in this paper twelve different empirical resistance coefficients expressed in terms of manning's roughness are used apiece in seventeen known compositing methods. the data obtained from ten different cross-sections of the sefidrood river, iran, are used for the evaluation of the empiricalformulas. the present case-study is selected from a reach with gravel bed topology. then no remarkable bed f...

Alluvial slopes are piedmonts characterized by parallel steam channels rather than alluvial fans. They are common landforms in extensional basins of the south-western United States but have received little attention from geomorphologists or sedimentologists. Persistence of channellized flow across piedmonts, as opposed to sheetflooding due to loss of flow confinement on alluvialfan surfaces, di...

The fluvial system is a major concern in modeling landform evolution in response to tectonic deformation. Three stream bed types (bedrock, coarse-bed alluvial, and fine-bed alluvial) differ in factors controlling their occurrence and evolution and in appropriate modeling approaches. Spatial and temporal transitions among bed types occur in response to changes in sediment characteristics and tec...

Field surveys of channel width w and drainage area A in bedrock channel reaches reveal relationships where w 5 cA, similar to the classic hydraulic geometry of alluvial channels. Data from five mountain channel networks support the assumption used in many landscape evolution models that an alluvial hydraulic geometry relationship where b 5 0.3–0.5 holds for bedrock channel systems. Although the...

Rivers around the world are being regulated by dams to accommodate the needs of a rapidly growing global population. These regulatory efforts usually oppose the natural tendency of rivers to flood, move sediment, and migrate. Although an economic benefit, river regulation has come at unforeseen and unevaluated cumulative ecological costs. Historic and contemporary approaches to remedy environme...

Little is known about the importance of drainage/irrigation channels and biogeochemical processes in arsenic distribution of shallow groundwaters from the Hetao basin. This investigation shows that although As concentrations are primarily dependent on reducing conditions, evaporation increases As concentration in the centre of palaeo-lake sedimentation. Near drainage channels, groundwater As co...