Tsunami evacuation zone boundary mapping : Greater Port Vila and Greater Luganville, Vanuatu

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Lukovic, B.; Power, W.L.; Heron, D.W. 2016 Tsunami evacuation zone boundary mapping : Greater Port Vila and Greater Luganville, Vanuatu. Lower Hutt, N.Z.: GNS Science. GNS Science report 2016/01 17 p.

Abstract: This report has been prepared in support of the Risk Mapping and Planning for Urban Preparedness Project (RMPUP Project) as part of the Mainstreaming Disaster Risk Reduction Project (MDRR) being implemented by the Vanuatu Meteorology and Geohazards Department (VMGD). Stage 3 of the RMPUP Project covers the Urban Risk Management Strategy, and Tsunami Evacuation maps are an integral part of that strategy. Tsunami is a significant hazard in Vanuatu, but when effective warning systems are combined with pre-planned evacuation zones, potential escape routes, exercises, and public education, casualties can be greatly reduced. The LiDAR data used to generate the high quality digital elevation models (DEM) of Port Vila and Luganville that were used in this study were collected during a 2012/13 survey. Vanuatu is issued with warnings from the Pacific Tsunami Warning Center (PTWC) about forecast approaching tsunami based on recorded earthquakes and wave gauge data. Numeric modelling of 15 tsunami generating earthquake scenarios was undertaken earlier in the RMPUP Project to provide an estimate of maximum credible tsunami amplitude at coast from all possible sources affecting the region. All of this information is required for the development of the evacuation maps and has been used for this work. The creation of tsunami evacuation maps is a complex process that starts with development of indicative, “raw” evacuation zones using one of the established methodologies, which are later modified based on local knowledge and used to create a final product through community engagement and by implementing defined operational procedures. This report focuses on development of three raw tsunami evacuation zones, the Red, Orange and Yellow Zone. The Red Zone is the highest potential risk tsunami zone and is the first place people should evacuate from in the event of any sort of tsunami warning. The Orange Zone matches a 1–3 m threat level warning issued by PTWC and is to be evacuated in the case of such a warning. The Yellow Zone matches the maximum credible tsunami wave amplitude and 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 Yellow Zone should also be evacuated in the case of an official warning by PTWC for an approaching tsunami greater than 3 metres above tide level. The Orange and Yellow Zones were developed using a rule-based methodology implemented in GIS. This methodology is widely used in New Zealand for developing evacuation zones and it implements different attenuation rules for open coast, shallow harbours and rivers. The input data for developing the evacuation zones include a DEM, an estimated maximum tsunami wave amplitude at the coast, the high-tide level and a dataset representing water features such as sea, rivers and lagoons across which the tsunami propagates and affects the adjacent land. The Red Zone was developed from DEM by applying a simple ‘bathtub’ elevation rule. (auth)