FLOOD09481

• County: Statewide
• Community: State
• Stream Name: All
• Basin: Statewide
• Title: Practices in Detention of Urban Stormwater Runoff
• Date: 1/1/1974
• Prepared For: American Public Works Association
• Prepared By: American Public Works Association
• Floodplain - Doc Type: Educational/Technical/Reference Information

of the areas of our nation have developed and
increased in population, the need to develop
adequate water supplies has grown. In some
areas, surface and groundwater supplies are
sufficient to meet expected growth; but in
other areas surfacewater supplies are not
adequate and groundwater supplies are being
rapidly depleted. Stormwater can be used to
augment depleted water supplies. The
storm water may be collected, treated (if
n e c e s s a r y ) and used for groundwater
recharge, or it may be collected for direct use
in applications not involving human or animal
consumption. In previous years, stormwater
runoff was regarded as an evil to be disposed
of as quickly as possible. It is now often
considered as a valuable resource not to be
wasted. Storm water rurloff has been aptly
termed "a resource out of place." Use of
stormwater will depend on two factors - the
ability to collect and store such water, and
the ability to economically treat the polluted
storm water runoff.

Alternative Solutions
In addition to on-site detention of runoff,
other alternative and/or supplementary means
of providing solutions to the problems of
urban stormwater management encountered
in abating or reducing pollution and local
flooding include the following:
I. separation of combined sewers;
2. enlargement of sewer system capacities
by constructing relief sewers;
3. temporary storage of stormwater in
systems of underground tunnels;
4. construction of stormwater treatment
facilities;
5. enlargement of present wastewater
treatment facilities to handle peak flow
rates;
6. infIltration or injection of stormwater
into underground waters;
7. flood-plain zoning to limit, or prevent,
the development of land in flood-prone
areas;
8. flood-proofing of structures; and
9. soil erosion and siltation control
measures.
Not all of these alternatives are mutual1y
exclusive to stormwater detention, or to each

other. For example, the recognition that
urban stormwater runoff is polluted will lead
to requirements for treatment. The use of
storm water detention and treatment of
stormwater runoff are complementary
solutions because detention is an essential
step in treatment.
Some factors to consider when comparing
the alternatives, and which were investigated
and considered in this study are:
I. system reliability as a function of nature,
man, and available technology;
2. degree of effectiveness of the method in
preventing and/or reducing flooding and
pollution problems for various rainfall
intensities and duration;
3. flexibility of the proposed solution for
adapting to changing urban conditions
and possible future requirements of
stormwater treatment and/or reuse;
4. evaluation of corollary advantages and
disadvantages of the proposed solution;
5. ease of implementation of the solution,
considering the potential inconveniences
caused by the solution and the
availability of needed resources;
6. initial construction cost; and
7. operation and maintenance costs.
Other factors that should be considered
by local public agencies in making decisions
concerning the selection of methods for
handling runoff are:
1. legal basis;
2. needed local and/or state legislation;
3. financing, construction, operation and
maintenance;
4. compatibility with methods adopted
and/or planned by other jurisdictions
within the same watershed'; and
5. public acceptability of the proposed
management, planning and
implementation.

THE STUDY
The objective of the study was to
investigate and report on current practices in
providing, operating and maintaining facilities
for the temporary storage (detention) of
excess urban stormwater runoff on the site
where it originates. Concepts, techniques,
applications, costs, problems, legislation, legal

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