Comparison of three landslide runout models on the Turnoff Creek rock avalanche, British Columbia

Transcription

1 Landslide Processes: From geomorphologic mapping to dnamic modelling. A tribute to Prof. Dr. Theo van Asch CERG, UU & US - Strasbourg, 6-7 Februar 2009 Comparison of three landslide runout models on the Turnoff Creek rock avalanche, British Columbia Santiago Beguería Consejo Superior de Investigaciones Científicas, Zaragoza, Spain Menno J. Van Hees Department of Phsical Geograph, Universit Utrecht. Utrecht, The Netherlands Marten Geertsema Ministr of Forests and Range, British Columbia, Canada

2 The Turnoff Creek landslide M. Gertsema (2006) Hdrogeomorphic hazards in northern British Columbia

3 The Turnoff Creek landslide

4 The Turnoff Creek landslide

5 The Turnoff Creek landslide Location: 57º 01 N, 123º 17 W Date: 1992 (?) Volume: 4 M m 3 Length: 2 km H/L: 0.28 Turnoff Creek Halfwa River General view, front

6 The Turnoff Creek landslide Litholog: shales and sandstones W Nearb torrent

7 The Turnoff Creek landslide Tpe: Rock slide debris avalanche

8 Anti-scarps above Turnoff The Turnoff Creek landslide

9 The Turnoff Creek landslide Material left in the upper part (2 Mm 3 )

10 The Turnoff Creek landslide translational ridges View from above

11 Scarp The Turnoff Creek landslide

12 Scarp, upper part The Turnoff Creek landslide

13 General view, front The Turnoff Creek landslide

14 General view, lateral The Turnoff Creek landslide

15 Deposit, vertical view The Turnoff Creek landslide

16 The Turnoff Creek landslide run-up deposit: sandstone and shale blocks and rubble, almost no soil General view, spreading

17 Modelling approaches Goal: to model the run-out of the avalanche. Codes: DAN_W (Hungr, 1995) DAN_3D (McDougall & Hungr, 2004) MassMov2D (Beguería et al., in prep.)

18 Modelling approaches Goal: to model the run-out of the avalanche. Codes: DAN_W (Hungr, 1995) DAN_3D (McDougall & Hungr, 2004) MassMov2D (Beguería et al., in prep.) Assumptions: Saint-Venant equation (shallow water aproimation) One-phase flow Depth-integrated solution

19 Fundamental equations Mass and momentum conservation (MassMov2D) ( ) ( ) = 0 hv hu t h ( ) ( ) ( ) ( ) f f S q S g c = gh c k v u v v t v S q S g c = gh c k u v u u t u + +

20 Fundamental equations Mass and momentum conservation (MassMov2D) ( ) ( ) = 0 hv hu t h ( ) ( ) ( ) ( ) f f S q S g c = gh c k v u v v t v S q S g c = gh c k u v u u t u + + flow thickness flow velocit - flow velocit -

21 Fundamental equations Mass and momentum conservation (MassMov2D) h t ( hu) ( hv) flow thickness flow velocit - flow velocit - = 0 u t v t u v v convective acceleration pressure acceleration local acceleration u u v v u k k ( c ) ( ) gh = c g S + q S ( c gh) = c g ( S + q S ) slope friction f f

22 Rheolog Sf : frictional-turbulent (Voellm model) S f = tan ϕ' + 2 u ξ h

23 Rheolog Sf : frictional-turbulent (Voellm model) S f 2 u = tan ϕ' + ξ h apparent friction angle (-) turbulence coefficient (L/T 2 )

24 DAN_W One-dimensional Saint-Venant equation (shallow water assumption) tangential component of the weight + tangential internal pressure resultant + basal resisting force Lagrangian solution (finite elements) flow thickness (L) t = 100s distance (L)

25 DAN_3D Two-dimensional Saint-Venant equation + mass and momentum transfer between the landslide and an erodible base Mesh-less numerical method (particle tracking)

26 MassMov2D Two-dimensional Saint-Venant equation Eulerian solution (finite differences), second order accurate (La-Wendroff)

27 MassMov2D Wartschenbach Creek Faucon Creek

28 Simulation Pre- and post-event DEM pre-event post-event

29 Simulation Initial volume and deposition; slipping surface (post-pre DEM)

30 Simulation Velocit estimation: run-up formulas Run-up: m a

31 Simulation Velocit estimation: run-up formulas Evans et al. (1989); Hungr et al. (1984) u = 2g r run-up height (L) r V G = = = V G u g 2 cos tan θ ( θ θ ) 0 run-up slope (º) approach slope (º) 1 + gh cosθ 2 2u ( tan ϕ cosθ sin θ )

32 Simulation Velocit estimation: run-up formulas Evans et al. (1989); Hungr et al. (1984) u = 2g r Evans: m s-1 r V G = = = V G u g 2 cos tan θ ( θ θ ) gh cosθ 2 2u ( tan ϕ cosθ sin θ ) Hungr (h = 15 m, ϕ' = 5-15º): m s-1

33 Simulation Heuristic approach to parameter calibration: Final deposit (etent, thickness) Velocit in the run-up area S f = tan ϕ' + 2 u ξ h

34 Results Best parameter set: ξ (m s -1 ) ϕ (º) DAN_W DAN_3D MassMov2D / 5.5

35 Results DAN_W: Ma vel.: 21 m s -1 Overestimation terminal section

36 Results DAN_3D: Ma vel.: 28 m s -1 (Evans) Deposition shape, quite well predicted. Under-estimation of deposit thickness. Largest part remained at the bottom of the slope.

37 Results MassMov_2D: ξ=300, ϕ = 11.5º Ma vel.: 18.3 m s -1 (Hungr) Deposition shape, quite well predicted. Under-estimation of deposit thickness. Largest part remained at the bottom of the slope.

38 Results MassMov_2D: ξ=300, ϕ = 11.5º ξ=300, ϕ =5.5º

39 MassMov_2D: Results

40 MassMov_2D: Results

41 Conclusions Numerical simulation codes have proved to be a convenient tool for understanding landslide and rock avalanche dnamics. Simple codes allow testing new modelling concepts. The are potentiall useful for hazard / risk analsis. 1D codes are fast and convenient, but landslides usuall show a comple behaviour. Two 2D codes provided satisfing results, although the were not completel equal: further research is needed.

42 Landslide Processes: From geomorphologic mapping to dnamic modelling. A tribute to Prof. Dr. Theo van Asch CERG, UU & US - Strasbourg, 6-7 Februar 2009 Thank ou! Santiago Beguería Consejo Superior de Investigaciones Científicas, Zaragoza, Spain Menno J. Van Hees Department of Phsical Geograph, Universit Utrecht. Utrecht, The Netherlands Marten Geertsema Ministr of Forests and Range, British Columbia, Canada