FLOOD04080

• Designation Number: 226
• County: Jefferson
• Community: Lakewood
• Stream Name: Henry's Lake Drainageway
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Henry's Lake Drainageway
• Date: 7/1/1983
• Designation Date: 1/1/1984
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Immediately upstream of Carr Street, the inadequate culvert along with road
embankment, force the flood waters to the north inundating several residences. A
portion of these flows will continue north along Carr Street.

The 100-year runoff is contained in a natural channel from above the ponds to
South Pierce Street (Station 23+80 to Station 30+50). There are minimal hazards in
this unimproved open space. On the south side of Hampden Avenue, approximately 50%
of the total flow at this point continues to flow east along the service road and
out of the study area.

Through the foothills golf course (Station 84+90 to Station 117+90), the
100-year floodplain meanders through the low lying areas along the course.
Generally the 100-year runoff depths are I-foot to 3-feet with velocities ranging
from 2 to 4 fps. Minimal damage is incurred in this reach except for those caused
by inundation to the improved open space areas.

The church property at the southwest corner of the service road and Pi erce
Street lies within 100-year floodplain in that area. The floodplain above the
church completely inundates the service road and adjacent areas up to South Teller
Street, which is the point of origin of the original flow split.

Above the golf course is Henry's Lake, which is the upper limit of the flood
hazard area delineation study. The lake provides approximately 18 acre-feet of
flood storage from the crest of the service spillway to the crest of the emergency
spillway. During the 100-year runoff, peak discharges pass over the emergency
spillway, but the embankment is not overtopped.

C. Flow Split Drainageway

As described in the previous section, a major flow split occurs at the upstream
side of the culvert beneath Hampden Avenue. The flow splits east along the south
service road to Pierce Street, leaving the Henry's Lake Basin. The flows then
combine with local runoff from a direct flow area to Bear Creek. Approximately half
of the total flow goes north beneath Hampden Avenue and the remaining flow continues
east along the service road. The flood hazards caused by that portion which flows
north are described below.

The 100-year floodplain in the lower reach (Station 0+00 to Station 9+00)
passes over both South Kendall Street and West Florida P1 ace and wi 11 inundate
several residences presently under construction. Between Station 11+70 and Station
23+80, the drai nageway passes through three small ponds with earthen embankments.
On the upper two ponds, the 100-year runoff overtops a portion of the embankment in
excess of 1.0-foot, which could cause breaching and possible failure of the
embankment. The lower pond essentially passes the 100-year runoff over an emergency
spillway and does not overtop the embankment.

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