TSUNAMI EVACUATION ZONE MAPS & AWARENESS PLANS A CONSULTATION STRATEGY

Transcription

1 TSUNAMI EVACUATION ZONE MAPS & AWARENESS PLANS A CONSULTATION STRATEGY The difference between Tsunami Evacuation Zone Maps and the Council s Resource Management and Hazard Plans is that there are no policies or rules attached to the evacuation areas they are simply for life safety reasons

2 Back Ground Drivers It is well known that coastal communities in New Zealand are at risk from tsunami; historical (palaeotsunami research), recent and in the future Nine tsunamis may have inundated our coastline in the last 5,000 years > 5 m height; two were recorded in 1848 and 1855 To be able to quantify this hazard risk Council engaged GNS Science to assess the risk for the entire coastline of the District Potential tsunami inundation maps, and subsequent evacuation maps, were prepared following the Ministry of Civil Defence Emergency Management (MCDEM) Tsunami Evacuation Zone Guideline (MCDEM 2008) currently reviewed and out for consultation

3 Geographic Location at Risk District comprises approximately 1,800 km of coast line Largest population centres Blenheim and Picton Blenheim in the Wairau Valley sits at about 5 m above sea level and 8.5 km from the Cook Straight Picton at the head of the Queen Charlotte Sound, about 40 km from the open ocean sits at about 15 m above sea level in the town center Other smaller settlements around the coastline, both within the Sounds, e.g. Havelock and along the open coast, e.g. Rarangi, or at some distance from the open coast, e.g. Seddon and Ward

4 Tsunami Impact Analysis Parameters Hikurangi Subduction Zone Wairarapa Fault Cook Straight Combined Scenario of both faults: near distance source tsunami effect Review of Tsunami Hazards in New Zealand W. Power 2013: long distance source tsunami effect of the South American Coast, e.g. Chili Level 2 approach: rule based attenuation of potential run-up height depending on distance inland from the coast

5 Tsunami Impact Analysis Parameters The Hikurangi and Wairarapa Fault scenarios used in the modelling were extreme events with return periods in the order of 2,500 years, which was a standard return period for tsunami evacuation planning Level 2 is generally regarded as an interim approach because of its conservatism, particularly when used in areas of high population density The results are not intended to be used for restricting land use or development, because the scenarios were rare events beyond normal planning timeframes for land use.

6 Domain Boundaries and Wave Heights Domain Boundaries Coastal Domain Name and Domain Code (Power 2013) Largest threat level included (from MCDEM 2008) Doubled for run-up High Tide Water elevation at coast Cloudy Bay m 10.0 m 0.6 m 10.6 m Clifford bay m 10.0 m 0.6 m 10.6 m Cape Campbell m 10.0 m 0.6 m 10.6 m Needles Point m 10.0 m 0.6 m 10.6 m Cape Soucis (Raetihi) m 10.0 m 1.5 m 11.5 m Cape Stephens m 10.0 m 1.6 m 11.6 m Chetwode Islands m 10.0 m 1.2 m 11.2 m Cape Jackson m 10.0 m 0.8 m 10.8 m Tory Channel m 10.0 m 0.6 m 10.6 m Coastal Domain Name Largest Domain threat level Doubled Water Code High Allowance for included for runup coast elevation (Power Tide subsidence (from Power 2013) 2013) Cloudy Bay m 21.2 m 0.6 m 1.0 m 22.8 m Clifford bay m 21.4 m 0.6 m 22.0 m Cape Campbell m 21.6 m 0.6 m 22.2 m Needles Point m 21.2 m 0.6 m 21.8 m Cape Soucis (Raetihi) m 19.8 m 1.5 m 21.0 m Cape Stephens m 20.4 m 1.6 m 22.0 m Chetwode Islands m 19.0 m 1.2 m 20.2 m Cape Jackson m 19.4 m 0.8 m 20.2 m Tory Channel m 22.4 m 0.6 m 2.0 m 25.0 m at

7 Tsunami Inundation Map - Example

8 Evacuation Zone Definitions 1 of 3 MCDEM (2008) define the Red Zone as a shore-exclusion zone that can be designated off limits in the event of any expected tsunami. This represents the highest risk zone and is the first place people should evacuate from in any sort of tsunami warning. People could expect activation of this zone several times during their life. The Red Zone is to be evacuated in response to the m threat level warning.

9 Evacuation Zone Definitions 2 of 3 MCDEM (2008) define the Orange Zone as the area evacuated in most if not all distantand regional-source official warnings (i.e., warnings that extend beyond the red zone, for tsunami from sources more than one hour of travel time away from the mapped location). The Orange Zone matches the 3 5m threat level warning and is to be evacuated in the event of either the 1 3m, or 3 5m threat level warning being issued. The Orange Zone encompasses the Red Zone and care should be taken when maps show these layers. In a situation that requires Orange Zone evacuation it is preferable to say Evacuate Orange and Red Zones, rather than Evacuate the Orange Zone in order to avoid ambiguity.

10 Evacuation Zone Definitions 3 of 3 MCDEM (2008) define the Yellow Zone as covering the maximum credible tsunami, including the highest impact events. People should evacuate this zone in natural or informal warnings from a local source event. The Yellow Zone takes into account the worst cases from both modelling and known geological deposits and has been designed to encompass the area inundated by the tsunami with a 2500 year return period at the 84% confidence level (Power 2013). The Yellow Zone is designed primarily for use as a self-evacuation zone in the event of a strongly felt earthquake (one that it is hard to stand up in) or a long duration earthquake (one that lasts for longer than one minute). The earthquake does not need to be both long and strong. In many cases it will be one or the other and making this clearly understood by the public is an education challenge. These earthquakes usually have a local source and if they generate a tsunami it will have a quite short arrival time for which immediate self-evacuation is necessary. The Yellow Zone should also be evacuated in an official warning for larger than the 3 5 m threat level or in the case of a natural or informal warning where the potential wave height is unknown. While the Yellow Zone encompasses the Orange and Red zones, care should be taken when maps show these layers. In a situation that requires Yellow Zone evacuation it is preferable to say Evacuate All Zones, rather than Evacuate the Yellow Zone in order to avoid ambiguity.

11 Consultation Strategy Process

12 Consultation Process Tools Structured Decision Making Process (SDM): identification of values, objectives, and performance measures for each of the stakeholders, e.g. Tsunami Working Groups, Emergency Services, Utility Services. All values are treated as equally legitimate under SDM. Smart Maps: the benefits vs paper based environment are numerous especially in relation to community consultation Tsunami Open Days: an exhibition style process to give very body the opportunity to voice their thoughts and gain a better understanding

13 Consultation Process and Time Frame

14 Consultation Process Risks

15 Tsunami Evacuation Zones Outcome Examples

16 The results indicate that while Blenheim is sufficiently distant from the coast to be outside of the evacuation zones, many smaller communities fall inside the zones and it would be prudent to develop evacuation plans for these settlement