Gravity current hazard prediction model for lahars, landslides and avalanches
DOI: 10.1063/10.0000637
Gravity current hazard prediction model for lahars, landslides and avalanches lead image
Lahars, landslides, avalanches and other geophysical events undergo surges as they occur with one initial release of geophysical material often followed by other releases. These releases are called gravity currents and are predominately any horizontal, gravity-driven flow.
Allen et al. study the propagation of surges as pulses in gravity currents. Their work builds upon previous studies of dam-break style flows, which have only considered a single release of material. In doing so, the authors theoretically extend what is known as a lock-release problem for shallow-water equations to a double-release case.
“We demonstrate that to accurately predict properties of geophysical flows, such as run-out length, speed, depth, and erosion or deposition, the release dynamics or combining of flows downstream must be considered,” said author Paul Allen. “Critically, a piecemeal or variable rate of release can be more hazardous downstream than an abrupt or continuous release.”
The authors classified the phased-lock release problem in a range of possible solutions based on the Froude number and a dimensionless separation time. They discovered multiple surges of material in a geophysical flow are much more harmful than one large release.
“For small values of the separation time, the flow behaves like a single release. For large values, the first and second release behave independently. However, for intermediate values, the two events interact, creating more complex internal dynamics,” said Allen.
This model can be used to estimate the qualitative behavior of a pulsed gravity flow. In the future, the authors want to quantify to what extent the variation in pulse dynamics captured by this shallow-water model can be observed in a real-world flow.
Source: “Pulse propagation in gravity currents,” by P. A. Allen, R. M. Dorrell, O. G. Harlen, R. E. Thomas, and W. D. McCaffrey, Physics of Fluids (2020). The article can be accessed at https://doi.org/10.1063/1.5130576 .
