Analogue models are representative of a natural prototype if they are properly scaled and if the materials used show a similar rheological behaviour as the natural prototype. In analogue or physical modelling of geological processes certain scaling rules should be followed in order to make the model a good analogue of the natural prototype. The theory of these rules was first introduced by Hubbert [1937] and was later discussed by Hubbert [1951], Horsfield [1977], Shemenda [1983], Richard [1991], Davy and Cobbold [1991] and Cobbold and Jackson [1992].

According to Hubbert [1937], a model is properly scaled to its natural counterpart if it is geometrically, kinematically and dynamically similar. An analogue model and a natural prototype are geometrically similar if all the corresponding lengths are proportional and all the corresponding angles within the bodies are equal. For kinematic similarity, the geometrically similar model and prototype have to undergo similar changes of shape and/or position, where the time required for any change in the model is proportional for the corresponding change in the prototype [Ramberg, 1967]. Finally, for dynamical similarity between a geometrically and kinematically similar model and prototype, the two bodies have to have similar ratios and distributions of different kinds of driving and resistive forces (gravitational, frictional and viscous) acting on the different particles of the body.