| Cellular Automata
(CA) represent a formal frame for dynamical systems, which evolve on the
base of local interactions. Some types of landslide, such as debris flows,
match well this requirement. The latest hexagonal release (S3–hex)
of the deterministic model SCIDDICA, specifically developed for simulating
debris flows, is described. For CA simulation purposes, landslides can be
viewed as a dynamical system, subdivided into elementary parts, whose
state evolves exclusively as a consequence of local interactions within a
spatial and temporal discretum. Space is the world of the CA, here
constituted by hexagonal cells. The attributes of each cell ("substates")
describe physical characteristics. For computational reasons, the natural
phenomenon is "decomposed" into a number of elementary
processes, whose proper composition makes up the "transition
function" of the CA. By simultaneously applying this function to all
the cells, the evolution of the phenomenon can be simulated in terms of
modifications of the substates.
SCIDDICA S3–hex exhibits a great
flexibility in modelling debris flows. With respect to the previous
releases of the model, the mechanism of progressive erosion of the soil
cover has been added to the transition function. Considered substates are:
altitude; thickness and energy of landslide debris; depth of erodable soil
cover; debris outflows. Considered elementary processes are: mobilisation
triggering and effect (T1), debris outflows (I1), update of
landslide debris thickness and energy (I2), and energy loss (T2).
Simulations of real debris flows, occurred in Campania
(Southern Italy) in May 1998 (Sarno) and December 1999 (San Martino V.C.
and Cervinara), have been performed for model calibration purposes; some
examples of analysis are briefly described. Possible applications of the
method are: risk mapping, also based on a statistical approach; evaluating
the effects of mitigation actions (e.g. stream deviations, topographic
alterations, channelling, embankments, bridges, etc.) on flow development. |