Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2019-11 Manuscript under review for journal Nat. Hazards Earth Syst. Sci. Discussion started: 14 February 2019 c Author(s) 2019. CC BY 4.0 License. Significance of substrate soil moisture content for rockfall hazard assessment Louise Mary Vick1, Valerie Zimmer2, Christopher White3, Chris Massey4, Tim Davies5 1Institute of Geosciences, UiT The Arctic University of Norway, Dramsveien 201, Tromsø 9009, Norway 5 2State Water Resources Control Board, 1001 I Street, Sacramento, California 95814, USA 3Resource Development Consultants Limited, 8/308 Queen Street East, Hastings, Hawkes Bay, New Zealand 4GNS Science, 1 Fairway Drive, Avalon 5010, New Zealand 5Department of Geological Sciences, University of Canterbury, Christchurch 8041, New Zealand 10 Correspondence to: Louise M. Vick (
[email protected]) ORCHID: https://orcid.org/0000-0001-9159-071X Abstract. Rockfall modelling is an essential tool for hazard analysis in steep terrain. Calibrating terrain parameters ensures that the model results accurately represent the site-specific hazard. Parameterizing rockfall models is challenging because rockfall runout is highly sensitive to initial conditions, rock shape, size and material properties, terrain morphology, and 15 terrain material properties. This contribution examines the mechanics of terrain scarring due to rockfall on the Port Hills of Christchurch, New Zealand. We use field-scale testing and laboratory direct-shear testing to quantify how the changing moisture content of the loessial soils can influence its strength from soft to hard, and vice versa. We calibrate the three-dimensional rockfall model RAMMS by back analysing several well-documented rockfall events, adopting dry loessial soil conditions.