Calibration of numerical models for small debris flows in Yosemite Valley, California, USA

Abstract

Abstract. This study compares documented debris flow runout distances with numerical simulations in the Yosemite Valley of California, USA, where about 15% of historical events of slope instability can be classified as debris flows and debris slides (Wieczorek and Snyder, 2004).To model debris flows in the Yosemite Valley, we selected six streams with evidence of historical debris flows; three of the debris flow deposits have single channels, and the other three split their pattern in the fan area into two or more channels. From field observations all of the debris flows involved coarse material, with only very small clay content.We applied the one dimensional DAN (Dynamic ANalysis) model (Hungr, 1995) and the two-dimensional FLO-2D model (O'Brien et al., 1993) to predict and compare the runout distance and the velocity of the debris flows observed in the study area. As a first step, we calibrated the parameters for the two softwares through the back analysis of three debris-flows channels using a trial-and-error procedure starting with values suggested in the literature. In the second step we applied the selected values to the other channels, in order to evaluate their predictive capabilities.After parameter calibration using three debris flows we obtained results similar to field observations We also obtained a good agreement between the two models for velocities. Both models are strongly influenced by topography: we used the 30 m cell size DTM available for the study area, that is probably not accurate enough for a highly detailed analysis, but it can be sufficient for a first screening.

An equivalent fluid/equivalent medium approach for the numerical simulation of coastal landslides propagation: theory and case studies

“…The values that have been used in the subaerial part are reasonable when compared with similar events that are reported in the literature (Bertolo and Wieczorek, 2005;Revellino et al, 2004). For the submerged path, a lower value of the turbulence 33 1 Figure 8.…”

The efficiency of a risk reduction program for debris-flow disasters – a case study of the Songhe community in Taiwan

“…Although the scale of debris flows depends on precipitation and available transport sediment, only precipitation was used as a proxy in the FLO-2D model because of the difficult question of whether sediment will be (re) mobilized. The steps for beginning a simulation with FLO-2D, which include obtaining topographic data and developing flood hydrology, were proposed by Bertolo and Wieczorek (2005). Since an inflow flood hydrograph was required, a triangular hydrograph was used to simplify the process, and the peak discharges were evaluated using the rational formula based on small areas of watersheds (Pilgrim and Cordery, 1993).…”

Estimated probabilities, volumes, and inundation area depths of potential postwildfire debris flows from Carbonate, Slate, Raspberry, and Milton Creeks, near Marble, Gunnison County, Colorado

“…The FLO-2D model has previously been used to estimate postwildfire inundation in Colorado (Elliott and others, 2005). FLO-2D also was used in Yosemite National Park to simulate debris flows using field evidence to calibrate the model (Bertolo and Wieczorek, 2005). The model uses a specified input hydrograph, volumetric sediment concentration, existing topography, and roughness estimates to route a debris flow from the basin outlet of the originating tributary to the depositional area on the debris-flow fan.…”