2.7.2 Levels of Service – Flooding The standard of building flooding protection specified in the Building Act 2004 is a well- recognised standard and is likely to remain for new housing and a goal for existing property. The Act requires new houses and habitable buildings to be designed with the floor level that will not be flooded by a storm event with a 50 year ARI. It also requires that a 10 year ARI event not to cause nuisance to other properties. This applies only to the building of new houses, but there is an implicit indication that they are appropriate standards for older properties too. The safe floor level requirement in a 50 year ARI event can be achieved by several methods: • setting of minimum floor levels, and/or • a pipe network to take some/all stormwater, and/or • surface storage/ponding and/or • providing a secondary overflow path. Often a pipe network is constructed to deal with a 5 year ARI storm event (Q), but c5 an be less or sometimes more. Surface methods of secondary overflow or acceptable ponding storage are then required to cope with storm runoff in excess of a 5 year ARI event and up to a 50 year ARI event will enable house floor levels not to be flooded. To prevent nuisance to other property in a 10 year ARI event requires such ponding storage to be limited to the road. The challenge will be to ensure that surface drainage around houses built prior to 2004 can achieve a similar performance and that the standard can be maintained in the face of further urban growth and climate change. There is a trend towards increasing customer expectation and lower tolerance levels. Significant work has been undertaken both locally and nationally to understand the components of stormwater management through soakage, detention and conveyance and to maximise the effectiveness of each. Once a drainage area is thoroughly understood, the infrastructure is installed and the customers’ expectations managed. To this end an important report1 has been drafted based on the Blenheim system. The report examines the attributes of a stormwater system, the factors affecting surface drainage, previous and current design criteria and a review of best practice from around the country. The report has yet to be finalised but provides an excellent platform for future stormwater design. 2.7.3 Levels of Service – Service Response Times Customers will continue to require a speedy response to service requests. The current performance standards appear to be adequate. The existing model using directly employed service operatives supplemented at short notice by local contractors available to respond to emergency needs appears to be working satisfactorily. The system is tested under duress during storm events. The introduction of the ‘Floodwatch’ programme to the MDC web-site has been very popular. The site is able to give the latest information on the quantity of rainfall recorded at the MDC weather stations and the levels of the major rivers in the district. The information is of primary benefit to the rural population but is also widely accessed by urban dwellers during storms. There are no immediate plans to develop the site further. The Blenheim Stormwater Strategy provides an excellent framework for analysing needs and for planning and implementing future improvements. 1 Procedures for Reviewing Blenheim Stormwater Capacity and Providing New Areas. MDC Aug 2014 Page 24