Tag: management

Currently it is a condition of township establishment, set by the Johannesburg Roads Agency (JRA) that the storm water discharge from any new township development is limited to a 1:5 year recurrence interval per development and that attenuation facilities should be provided to attenuate storms of up to 1:25 year recurrence interval post development.

 

Storm water will be collected and transported by means of an underground pipe system and discharged in the attenuation dam s/ ponds. The proposed storm water system is divided into infrastructure required to drain the minor storm water flood (1:5 year recurrence period) and the major storm water flood (1:25 year recurrence period).

 

The minor storm water system consist primarily of lateral kerb inlets, junction boxes, field inlets, overflow channels and pipe culverts. Pipe culverts vary in size from 450mm up to 1200mm.

 

The major storm water system primarily consists of pipe culverts, rectangular channels (covered and open), trapezoidal channels and portal culverts. The most common section, the rectangular channel, varies in width from 1.8m to 4.0m wide. These channels are placed in municipal stands or within road reserves. Channels in municipal stands are usually open, but are fenced off with 1.8m high “flat-wrap” barbed wire fencing. Rectangular channels in the road reserves are always covered.

 

As most of the storm water will be directed into pipes, less water will reach the wetland. To solve this problem it was suggested that the storm water be directed into the wetland and artificial dam. The storm water cannot be discharged directly into the wetland and to prevent this from taking place the following measures will be implemented:

• Water will be collected in attenuation
• The attenuation ponds will be built in such a way that the water will not be released directly into the wetland
• The attenuation pond will allow for over flow and the slow release of water into a swale area before reaching the
• The attenuation pond and swale area will be located within the first 10m of the proposed buffer zone.