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

experience with the concept of on-site
detention of storm water runoff.
6. Most of the respondents to the
survey questionnaire stated that the concept
of on-site detention was worthy of
consideration.
7. The use of on-site detention of
runoff was found to be the most desirable
method of runoff control in some flood-prone
or erosion-prone areas of the country.

8. New methods of stormwater
detention (such as the use of porous
pavements) and other methods of reducing
runoff rates appear to have application where
climate-, topography and soil conditions are
suitable.
9. Attitudes on the use of on-site
detention of runoff were generally favorable;
however, land developers want to be assured
that applicable requirements of local and state
public agencies are applied uniformly and
with flexibility,
10. Legislation pertaining to on-site
detention of stormwater ranges from very
detailed requirements to almost none. No
building codes were found to forbid detention
of rainfall on roofs of buildings. Several local
building codes specified criteria and
standards. Local requirements for on-site
detention of runoff were most often found in
subdivision regulations, zoning ordinances,
sewer permit ordinances and local building
codes.
II. Legal aspects of detention storage
were found to be poorly defined. Drainage
laws were found to vary considerably
throughout the country and the legal aspects
of detention storage, as a relatively new
concept, were also found to vary, Safety
hazards of detention ponds, the authority to
require on.site detention, the amount of
storage required, the legal responsibility for
maintenance and operation, the burden of
facility cost, and the relationship of detention
storage to water-right laws all are important
considerations.
12. Costs of stormwater detention
facilities were found to vary with the type of
facility as welJ as its geographic location. Cost

figures identified include $5,500 per acre-foot
of storage (estimated by the Metropolitan
Sanitary District of Greater Chicago) to $30
per residential lot of average size for sediment
basins in Maryland.
\3. Several methods of financing are
available. It was found that land developers
were often required to bear the entire cost of
the construction of detention facilities in the
same fashion that they must pay for sewer
construction. In existing land developments.
costs were not usually borne directly by
property owners in the area served by the
facility.
14. The economics of on-site detention
were often favorable in both new
developments and in existing urbanized areas.
Besides controlling problems resulting from
excessive storm water runoff rates, detention
storage facilities can be utilized to: serve as
aesthetic improvement of an area, provide
recreational opportunities, and supplement
local water supplies (in some geographic
areas) .
IS. Design of detention storage facilities
is complicated by a number of factors
including accurate determination of runoff
rates (both existing and future), availability of
space for construction of facilities, capacity
of downstream facilities to handle outflows,
and the need to build the facilities to be
aesthetically pleasing and compatible with the
local environment. The design of detention
storage on rooftops is impeded by the
reluctance of builders, architects and building
owners to store water purposefully on roofs
of buildings.
16. Problems of implementation of
on-site detention of stormwater are not
significantly different from the
implementation of other public works
facilities, especially in areas where the
concept is new. Educational programs
documenting the need and usefulness of such
techniques can be helpful.
17. The biggest problem of implementing
effective storm water detention programs is in
obtaining cooperation from neighboring local
jurisdictions. Since major floods in a
community are often the result of excess

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