Landslide dams can flood upstream areas when lakes form behind them, and inundate areas downstream if they fail/breach. The stability of landslide dams is difficult to assess, but most landslide dams fail by overtopping, usually after the first significant rainfall after formation. About 40% of dams breach one day after their formation, whereas up to 85% fail within one year of their formation.
The Dimensionless Blockage Index (DBI) is the most commonly used geometric index used to assess dam stability. Research of past failures has determined that the stability of a landslide dam is related to the ratio of the dam volume, considered the main stabilizing factor since it controls the dam self-weight, and the watershed area upstream of the dam, considered as the main destabilizing factor since it controls the channel discharge and stream power and indirectly the dam shape.
Using the newly released New Zealand Landslide Dam Database, we have re-analysed the DBI and determined Probability of Failure (POF) values using the same parameters described above. The tool is provided as an indicative preliminary forecast on the stability of landslide dams and should not be used as a replacement or substitute for site-specific analyses and assessments.
The tool can be opened in a new window by clicking the link below, or can be used directly below in the frame.
The data and model on which this Tool is based, and the creation of the tool, were prepared by the Institute of Geological & Nuclear Sciences Limited (GNS Science) as part of a New Zealand Government funded research project (MBIE Endeavour - C05X1709). The information is derived from multiple data sources, including third party data, which are at various scales and resolutions. The tool in this context is defined as the data, model and process that allows the user to forecast the probability of failure of a landslide dams based on landslide dam height and volume, and upstream catchment area. The algorithm (model) underpinning the tool is based on the DBI.
As there is always uncertainty associated with the data used and the models developed from it, GNS Science gives no warranties of any kind concerning its assessment and estimates, including accuracy, completeness, timeliness or fitness for purpose, and accepts no responsibility for any actions taken based on or reliance placed on the forecasts by any person or organisation. GNS Science excludes to the full extent permitted by law any liability to any person or organisation for any loss, damage or expense, direct or indirect, and however caused, whether through negligence or otherwise, resulting from any person or organisation's use of or reliance on the Tool, the results from it and the data it is based on.
The DBI considers three geomorphometric parameters (dam height and volume and upstream catchment area), and is thus indicative only for preliminary forecasting on the stability of landslide dams. It is not a substitute for a deterministic breach model that estimates hydrographs resulting from dam failures. It is recommended that on-site assessment of dam stability be carried out, particularly where people, buildings and infrastructure could be at risk. The Tool is intended to be used by suitably qualified people (e.g., professional engineering geologists and geotechnical engineers) as part of their regional-scale ‘desktop’ assessment. This Tool should not be used as a replacement or substitute for site-specific analyses and assessments.
Ermini L, Casagli N (2003) Prediction of the behaviour of landslide dams using a geomorphological dimensionless index. Earth Surface Processes and Landforms 28(1):31-47.
Costa JE, Schuster RL (1988) The formation and failure of natural dams. Geological society of America bulletin. 100(7), pp1054-1068.
Fan X, Dufresne A, Subramanian SS, Strom A, Hermanns R, Stefanelli CT, Hewitt K, Yunus AP, Dunning S, Capra L and Geertsema M (2020) The formation and impact of landslide dams–State of the art. Earth-Science Reviews 203:103116, DOI: https://doi.org/10.1016/j.earscirev.2020.103116.
Massey CI, Townsend DB, Dellow GD, Lukovic B, Rosser BJ, Archibald GC, Villeneuve M, Davidson J, Jones KE, Morgenstern R, Strong DT, Lyndsell BM, Tunnicliffe J, Carey JM, McColl ST (2019) Kaikoura Earthquake Short-Term Project : landslide inventory and landslide dam assessments. Lower Hutt, N.Z.: GNS Science. GNS Science report 2018/19. 43 p.; doi: 10.21420/G2FP82.
Morgenstern R, Massey CI, Rosser BJ, Archibald GC (2021) Landslide dam hazards : assessing their formation, failure modes, longevity and downstream impacts. p. 117-123; doi: 10.1007/978-3-030-60319-9_12 IN: Vilímek, V.; Wang, F.; Strom, A.; Sassa, K.; Bobrowsky, P.T.; Takara, K. (eds) Understanding and reducing landslide disaster risk. [WLF 2020]. Volume 5, Catastrophic landslides and frontiers of landslide science. Cham: Springer. ICL contribution to landslide disaster risk reduction.
Morgenstern, R., Wolter, A., Cox, S.C., Lukovic, B., Bain, D., Sirohi, A., Bruce, Z., Jones, K., Rosser, B., Townsend, D., Massey, C. (2023). The New Zealand Landslide Dam Database, v1.0. Landslides 25:1-14.
Tacconi Stefanelli, C., Segoni, S., Casagli, N., Catani, F. (2016). Geomorphic indexing of landslide dams evolution. Engineering Geology, 208:1-10.
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