This document defines key terms related to storm drainage and subsurface drainage systems. It includes definitions for various components of drainage systems like catch basins, downspouts, detention facilities, impervious surfaces, and more. It also provides guidance on sizing rainwater piping based on the area being drained and tables specifying the maximum roof area for different downspout diameters and slopes.

1. E. Storm and Sub-surface
Drainage System
Planning and design of ground and sub-surface drains,
downspouts, floor and roof

2. STORM DRAINAGE – conveys storm water to a satisfactory
terminal
Sec. 904. Storm Drainage System NBCP
(a) Rainwater drainage shall not discharge to the sanitary sewer
system.
(b) Adequate provision shall be made to drain low areas in
buildings and their premises.

3. Definition of Terms
Building Storm Drain - A building storm drain is that part of the piping of
a storm water drainage system that begins at the connection to the
building drain at a point five (5) feet outside the established line of the
building or structure, and that conveys storm water to the approved
point of disposal.

4. Definition of Terms
Catch basin - A structure that captures surface runoff and discharges it
into an underground storm drain pipe system.

5. Definition of Terms
Creek - Any and all surface water routes generally consisting of a
channel having a bed, banks, and/or sides in which surface waters
flow from the drainage of higher to lower ground, whether perennial or
intermittent, but excluding flows that do not persist for more than
twenty-four (24) hours after cessation of a one-half (½) inch rainfall
within a 24 hour period, October through March.

6. Definition of Terms
Curb and Gutter - A concrete surface facility that directs runoff into catch
basins of curb inlets.

7. Definition of Terms
Design Storm - The high water level for the frequency storm that a
particular system or system component must be designed to carry. To
determine which frequency storm is to be used in a particular situation

8. Definition of Terms
Detention Facilities - The holding of runoff for a short period of time and
then releasing it at a controlled rate into the area storm drain system.

9. Definition of Terms
Drainage Facilities - Pipes ditches, detention basins, creeks, culvert
bridges, etc., used singularly or in combination with each other for the
purpose of conveying or storing runoff.

10. Definition of Terms
Easement - An area along the line of any public storm drain (or other
utility line) that is located outside of an existing dedicated storm drain
easement, road easements or right-of-way, and that allows practical
access to the facility for maintenance and other necessary work
related to the facility.

11. Definition of Terms
Floodplain - Any area of land subject to inundation by water from any
source; particularly any area designated as being within the floodway
or one-hundred year flood boundary in the most recent available data
surface elevation more than one foot.

12. Definition of Terms
French Drain - A covered trench that has been excavated and filled with
washed gravel around a perforated delivery pipe installed to receive
storm water. A French Drain is only effective where the soil where it is
installed is porous enough to permit
Leach Line - Same as “French Drain”

13. Definition of Terms
Grade - Grade or Slope is the vertical change in elevation divided by the
horizontal distance between the same two points. Slope is usually
expressed in feet per foot (rise over run). Grade is often expressed as
a percentage (rise divided by run X 100).

14. Definition of Terms
Impervious Surface Area - Areas of land that do not absorb or resist
absorption of rainwater or runoff. Under normal conditions, soil and
gravel areas on undeveloped land absorb a significant amount of
surface water, mitigating runoff effects on downhill properties.
Impervious surface areas created by development include but are not
limited to roofs, concrete and asphalt sidewalks, patios, driveways,
parking lots and compacted, gravelled, oiled, macadam and other
prepared surfaces.

15. Definition of Terms
Invert - The bottom or flow line of a channel, pipe, or manhole.

16. Definition of Terms
Natural Location - The location of those channels, swales and other
water conveyance systems existing prior to human development and
as indicated on the earliest available documented topographic
contours or other reliable information such as maps or photographs.

17. Definition of Terms
On-Site Detention - Storage of excess runoff on a development site prior
to its entry into the public storm drain system and gradual release of
the stored runoff after the peak of the runoff event has passed.

18. Definition of Terms
Peak Discharge - The maximum water runoff rate (cfs) determined for
the design storm.
Plans - Construction plans, including system site plans, storm drain
plans and profiles, cross sections, detailed drawings, etc., or
reproduction thereof, showing the location, character, dimensions,
and details for the work proposed, and approved or to be approved by
the Director and/or City Engineer. When approved such plans
become a supplement to these standards.

19. Definition of Terms
Private Storm Drain - A storm drain that is located on private property,
that serves more than one structure on a premises and/or parking lot
catch basins, and that is not maintained by the City

20. Definition of Terms
Sedimentation - The deposition of soil, other mineral materials and
debris carried by storm water runoff and deposited at a lower
elevation as a result of slack water or the withdrawal of flood waters.
Silt - Fine textured soil particles including clay, colloidal materials and
sand, as differentiated from coarse sand and gravel.
Siltation - 1) The deposition of waterborne silt and 2) the smoothing or
cementing effect of the deposition of silt over sand and gravel beds
when the transporting water evaporates.

21. Sizing Rain Water Piping
Some places permit this water to run off into the septic tank or
public or private sewer; others to be drained into a dry well. It is
recommended that rain water be kept separate from sewage and
a separate pipe be used to connect the drained area with the
disposal area. The drainage piping can be a smaller, more
economical size; the danger of flooding the sewage system
during cloudburst is eliminated.
Storm-water piping size is determined by the area drained in
horizontal projection (the flat area in square feet on which rain
may fall).

22. Storm Water Nomenclature
 1.Sandwich Roof Panel
 2. Screw Bolt & Roof Cap
 3. End Cap
 4. Gutter Hanger
 5. Water Gutter
 6. Roof Drain
 7. Water Box (PVC)
 8. Gutter Supporter
 9. Down Spout (PVC)
 10. Sandwich Wall Panel
 11. Screw Bolt & Wall Cap
 12. Purlin
 13. Girth
 14. Gutter Support Bolt

23. Storm Water, Area Drain/Catch Basins/Catchpit, Roof Terminals

24. (FLASHING - a piece of sheet metal fitted under another piece of flat
metal or wood over which is expected to run)

25. CATCH BASIN - liquids are retained to deposit settleable material
DOWNSPOUT - the vertical portion
HOUSE STORM SEWER - is the pipeline from the building to the
public storm sewer system
(FLASHING - a piece of sheet metal fitted under another piece of flat
metal or wood over which is expected to run)
LEADER (CONDUCTOR) - from building gutter to
downspout/conductor
STORM WATER – rainfall/precipitation

26. Catch Basin

27. Downspouts

28. SIZE OF DOWNSPOUT
DIAMETER OF
PIPE (mm)
DIAMETER OF
PIPE (in)
MAX.
OBTAINED
ROOF AREA
(sq.m)
2% SLOPE
MAX.
OBTAINED
ROOF AREA
(sq.m)
3% SLOPE
MAX.
OBTAINED
ROOF AREA
(sq.m)
4% SLOPE
75 3 114 142 170
100 4 242 315 388
125 5 438 566 694
150 6 700 903 1105
1888 2313
200 4 1463 3309 4055
250 10 2563 5290 6480
300 12 4100
350 14 5576 7203 8830