Although the recurrence interval represents the long-term
avera~e score period between floods of a specific magnitude, rare
floods could occur at short intervals or even within the same year.

4