Stability of Armour Layers in Rivers

Abstract

The importance of both the overpassing and the embedding of river bed particles is demonstrated by experiments. When a single layer thick armouring layer of uniform d\d1 size particles on a bed of uniform finer d\d2 size particles is broken at one location the stability of the remainder of the armour layer depends on the tendency of the d\d1 particles to embed into the surface of d\d2 particles. If a d\d1 size particle is seated in the exposed position on the surface of the d\d2 sized bed sediment it may, by virtue of its exposure to the flow, be preferentially entrained and it may then overpass the finer bed sediment. Alternatively, the d\d1 particle may be too large for overpassing and it will become embedded. Armour layers composed of particles which embed, tend to be more stable.