Logjam attenuation of annual sediment waves in eolian-fluvial environments, North Park, Colorado, USA

Abstract

Sediment waves, a term that describes the fluvial transport of a discrete sediment influx, have been studied in regard to channel response to infrequent catastrophic events, such as mass movements or dam removal. However, few researchers have studied (1) the potential presence of sediment waves of annual or sub-annual scale in mixed eolian-fluvial geomorphic environments or (2) the role of large wood in sediment wave dispersal. This study addresses both topics through observations of North Sand Creek and East Sand Creek, which flow alongside the active sand dunes of North Sand Hills and East Sand Hills, respectively, in North Park, Colorado. The creeks experience similar seasonal, asynchronous cycles of eolian influx and fluvial transport, although North Sand Creek receives a greater volume of eolian sand. We use repeat photography and repeat measurement of ephemeral terraces to determine whether each creek experiences a sediment wave, and we use repeat measurement of logjam sand wedge volume to examine changes in sand storage associated with logjams over time. Results indicate that North Sand Creek experiences a highly translative sediment wave that is attenuated by logjams. East Sand Creek, on the other hand, does not experience a sediment wave.