tsunami_hazard (FeatureServer)

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Service Description: Tsunami Hazard areas for the Gisborne district as identified by the GNS 2015 study.

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Description: Gisborne District Council (GDC) is interested in taking a risk-based approach to managing its natural hazards. In order to gain a better understanding of and manage the tsunami hazard affecting the region GDC has plans to undertake probabilistic tsunami hazard mapping for all its major communities along the coast. GDC has begun this effort by contracting GNS Science to conduct a pilot study, focussing on conducting probabilistic tsunami hazard mapping for Gisborne City and Wainui Beach. GNS Science previously undertook two tsunami inundation studies commissioned by GDC for the coastal communities of: Gisborne and Wainui in 2009 (Wang et al., 2009), and Tokomaru Bay, Hicks Bay, and Te Araroa in 2012 (Barberopoulou, et al., 2012). These studies were intended to inform evacuation planning and model inundation from a set of source scenarios. Since then, GNS Science has produced results from its national probabilistic tsunami hazard model (Power, 2013), which estimates the size of the tsunami at the coast for specified probabilities. This information has been used here as the basis for developing a probabilistic understanding of the tsunami hazard inland in Gisborne City and Wainui. The Tsunami Land-Use & Evacuation Planning Workshop was held in Gisborne in October, 2014 to consider the implications of the GNS Science Review of Tsunami Hazard in New Zealand and to determine best practice to address inconsistencies in the application of tsunami science for evacuation and land use planning. One of the issues identified in this workshop was the modelling level requirements for different purposes (e.g., evacuation, land use planning) and circumstances (e.g., remote coastlines or high-density urban populations). The subsequently revised Director’s Guidelines for Tsunami Evacuation Zones recommended the use of “Level 3 or 4” probabilistic mapping to provide results with sufficient accuracy for land use planning purposes. In this report GNS Science presents results from a “Level 3” tsunami inundation study conducted for Gisborne City and Wainui Beach. The “Level 3” approach consists of identifying tsunami scenarios consistent with the tsunami hazard on specified timeframes, modelling of these scenarios, and combining the results into a map of tsunami hazard. From this maps of expected inundation flow depths were produced at Average Recurrence Intervals (ARIs) of 100, 500, 1000, and 2500 years. A further analysis was conducted, using only the scenarios arising from local tsunami sources. These were combined with models of population fragility to assess the level of tsunami risk in terms of annual fatality probability assuming no mitigation.

Copyright Text: Gisborne District Council, GNS

Spatial Reference: 2193 (2193)

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Supported Operations: Query ConvertFormat Get Estimates