[Previous] | [Session 46] | [Next]
H. Miyamoto (Univ. Tokyo), G. Komatsu (IRSPS), K. Ito (OYO Corp.), H. Tosaka (Univ. Tokyo), T. Tokunaga (Univ. Tokyo)
The Martian outflow channels are considered to have been formed by catastrophic water flood processes analogous to the Lake Missoula floods responsible for the formation of the Channeled Scabland in Washington State [e.g., Baker and Milton, 1974]. The estimations of peak discharge rates and total amounts of water play critical roles for the discussion of the Martian water cycle. Therefore, for a more realistic estimation we developed a three-dimensional numerical code of surface flows coupled with subsurface flows. Coupling both surface and subsurface flows in the model is very important because the origin of the outflows is thought to be strongly linked to subsurface aquifers [e.g., Baker, et al., 1991]. Our model can calculate air-water movements on the surface and in the subsurface under various hydrological and geological conditions. We concentrated on the water movement as the first step. We applied our model to the glacial Lake Missoula floods to test our code and to study parameter sensitivities. We followed the glacial lake failure scenario and gave a well-constrained high discharge rate at an area of the lake failure. After the breakout, the flood water flows down-slope and covers a wide area. We compared the calculated areal coverage of the floods and the peak water levels with field observations. We obtained a reasonable result of the water coverage within a DTM containing the Cordilleran Ice Sheet. And also the computed time sequential behaviors of the floods, such as the hydraulic ponding in the Pasco Basin, are consistent with the field data. However, there are significant discrepancies in terms of the water depths between the calculated values and some field observations. This may indicate that the history of the floodings is more complex than our assumption.