Urban Stormwater Stream Channels

The management and operation of the stormwater carrying urban stream channels and pumping stations is very similar to that of rural land drainage. It involves 25 km of minor watercourses and 10 pumping stations. Several of the watercourses and pumping stations drain a mixture of urban and rural land.

Differences are that a higher level of service is required for flood management. The channel network should be able to cope with a 1 in 50 year return period flood event so as to meet the standards that the Building Act imposes on building floor levels. Pumping stations are required when local stormwater runoff coincides with high water levels in the receiving rivers.

The hydraulic requirements of these channels are determined by the stormwater pipe network feeding into them. This stormwater pipe network is dealt with by another section of Council under a different asset management plan. The design of these two components is being integrated as part of the stormwater strategy.

The manner in which Council deals with its urban stormwater is under a continued evolving review as part of an interdepartmental Council stormwater strategy. This includes design guidance for determining the likely runoff quantities, pipe network capacity, pumping stations capacity, receiving watercourse capacity, water quality aspects and required resource consents.

Removal of aquatic weed from urban watercourses is also for aesthetic and health reasons as well as hydraulic efficiency.