R
Storm Water Disposal:
4
Requirements:
4.1
General:
4.1.1
Deemed to satisfy is part R of NBR where means of control and disposal of storm water is in
accordance with Part R-4.2: provided that the storm water system in:
Interconnected complexes is according to 4.2.2
Townships underlain with dolomite with class designation D2 and D3 (see SANS 1936-1) must comply
with SANS 1936-3
4.1.1.a
4.1.1.b
4.2
Storm water control and disposal:
4.2.1
4.2.1.1
General
Storm water from roof, paving, immediate vicinity of building shall not damage
building interior, structure, structural elements or accumulate in manner that
inconveniences occupant.
Storm water disposal arrangements shall:
not result in undercutting of foundations
drain away from building by gravity, not accumulate near external walls
provide drainage for sites that are water logged, or occasionally water logged
being capable of being readily cleaned and maintained
NOTE: Storm water disposal arrangements include:
roof valleys, gutters, downpipes, other means of dispersing water off roof.
any surface storm water drains, channels, below-ground storm water drains
necessary to drain water
Valleys and gutters to be sized according to 4.3 or by rational design by competent
person.
NOTE: The following provide guidance on design of valleys and gutters:
The South African Steel Construction Handbook
EN 12056-3
4.2.1.2
4.2.1.2a
4.2.1.2b
4.2.1.2c
4.2.1.2d
4.2.1.2a
4.2.1.2b
4.2.1.3
4.2.1.3.a
4.2.1.3.b
Design: Spec: Site:
Design: Spec: Site:
4.2.1.4
4.2.1.5
Where required by local authority, storm water should discharge into municipal storm
water system within road reserve or servitude.
Where permitted by local authority, storm water may discharge into street under
conditions set by local authority.
4.2.2
4.2.2.1
Storm water disposal arrangements in interconnected complexes:
Storm water disposal arrangements in interconnected complexes shall comply with
4.2.1 and signed by competent person (Civil Engineer) to comply with the following:
4.2.2.1a
Storm water should be controlled, routed and discharged according to 4.2.2.2 to
4.2.2.8 without eroding land, contaminating water resources, or compromising
environmentally sensitive areas.
4.2.2.1b
Storm water structures shall perform within parameters of:
4.2.2.1b1 design hydraulic load
4.2.2.1b2 maintenance (self-cleaning velocities as well)
4.2.2.2
Major & Minor storm water systems shall be design for both 50 & 2 years design flood
recurrence intervals.
4.2.2.3
Terraces created for dwellings shall be capable of being drained by gravity
4.2.2.4
Storm water shall not be concentrated so as to cause erosion
4.2.2.5
Velocity of storm water in road-edge channels associated with minor storm shall not
exceed:
4.2.2.5a
3m/s in lined channels
4.2.2.5b
1,5m/s in unlined channels comprising coarse non-colloidal gravel
4.2.2.5c
1,1m/s in other unlined channels
4.2.2.6
Channels in soils susceptible to erosion shall be lined
4.2.2.7
The min. dia. of pipes in servitudes shall not be less than 300mm, unless otherwise
directed by local authority
4.2.2.8
Storm water structures shall be designed to have sufficient velocity to facilitate
maintenance, with access to pipes for cleaning to be provided at least every 40m, and
pipe gradients according to Table 1. (see CSIR’s guidelines for human settlement planning and design)
4.3
Gutters and downpipes:
Design: Spec: Site:
4.3.1
4.3.2
Roof, eaves and valley gutters to have cross-sectional area of not less than that in
Table 2.
Internal cross-sectional area of downpipes shall be min. 4400mm2 and not less than
100mm2/m2 of roof plan area served by such downpipe.