Sediment Transportation Mechanics: Q. Genetic Classification of Valley Sediment Deposits

Valley fluvial sediment deposits are classified according to origin. All such deposits are intergradational, but most can be classified as dominantly transitory channel deposits, lag deposits, lateral or vertical flood plain accretions, splays, channel fill, or colluvium. Mass movements, especially mudflows but also debris avalanches and earthflows in places, form significant deposits under limited circumstances. Other terms are useful for typical surface forms, subdivisions or associations of types of deposits. Point bars are the most conspicuous forms of lateral accretion. Vertical accretion includes natural levee, backland and backswamp deposits, although splays are also important in natural levees. Channel fills range from coarse-grained to fine clay plugs. Alluvial fans and deltas are associations of type of deposits, characteristic of specific topographic situations. Valley plugs are fan-like local concentrations along filled channels, with characteristic splays, but not in typical alluvial fan locations.