Model Development for Two-Phase Thin Layer Flows and Validation Using Debris Flows at Tungurahua, Ecuador and Ruapehu, New Zealand

Mudflows are one of the most common natural hazards; they occur frequently associated with heavy rainfall, earthquakes or other unusual phenomena. They often cause a great loss of life and property. This research will use field studies of an actual large volcanic mudflow that occurred in New Zealand in March 2007. It is proposed to develop and test a computer model that simulates such flows that are a mixture of solid particles and water. An important part of this study is to determine the degree of certainty or uncertainty that is possible in forecasts of future mudflows. Analysis of field measurements will provide the basis for testing and improving the computer model. A careful series of computer simulations will be done to sequentially reproduce the field measurements taken of the actual flow. The results of this process can be analyzed to increase the confidence level in forecasting of similar and smaller mudflows elsewhere in the world. A secondary goal of the project will be to forecast smaller mudflows at a volcano in Ecuador that is currently producing similar destructive flows nearly every week due to heavy rainfall. The model and analysis resulting from this study will allow a better means to make sound predictions of hazard risk for similar flows in the future. The flow of geologic material mixed with interstitial fluid is a complex process activating physics across many length and time scales. This project will extend the TITAN2D computational environment to include fluid-solid flows, and to test these models using data collected from field studies at Ruapehu, New Zealand. Statistical analysis will probe questions of sensitivity to parameters, and of model and measurement error, and will provide a quantitative basis for prediction. A special focus of this effort is to model and calibrate the March 2007 breakout flow of the crater lake at Ruapehu Volcano in New Zealand. Working closely with colleagues at Massey University, the team will use data they collected in their study of the 2007 breakout to further refine mathematical and statistical models. The colleagues at Massey had instrumented Ruapehu, which allowed them to collect an exceptional data set from this important flow event. These data include pre- and post-event aerial LiDAR and digital photographic surveys that show postevent changes in channel morphology, sediment erosion, and redistribution. In addition, instruments for innovative applications of mechanical, electro-magnetic, vibration, and pressure detection systems provide measurements of velocities, sediment distribution, flow behavior, and erosion/deposition processes within the rapidly moving sediment-water slurries of this event. This unique dataset will enable unparalleled testing and calibration of flow models. Coupled with statistical methodology, these results will serve as a standard against which a new generation of numerical and physical mass-flow models can be calibrated and refined. Data from this project will be of particular interest to groups studying the broader-scale problem of hazards related to eruptions of similar volcanoes elsewhere. Refinement of the TITAN model to forecast smaller flow events is planned by testing it at the recurrent events (on a weekly time-frame) at Tungurahua Volcano in Ecuador.