FLOOD08316

• County: Statewide
• Basin: Statewide
• Title: Flood Hazard News The 1997 Floods in the District
• Date: 2/11/1998
• Prepared For: State of Colorado
• Prepared By: UDFCD
• Floodplain - Doc Type: Educational/Technical/Reference Information

MAINTENANCE PROGRAM
ACITVITIES
by
Mark R. H......, P.E.
Chicl; Madooanco Progrom

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Routine Maintenance
Through the routine maintenance
program $716,500 was spent in 1997
for mowing and debris pickups on
approximately 210 different sections of
drainageways within the District
boundaries. This equates to a total of
nearly 100 miles of drainageways in the
Denver area that were given routine
maintenance.
The amount of money spent on
rontine work this year is up
substantially over last year. This is the
result of an increased frequency of
mowing on certain drainageways.
Some of the more wban drainageways
now receive four to five mowings per
year. Three to four mowings per year
was inadequate for effective weed
control and for overall appearance.
Other drainageways we maintain
are more rural in character. On
portions of some of these drainageways
we have taken the opportunity to reduce
or eliminate our mowing activities.
This bas been done to encourage habitat
and leave a more natural character in
the drainageway corridor.

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Restoration Maintenance
In 1997 the restoration program
completed $841,000 of work.
Restoration projects typically address
isolated drainage problems where the
solution involves small scale
constnJction. Ninety-four individual
activities were completed during the
year.
In last year's Flood Hazard News
we described a site on Lena Gulch at
the confluence with Clear Creek
where, through natoral processes, Clear
Creek had captured the lower 300 feet
of Lena Gulch. The result was a 50-
foot wide pool of slow-moving water in
Lena Gulch that bas experienced some
sedimentation and bas contributed to
insect populations and to uncontrolled
vegetation. On the other hand our
~s""""""nt bas been that the changed
conditions on Clear Creek and Lena

Gulch have not elevated the l00-year
floodPlain. Thus, there bas been little
incentive to move rapidly to recoustruct
the confluence of these two creeks.
In contrast to the Lena Gulch site
described above two other sites have
also had increased sediment and
vegetation, but they have also
experienced a loss of flood-canying
capacity. Tucker Gulch in Golden was
improved about five years ago.
Through earlier land-use decisions the
channel was already limited to a
confined right-{)f-way pinched between
streets and residences. During the
design the project participants made the
decision to not expand the right-{)f-way.
That resulted in a narrow concrete-lined
channel with little or no surplus flood-
carrying capacity. When sediment
accumulated and vegetation took root it
became necessary for maintenance
crews to remove to material to restore
the intended capacity to the creek.
The other similar site is on South
Boulder Creek on the east side of
Boulder, Colorado. As with Tucker
Gulch, South Boulder Creek bas
experienced sedimentation and
dramatic vegetation growth in the 20
years since it was improved. The
resultant flooding threat was recognized
by nearby landowners and city officials.
To restore the channel capacity a plan
was developed to remove the sediment
and vegetation.
The excess material needed to be
removed from the channel cross-
sections of both Tucker Gulch and
South Boulder Creek in order to
maintain them in a manner that was
consistent with the intent of their
original designs. Accomplishing this

maintenance work caused some
discomfort for the involved parties.
First, it was a time<Onsuming process
to acquire federal permits to carry out
this kind of local maintenance work. A
second issue was that some of the
neighbors objected to the removal of the
material. To them the vegetation was a
welcome addition to otherwise stark
drainage channels.

Rehabilitation Maintenance
Twenty-eight projects were at
various stages of design or construction
during 1997. Those projects are listed
in the accompanying table titled
~STATUS OF MAINTENANCE
REHABILITATION PROJECTS".
Rehabilitation projects usually take the
form of consultant -designed repairs that
are intended to address severe problems
that have occurred on a previously
improved drainageway. By the end of
1997 the District will have spent about
$2,178,000 on rehabilitative design and
construction for the year. A few of the
unique projects are discussed below.
East ofIrma Drive at l04th Avenue
in Nortbglenn there is a detention pond
on Grange Hall Creek. The pond
serves as both stormwater detention and
as a surface water re-use program run
by the City of Nortbglenn. The existing
108-inch outlet passes under an unused
30-foot high railroad embankment
The outlet pipe had deteriorated to the
point that it was being held up with
railroad timbers. Through a combined
project with the District's construction
program and the City ofNortbglenn the
pipe and outlet systems are being
replaced. The contractor is laying the
pipe in an open cut and is backfilling

Before and after views of Lena Gulch in Wheat Ridge.

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