Sediment transfer and storage in dryland headwater streams

Channel Form, Flows and Sediments of Endogenous Ephemeral Rivers in Deserts

“…Leopold et al were able to provide a loosely deterministic relation between a hydraulic parameter -unit discharge -and the depth of scour (Figure 13.17). This has been corroborated from observations made in a small sand-bed tributary of Walnut Gulch, southern Arizona, though, here, the relation establishes itself only at flows that have unit stream power >10-15 W/m 2 (Powell et al, 2007) (Figure 13.19(b)). Foley (1978) has gone further in his explanation by suggesting that the depth of scour is determined by the amplitude of migrating antidunes that form under upper flow regime conditions.…”

“…(b) Specific scour volume as a function of unit stream power for reaches of three headwater channels of Walnut Gulch. The least-squares curve refers to bivariates where specific scour volume ≥0.1 m 3 /m 2 (afterPowell et al, 2007).…”

Distinctiveness and Diversity of Arid Zone River Systems

“…Many other recent studies or overviews have also tended to focus on the river types in these drylands (e.g. Cohen and Laronne, 2005;Hassan, 2005;Thomas, 2005;Powell et al, 2007;Pollen-Bankhead et al, 2009), in many cases unwittingly reinforcing the impression that these characteristics apply to most or all dryland rivers. This poses some important, interrelated questions.…”

Patterns of grain‐size dependent sediment transport in low‐ordered, ephemeral channels

“…This derivation of boundary shear stress is an approximation of the fl uid stress borne by the bed grains and while commonly employed in a wide range of geomorphic studies (e.g. Batalla and Martin-Vide, 2001;Habersack and Laronne, 2001;Tucker et al, 2006;Powell et al, 2007), it uses assumptions (e.g. steady, uniform fl ow) that are often violated in natural fl ows.…”