Thames and Sea Level Rise

Transcription

1 Thames and Sea Level Rise Risks For Thames - Groundwater and Coastal Flooding Comparison with Dunedin Latest Government Guidance Thames Has High Risk Compared With Other Cities and Towns We need to Plan for this slowly unfolding red zone Presentation to Thames Community Board 6 November 2017 Denis Tegg

2 Temperatures and Sea Are Rising Faster

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4 Tararu Tidal Gauge Sea Level Rise 10mm per year?

5 Sea Level Rise Projections Ministry for Environment 2017 US Climate Science Report November 2017 Based on IPCC 2014 Based on Latest Research to 2017

6 November 2017 Very Latest Projections Relative to 2000, globally the sea is very likely to rise:- 0.1m 0.2m by 2030 (*locked in) 0.2m 0.4m by 2050 (*locked in) m by 2100 up to 2.5m is plausible * future pathways have little effect in first half of this century

7 Dunedin s Groundwater Issues Otago Regional Council

8 Dunedin Investigates Overseas Groundwater Solutions

9 South Dunedin No direct sea flooding - just risk of rising groundwater:- 0.3 m of sea level rise requires localised pumping anticipated m of sea level rise requires interception of all sea water at coastal margins Beca Report 2014

10 South Dunedin Groundwater Ponding Areas anticipated by 2040

11 Sea Level Rise Poses Two Threats to Thames Rising Groundwater Initial threat is rising groundwater level on Thames foreshore, forced up by rising sea level/storm surges Coastal Flooding Rising sea levels will lead to more frequent extreme storm surge events and eventually to permanent flooding (inundation)

12 Thames - Present Day King Tides Through storm water drains From sea On the foreshore groundwater is 0.3m 1.2m above sea level and rises and falls with the tide * *Richmond Villas site

13 Waikato Regional Council Inundation Tool WRC Inundation Tool maps to here plus sea level rise

14 Thames with present day storm tide and 0.2m of sea level rise (2030?) may have more extensive groundwater affected areas than Dunedin with 0.3m of sea level rise (2040?)

15 Thames with present day maximum tide and 0.5m of sea level rise but no storm surge or wave effects

16 Thames with mid range storm tide and 0.5m of sea level rise but no wave effects

17 Thames with mid range storm tide and 1.0m of sea level rise but no wave effects

18 Extreme Sea Floods More Frequent Present Day 1-in-100 Year Extreme Storm Tides Become a 6-Monthly Event With a 50cm Rise Daily Event With 1m of Sea Level Rise

19 River Flats or Reclaimed Over Marine Sediment

20 Thames Foreshore Is Sinking Adds to Risk of Rising Seas Location Rate of Settlement Sea Level Rise is Added to Subsidence Rate to Calculate Local Sea Level Rise 1991 KRTA Report Richmond St 1995 Frank Millington Burke St Ferguson Drive mm since mm 16mm a year 1997 TCDC Memo NW Corner Moanataiari subdivision 2017 Richmond Apartment block site Slumped 1m since mm a year 5mm + 5mm =10mm a year - 0.5m in 50 years 10mm + 10mm = 20mm a year - 1.0m in 50 years

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22 2017 MfE Guidance to Councils Update on Climate Change Updated to include latest science on sea level rise Adaptation work program 285 pages - substantial new content on: Risk assessment Community engagement Adaptive planning Outlines a ten-step decision-making process that councils and communities can follow when planning for the effects of climate change on coastal hazards. The Guidance should be adopted as Council s Strategy on Coastal Hazards Draft copy available

23 Guidelines provide minimum transitional values provided to assist councils in the short-term. Major new developments or intensification of existing development (Category A) need to consider a high sea-level rise value of 1.9 metres and timeframe to 2150

24 How will this effect new major development west of red line? 1.9 m Category A :- < 1.9m line greenfield development change in land use intensification major new infrastructure

25 How does Thames compare with other cities and towns? Figures are for buildings only Do not include the cost of infrastructure - roads, bridges, or below ground assets such as storm water and wastewater. The building replacement costs are based on NZ$2011 figures

26 Building use count for Thames for the m zone Building count comparison for the m zone Residential 176 Commercial 1 Industrial 16 Critical 0 Community 17 Other 107 Thames 302 Tauranga 141 Nelson 125 Lower Hutt 102 Whakatane 495 Total 302

27 Count of buildings in the 0m 1.5m above sea level zone Thames is ranked the 8th at risk urban area in New Zealand. Whitianga is 14 th

28 Building use count for Thames for the m zone Building use count for Thames Coromandel District for the m zone Residential 863 Commercial 108 Industrial 102 Critical 7 Community 17 Other 499 Residential 2,314 Commercial 142 Industrial 278 Critical 10 Community 35 Other 1180 Total 1,596 Total 3,959

29 On a buildings per capita per town basis Napier and Thames are the most at risk urban areas in New Zealand. Whitianga is third.

30 Building replacement cost in the 0m 0.5m above sea level zone Thames is ranked the 8th at risk urban area in New Zealand. (NZ $2011)

31 Building replacement cost in the 0m 1.5m above sea level zone Thames is ranked the 13 th at risk urban area in New Zealand. Whitianga is 16 th

32 Replacement Cost $2011 of Buildings for Thames 0m to 0.5m $43,868, m to 1.0m $192,707, m to 1.5m $148,777,225 0m to 1.5m $384,752,964 0m to 3.0m $557,533,142 Figures do not include:- land value water and waste systems power, telecom, fibre sewage treatment plant roads airfield = $0.4 billion = $0.6 billion

33 Building Replacement Comparison - Towns/Cities - 0m to 1.5m Thames $384,752,964 Tauranga $809,435,870 Whangarei $390,618,072 Motueka $398,119,992 Nelson $713,845,001 Whakatane $519,744,902 Central Auckland Zone $891,027,951 Building Replacement Comparison - Local Authorities - 0m to 1.5m Thames-Coromandel $857,036,722 Tauranga City $778,073,512 Far North District $121,596,189 Whangarei District $570,712,749 Nelson City $643,255,071 Dunedin City $1,529,905,764 Auckland $2,184,788,932

34 77% of lowest lying roads in NZ are in Waikato and most of these in Hauraki/Coromandel In the lowest-lying m elevation band, 720 km of road network (mostly local roads) was identified nationally. Approximately 77% (561 km) of these roads are located in the Waikato... emphasising that most roads in this region hug the coast

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36 Road Length Comparison - Towns/Cities - 0m to 1.5m Road Length Comparison - Local Authorities - 0m to 1.5m Thames 18.7 km Thames-Coromandel km Dunedin 72 km Tauranga City 30.0 km Whangarei 18.8 km Hauraki km Christchurch 22.6 km Whangarei District 37.2 km Nelson Wellington Central Auckland 40.6 km 12.5 km 15.2 km Whakatane Dunedin City Tasman 89.3 km 116 km km

37 Nationwide

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39 Dunedin Thames we have a problem Thames has a very strong case for funding and advice from Central Government and LGNZ Thames has a Groundwater Problem PLUS a Direct Sea Flooding Problem Our community, TCDC and our MP need to combine forces to ensure Thames gets the help it needs

40 New Government Has Promised Help Climate Change will be a top priority Commence an urban redevelopment and adaptation programme, with a focus on urban communities subject to sea level rise working with those communities, their local authorities and other stakeholders. * * Labour Party Manifesto 2017

41 Leadership Actions for Community Board ask Council to sign LGNZ Climate Change Declaration make Board submission on Coastal Management Strategy adopt MfE Guidance, and ask Council to provide funds in LTP for :- urgent hazard mapping and risk assessment public engagement include sea flood hazards in District Plan Climate Change Adaption Plan support Council lobbying for Government help

42 Leadership Actions for District Council sign LGNZ Climate Change Declaration adopt 2017 MfE Guidance as Coastal Hazard Strategy ensure LTP has funds for:- urgent mapping and expert risk assessment engagement with community review District Plan/LIMs adaption planning including an Adaption Plan and Opportunities Plan lobby new Government for funds/expertise

43 Slowly Unfolding Red Zone No Need to Panic Denial/Inaction leads to But it s Reckless to Delay Careful Planning and Adaption