This dataset defines the maximum tsunami height (maximum amplitude) expected to be exceeded once every 100, 500, 1000 and 2500 years on average at the 50th and 84th percentile of confidence, as estimated by the model described in Power et al. (2022). The dataset also defines the coastal sections that were used for this modelling. The expected maximum tsunami heights are presented for each of these coastal sections. Please note that the expected maximum tsunami height will typically only occur at one location within each coastal section. It is a conservative (pessimistic) assumption if this height is used throughout the section. DOI: https://doi.org/10.21420/C3CK-FB93 Cite data as: GNS Science. (2022). National Tsunami Hazard Model (NTHM) 2021 [Data set]. GNS Science. https://doi.org/10.21420/C3CK-FB93 Cite report as: Power, W.L.; Burbidge, D.R.; Gusman, A.R. 2022 The 2021 update to New Zealand's National Tsunami Hazard Model. Lower Hutt, N.Z.: GNS Science. GNS Science report 2022/06. 63 p.; doi: 10.21420/X2XQ-HT52

This dataset defines the maximum expected tsunami height (maximum amplitude) for return periods of 100, 500 and 2500 years at the 50th and 84th percentile of confidence, as estimated by the model described in Power (2013). The dataset also defines the coastal sections that were used for this modelling. The maximum expected tsunami heights are presented for each of these coastal sections. Please note that the maximum expected tsunami height will typically only occur at one location within each coastal section. It is a conservative (pessimistic) assumption if this height is used throughout the section. DOI: https://doi.org/10.21420/2Y8C-2D58 Cite data as: GNS Science. (2013). National Tsunami Hazard Model - 2013. GNS Science. https://doi.org/10.21420/2Y8C-2D58 Cite report as: Power, W.L. (compiler). 2013. Review of Tsunami Hazard in New Zealand (2013 Update), GNS Science Consultancy Report 2013/131. 222 p. A database for the 2021 version of the NTHM is under development.

The DamSite points signify the location of landslide dams and are situated at the upstream end of each dam. The point position is exactly on the river centreline so that river and catchment metrics can be systematically calculated. For consistency, river centrelines were generated using the 8 m national DEM for New Zealand (LINZ, 2012). For this reason, DamSite points may not always be immediately adjacent to the Dam polygons. There is always one DamSite point for one Dam polygon.

The Dam polygons signify the area of landslide debris that blocked the watercourse, forming the landslide dam. Where possible, this includes only the debris that formed the dam while other debris that did not block the watercourse has been mapped separately into the DebrisTrail feature class. Occasionally, the Dam polygon may be representative of the whole landslide deposit. In some instances, the dam no longer exists in the landscape and its extent has been interpreted. The Dam was delineated using a variety of methods from manual mapping on 1 m resolution LiDAR to unsupervised techniques using remote sensing. The quality of data (e.g., resolution, accuracy, etc.) therefore varies depending on the technique used (linked to the QualityRankings table). This feature class contains attributes that are specific to the landslide dam.

The QualityRankings table records the quality of each source dataset or reference. Where multiple references are given in the feature classes, the ranking of the highest overall quality record is assigned to the dataset. For example, if a previously-mapped dataset was updated by the Version 1.0 NZ Landslide Dam Database authors using more recent satellite imagery or terrain models, then the metadata record for the updated mapping is linked to the landslide DamSite points via the Metadata ID field. In Version 1.0 of the database, this table contains attributes that are specific to the quality of the whole source dataset, not individual landslide dams. This might be improved in future versions of the database.

Version 1.0 of the New Zealand (NZ) Landslide Dam Database (NZLDD) has been developed by GNS Science and contains recent, historic and prehistoric landslide dams in NZ, defined as significant, ephemeral or enduring blockages of a watercourse by a landslide. Note that Debris Trail and Dam, as mapped here, together comprise the landslide deposit, with the Dam limited to the part of the deposit damming its respective watercourse, i.e., the deposit that lies within the valley bottom. Version 1.0 contains many catalogued landslide dams, but is not a complete database of all landslide dams that have ever occurred in NZ. The database comprises five spatial datasets in New Zealand Transverse Mercator 2000 (NZTM2000) projection and one table. The database together with a full description of the data has been published by Morgenstern et al. (2023) (accessed from https://doi.org/10.1007/s10346-023-02133-4) and can be downloaded as an ArcGIS geodatabase from https://doi.org/10.17605/OSF.IO/NW6MT. Journal article: Morgenstern R, Wolter A, Cox SC, Lukovic B, Bain D, Sirohi A, Bruce ZRV, Jones KE, Rosser BJ, Townsend DB, Massey CI. 2023 The New Zealand Landslide Dam Database, v1.0. Landslides, 21: 121-134; https://doi.org/10.1007/s10346-023-02133-4 Data: Morgenstern R, Wolter A, Cox SC, Lukovic B, Bain D, Sirohi A, Bruce ZRV, Jones KE, Rosser BJ, Townsend DB, Massey CI. 2023 The New Zealand Landslide Dam Database, v1.0. OSF. https://doi.org/10.17605/OSF.IO/NW6MT Metadata: New Zealand Landslide Dam Database Version 1.0. https://doi.org/10.21420/47GZ-A116

The Lake polygons signify the known or inferred area inundated by landslide-dammed lakes. In many instances the lake no longer exists in the landscape and its extent was inferred based on geomorphic features such as sedimentary plains, wetlands, and deltas. If no obvious signs of a past lake exist for a particular case study, a lake was not mapped. Where the landslide-dammed lakes still exist today (typically for large, enduring dams), the current lake extent was taken from the LINZ topographic 1:50,000 scale mapping (LINZ, 2020a, 2020b). These are likely not the initial or maximum lake extents, particularly for old dams. The Lake was delineated using a variety of methods from manual mapping on 1 m resolution LiDAR to using the LINZ 1:50,000 scale map data. The quality of data (e.g., resolution, accuracy, etc.) therefore varies depending on the technique used (linked to the QualityRankings table). This feature class contains attributes that are specific to the landslide-dammed lake.

The Source polygons signify the source area of the landslide that formed the landslide dam. The Source was delineated using a variety of methods from manual mapping on 1 m resolution LiDAR to unsupervised techniques using remote sensing. The quality of data (e.g., resolution, accuracy, etc.) therefore varies depending on the technique used (linked to the QualityRankings table). This feature class contains attributes that are specific to the landslide source.

The DebrisTrail polygons signify the debris trail of the landslide, defined as the deposit between the Source and Dam, and it can also include debris that did not block the watercourse. Debris trails were not mapped if the deposit extent matched the Dam extent. The DebrisTrail was delineated using a variety of methods from manual mapping on 1 m resolution LiDAR to unsupervised techniques using remote sensing. The quality of data (e.g., resolution, accuracy, etc.) therefore varies depending on the technique used (linked to the QualityRankings table). This feature class contains attributes that are specific to the landslide debris trail.