Stormwater and Drainage

Transcription

1 Stormwater and Drainage Overview The Stormwater and Drainage activity includes the various functions of the land drainage schemes and resultant flood protection. Our Aim We aim to prevent or minimise the adverse effects of surface flooding and stormwater discharge. Why is the Council Involved? Both our Council and the Canterbury Regional Council (Environment Canterbury) have joint responsibilities regarding the management of stormwater drainage, flood control and stormwater quality in our district. We provide drainage services where communities have requested our involvement or where it is efficient that we need to be involved. This includes managing drainage in localised areas to protect them from the negative effects of surface flooding. Stormwater is rainfall that has run off hard surfaces such as roofs, roads, land and car parks. We monitor and audit stormwater systems to ultimately minimise any flooding damage to property and/or the environment. Community Outcomes The Stormwater and Drainage activity described in this section primarily contributes to two of our community outcomes:- 1. A desirable and safe place to live: - We have attractive, well designed townships - Communities have access to adequate health and emergency services, and systems and resources are available to meet civil defence emergencies - Risks to public health are identified and appropriately managed 2. A place with essential infrastructure: - We have a strong emphasis on service delivery across all infrastructure, including roading, water (for drinking and development), waste water, stormwater and solid waste Council Owned Assets We do not have many assets in relation to stormwater and drainage, but do own and maintain the following land drainage schemes and physical assets: - Ashworths drains - Leithfield Outfall drain - Newcombes Road drains - Dock Creek - Dry Gully - Goldminer s Gully - Jed River drains - Pipes, sumps, inlets and outlets (Amberley, Hanmer Springs, Hawarden, Waikari, Cheviot, Motunau Beach

2 Current Situation The four land drainage schemes (Ashworths, Leithfield Beach, Newcombes and Jed River) were originally set up by the former North Canterbury Catchment Board. We have only a very small quantity of stormwater pipes in our townships, as most stormwater is disposed of to kerb and channelling, then via open drains. Significantly, there are approximately 100 metres of stormwater pipe in Hanmer Springs and approximately 560 metres of stormwater pipe in Amberley. Much of the District s stormwater disposal systems are maintained by private, individual property owners, such as on-site soakage disposal, open drains or creeks, piped networks outfalls, silt traps, and detention structures. After two significant rainfall events, especially in and around Amberley area in 2008, we reviewed the adequacy of our current stormwater systems. The recommendations were to carry out some major capital works to reduce the impact of surface flooding on both Amberley Township and Amberley Beach. The works were to include diversion drains to behead the surface flows from north of Amberley, to discharge them to natural waterways outside the urban area, and some realignment of drains discharging to the lagoons north and south of Amberley Beach. Because of the time taken to obtain approved resource consents, exacerbated by the Canterbury earthquakes in 2010 and 2011 and appeals lodged against the consents granted after lengthy hearings, only two major physical works have been completed to date. These were the flood diversion works from Dock Creek along Lawcocks Road, and a piped outfall of the Leithfileld Outfall Drain into the sea. However, with consents now finalised (in early 2015) for three more significant capital projects, work is expected to be completed for flood diversion works in the Amberley swamp area (including for an outlet culvert under Stanton Rd) and from Dry Gully across to Mimimoto lagoon, with majority completion before the end of the 2015/16 financial year and the balance of the works staged across the following two years. Plans for the Future A flood flow diversion from the Eastern Drain across to the Amberely North lagoon is proposed for the 2018/19 year to complete the flood mitigation works covered by the 15 consents mentioned above. All funding is from a special rate struck over the entire Amberley Ward. AECOM Consultants will finalise an application in 2015 for a global consent for management of stormwater from future residential developments in Hanmer Springs. In anticipation of the stormwater management plan successful approval, we have identified stormwater improvement works to be undertaken in 2015/2016 costing $148,000 and a further $43,032 of works to be done in 2016/2017. As with the Amberley Ward, this will be funded by a separate rate over all properties in the Hanmer Springs Ward. Through communicating with the communities of Motunau Beach, Hawarden and Waikari, we are gaining a better understanding of historic flooding areas, which will help us deal to these issues before they repeat themselves again. $126,645 will be spent on improvement works across these three townships over the next two years to resolve the community s initial concerns. We will continue to develop a district-wide stormwater catchment and management plan. This includes undertaking a range of tasks required to ensure that we fully understand the flow of all our district-wide drainage systems from land to sea, and that we subsequently have effective stormwater systems and programmes in place with appropriate maintenance regimes. Once we fully understand the stormwater run-off in the upper catchment reaches prior to each urban area, we will then aim to progressively move towards managing all of our urban stormwater responsibilities in a more holistic, integrated and life cycle way. This will include the potential to do

3 remedial works to the stormwater flow paths prior to urban boundaries and thus alleviate the historic problems encountered to date. We are aware that there has been a subtle change to rainfall events, with more intense rainfall experienced in the catchments than noted before, putting more stress upon the capacity of our current stormwater infrastructure than historically designed for. The district-wide catchment and management plans will go a long way to better understanding these potential pinch-points and resultant flood risk areas. Major Projects Planned Project Hanmer Springs improvement works Amberley and Leithfield improvement works Cheviot, Hawarden, Motunau Beach, Waikari Year Planned 2015/ / / $148,000 $172,000 $87,193 $52,630 $167,155* 101,000 District wide assets $95,700 $98,169 $100,734 $794,540* *Total cost for the 7 year period from 2018 till 2024/25 Funding Activity Operational Costs Capital Costs Stormwater & Drainage 100% Targeted Rate based on the area benefiting. Significant Council capital expenditure is funded by a loan as per the Council s Internal Financing Policy. If loans are not raised, then it will be from targeted rates. If any of the Capital Expenditure caters for future growth of the scheme, then that portion of the expenditure that relates to growth may be funded from future users via Development Contributions and Financial Contributions. Maintenance and Operating We plan to continue to maintain our small drainage systems, as well as other targeted rate drainage channels currently in place. Annual maintenance has been limited to occasional on-going drain clearing. Contractors will be engaged to carry out regular works to maintain the system in a functionary condition, as and when needed. Assumptions and Risks We are assuming that land-owners will give their support and approval for any flood mitigation construction works that we may undertake.

4 Significant Negative Effects There is potential for significant negative impacts on the environment and private property due to occasional flooding, but this is offset by ensuring that the disposal of stormwater is done in a manner that minimises contaminants and eases peak flows. Drainage systems may not always cope with changes in volumes of rainfall, with subsequent negative effects of flooding on roads and properties. This may cause additional social problems in living quality, public health and access to and safety of transport systems. However, such problems are mitigated to some extent by the provision of stormwater systems to cope with flooding. Drain clearances can have adverse effects on biodiversity, ecosystems and water quality, but such clearances are obviously necessary, and the negative effects that they have are short lived, with no implications for sustainability. All negative environmental impacts are assessed for mitigation, elimination or isolation, with management plans and processes in place to manage these effectively through the maintenance period and afterwards. Emergency Management In an emergency, particularly a civil defence emergency, we will continue to deliver services as long as it is safe and practical to continue to do so. Stormwater and drainage will receive priority in the event of emergencies involving flooding. Financial Summary A financial summary for this activity is shown in a separate document.

5 Stormwater and Drainage Performance Measures Community Outcomes 1. A desirable and safe place to live 2. A place with essential infrastructure Key Performance Area System Adequacy Performance Measure Description Measure the number of flooding events that occurs through a financial year, with a flooding event being an overflow from a service provider maintained stormwater system that enters a habitable floor. Measure the number of habitable floors that are affected through each flood event, per 1000 properties paying targeted rates for the maintenance of this stormwater system. Performance Target Issue Reported flooding events Habitable floors affected per flooding event Performance Target Outcome Measurement Method Flooding events will be recorded separately, where 1 or more habitable floors are affected (observed or reported to the service provider). Known and reported flooded habitable floors will be captured on the CSR system for end of year reporting. Current Performance New measure. NCS CSR will have to be updated to record and measure this kpi for all habitable floors flooded in all target rated areas. No habitable floor areas on record for flooding in 2013/2014, nor 2014/2015 to date. New measure. No record for current performance (as above). New target stormwater rate proposed in draft LTP for Hawarden, Waikari, Motunau Beach and Cheviot. Once this has been formally adopted, then the total number of maintained properties can be calculated including for the current

6 target areas of Amberley and Hanmer Springs. Discharge compliance Measurement of service provider's compliance with the numerous resource consent conditions for discharge from the various stormwater systems. Measurement of service provider's compliance with the numerous resource consent conditions for discharge from the various stormwater systems. Measurement of service provider's compliance with the numerous resource consent conditions for discharge from the various stormwater systems. Abatement Notices Infringement Notices Enforcement Notices As logged from consent monitoring reports from ECan. An abatement notice is a written direction requiring certain action to be taken or ceased issued under section 17 of the Resource Management Act. As logged from consent monitoring reports from ECan. Infringement notices and fines can be issued for failure to comply with an abatement notice. As logged from consent monitoring reports from ECan. An Enforcement Notice is an order made by the Environment Court that may require certain actions to be taken or ceased, or money to be paid, within a specified time. No recorded abatement notices issued by ECan for HDC through 2013/2014, nor No recorded infringement notices issued by ECan for HDC through 2013/2014, nor No recorded enforcement notices issued by ECan for HDC through 2013/2014, nor

7 Measurement of service provider's compliance with the numerous resource consent conditions for discharge from the various stormwater systems. Convictions The measure will be a tally of all successful prosecutions against the Council for resource consent noncompliance. Environment Canterbury undertakes prosecutions where there has been a significant contravention of the Resource Management Act. No recorded convictions against HDC from prosecutions (successful or unsuccessful) by ECan through 2013/2014, nor Response Time Measured median response time period taken by service provider official to attend to a floor-flood event complaint from a customer. Median call-out attendance time < 2 hours The CSR system will be used to measure the time from when the customer s call was first received and when a service provider attended a to a floorflood event complaint. The median time taken will be used as the end of year result. New measure. NCS CSR will have to be updated to record and measure this kpi for median response call-out time period for officer to respond to a floor-flood complaint from a customer. No floor-flooding events recorded for 2013/2014, not

8 Customer Satisfaction Measured as the total number of complaints received for poor performance of all service provider maintained stormwater systems (over the financial year), per 1000 properties paying targeted rates for maintenance of all service provider maintained stormwater systems across the district. Complaints received The CSR system will be used to tally all poor performance complaints about stormwater systems logged in the CSR system annually. 13 poor performance complaints logged in our NCS CSR system to date for stormwater in target rated areas in 2014/2015, covering 1407 properties paying targeted rates for maintenance; thus giving a ratio of 9.23 complaints per 1000 paying properties to date. Measurement Period: All of the performance measures will be measured annually and reported in the Council s Annual Report each October.