The Author was to be congratulated for his initiative in proceeding with the tricky study of scour. Because scour took place under water (and mostly during floods) its study was not so easy. It was the energy of the water, obtained from its velocity, which was capable of moving a certain quantity of solid particles over the riverbed. If the supply from upstream was insufficient, scour took place. On the other hand, if velocity dropped, the same amount of material could not be carried away any more.
The author had stated that the curves were based on a limiting value of the shear stresses set up in the soil, whereas their general shape was typical of the relationship based upon a fixed permissible value of the settlement. An alternative explanation might possibly be that with wider footings the zone of influence would spread down into weaker material.
Much credit was due to the Authors for defining, for the first time in this country, the problem of 'collapsing sand' and also for proposing a method for the prediction of the behaviour of this treacherous material. The writer had been struck by the similarity of this soil to loess, in both consolidation and shear characteristics. Deposits of loess occurred in many countries, but the formation, mineralogy and particle sizes appeared to be quite different. A comparison of these other properties was beyond the scope of this discussion.