Presentation by NOBRG to Expert

PanelInlet Erosion and SLR at Waitohu Inlet

by John Maassen (reviewed by

Richard Heerdegen)���1

my experience • 25 years environmental lawyer acting principally for local

authorities ( regional and territorial) in lower NI

• Certified Commissioner under RMA

• co-owner of 8 Moana Street on banks of Waitohu Stream as a beach property

• I am not a scientist but Richard Heerdegen is.

• Notwithstanding this I am professionally trained in the critical analysis of science and prediction and knowledge frameworks that inform natural and physical resource planning.

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bundle of materials

• supporting statement on NZCPS from Ass.-Professor Rosier on NZCPS

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who are we ?• we have residences and holiday homes at northern end of Otaki Beach most between

200-350 m back from the active foredune. Many are retired.

• many of us are members of the Waitohu Stream Care Group a group of active volunteer conservationists focussed on wetland and dune restoration implemented in consultation with GW. This is regionally recognised conservation group and it has massively improved wetland health and significant growth in the dune system

• we are affected by the IEHL lines in Shand 2012 based on an 50 or 100 year “unmanaged scenario” for Waitohu Inlet.

• Consequence is proposed “relocatable overlay” in PDP controlling minor (>10 m2) extensions to existing buildings

• “Unmanaged” in this context means discontinuation of the periodic inlet cut ( using a digger) at the mouth of the Waitohu Stream between defined envelope of Northern and Southern trigger points undertaken by GWRC and as provided for in the GW Regional Plan

• If Waitohu Inlet is managed Shand 2012 predicts SLR will not cause erosion of NOBRG properties within 100 year time frame

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Otaki BeachBabbacombe

Avenue

Simcox Street

Caugh

ley

Pla c

eScot

t Ave

nue

Konini Street

Kowhai Street

Rupini Stree t

Scott Avenue

Duncan Way

Rata Street

Tasman Road

Hea

lth C

amp

Roa

d

Mah

oe St

reet

Seagra ss Pla ce

Babbacombe

Avenue

Nor

folk

Cre

scen

t

Karaka Street

Koromiko Street

Tasman Road

To i Street

Nga

io St

reet

Manuka Street

Moa

na St

reet

Marine

Parade

LegendOperative District Plan

7.5m Coastal Yard Rule

Estimated 100m Rural Set Back

Proposed District PlanRural No Build CHMA

Urban Relocatable Build CHMA

Urban No Build CHMA

Date: 6/12/2012

0 30 60 90 12015

Meters

¯

Comparison of Operative District Plan and Proposed District Plan

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relocatable overlay

Report Title: Kapiti Coast Erosion Hazard Assessment - 2012 Update Reference No. 2012-8CRep Version: Final Status: For council consideration

Client: Kapiti Coast District Council Date: 8th August, 2012

32

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1948 alignment see slide 15

alleged hardwall structures1

2

Caughle

y P

lace

Byron Brown Place

Konini Street

Kowhai Street

Rupini Street

Scott Av enue

Duncan Way

Simcox St reet

Rata Street

Norfolk Crescent

Mah

oe St

reet

Seagrass Place

Heal

th Ca

mp

Road

Robert Mck e en St

reet

Old Coach Road

Babb

acom

be

Avenue

Scott Aven u e

Norf

olk

Cre

scen

t

Karaka Street

Koromiko Street

Tasman RoadNg

aio

Stre

et

Toi Street

Manuka Street

Tasman Road

Moa

na St

reet

Marin

e Pa

rade

191621

2314 1511 12 13

2024

08 09 1006 07

0518

2204

1702 0301

Map 01C Natural Hazards

LEGEND

F L O O D

FAULT AVOIDANCE AREAS

COASTAL HAZARDMANAGEMENT AREAS

River Corridor

Stream Corridor

Overflow Path

Residual Overflow Path

Fill Control Zones

Storage

Ponding

Residual Ponding

Well Defined

Well Defined Extension

Distributed

Uncertain Constrained

Uncertain Poorly Constrained

Rural No Build

Urban Relocatable Build

Urban No Build

EROSION SUSCEPTIBILITY

Very High

High

Moderate

1:10,000Scale / A30 50 100 150 20025

Meters NLast AmendedNotification Date: 29 November 2012

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no build

relocatable

modelled 1% AEP

• NOBRG supports others in many aspects of their challenge to the coastal hazard lines. We disagree with the entire managed and unmanaged inlet hazard assessment methodology for Waitohu Inlet

• NOBRG shares concerns regarding Shand 2012 already expressed by Joan Allin. I have also read the statement given to you by my colleague on legal matters Chris Mitchell and agree with it.

• NOBRG brings a locality specific perspective.

• NOBRG has submitted on the PDP which incidentally only has an intended life of 10 years

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dunes

wetland

Sims

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12 3

45

6

7

Photo 1 looking East���11

Location 2 looking South���12

Photo 3 - looking towards dune���13

Photo 4 - looking North���14

Photo 5 - looking North���15

Photo 6-looking South���16

Photo 7 -looking North���17

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Report Title: Kapiti Coast Erosion Hazard Assessment - 2012 Update Reference No. 2012-8CRep Version: Final Status: For council consideration

Client: Kapiti Coast District Council Date: 8th August, 2012

89

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Changes in inlet geomorphology since 1970

north of Konini St• Approximately 183,000m3 ( i.e. 61,000m2 x 3m high) more sand

deposition to form regionally outstanding dune system

• Major dunes now have RL of 7 m above msl

• Dunes and residential land have been massively re-vegetated with dune grasses and secondary native species including pingao, ti kouaka, harakeke and ngaio.

• Foredunes established by Waitohu Stream Group have grown 4m in height in last decade showing sand replenishment. Prograding is ongoing and rapid with 34 m forward movement since 2004

• 20 houses built

• Roads and infrastructure constructed

• See Dawe “ Waitohu Stream Mouth Cutting Guidelines”

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Your task ?• set by term of reference - international best practice in

“hazard management and assessment"

• Robert Schofield says your task confined to “science” implying there is a bright line between policy and science and that hazard management is a “hard science” rather than an evolving science with ongoing development of predictive models in response to environmental demands

• Hazard management is not a value free science but sits within planning construct and involves judgments and assumptions that have a political dimension eg what levels of future management will be factored into the analysis of risk

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What is the statutory context ?

• RMA is about sustainable management of natural and physical resources

• Where physical resources exist hazard resilience should the focus and that recognises and provides for community endorsed resilience planning

• The RMA plans are not the best vehicle to inform the public about coastal hazards and isn't its primary function

• The physical resources of a developed area are there and hence qualitatively different situation to new development

• Resilience is not solely an issue delivered through the RMA but involves locally targeted management plans prepared in consultation with the community

• KCDC has not made provision for resilience planning at the local scale and done nothing about that since.

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Core Principles We Advance

• Hazard management involves assessment of risks based on sensible assumptions-it is not simply scenario modelling without assessment of plausibility and reasonableness of underlying assumptions ( see RMS s5 and NZCPS)

• Hazard management cannot be divorced from local community input and decisions on mitigation and management options-it is a process not divorced from community endorsed adaptation plans

• Models should be used that have realistic parameters based on detailed knowledge of local coastal geomorphology and processes

• Long term trend analysis should inform assessment of the reliability of predictions

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NOBRG’s essential criticisms of Waitohu Inlet “non- managed”

IEHL Shand 2012• Scenario modelling parading as risk assessment. Fallacy 1

• “Unmanaged” is treated in an undifferentiated way i.e does not distinguish between hard structure management and soft engineering management that occurs at the Waitohu inlet yet in terms of risk assessment and practicability they are qualitatively different. Fallacy 2. Note fn 2 Shand 2102 - the terms of reference said “unmanaged” was only to include removal of seawalls not current inlet management and Shand 2012 operates outside its terms of reference see Section 1 Shand 2012 note also “natural” Dahm and Map 01 D

• “Unmanaged” scenario for Waitohu Stream is used but is an implausible scenario that has no basis in current local government policy and represents a low risk . Fallacy 3

• The guide walls in the Waitohu Stream reported in Shand 2012 section 4.4.3 don't exist other than a few submerged rocks and certainly wouldn't justify in themselves such major differences between the managed and unmanaged scenarios Fallacy 4

• Shand 2012 makes no allowance for positive sediment budget and long term prograding trend of coastal margin at Otaki Beach. Fallacy 5

• Shand 2012 uses an erosion recession factor for IEHL using as a baseline the most extreme southerly and northerly inlet envelope based on a desktop review of the aerial photographic record of the last century. In the southerly direction (affecting NOBRG) this is based on 1948 Waitohu mouth inlet alignment. Yet the geomorphology of the spit from coastal processes and human activity including publicly funded programs for dune restoration has dramatically changed since 1970 and makes that baseline alignment both very unlikely and impossible to occur in a sudden and incorrectible way.. Fallacy 6

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Report Title: Kapiti Coast Erosion Hazard Assessment - 2012 Update Reference No. 2012-8CRep Version: Final Status: For council consideration

Client: Kapiti Coast District Council Date: 8th August, 2012

32

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1948 alignment

1

2

historical shore line

Otaki Beach Long Term Shoreline Trend• Since 1847 there has been 200mm SLR and a

seaward migration of the coastal margin in excess of between 200m 400 m —see previous slide

• Particulate outflow from major rivers , coastal processes and human activity (farming and land clearance and development ) cause a prograding shoreline . Ongoing seaward migration since dune restoration program commenced demonstrate consistent positive net sediment budget

• Extensive undeveloped foredune system on coastal esplanade

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Key Points on Waitohu

• mean flow around 1 cumec/s

• predominant trend for mouth is in a northerley direction- combination of sediment transport and predominant wave direction see slide 19

• no visible rvier protection works as state in Shand 2012 other than a few barely visible rocks

• mud bottom in reach next to houses on Moana Street with clear channel

• alignment is easily corrected at the inlet because of low base flow by sand bunding of approximately 2 m height and open cut method

• 1in 100 year flood events modelled by GW show no change in Waitohu alignment with most overflow sitting in wetland which has significantly improved overflow absorption capabilities= see slide 7

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Waitohu hydrology statistics

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Waitohu inlet management

• See Waitohu Stream MouthCutting Guidelines GW October 2010

• Instituted to protect farmland and dune system to North

• Carried out by GW

• See letter advice to KCDC in October 2012 following Shand 2012 report

• Provided for in regional plan

• Provided for in draft regional plan

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the CBA of the existing management of the Waitohu

• Cost approx $4000

• Houses benefitting at around 30 or $5million

• Regionally important dunes protected

• Community infrastructure protected

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Soft Engineering Management of Waitohu inlet will continue

• cut provided for in draft GW regional plan

• funded in GW’s Long Term Plan

• CBA strongly favours continuation

• Provides for positive dune restoration

• Dawe “ Waitohu Stream Mouth Cutting Guidelines” section 8.4

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Most recent cut June 2012

• to protect farmland to north

• bund put in at 2 m high

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District Coastal Strategy 2006

• Identifies Northern beaches as having long term shoreline advance pp 51 -56

• Recognises and encourages soft-engineering hazard management pp 55-58

• Reinforces local community input p 58

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flaws in KCDC process that have made people so annoyed

• no draft plan-always a mistake when doing a zero based review

• no hazard resilience planning

• no community and locality specific consultation

• working assumptions contrary to approved Council strategies e.g. non-managed scenario modelling

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flaws in planning analysis

• Mis-reading of NZCPS- See Ass.-Professor Rosier Statement

• No risk and CBA analysis

• No overall strategy linked to community approved solutions and vision of hazard resilience

• Unworkable rules and other “methods”

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Fallacy 1- Scenario modelling is not risk assessment

• Scenario modelling is the use of a defined set of values, assumption and methods without allowance for or justification of uncertainty , probability and Historical Trend Analysis. 1948 alignment of Waitohu Stream is a scenario not a probable outcome. As a first level assessment to use as discussion/ consultation document for the purposes of developing refined community based hazard risk management framework Shand 2012 might be fine ( we don't think so) but it is certainly not the end point. Speculative scenario modelling arises out of scientist mis -reading planning policy requirements- see Joan Allin’s paper

• All the literature points to risk analysis, allowing for community approved management and factoring in local coastal processes as key elements in hazard management and risk assessment with an eye to developing strategies for the long term

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Fallacy 2 and 3-Non management of Waitohu inlet is

a fanciful assumption• Makes no rational sense as a working

assumption based on CBA

• Directly contradicts Coastal Strategy of KCDC

• Contradicts advice and policy of GW Regional Council- distinction between functions

• Letter GW October 2012

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Hardwall management doesn't exist in Waitohu Stream -Fallacy

4• please verify for yourself in site visit see photo 5 and Shand 2012 Fig 4.4

• 3 Qs

• What is the hardwall management referred to the presence of which informed the choice of the 1948 onwards aerial record for the non managed scenario and the 1957 onwards alignment for the managed scenario?

• Why is it reasonable to assume the hardwall management plays any significant role in current hydrology and coastal processes affecting the alignment of the Waitohu Stream compared with the more significant changes in geomorphology , vegetation and structures developed or built since 1960?

• Why is it reasonable and what would be the mechanisms by which this hardwall management would ceased to exist as postulated by Shand 2012?

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Fallacy 5- positive net sediment budget and long term trends

ignored

• Historical Trend Analysis provides important empirical data on local responses to SLR

• Sediment budgets will affect shoreline erosion rates

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“Sea Level Rise – A New Zealand Context” Iain Dawe, Greater Wellington Regional Council

!6.2.1 Prograding Shores

!!!!!!!!!!!!!6.2.1 Prograding Shores Sea level rise will occur on top of the range of natural processes that already occur in a beach. A beach may have one of three states. It may be prograding or growing, it may be actively eroding, or it may be stable (i.e. neither eroding or prograding). The state that a beach is in largely depends on the supply of sediments to a shoreline. Sediment may come from rivers that supply surrounding beaches, the continental shelf and transported onshore by waves, or it may come from material eroded from surrounding shorelines and transported in the beach system. !A beach that is prograding has a ready supply of sediments and the wave and current activity by which to transport those sediments onto the shore. These beaches will generally respond quite well to sea level rise and may experience very little effects aside from an adjustment in the rate of progradation. However, this very much depends on the continual supply of sediments which may be altered if climatic changes modify local meteorological and hydrological conditions. !!!!!!!!!!!!!

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Fallacy 6- baseline assumptions of inlet alignment uses single statistically insignificant historical data point that does not account for recent multi-decadal changes in inlet processes and geomorphology

• single data point is not statistically significant and better assessment of realistic envelope is say 80th percentile over last 30 years

• the 1948 inlet alignment used as the baseline for additional inlet erosion from SLR would require: erosion of 7m high dunes, erosion of 183 K m3 of vegetated sand dunes, erosion of Moana Street and erosion of at least 7 residential properties. All by a stream with a mean flow of 1 cumec/s See slide 32

• All without any realignment by human intervention- “environmental fatalism”

• Shand 2012 says existing dunes will constrain Waitohu alignment for some purposes i.e. managed scenario but not other i.e. non managed , see section 4.4.3

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the danger of drawing lines as opposed to management zones

when SLR is the issue• the central Q-what are these lines

for and who are they for?

• SLR is not like flood hazard assessment based on highly accurate hydrological models

• People are mislead by lines as they assume you are protected if outside line and certain to be affected if not. Risk management is not best delivered by lines in a map unless they are no build zones based on clearly predictable erosion hazards within realistic time periods.

• If intensification in Otaki Beach is the risk to be managed why not encourage maintaining low density development through coastal zones in response to amenity, landscape and hazard grounds. See Otaki Beach low density zoning as an example.

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Caughley

Plac

e

Byron Brown Place

Konini Street

Kowhai Street

Rupini Street

Scott Av e nue

Duncan Way

Simcox Street

Rata Street

Norfolk CrescentMah

oe St

reet

Seagrass

Plac e

Heal

th Ca

mp

Road

Robert Mc k een

Stre

et

Old Coach Road

Babb

acom

be

Avenue

Scott Aven ue

Nor

folk

Cre

scen

t

Karaka Street

Koromiko Street

Tasman RoadNg

aio

Stre

et

Toi Street

Manuka Street

Tasman Road

Moa

na St

reet

Mar

ine

Parade

Mar

ine

Para

de

1916

21

2314 1511 12 13

20

24

08 09 1006 07

0518

2204

1702 03

01

Map 01A Plan Zones

LEGEND

Z O N E S

M I S C E L L A N E O U S

Living Environment

Residential

Beach Residential

Ngarara

Waikanae North DevelopmentWorking Environment

Airport

Town Centre

District Centre

Civic and Community

Industrial

Local Centre

Outer Business CentreRural Environment

Rural Dunes

Rural Plains

Rural Hills

Rural Residential

Rural Eco Hamlet

Future Urban DevelopmentOpen Spaces

Open Space (Conservation & Scenic)

Open Space (Recreation)

Open Space (Local Parks)Other

Private Recreation and Leisure

River Corridor

P R E C I N C T S

1. Pekawy2. Peka Peka North Rural Residential3. Ferndale4. Meadows5. Ngarara6. Waikanae Golf Residential

General Precincts

District Centre Structure Plan Area

Focused Infill

Medium Density Housing

Low Density Housing

District Centre Structure Plan Precinct

Ihakara St West Precinct

Water Collection AreaAirport Precincts

Airport Curtilage

Airport Core

Airport Mixed Use

Airport Heritage

Airport Buffer

North Island Main Trunk Railway

1:10,000Scale / A30 50 100 150 20025

Meters NLast AmendedNotification Date: 29 November 2012

General Precincts (G.P.):

F.I.

M.D.H.

L.D.H.

G.P.1

The findings we would like you to make

• Scenario modelling is not the same as risk assessment and the next step for KCDC is to develop a more refined risk analysis based on better understanding of the specific geomorphological conditions of each inlet including changes over time and allowing for significant uncertainties in long term predictions. This refinement should be undertaken by KCDC . Individual ratepayers should not be required to disprove “generic” scenario based hazard assessments divorced from specific understanding of local geomorphology and coastal and hydrological processes.

• Hazard Risk Assessment from SLR is an iterative process with community input and involves developing reliable models for specific sections of the coast that are verified through long term monitoring and regular updating.

• Hazard Risk Assessment from SLR involves making reasonable assumptions including allowing for community funded adaptation and management methods that are expected during the relevant planning horizon including management measures by Greater Wellington Regional Council

• The Shand 2012 managed scenario for the Waitohu Inlet in part relies on the presence of river protection works on the true left bank of the Waitohu Stream in the reach before taking its final turn to the sea.These hardwall structures don't exist (or if they are there are virtually non-existent to the naked eye) and conversely the un- managed scenario purports to assess the the effect of their absence. These works are not plausibly the cause of recent or influential in future alignments of the Waitohu Stream because of more significant geomorphological change that has occurred.

• Hazard Risk Assessment of increased coastal and inlet erosion from SLR should be informed by and validated against Historical Trend Analysis and include allowance for local coastal processes including sediment deposition

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• Hazard Risk Assessment of additional inlet erosion from SLR from the mouth of the Waitohu Stream should be based on realistic Waitohu Inlet envelope allowing for existing management reasonably expected to continue and should not use historical alignments (such as the 1948 alignment involving the Waitohu almost half a kilometre upstream entering through houses, roads and 7 m high vegetated sand dunes before exiting to the sea ) as a baseline when significant multi-decadal changes in inlet geomorphology have plainly occurred as well as significant human development.

• Under current management practices “unmanaged IEHL’s” at Waitohu Stream predicted in Shand 2012 is a low risk and are not scientifically defensible and ( subject to expert planning analysis) a sufficient method for managing any residual risk of further development occurring in the coastal area is a zoning that maintains low density character of existing development.

• Shand 2012 goes beyond its terms of reference by disregarding continuation of inlet channel management and in any event this is not an appropriate assumption to make given these structures are under another local government authorities control not KCDC

please tell us why you disagree

• please justify your analysis

• specifically based on current geomorphology and patterns of development what are the hydrological and coastal processes you model that could plausibly in the near future bring about a baseline 1948 alignment for the Waitohu Stream Inlet and that couldn't be easily prevented by timely and modest intervention

• state assumptions regarding regulatory requirements- Again, you dont need to draw lines anticipating erosion in 100 years

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the reason you are appointed

• community concern

• faces massive potential liability for negligently characterising large number of properties as hazard prone and need you to are them a steer as to whether Shand 2012 is a scientifically defensible assessment

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references

1. Kapiti Coast : Choosing Futures “Coastal Strategy (2006)

2. AS/NZ ISO 3100 : 2009 “Risk Management-Principles and Guidelines”

3. New Zealand Coastal Policy Statement 2010

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references cont…4.  Ramsay, D.L., Gibberd, B., Dahm, J., Bell, R.G. (2012) “Defining coastal hazard zones and setback lines. A guide to good practice.” National Institute of Water & Atmospheric Research Ltd, Hamilton, New Zealand. !

5. Dawe “ Waitohu Stream Mouth Cutting Guidelines and Management Review” Greater Wellington Regional Council” , October 2010 6. Letter of Intent CEO of GW to KCDC dated 29 October 2012  !    

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