11.1 ISSUES OBJECTIVES POLICIES RULES Land Stability Assessment Areas PERFORMANCE STANDARDS 8

Transcription

1 11 NATURAL HAZARDS 11.1 ISSUES OBJECTIVES POLICIES RULES Land Stability Assessment Areas PERFORMANCE STANDARDS RULES Fld Hazard Overlay PERFORMANCE STANDARDS RULES Kai Iwi Castal Hazard Overlay 10 Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-1

2 11 NATURAL HAZARDS The District is affected by a number f natural hazards. Parts f the urban area are particularly prne t flding, while the cast and hill cuntry are affected by land instability and ersin. The District is als dissected by fault lines and is vulnerable t sea level rise and tsunami. The natural hazards ccurring in the District have an impact n current and future develpment. They can cause lss f human life and significant damage t private prperty, rads and ther District assets. They can als cause damage t the natural envirnment. It is recgnised that while a hazard may be present, the hazard ptential is nly realised when there are land use activities, buildings r structures and imprtant natural values in the vicinity f the hazard. It is nt pssible t eliminate hazards, but it is pssible t manage the lcatin, design and peratin f land use activities and hazardus facilities t avid, remedy r mitigate the ptential adverse effects f hazards n human life, prperty and the envirnment. The Act requires bth the reginal and district cuncils t share management respnsibility fr the natural hazards f flding, subsidence, seismic, vlcanic and tsunami hazards, as well as fr hazardus substances. The Reginal Plicy Statement defines the management respnsibilities f lcal authrities fr natural hazards and hazardus substances ISSUES Variety f Natural Hazards The District is affected by a number f natural hazards. The mst significant nes are flding, strms, tsunami, ersin and earthquakes. Knwledge f the lcatin and characteristics f natural hazards and their impacts n surrunding develpment and the envirnment is far frm cmprehensive. This alng with lack f public awareness hinders the avidance and mitigatin f thse hazards Inapprpriate Land Use in Areas at Risk f Natural Hazards Inapprpriate land use and ccupatin f areas at risk frm earthquake, flding, pnding land instability can cause unnecessary risks fr peple and prperty Fld Hazard Risk Much f the urban area f Whanganui is built upn the banks f the Whanganui River (Te Awa Tupua). Sme f the lwer lying areas twards the bttm f the catchment, alng with sme tributaries and Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-2

3 drains including Churtn Creek and the Matarawa Stream, are prne t ccasinal flding putting peple, prperty and infrastructure at risk OBJECTIVES Infrmed Cmmunity f Natural Hazard Risks A cmmunity infrmed abut the ptential risks f natural hazards t peple and prperty in the District Aviding and Mitigating Natural Hazards The risks f natural hazards thrugh inapprpriate subdivisin and develpment are avided r mitigated whilst minimising adverse effects n natural, cultural and eclgical values Riverfrnt Develpment T ensure that develpment f the Whanganui riverfrnt recgnises and mitigates against the ptential fld hazard frm the Whanganui River Fldwater Inundatin Minimise the risk t peple, prperty and infrastructure frm fldwater inundatin POLICIES Prmte Imprved Understanding f Natural Hazards Prmte imprved understanding f natural hazards as develpment cnstraints and better knwledge and awareness f the risks t peple and prperty in the District Prtectin frm Natural Hazards Avid r minimise risk f lss f life r injury r envirnmental damage due t use r develpment in hazard prne areas Natural Hazard Precautinary Apprach Adpt a precautinary apprach in relatin t use r develpment affected by ptential natural hazards, especially where hazards are nt well understd r the effects f natural prcesses are difficult t assess r where the effect f activities n natural hazards are nt well understd Getechnical Reprt In assessing resurce cnsents Cuncil will require cnfirmatin, including as apprpriate the preparatin f a getechnical reprt, as t the suitability f the site fr subdivisin, use r develpment and that the effects f the hazard shall be avided, remedied, mitigated. Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-3

4 Land Instability Identify areas susceptible t land instability where assessment f the hazard risk is required befre land use r subdivisin activities are carried ut. Where there is an unacceptable getechnical risk cnsent shall be declined Fldwaters In designing earthwrks r radwrks any adverse effects f diverting fldwaters shuld be avided, remedied r mitigated Fld Mitigatin in the Arts and Cmmerce and Riverfrnt Znes Utilise alternative fld hazard mitigatin techniques in the Arts and Cmmerce and Riverfrnt Znes Adpt a 1 in 200 Year Fld Level Subdivisin and land use develpment must be managed in any area identified as being inundated in a 1 in 200 year fld event New Buildings in Fld Prne Areas Avid the erectin f new buildings in areas f higher prbability f fldwater inundatin (Area A) where this may induce r accelerate the impacts f flding n peple and prperty Reduce Risk t Existing Buildings Reduce the impacts f fldwater inundatin in fld prne areas, by requiring that alteratins r additins t existing buildings and structures adpt resilient building methds Hazard Mitigatin Mitigate fld hazard impacts assciated with the erectin f new buildings and structures in areas f mderate prbability f fld water inundatin (Area B) New Alltments in Fldable Areas Avid subdivisin which creates new alltments n sites where future develpment may increase the expsure f peple and prperty t inundatin frm a 1 in 200 year fld event Critical Infrastructure in Fldable Areas Avid the establishment f new critical infrastructure in the Fld Hazard Overlay unless there is satisfactry evidence t shw that critical infrastructure; a. Will nt be adversely affected by a 1 in 200 year fld event Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-4

5 b. Will nt cause any adverse effects n the envirnment in the event f a fld c. Is unlikely t cause a significant increase in the scale r intensity in the event f a fld d. Cannt be reasnably lcated in an alternative lcatin It is accepted that there are telecmmunicatin facilities such as verhead r undergrund cables r masts, that can be sited in fld hazard areas withut undue risk t the equipment and cmmunity r adverse effects n the envirnment in the event f a fld, and prvisin fr these facilities has been included accrdingly RULES - LAND STABILITY ASSESSMENT AREAS This sectin cntains the rules that apply t future activities in the Land Stability Assessment Areas, which cvers areas f land instability in the urban area f Whanganui. There are tw Land Stability Assessment Areas. Investigatin f the extent f the land in the District at risk f land slip has identified a list f areas which are pririties fr further study. These areas will be examined t identify the extent f susceptibility t land instability hazards. These hazard prne areas will be incrprated int the Land Stability Assessment Areas verlay as investigatins are cmpleted. The investigatins d nt cnsider existing structures, rather the fcus is n the underlying gelgy and data f histric landslides as a guide t ptential risks f future land instability. Existing lawfully established structures are assumed t be fit fr purpse. The applicatin f the verlay t particular prperties des nt diminish the suitability f existing structures fr habitatin r use. Rather the fcus f regulatin f activities in the LSAA verlay is t ensure that any future land disturbance activities are managed apprpriately t avid any increased risk t peple r prperty in the wider vicinity. Seven areas have been investigated and the fllwing reprts prepared: Hillside Stability Study Anzac Parade/Putiki Drive, June 2011; Shakespeare Cliff, Whanganui Building Line Restrictin, Amended Reprt, Nvember Land Stability Assessment Areas Ikitara Rad, Bastia Hill and Durie Hill, Risk Study Reprt, May 2014 Land Stability Assessment Areas Mwhanau and Rberts- Patersn, Risk Study Reprt, July 2015 The ptential risks t peple and prperty resulting frm any future Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-5

6 develpment in these areas will be managed thrugh the Plan t achieve sustainable management. Future research relating t ptential land instability will fcus n the fllwing remaining areas: Parkdale/Christies Hill/Virginia Rad Putiki Areas Marybank Area In the Land Stability Assessment Areas instability and damage may ccur frm natural ersin prcesses r frm activities which are incmpatible with the sft rck f these escarpments. These ersive prcesses may lead t slips and cnsequent lss f prperty and landscape. The purpse f the Land Stability Assessment Area is t recgnise its ptentially hazardus characteristics and ensure that effects frm incmpatible activities causing r accelerating natural ersin, are avided r mitigated Permitted Activities The fllwing are permitted activities: a. Any activity permitted in an underlying zne and nt excluded by Rules , , r b. Maintenance and minr upgrading f existing netwrk utility facilities (excluding excavatin r trenching) Cntrlled Activities The fllwing are cntrlled activities prvided perfrmance standard is cmplied with: a. Excavatin, cnstructin, alteratin r mdificatin t any structure r retaining wall. Cuncil retains cntrl ver: i. Implementatin f cnditins t ensure that the excavatin and cnstructin, alteratin r mdificatin t any structure r retaining wall des nt wrsen r accelerate the risk f land instability n the site r surrunding area. b. Netwrk utilities invlving excavatin, trenching r cnstructin t any structure r retaining wall. Cuncil retains cntrl ver: i. Implementatin f cnditins t ensure that the excavatin and cnstructin f any structure r retaining wall des nt wrsen r accelerate the risk f r level f ersin n the site r surrunding area. Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-6

7 c. Vegetatin clearance (greater than 5m 2 area annually). Cuncil retains cntrl ver: i. Implementatin f cnditins t ensure that the activity des nt wrsen r accelerate the risk f r level f ersin n the site r surrunding area Restricted Discretinary Activities The fllwing are restricted discretinary activities prvided perfrmance standard is cmplied with: a. Any restricted discretinary activity in an underlying zne and nt excluded by Rules r Cuncilrestricts its discretin t the matters identified in the underlying Zne fr the prpsed activity and t: i. Whether the activity cntributes t land instability. b. Subdivisin fr bundary adjustment where n additinal building platfrms are created. Cuncil restricts its discretin t the matters identified in the underlying zne fr the prpsed activity (this includes the matters Cuncil has limited its cntrl t fr subdivisin in the Outer Cmmercial Zne) where applicable and t: i. Whether the subdivisin cntributes t land instability Discretinary Activities The fllwing are discretinary activities: a. Any discretinary activity in an underlying zne nt excluded by Rule ; b. Subdivisin where additinal building platfrms are created in Area B and where Rule is cmplied with;r c. Vegetatin clearance (greater than 5m 2 area annually), where Rule is nt cmplied with Nn-Cmplying Activities The fllwing are nn-cmplying activities: a. Excavatin where Rule is nt cmplied with; b. Subdivisin where additinal building platfrms are created in Area A, r where Rule is nt cmplied with fr sites in Area B; c Cnstructin, alteratin r mdificatin f any structure r retaining wall where Rule is nt cmplied with; Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-7

8 d Netwrk utilities invlving excavatin, trenching r cnstructin f any structure r retaining wall where Rule is nt cmplied with; r e. Any ther activity which is nt prvided fr as a permitted, cntrlled r discretinary activity PERFORMANCE STANDARDS Land Stability Assessment Areas Getechnical Reprt Where required by rules , , r , the persn prpsing t undertake the activity shall prvide Cuncil with a reprt frm a suitably qualified and experienced getechnical engineer, prir t cmmencement f any wrks nsite. Cuncil shall cnsider this rule is cmplied with where the reprt cnfirms that: 1. The risk f the activity is n mre than Iw, using the qualitative risk assessment prcess described in Practice Nte Guidelines fr Landslide Risk Management 2007 (Australian Gemechanics Sciety, 2007); and 2. Assciated wrks will nt wrsen r accelerate land instability n the site r surrunding area. Nte: Cuncil shall maintain a list f suitably qualified and experienced getechnical engineers RULES FLOOD HAZARD OVERLAY Permitted Activities The fllwing are permitted activities (excluding sites in the Arts and Cmmerce Zne and Riverfrnt Zne) prvided they cmply with perfrmance standards : a. Earthwrks (prvided they cmply with Chapter 14); b. Building maintenance and minr wrks; c. Minr upgrades t infrastructure; and d. New infrastructure (excluding critical infrastructure) including buildings up t 5m 2 grss flr area Restricted Discretinary Activities The fllwing are restricted discretinary activities (excluding sites in the Arts and Cmmerce Zne and Riverfrnt Zne) prvided they cmply with perfrmance standards : Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-8

9 a. New buildings and structures in Fld Risk Area B; b. Additins and alteratins t existing buildings;and c. Subdivisin t create bundary adjustments r cnversin f leasehld t freehld titles. Cuncil s discretin is restricted t: i. The establishment f a suitable finished flr r grund level ii. iii. iv. after allwing fr freebard abve the 200 year fld level n the subject site; The prvisin f, and ability t, achieve safe access/egress; In additin t establishing a finished flr r grund level in (i) abve, the requirement fr, and use f, resilient building methds that prvide resilience fr up t a 1 in 200 year fld event; and The avidance f significant diversin f fld flws as a result f the develpment. Nte: Fr the purpses f this rule, buildings r structures assciated with infrastructure are excluded Discretinary Activities The fllwing are discretinary activities (excluding sites in the Arts and Cmmerce Zne and Riverfrnt Zne): a. New critical infrastructure and wrks t critical infrastructure nt prvided fr as permitted r restricted discretinary activities; and b. Earthwrks that d nt cmply with perfrmance standard Nn-Cmplying Activities The fllwing are nn-cmplying activities (excluding sites in the Arts and Cmmerce Zne and Riverfrnt Zne): a. Subdivisin, excluding bundary adjustments r cnversin f leasehld t freehld titles; b. New buildings and structures in Fld Risk Area A; and c. New buildings and structures and additins t existing buildings and structures that d nt cmply with perfrmance standard Nte: Fr the purpses f this rule, buildings r structures assciated with infrastructure are excluded. Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-9

10 11.7 PERFORMANCE STANDARDS Fld Hazard In the Arts and Cmmerce Zne and Riverfrnt Zne, structures shall be required t meet the fllwing: New buildings and additins t buildings are required t be designed and cnstructed t either: a. Be prtected frm inundatin; r b. Be able t recver efficiently fllwing inundatin Fr all new buildings r additins t existing buildings, the fllwing minimum freebard level abve the 0.5% AEP (200 year event) shall be required: a. 0.5 metres fr ccupied buildings, AND b. 0.2 metres fr nn-habitable buildings c. N freebard will be required fr i. carprts and ther similar nn-enclsed structures, and, ii Earthwrks infrastructure where inundatin by fldwater in a 200 year event will nt adversely affect the level f service prvided. Earthwrks shall nt alter the existing grund level in a manner that diverts fld flws r adversely affects channel capacity RULES KAI IWI COASTAL HAZARD OVERLAY This sectin cntains the rules that apply t activities in the Kai Iwi Castal Hazard Overlay which applies t land alng the cast at Kai Iwi. The Kai Iwi Castal Hazard Overlay cmprises three areas: Kai Iwi Extreme Risk Area; Kai Iwi High t Mderate Risk Area; and Kai Iwi Safety Buffer Area. The Kai Iwi Castal Hazard Overlay stems frm the knwledge that it is nt pssible t cntrl the ccurrence f natural hazards, hwever it is pssible t reduce the hazard ptential t prtect human life, prperty and the envirnment. The ptential fr castal ersin in sme castal areas is severe. At Mwhanau, the cliffs have been subject t significant ersin. The reductin f hazard ptential needs t address: The lcatin and peratin f new land use activities in areas affected by natural hazards; Prtectin f existing develpments in high risk areas; and Land instability. Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-10

11 Traditinally there is a reluctance t identify and recgnise hazards as develpment cnstraints as there is cncern that the identificatin will alarm peple and reduce the value f prperties. Hwever, nt recgnising the presence f hazards can als lead t increased risks f envirnmental damage, prperty damage r lss f life. The purpse f the Kai Iwi Castal Hazard Overlay is t recgnise the castal landslip hazard risk at Kai Iwi and t ensure that any future develpment in this area ccurs in a way that minimises risks t bth peple and prperty Applicatin f Rules The rules in this sectin apply where structures in the Kai Iwi Castal Hazard Overlay are being cnstructed, extended r altered r when earthwrks r subdivisin f land is prpsed. The rules in this sectin apply in additin t all the rules which apply in the underlying zne Precedence f Rules Where there is a cnflict between rules f the underlying zne and the rules f this verlay, the mre stringent activity status applies Permitted Activities Any activity ther than a prhibited, cntrlled r discretinary activity is permitted in the Kai Iwi Castal Hazard Overlay subject t the prvisins f the underlying zne Cntrlled Activities The fllwing are cntrlled activities in the Kai Iwi Castal Hazard Overlay: a. Subdivisin fr the purpse f minr bundary adjustments and alteratins r vesting f reserves. Refer t Sectin 13 fr subdivisin perfrmance standards Restricted Discretinary Activities The fllwing are restricted discretinary activities: a. Erectin f any building r structure in the Safety Buffer Area; b. Erectin f any nn-habitable building r structure in the High t Mderate Risk Area; c. Extensin/alteratin t any building r structure in the Safety Buffer r High t Mderate Risk Area; d. Demlitin f a building r structure in the High t Mderate Risk Area; Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-11

12 e. Earthwrks r vegetatin clearance; f. Subdivisin f land in the Safety Buffer Area r partly in the High t Mderate Risk Area ther than allwed by a cntrlled activity fr the Kai Iwi Castal Hazard Overlay; g. The installatin, alteratin r remval f wrks designed t mitigate the effects f castal hazards; h. The erectin, maintenance r cnstructin f any netwrk utility in the Safety Buffer Area and the High t Mderate Risk Area. Cuncil s discretin is restricted t: i. Whether the prpsal wuld be cnsistent with the bjectives and plices relating t the Natural Hazard Ptential as set ut in Chapter 11; ii. iii. iv Prhibited Activities The extent t which activities and buildings and structures can be relcated r demlished with minimal disturbance t the site r adjacent site; The degree t which the prpsal is likely t: Accelerate, wrsen r result in further damage t that land, ther land, r structures r buildings caused either directly r indirectly by ersin; Be subject t ersin r cliff failure; Reduce the net risk f castal hazards; Prvide fr the dispsal f strmwater and wastewater including discharges frm septic tanks; and Whether, in the High-Mderate Risk Area r Safety Buffer Area, cnsent shuld be granted fr a limited duratin. The fllwing are prhibited activities fr which n resurce cnsent shall be granted: a. The erectin f r extensin t, any building r structure ther than structures fr castal management in the Extreme Risk Area; b. Erectin f any ccupied building r structure in the High t Mderate Risk Area; c Subdivisin f land in the Extreme Risk Area r whlly within the High t Mderate Risk Area, ther than allwed by cntrlled activity fr the Kai Iwi Castal Hazard Overlay; d. Installatin f septic tanks r sakage pits in the High t Mderate Risk Area and the Extreme Risk Area; Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-12

13 e. Cnstructin f any new netwrk utility in the Extreme Risk Area. Nte: Cnsents may als be required frm the Manawatu-Wanganui Reginal Cuncil fr activities invlving sil disturbance r vegetatin clearance. Whanganui District Plan (15 January 2018) Chapter 11 Natural Hazards 11-13