• 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”

Thames and Sea Level Rise

Presentation to Thames Community Board 6 November 2017

Denis Tegg – www.teggtalk.wordpress.com

Temperatures and Sea Are Rising Faster

Tararu Tidal Gauge 2011 – 2017 Sea Level Rise 10mm per year?

Sea Level Rise Projections

Ministry for Environment 2017 US Climate Science ReportNovember 2017

Based on IPCC 2014 Based on Latest Research to 2017

Relative to 2000, globally the sea isvery likely to rise:-▪ 0.1m – 0.2m by 2030 (*locked in)▪ 0.2m – 0.4m by 2050 (*locked in)▪ 0.3 – 1.3m by 2100 – up to 2.5m is

“plausible”

* “future pathways have little effect in first half of this century”

November 2017Very Latest Projections

Dunedin’s Groundwater Issues – Otago Regional Council

Dunedin Investigates Overseas Groundwater Solutions

No direct sea flooding - just risk of rising groundwater:-• 0.3 m of sea level rise requires localised pumping –

anticipated 2040• 0.8 m of sea level rise requires interception of all sea

water at coastal margins

South Dunedin

Beca Report 2014

South Dunedin GroundwaterPonding Areasanticipated by 2040

Sea Level Rise Poses Two Threats to Thames

Rising GroundwaterInitial threat is rising groundwater level on Thames’ foreshore, forced up by rising sea level/storm surges

Coastal FloodingRising sea levels will lead to more frequent extreme storm surge events and eventually to permanent flooding (inundation)

Thames - Present Day King Tides

Through storm water drains From sea

On the foreshore groundwater is 0.3m – 1.2m above sea leveland rises and falls with the tide * *Richmond Villas site

WRC Inundation Tool maps to hereplus sea level rise

Waikato Regional Council Inundation Toolhttp://coastalinundation.waikatoregion.govt.nz/

Thames with present daystorm tide and 0.2m of

sea level rise (2030?) mayhave more extensivegroundwater affected areas than Dunedinwith 0.3m of sea level rise – (2040 ?)

http://coastalinundation.waikatoregion.govt.nz/

Thames with present day maximum tide and 0.5mof sea level rise but no storm surgeor wave effects

http://coastalinundation.waikatoregion.govt.nz/

Thames with mid rangestorm tide

and 0.5m ofsea level rise

but no wave effects

http://coastalinundation.waikatoregion.govt.nz/

Thames with mid rangestorm tide and 1.0m of sea level rise but no wave effects

http://coastalinundation.waikatoregion.govt.nz/

Present Day1-in-100 YearExtreme Storm TidesBecome a 6-Monthly Event With a 50cm Rise

Daily Event With 1m of Sea Level Rise

Extreme Sea Floods More Frequent

River Flats or Reclaimed Over Marine Sediment

Thames Foreshore Is SinkingAdds to Risk of Rising Seas

Location Rate of Settlement

1991 KRTA Report Richmond St

300-500mm since 1977

1995 Frank Millington Burke St

500mm

Ferguson Drive 16mm a year

1997 TCDC Memo NW Corner Moanataiari subdivision

Slumped 1m since 1968

2017 Richmond Apartment block site

13mm a year

Sea Level Rise is Added to Subsidence Rate to CalculateLocal Sea Level Rise

5mm + 5mm =10mm a year - 0.5m in 50 years 10mm + 10mm = 20mm a year - 1.0m in 50 years

Update on Climate Change Adaptation work program

• Updated to include latest science on sea level

rise

• 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.

2017 MfE Guidance to Councils

The Guidance should be adopted as Council’s Strategy on Coastal Hazards

Draft copy available –https://www.greens.org.nz/sites/default/files/CH_Guide_Draft4-webversion.pdf

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

1.9 m Category A :-

➢ greenfield development➢ change in land use➢ intensification➢ major new infrastructure

How will this effect new major developmentwest of red line?

< 1.9m line

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 replacementcosts are based on NZ$2011 figures

Building use count for Thamesfor the 0 – 0.5 m zone

Building count comparisonfor the 0 – 0.5 m zone

Residential 176 Commercial 1

Industrial 16 Critical 0

Community 17 Other 107

Thames 302Tauranga 141

Nelson 125 Lower Hutt 102Whakatane 495

Total 302

Count of buildings in the 0m – 1.5m above sea level zoneThames is ranked the 8th at riskurban area in New Zealand.

Whitianga is 14th

Building use count for Thamesfor the 0 – 1.5 m zone

Building use count for Thames Coromandel District

for the 0 – 1.5 m zone

Residential 863 Commercial 108

Industrial 102 Critical 7

Community 17 Other 499

Residential 2,314Commercial 142

Industrial 278 Critical 10

Community 35Other 1180

Total 1,596 Total 3,959

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

Whitianga is third.

Building replacementcost in the0m – 0.5m above sea level zoneThames is rankedthe 8th at riskurban area in New Zealand.

(NZ $2011)

Building replacementcost in the 0m – 1.5m above sea level zoneThames is rankedthe 13th at riskurban area in New Zealand.

Whitianga is 16th

Replacement Cost $2011of Buildings for Thames

0m to 0.5m $43,868,520

0.5m to 1.0m $192,707,219

1.0m 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

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

Building Replacement Comparison -Towns/Cities - 0m to 1.5m

Thames $384,752,964Tauranga $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

77% of lowest lying roads in NZ are in Waikato and most of these in Hauraki/Coromandel

“In the lowest-lying 0–0.25 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”

Road Length Comparison -Local Authorities - 0m to 1.5m

Thames-Coromandel 102.6 km

Tauranga City 30.0 km

Hauraki 685.6 km

Whangarei District 37.2 km

Whakatane 89.3 km

Dunedin City 116 km

Tasman 110.9 km

Road Length Comparison -Towns/Cities - 0m to 1.5m

Thames 18.7 kmDunedin 72 km

Whangarei 18.8 km

Christchurch 22.6 km

Nelson 40.6 km

Wellington 12.5 km

Central Auckland 15.2 km

Nationwide

Thames has a very strong case for funding and advice from Central Government and LGNZ

Our community, TCDC and our MP need to combine forces to ensure Thames gets the help it needs

Dunedin Thames we have a problem

Thames has a GroundwaterProblem PLUS a Direct Sea FloodingProblem

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

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 2018-2028 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

Lead

ers

hip

Actions for District Council

• sign LGNZ Climate Change Declaration• adopt 2017 MfE Guidance as Coastal Hazard Strategy• ensure 2018-2028 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

Lead

ers

hip

“Slowly Unfolding Red Zone”

Denial/Inaction leads to …No Need to Panic

But it’s Reckless to

Delay Careful

Planning and Adaption