FLOOD01805

• County: Statewide
• Community: State of Colorado
• Title: A Utility Approach to Comprehensive Storm Water Management
• Date: 7/28/1983
• Prepared For: Roger E. Krempel
• Prepared By: Marc Engomen
• Floodplain - Doc Type: Project

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Question raised most often by the public and
elected officials concerned the use of the
lOO-year storm as the major design storm. Many
people questioned the need to invest so much
money to provide protection from an event which
might occur in their lifetimes.

This experience causes one to wonder how
many proposed storm drainage programs across the
country have fail ed because the publi c, through
their elected officials, do not find the IOO-year
flood an acceptable criterion for the design of
major drainage improvements. Some communi ties
may find the adoption of a less stringent design
criteria, based perhaps on the 50-year stann,
will reduce the public resistance to the imple-
mentation of capital improvement fees. Such a
change in criteria might well mean the difference
between succeSSfully implementing a storm drain-
age program or not, at a fairly small reduction
in the level of protection provided.

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*This nomograph was originally developed for the
average sized subdivision in Fort Collins {40 to
60 acres}. The nomograpn can be "adjusted" for
subdivisions of different areas using the following
formula:

where:

V' V (1.2A-0.05)
V' volume of on-site detention adjusted
for area, in cubic feet per acre.
V volume of on-site detention provided,
in cubic feet per acre.
A = tributary area, in acres.
,

The adjusted volume, V'. should be entered into the
no~graph to obtain the appropriate reduction fac-
tor.

Figure 2. On-site detention reduction
factor nomograph.

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Summary/Conclusions

Stormwater is indeed a difficult resource to
manage. Natural drainageways, creeks and rivers,
man-made irrigation features such as lakes and
canals, and more recent storm drainage facilities
including open channels, storm sewers and deten-
tion ponds are interwoven in a large and c~~plex
drainage system, and are an integral part of the
overall urban environment. Thorough analysis~
made possible by recent advances in .drainage
technology, has shown that policies of the past
have been unable to keep pace with many cities1
rapid growth. Floods have occurred in the past
and will continue to occur if the inadequacies of
the exi sti n9 drai nage system remai n uncorrected.

But avoiding potential flood damage is only
a part of the picture. Associated concerns such
as ineffective maintenance operations. nuisance
flooding, and potential liability must also be
addressed. Experience has shown that continued
urbanization dramatically affects the drainage
system, requiring local government to consider
not only existing drainage problems. but to
anticipate and address the drainage concerns of
the future.

This paper has attempted to share some of
the key elements in the City of Fort Collins'
plan for effective stonnwater management. The
pri nc ; pIes estab 1 i shed in the ordi nance of 1976
provide a firm foundation for later policies and
decisions. Dividing the city into separate
drainage basins and preparing individual basin
master plans has allowed us to fit the many
pieces of the storm drainage puzzle together and
see the bigger picture. Collecting the diverse
storm drainage activities of the City into a
single unit - a utility - with its own staff.
regul ations, budget and sources of revenue ~ has
enabled us to give 5tormwater management a focus
so that drainage problems can be solved. The
monthly utility fee for operations and mainte-
nance has increased the effectiveness of the
existing drainage program. The new utility and
basin fees for cap-ital improvements provide
. for the cons tructi on of the storm drai nage
facilities necessary to correct todays problems
and meet the needs of the future. And work.ing to
enhance the publ i c awareness of storm drai nage
issues has secured the successful implementation
. o-f-thh major' new program~ . .---~-- ---~_., ,-

The development of a comprehensive stonn-
water management has been an evolutionary pro-
cess. Changes in technol 09Y, in management
strategies and in the public attitude toward
storm drainage have shaped Fort Collins' stann-
water program. It is a sound program, based on
the best available information and developed over
a period of years, aimed at providing a safe and
effective drainage system for the residents of
Fort Collins at a fair and reasonable cost.

But stormwater management must co"tinue to
be an evol ut i onary process. chang; og a s the
pub 1 i c and the City 1 earn more about storm
drainage, adapting 'to changing corrrnunity percep-
tions and needs. Only in this manner can our
goal of effective overall management of our
unique stormwater resource be achieved.

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