WSP06003

• File Number: 8449.900
• Description: Bear Creek
• State: CO
• Basin: South Platte
• Date: 11/1/1991
• Author: City of Lakewood
• Title: Bear Creek Lake Preliminary Environmental Assessment Wetland Task Report
• Water Supply Pro - Doc Type: Publication

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ES ENGINEERING.SCIENCE

further upstream are additional attractive habitat characteristics. The wildlife
habitat values of the existing wetlands are considered to be high for songbirds,
waterfowl, hawks and owls, shore and wading birds, deer, and small- and medium-
sized mammals. A large number of bird species have been documented in these
areas (City of Lakewood, 1989). Major heron rookeries are not present in these
wetlands, although some nesting or roosting by the great blue heron and black-
crowned night heron probably occurs by a small number of individuals or pairs.

The wetlands are not suspected of supporting significant fish spawning or rearing
habitats because both Bear Creek and Turkey Creek flows are apparently separated
from adjacent wetlands by sharply-defined channels. Field observations suggest an
absence of side channels and interconnected floodplain ponds that could function as
shallow-water fish breeding and rearing sites. Shallow-water and relatively slow-
flow areas are limited to the mouths of both creeks where they enter the lake's
upper end. Both creeks support an aquatic life community, with the larger Bear
Creek having a more well-developed fishery because of its size, greater amount of
habitat, and larger volume of water. The shoreline and tributary wetlands do not
appear to provide significant aquatic life habitat because of the absence of standing
water and their location above the normal pool level. Indirectly, the wetlands help
maintain aquatic life in Bear Creek Lake by contributing organic nutrients that
result from decaying plant parts. These nutrients help support the aquatic food
chain. Pulses of these nutrients enter the lake during the spring and late fall
months.

The location and elevation of floodplain wetlands suggest that these areas would
play an important role in altering the timing and velocity of upstream flood flows
that enter the reservoir because of intense summer thunderstorms or spring runoff.
The overall importance of such alterations to the Bear Creek watershed below the
lake is masked by the nearby presence of Bear Creek dam. The wetlands upstream
of the lake are important in retaining and stabilizing some of the sediments
transported from upper reaches of the watershed during floods or high flows. The
deposition of sediment and the expansion of willows and cottonwoods on the
sediment deposits at both creek mouths is evidence of this process. Soil eroded
from adjacent uplands are effectively retained by wetlands which border the stream
channels. The floodplain wetlands may serve as ground water recharge locations
and as ground water discharge points for seepage from adjacent slopes. Evidence of
both discharge and recharge was noted during the field inspections.

SCENARIO EFFECfS

Potential inundation effects of each water storage scenario are summarized in the
following section. Both jurisdictional wetland and riparian areas are addressed
because of public and regulatory interests and the ecological and social values of
both types.

Method

Potential inundation effects were determined by plotting the pool elevation of
each storage s.cenario on a 1991 topographic map of the lake, the creek floodplains,

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