As a consequence, flood flows can take months to reach drainage basin sinks. This is not always the case however. Arid zone rivers with smaller catchments may discharge their runoff very rapidly. In short, a lot of work is done in a short time period on an irregular basis. Channel form varies according to different catchment and hydrological characteristics.
Local geomorphology can exert significant control on channel form and river behaviour.
The entrainment of sediment particles by wind follows roughly the same principles as particle entrainment by water, for wind is also regarded as a fluid medium. As with fluvial entrainment, once very small particles are taken into suspension they have a habit of staying there. Thus, small particles move further than larger ones. Even when moisture content is fractional, particles may be bound together by surface tension in the meniscuses between them. This is dependent upon particle size and is affected by a whole range of other possible variables, such as organic content, clay mineralogy, etc.